[flang] [llvm] [flang/flang-rt] Implement show_descriptor intrinsic, a non-standard extension. (PR #170389)

Valery Dmitriev via llvm-commits llvm-commits at lists.llvm.org
Tue Dec 2 15:25:23 PST 2025


https://github.com/valerydmit updated https://github.com/llvm/llvm-project/pull/170389

>From f232f55efd1824b68b30d6d46cf6232f7c186d52 Mon Sep 17 00:00:00 2001
From: Valery Dmitriev <valeryd at nvidia.com>
Date: Tue, 2 Dec 2025 14:37:33 -0800
Subject: [PATCH 1/4]     [flang/flang-rt] Implement show_descriptor intrinsic,
 a non-standard extension

    Reapply  #169137

    show_descriptor intrinsic prints details of a descriptor (extended
    Fortran pointer).
    It accepts a descriptor for any type and rank, including scalars.
    Requires use of flang_debug module.

    Example:
    program test
      use flang_debug
      implicit none
      integer :: a(4) = (/ 1,3,5,7 /)
      call show_descriptor(a(1:3))
    end program test

    and its output:
    Descriptor @ 0x7ffe01ec6a98:
      base_addr 0x563b7035103c
      elem_len  4
      version   20240719
      rank      1
      type      9 "INTEGER(kind=4)"
      attribute 0
      extra     0
        addendum  0
        alloc_idx 0
      dim[0] lower_bound 1
             extent      3
             sm          4
---
 .../include/flang-rt/runtime/descriptor.h     |   4 +-
 flang-rt/lib/runtime/descriptor.cpp           | 164 +++++++++++-
 flang-rt/lib/runtime/extensions.cpp           |   9 +
 flang-rt/unittests/Runtime/Descriptor.cpp     | 113 ++++++++
 flang/docs/Intrinsics.md                      |  43 ++++
 .../flang/Optimizer/Builder/IntrinsicCall.h   |   1 +
 .../Optimizer/Builder/Runtime/Intrinsics.h    |   5 +-
 flang/include/flang/Runtime/extensions.h      |   8 +
 flang/lib/Evaluate/intrinsics.cpp             |   2 +
 flang/lib/Optimizer/Builder/IntrinsicCall.cpp |  14 +
 .../Optimizer/Builder/Runtime/Intrinsics.cpp  |   7 +
 flang/module/__fortran_builtins.f90           |   3 +
 flang/module/flang_debug.f90                  |  14 +
 .../test/Lower/Intrinsics/show_descriptor.f90 | 241 ++++++++++++++++++
 flang/tools/f18/CMakeLists.txt                |   1 +
 15 files changed, 622 insertions(+), 7 deletions(-)
 create mode 100644 flang/module/flang_debug.f90
 create mode 100644 flang/test/Lower/Intrinsics/show_descriptor.f90

diff --git a/flang-rt/include/flang-rt/runtime/descriptor.h b/flang-rt/include/flang-rt/runtime/descriptor.h
index ff7ec050d32c7..40e30e3bf783f 100644
--- a/flang-rt/include/flang-rt/runtime/descriptor.h
+++ b/flang-rt/include/flang-rt/runtime/descriptor.h
@@ -510,7 +510,9 @@ class Descriptor {
 
   RT_API_ATTRS void Check() const;
 
-  void Dump(FILE * = stdout) const;
+  // When dumpRawType, dumps stringified CFI_type_*, otherwise
+  // try to canonicalize and print as a Fortran type.
+  void Dump(FILE * = stdout, bool dumpRawType = true) const;
 
   RT_API_ATTRS inline bool HasAddendum() const {
     return raw_.extra & _CFI_ADDENDUM_FLAG;
diff --git a/flang-rt/lib/runtime/descriptor.cpp b/flang-rt/lib/runtime/descriptor.cpp
index 5ede5f9d9f9ed..066e94232c003 100644
--- a/flang-rt/lib/runtime/descriptor.cpp
+++ b/flang-rt/lib/runtime/descriptor.cpp
@@ -292,14 +292,168 @@ RT_API_ATTRS void Descriptor::Check() const {
   // TODO
 }
 
-void Descriptor::Dump(FILE *f) const {
+static const char *GetTypeStr(ISO::CFI_type_t type, bool dumpRawType) {
+  if (dumpRawType) {
+#define CASE(x) \
+  case (x): \
+    return #x;
+    switch (type) {
+      CASE(CFI_type_signed_char)
+      CASE(CFI_type_short)
+      CASE(CFI_type_int)
+      CASE(CFI_type_long)
+      CASE(CFI_type_long_long)
+      CASE(CFI_type_size_t)
+      CASE(CFI_type_int8_t)
+      CASE(CFI_type_int16_t)
+      CASE(CFI_type_int32_t)
+      CASE(CFI_type_int64_t)
+      CASE(CFI_type_int128_t)
+      CASE(CFI_type_int_least8_t)
+      CASE(CFI_type_int_least16_t)
+      CASE(CFI_type_int_least32_t)
+      CASE(CFI_type_int_least64_t)
+      CASE(CFI_type_int_least128_t)
+      CASE(CFI_type_int_fast8_t)
+      CASE(CFI_type_int_fast16_t)
+      CASE(CFI_type_int_fast32_t)
+      CASE(CFI_type_int_fast64_t)
+      CASE(CFI_type_int_fast128_t)
+      CASE(CFI_type_intmax_t)
+      CASE(CFI_type_intptr_t)
+      CASE(CFI_type_ptrdiff_t)
+      CASE(CFI_type_half_float)
+      CASE(CFI_type_bfloat)
+      CASE(CFI_type_float)
+      CASE(CFI_type_double)
+      CASE(CFI_type_extended_double)
+      CASE(CFI_type_long_double)
+      CASE(CFI_type_float128)
+      CASE(CFI_type_half_float_Complex)
+      CASE(CFI_type_bfloat_Complex)
+      CASE(CFI_type_float_Complex)
+      CASE(CFI_type_double_Complex)
+      CASE(CFI_type_extended_double_Complex)
+      CASE(CFI_type_long_double_Complex)
+      CASE(CFI_type_float128_Complex)
+      CASE(CFI_type_Bool)
+      CASE(CFI_type_char)
+      CASE(CFI_type_cptr)
+      CASE(CFI_type_struct)
+      CASE(CFI_type_char16_t)
+      CASE(CFI_type_char32_t)
+      CASE(CFI_type_uint8_t)
+      CASE(CFI_type_uint16_t)
+      CASE(CFI_type_uint32_t)
+      CASE(CFI_type_uint64_t)
+      CASE(CFI_type_uint128_t)
+    }
+#undef CASE
+    return nullptr;
+  }
+  TypeCode code{type};
+
+  if (!code.IsValid())
+    return "invalid";
+
+  common::optional<std::pair<TypeCategory, int>> categoryAndKind =
+      code.GetCategoryAndKind();
+  if (!categoryAndKind)
+    return nullptr;
+
+  TypeCategory tcat;
+  int kind;
+  std::tie(tcat, kind) = *categoryAndKind;
+
+#define CASE(cat, k) \
+  case (k): \
+    return #cat "(kind=" #k ")";
+  switch (tcat) {
+  case TypeCategory::Integer:
+    switch (kind) {
+      CASE(INTEGER, 1)
+      CASE(INTEGER, 2)
+      CASE(INTEGER, 4)
+      CASE(INTEGER, 8)
+      CASE(INTEGER, 16)
+    }
+    break;
+  case TypeCategory::Unsigned:
+    switch (kind) {
+      CASE(UNSIGNED, 1)
+      CASE(UNSIGNED, 2)
+      CASE(UNSIGNED, 4)
+      CASE(UNSIGNED, 8)
+      CASE(UNSIGNED, 16)
+    }
+    break;
+  case TypeCategory::Real:
+    switch (kind) {
+      CASE(REAL, 2)
+      CASE(REAL, 3)
+      CASE(REAL, 4)
+      CASE(REAL, 8)
+      CASE(REAL, 10)
+      CASE(REAL, 16)
+    }
+    break;
+  case TypeCategory::Complex:
+    switch (kind) {
+      CASE(COMPLEX, 2)
+      CASE(COMPLEX, 3)
+      CASE(COMPLEX, 4)
+      CASE(COMPLEX, 8)
+      CASE(COMPLEX, 10)
+      CASE(COMPLEX, 16)
+    }
+    break;
+  case TypeCategory::Character:
+    switch (kind) {
+      CASE(CHARACTER, 1)
+      CASE(CHARACTER, 2)
+      CASE(CHARACTER, 4)
+    }
+    break;
+  case TypeCategory::Logical:
+    switch (kind) {
+      CASE(LOGICAL, 1)
+      CASE(LOGICAL, 2)
+      CASE(LOGICAL, 4)
+      CASE(LOGICAL, 8)
+    }
+    break;
+  case TypeCategory::Derived:
+    return "DERIVED";
+  }
+#undef CASE
+  return nullptr;
+}
+
+void Descriptor::Dump(FILE *f, bool dumpRawType) const {
   std::fprintf(f, "Descriptor @ %p:\n", reinterpret_cast<const void *>(this));
   std::fprintf(f, "  base_addr %p\n", raw_.base_addr);
-  std::fprintf(f, "  elem_len  %zd\n", static_cast<std::size_t>(raw_.elem_len));
+  std::fprintf(f, "  elem_len  %zd\n", ElementBytes());
   std::fprintf(f, "  version   %d\n", static_cast<int>(raw_.version));
-  std::fprintf(f, "  rank      %d\n", static_cast<int>(raw_.rank));
-  std::fprintf(f, "  type      %d\n", static_cast<int>(raw_.type));
-  std::fprintf(f, "  attribute %d\n", static_cast<int>(raw_.attribute));
+  if (rank() > 0) {
+    std::fprintf(f, "  rank      %d\n", rank());
+  } else {
+    std::fprintf(f, "  scalar\n");
+  }
+  int ty = static_cast<int>(raw_.type);
+  if (const char *tyStr = GetTypeStr(raw_.type, dumpRawType)) {
+    std::fprintf(f, "  type      %d \"%s\"\n", ty, tyStr);
+  } else {
+    std::fprintf(f, "  type      %d\n", ty);
+  }
+  int attr = static_cast<int>(raw_.attribute);
+  if (IsPointer()) {
+    std::fprintf(f, "  attribute %d (pointer) \n", attr);
+  } else if (IsAllocatable()) {
+    std::fprintf(f, "  attribute %d (allocatable)\n", attr);
+  } else {
+    std::fprintf(f, "  attribute %d\n", attr);
+  }
+
   std::fprintf(f, "  extra     %d\n", static_cast<int>(raw_.extra));
   std::fprintf(f, "    addendum  %d\n", static_cast<int>(HasAddendum()));
   std::fprintf(f, "    alloc_idx %d\n", static_cast<int>(GetAllocIdx()));
diff --git a/flang-rt/lib/runtime/extensions.cpp b/flang-rt/lib/runtime/extensions.cpp
index c110b0381890c..108d7b1923b99 100644
--- a/flang-rt/lib/runtime/extensions.cpp
+++ b/flang-rt/lib/runtime/extensions.cpp
@@ -467,6 +467,15 @@ void FORTRAN_PROCEDURE_NAME(srand)(int *seed) {
   rand_seed_lock.Drop();
 }
 
+
+void RTNAME(ShowDescriptor)(const Fortran::runtime::Descriptor *descr) {
+  if (descr) {
+    descr->Dump(stderr, /*dumpRawType=*/false);
+  } else {
+    std::fprintf(stderr, "NULL\n");
+  }
+}
+
 // Extension procedures related to I/O
 
 namespace io {
diff --git a/flang-rt/unittests/Runtime/Descriptor.cpp b/flang-rt/unittests/Runtime/Descriptor.cpp
index 4a7bb43a492af..f86ff4cf16a55 100644
--- a/flang-rt/unittests/Runtime/Descriptor.cpp
+++ b/flang-rt/unittests/Runtime/Descriptor.cpp
@@ -9,6 +9,7 @@
 #include "flang-rt/runtime/descriptor.h"
 #include "tools.h"
 #include "gtest/gtest.h"
+#include <regex>
 
 using namespace Fortran::runtime;
 
@@ -158,3 +159,115 @@ TEST(Descriptor, FixedStride) {
   EXPECT_TRUE(descriptor.IsContiguous());
   EXPECT_EQ(descriptor.FixedStride().value_or(-666), 0);
 }
+
+static std::string getAddrFilteredContent(FILE *fin) {
+  rewind(fin);
+  std::ostringstream content;
+  char buffer[1024];
+  size_t bytes_read;
+  while ((bytes_read = fread(buffer, 1, sizeof(buffer), fin)) > 0) {
+    content.write(buffer, bytes_read);
+  }
+  return std::regex_replace(
+      content.str(), std::regex("(0x[0-9a-fA-F]*)"), "[address]");
+}
+
+TEST(Descriptor, Dump) {
+  StaticDescriptor<4> staticDesc[2];
+  Descriptor &descriptor{staticDesc[0].descriptor()};
+  using Type = std::int32_t;
+  Type data[8][8][8];
+  constexpr int four{static_cast<int>(sizeof data[0][0][0])};
+  TypeCode integer{TypeCategory::Integer, four};
+  // Scalar
+  descriptor.Establish(integer, four, data, 0);
+  FILE *tmpf = tmpfile();
+  ASSERT_TRUE(tmpf) << "tmpfile returned NULL";
+  auto resetTmpFile = [tmpf]() {
+    rewind(tmpf);
+    ftruncate(fileno(tmpf), 0);
+  };
+
+  descriptor.Dump(tmpf, /*dumpRawType=*/false);
+  // also dump as CFI type
+  descriptor.Dump(tmpf, /*dumpRawType=*/true);
+  std::string output = getAddrFilteredContent(tmpf);
+  ASSERT_STREQ(output.c_str(),
+      "Descriptor @ [address]:\n"
+      "  base_addr [address]\n"
+      "  elem_len  4\n"
+      "  version   20240719\n"
+      "  scalar\n"
+      "  type      9 \"INTEGER(kind=4)\"\n"
+      "  attribute 0\n"
+      "  extra     0\n"
+      "    addendum  0\n"
+      "    alloc_idx 0\n"
+      "Descriptor @ [address]:\n"
+      "  base_addr [address]\n"
+      "  elem_len  4\n"
+      "  version   20240719\n"
+      "  scalar\n"
+      "  type      9 \"CFI_type_int32_t\"\n"
+      "  attribute 0\n"
+      "  extra     0\n"
+      "    addendum  0\n"
+      "    alloc_idx 0\n");
+
+  // Contiguous matrix (0:7, 0:7)
+  SubscriptValue extent[3]{8, 8, 8};
+  descriptor.Establish(integer, four, data, 2, extent);
+  resetTmpFile();
+  descriptor.Dump(tmpf, /*dumpRawType=*/false);
+  output = getAddrFilteredContent(tmpf);
+  ASSERT_STREQ(output.c_str(),
+      "Descriptor @ [address]:\n"
+      "  base_addr [address]\n"
+      "  elem_len  4\n"
+      "  version   20240719\n"
+      "  rank      2\n"
+      "  type      9 \"INTEGER(kind=4)\"\n"
+      "  attribute 0\n"
+      "  extra     0\n"
+      "    addendum  0\n"
+      "    alloc_idx 0\n"
+      "  dim[0] lower_bound 0\n"
+      "         extent      8\n"
+      "         sm          4\n"
+      "  dim[1] lower_bound 0\n"
+      "         extent      8\n"
+      "         sm          32\n");
+
+  TypeCode real{TypeCategory::Real, four};
+  // Discontiguous real 3-D array (0:7, 0:6:2, 0:6:2)
+  descriptor.Establish(real, four, data, 3, extent);
+  descriptor.GetDimension(1).SetExtent(4);
+  descriptor.GetDimension(1).SetByteStride(8 * 2 * four);
+  descriptor.GetDimension(2).SetExtent(4);
+  descriptor.GetDimension(2).SetByteStride(8 * 8 * 2 * four);
+
+  resetTmpFile();
+  descriptor.Dump(tmpf, /*dumpRawType=*/false);
+  output = getAddrFilteredContent(tmpf);
+  ASSERT_STREQ(output.c_str(),
+      "Descriptor @ [address]:\n"
+      "  base_addr [address]\n"
+      "  elem_len  4\n"
+      "  version   20240719\n"
+      "  rank      3\n"
+      "  type      27 \"REAL(kind=4)\"\n"
+      "  attribute 0\n"
+      "  extra     0\n"
+      "    addendum  0\n"
+      "    alloc_idx 0\n"
+      "  dim[0] lower_bound 0\n"
+      "         extent      8\n"
+      "         sm          4\n"
+      "  dim[1] lower_bound 0\n"
+      "         extent      4\n"
+      "         sm          64\n"
+      "  dim[2] lower_bound 0\n"
+      "         extent      4\n"
+      "         sm          512\n");
+  fclose(tmpf);
+}
diff --git a/flang/docs/Intrinsics.md b/flang/docs/Intrinsics.md
index 31bead9f8bfdc..6451fc48fc6a2 100644
--- a/flang/docs/Intrinsics.md
+++ b/flang/docs/Intrinsics.md
@@ -1414,6 +1414,7 @@ This is prefixed by `STRING`, a colon and a space.
 - **Class:** subroutine
 - **Syntax:** `CALL PERROR(STRING)`
 
+<<<<<<< HEAD
 ### Non-Standard Intrinsics: SRAND
 
 #### Description
@@ -1455,3 +1456,45 @@ The return value is of `REAL` type with the default kind.
 - **Standard:** GNU extension
 - **Class:** function
 - **Syntax:** `RESULT = RAND(I)`
+
+### Non-Standard Intrinsics: SHOW_DESCRIPTOR
+
+#### Description
+`SHOW_DESCRIPTOR(VAR)` prints (on the C stderr stream) a contents of a descriptor for the variable VAR,
+which can be of any type and rank, including scalars.
+Requires use of flang_debug module.
+
+Here is an example of its output:
+```
+Descriptor @ 0x7ffe506fc368:
+  base_addr 0x55944caef0f0
+  elem_len  4
+  version   20240719
+  rank      1
+  type      9 "INTEGER(kind=4)"
+  attribute 2 (allocatable)
+  extra     0
+    addendum  0
+    alloc_idx 0
+  dim[0] lower_bound 1
+         extent      5
+         sm          4
+```
+
+#### Usage and Info
+- **Standard:** flang extension
+- **Class:** subroutine
+- **Syntax:** `CALL show_descriptor(VAR)`
+
+#### Example
+```Fortran
+subroutine test
+  use flang_debug
+  implicit none
+  character(len=9) :: c = 'Hey buddy'
+  integer :: a(5)
+  call show_descriptor(c)
+  call show_descriptor(c(1:3))
+  call show_descriptor(a)
+end subroutine test
+```
diff --git a/flang/include/flang/Optimizer/Builder/IntrinsicCall.h b/flang/include/flang/Optimizer/Builder/IntrinsicCall.h
index 0ae9177f98fd8..b248106b51101 100644
--- a/flang/include/flang/Optimizer/Builder/IntrinsicCall.h
+++ b/flang/include/flang/Optimizer/Builder/IntrinsicCall.h
@@ -413,6 +413,7 @@ struct IntrinsicLibrary {
   template <typename Shift>
   mlir::Value genShift(mlir::Type resultType, llvm::ArrayRef<mlir::Value>);
   mlir::Value genShiftA(mlir::Type resultType, llvm::ArrayRef<mlir::Value>);
+  void genShowDescriptor(llvm::ArrayRef<fir::ExtendedValue>);
   mlir::Value genSign(mlir::Type, llvm::ArrayRef<mlir::Value>);
   mlir::Value genSind(mlir::Type, llvm::ArrayRef<mlir::Value>);
   mlir::Value genSinpi(mlir::Type, llvm::ArrayRef<mlir::Value>);
diff --git a/flang/include/flang/Optimizer/Builder/Runtime/Intrinsics.h b/flang/include/flang/Optimizer/Builder/Runtime/Intrinsics.h
index 30c3189366cec..1f751827309a4 100644
--- a/flang/include/flang/Optimizer/Builder/Runtime/Intrinsics.h
+++ b/flang/include/flang/Optimizer/Builder/Runtime/Intrinsics.h
@@ -111,12 +111,15 @@ void genSleep(fir::FirOpBuilder &builder, mlir::Location loc,
 mlir::Value genChdir(fir::FirOpBuilder &builder, mlir::Location loc,
                      mlir::Value name);
 
-
 mlir::Value genIrand(fir::FirOpBuilder &builder, mlir::Location loc,
                      mlir::Value i);
 mlir::Value genRand(fir::FirOpBuilder &builder, mlir::Location loc,
                     mlir::Value i);
 
+/// generate dump of a descriptor
+void genShowDescriptor(fir::FirOpBuilder &builder, mlir::Location loc,
+                       mlir::Value descriptor);
+
 } // namespace runtime
 } // namespace fir
 
diff --git a/flang/include/flang/Runtime/extensions.h b/flang/include/flang/Runtime/extensions.h
index f2765a5987ea1..40ce77112d183 100644
--- a/flang/include/flang/Runtime/extensions.h
+++ b/flang/include/flang/Runtime/extensions.h
@@ -25,6 +25,11 @@ typedef std::uint32_t gid_t;
 #else
 #include "sys/types.h" //pid_t
 #endif
+namespace Fortran {
+namespace runtime {
+class Descriptor;
+}
+} // namespace Fortran
 
 extern "C" {
 
@@ -111,5 +116,8 @@ float RTNAME(Rand)(int *i, const char *sourceFile, int line);
 // GNU extension subroutine SRAND(SEED)
 void FORTRAN_PROCEDURE_NAME(srand)(int *seed);
 
+// flang extension subroutine SHOW_DESCRIPTOR(D)
+void RTNAME(ShowDescriptor)(const Fortran::runtime::Descriptor *descr);
+
 } // extern "C"
 #endif // FORTRAN_RUNTIME_EXTENSIONS_H_
diff --git a/flang/lib/Evaluate/intrinsics.cpp b/flang/lib/Evaluate/intrinsics.cpp
index bbcb766274e7f..d69400e0ec188 100644
--- a/flang/lib/Evaluate/intrinsics.cpp
+++ b/flang/lib/Evaluate/intrinsics.cpp
@@ -1713,6 +1713,8 @@ static const IntrinsicInterface intrinsicSubroutine[]{
         {}, Rank::scalar, IntrinsicClass::impureSubroutine},
     {"second", {{"time", DefaultReal, Rank::scalar}}, {}, Rank::scalar,
         IntrinsicClass::impureSubroutine},
+    {"__builtin_show_descriptor", {{"d", AnyData, Rank::anyOrAssumedRank}}, {},
+        Rank::elemental, IntrinsicClass::impureSubroutine},
     {"system",
         {{"command", DefaultChar, Rank::scalar},
             {"exitstat", DefaultInt, Rank::scalar, Optionality::optional,
diff --git a/flang/lib/Optimizer/Builder/IntrinsicCall.cpp b/flang/lib/Optimizer/Builder/IntrinsicCall.cpp
index 3619e5bb942db..75a74eeb18417 100644
--- a/flang/lib/Optimizer/Builder/IntrinsicCall.cpp
+++ b/flang/lib/Optimizer/Builder/IntrinsicCall.cpp
@@ -727,6 +727,10 @@ static constexpr IntrinsicHandler handlers[]{
     {"shifta", &I::genShiftA},
     {"shiftl", &I::genShift<mlir::arith::ShLIOp>},
     {"shiftr", &I::genShift<mlir::arith::ShRUIOp>},
+    {"show_descriptor",
+     &I::genShowDescriptor,
+     {{{"d", asBox}}},
+     /*isElemental=*/false},
     {"sign", &I::genSign},
     {"signal",
      &I::genSignalSubroutine,
@@ -7884,6 +7888,16 @@ mlir::Value IntrinsicLibrary::genShiftA(mlir::Type resultType,
   return result;
 }
 
+void IntrinsicLibrary::genShowDescriptor(
+    llvm::ArrayRef<fir::ExtendedValue> args) {
+  assert(args.size() == 1 && "expected single argument for show_descriptor");
+  const mlir::Value descriptor = fir::getBase(args[0]);
+
+  assert(fir::isa_box_type(descriptor.getType()) &&
+         "argument must have been lowered to box type");
+  fir::runtime::genShowDescriptor(builder, loc, descriptor);
+}
+
 // SIGNAL
 void IntrinsicLibrary::genSignalSubroutine(
     llvm::ArrayRef<fir::ExtendedValue> args) {
diff --git a/flang/lib/Optimizer/Builder/Runtime/Intrinsics.cpp b/flang/lib/Optimizer/Builder/Runtime/Intrinsics.cpp
index 4d366135c305f..a5f16f89b260a 100644
--- a/flang/lib/Optimizer/Builder/Runtime/Intrinsics.cpp
+++ b/flang/lib/Optimizer/Builder/Runtime/Intrinsics.cpp
@@ -494,3 +494,10 @@ mlir::Value fir::runtime::genRand(fir::FirOpBuilder &builder,
       builder, loc, runtimeFuncTy, i, sourceFile, sourceLine);
   return fir::CallOp::create(builder, loc, runtimeFunc, args).getResult(0);
 }
+
+void fir::runtime::genShowDescriptor(fir::FirOpBuilder &builder,
+                                     mlir::Location loc, mlir::Value descAddr) {
+  mlir::func::FuncOp func{
+      fir::runtime::getRuntimeFunc<mkRTKey(ShowDescriptor)>(loc, builder)};
+  fir::CallOp::create(builder, loc, func, descAddr);
+}
diff --git a/flang/module/__fortran_builtins.f90 b/flang/module/__fortran_builtins.f90
index 4d134fa4b62b1..a9b60508785db 100644
--- a/flang/module/__fortran_builtins.f90
+++ b/flang/module/__fortran_builtins.f90
@@ -28,6 +28,9 @@
   intrinsic :: __builtin_c_f_pointer
   public :: __builtin_c_f_pointer
 
+  intrinsic :: __builtin_show_descriptor
+  public :: __builtin_show_descriptor
+
   intrinsic :: sizeof ! extension
   public :: sizeof
 
diff --git a/flang/module/flang_debug.f90 b/flang/module/flang_debug.f90
new file mode 100644
index 0000000000000..baab3b2477f49
--- /dev/null
+++ b/flang/module/flang_debug.f90
@@ -0,0 +1,14 @@
+!===-- module/flang_debug.f90 ----------------------------------------------===!
+!
+! Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+! See https://llvm.org/LICENSE.txt for license information.
+! SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+!
+!===------------------------------------------------------------------------===!
+
+module flang_debug
+
+  use __fortran_builtins, only: &
+    show_descriptor => __builtin_show_descriptor
+
+end module flang_debug
diff --git a/flang/test/Lower/Intrinsics/show_descriptor.f90 b/flang/test/Lower/Intrinsics/show_descriptor.f90
new file mode 100644
index 0000000000000..a0b8d3eb4348f
--- /dev/null
+++ b/flang/test/Lower/Intrinsics/show_descriptor.f90
@@ -0,0 +1,241 @@
+! RUN: bbc -emit-fir %s -o - | FileCheck %s
+
+module test_show_descriptor
+use flang_debug
+contains
+subroutine test_int
+! CHECK-LABEL:   func.func @_QMtest_show_descriptorPtest_int() {
+  implicit none
+  integer :: n
+  integer,allocatable :: a(:)
+  n = 5
+  allocate(a(n))
+! CHECK:           %[[C3:.*]] = arith.constant 3 : index
+! CHECK:           %[[C1:.*]] = arith.constant 1 : index
+! CHECK:           %[[C5:.*]] = arith.constant 5 : i32
+! CHECK:           %[[C0:.*]] = arith.constant 0 : index
+! CHECK:           %[[DUMMY_SCOPE_0:.*]] = fir.dummy_scope : !fir.dscope
+! CHECK:           %[[ALLOCA_0:.*]] = fir.alloca !fir.box<!fir.heap<!fir.array<?xi32>>> {bindc_name = "a", uniq_name = "_QMtest_show_descriptorFtest_intEa"}
+! CHECK:           %[[ZERO_BITS_0:.*]] = fir.zero_bits !fir.heap<!fir.array<?xi32>>
+! CHECK:           %[[SHAPE_0:.*]] = fir.shape %[[C0]] : (index) -> !fir.shape<1>
+! CHECK:           %[[EMBOX_0:.*]] = fir.embox %[[ZERO_BITS_0]](%[[SHAPE_0]]) : (!fir.heap<!fir.array<?xi32>>, !fir.shape<1>) -> !fir.box<!fir.heap<!fir.array<?xi32>>>
+! CHECK:           fir.store %[[EMBOX_0]] to %[[ALLOCA_0]] : !fir.ref<!fir.box<!fir.heap<!fir.array<?xi32>>>>
+! CHECK:           %[[DECLARE_0:.*]] = fir.declare %[[ALLOCA_0]] {fortran_attrs = #fir.var_attrs<allocatable>, uniq_name = "_QMtest_show_descriptorFtest_intEa"} : (!fir.ref<!fir.box<!fir.heap<!fir.array<?xi32>>>>) -> !fir.ref<!fir.box<!fir.heap<!fir.array<?xi32>>>>
+! CHECK:           %[[ALLOCA_1:.*]] = fir.alloca i32 {bindc_name = "n", uniq_name = "_QMtest_show_descriptorFtest_intEn"}
+! CHECK:           %[[DECLARE_1:.*]] = fir.declare %[[ALLOCA_1]] {uniq_name = "_QMtest_show_descriptorFtest_intEn"} : (!fir.ref<i32>) -> !fir.ref<i32>
+! CHECK:           fir.store %[[C5]] to %[[DECLARE_1]] : !fir.ref<i32>
+! CHECK:           %[[LOAD_0:.*]] = fir.load %[[DECLARE_1]] : !fir.ref<i32>
+! CHECK:           %[[CONVERT_0:.*]] = fir.convert %[[LOAD_0]] : (i32) -> index
+! CHECK:           %[[CMPI_0:.*]] = arith.cmpi sgt, %[[CONVERT_0]], %[[C0]] : index
+! CHECK:           %[[SELECT_0:.*]] = arith.select %[[CMPI_0]], %[[CONVERT_0]], %[[C0]] : index
+! CHECK:           %[[ALLOCMEM_0:.*]] = fir.allocmem !fir.array<?xi32>, %[[SELECT_0]] {fir.must_be_heap = true, uniq_name = "_QMtest_show_descriptorFtest_intEa.alloc"}
+
+  call show_descriptor(a)
+! CHECK:           %[[SHAPE_1:.*]] = fir.shape %[[SELECT_0]] : (index) -> !fir.shape<1>
+! CHECK:           %[[EMBOX_1:.*]] = fir.embox %[[ALLOCMEM_0]](%[[SHAPE_1]]) : (!fir.heap<!fir.array<?xi32>>, !fir.shape<1>) -> !fir.box<!fir.heap<!fir.array<?xi32>>>
+! CHECK:           fir.store %[[EMBOX_1]] to %[[DECLARE_0]] : !fir.ref<!fir.box<!fir.heap<!fir.array<?xi32>>>>
+! CHECK:           %[[LOAD_1:.*]] = fir.load %[[DECLARE_0]] : !fir.ref<!fir.box<!fir.heap<!fir.array<?xi32>>>>
+! CHECK:           fir.call @_FortranAShowDescriptor(%[[LOAD_1]]) fastmath<contract> : (!fir.box<!fir.heap<!fir.array<?xi32>>>) -> ()
+
+  call show_descriptor(a(1:3))
+! CHECK:           %[[LOAD_2:.*]] = fir.load %[[DECLARE_0]] : !fir.ref<!fir.box<!fir.heap<!fir.array<?xi32>>>>
+! CHECK:           %[[SHAPE_2:.*]] = fir.shape %[[C3]] : (index) -> !fir.shape<1>
+! CHECK:           %[[BOX_ADDR_0:.*]] = fir.box_addr %[[LOAD_2]] : (!fir.box<!fir.heap<!fir.array<?xi32>>>) -> !fir.heap<!fir.array<?xi32>>
+! CHECK:           %[[CONSTANT_4:.*]] = arith.constant 0 : index
+! CHECK:           %[[BOX_DIMS_0:.*]]:3 = fir.box_dims %[[LOAD_2]], %[[CONSTANT_4]] : (!fir.box<!fir.heap<!fir.array<?xi32>>>, index) -> (index, index, index)
+! CHECK:           %[[SHAPE_SHIFT_0:.*]] = fir.shape_shift %[[BOX_DIMS_0]]#0, %[[BOX_DIMS_0]]#1 : (index, index) -> !fir.shapeshift<1>
+! CHECK:           %[[ARRAY_COOR_0:.*]] = fir.array_coor %[[BOX_ADDR_0]](%[[SHAPE_SHIFT_0]]) %[[C1]] : (!fir.heap<!fir.array<?xi32>>, !fir.shapeshift<1>, index) -> !fir.ref<i32>
+! CHECK:           %[[CONVERT_1:.*]] = fir.convert %[[ARRAY_COOR_0]] : (!fir.ref<i32>) -> !fir.ref<!fir.array<3xi32>>
+! CHECK:           %[[EMBOX_2:.*]] = fir.embox %[[CONVERT_1]](%[[SHAPE_2]]) : (!fir.ref<!fir.array<3xi32>>, !fir.shape<1>) -> !fir.box<!fir.array<3xi32>>
+! CHECK:           fir.call @_FortranAShowDescriptor(%[[EMBOX_2]]) fastmath<contract> : (!fir.box<!fir.array<3xi32>>) -> ()
+  deallocate(a)
+end subroutine test_int
+
+subroutine test_char
+! CHECK-LABEL:   func.func @_QMtest_show_descriptorPtest_char() {
+  implicit none
+  character(len=9) :: c = 'Hey buddy'
+  call show_descriptor(c)
+! CHECK:           %[[C3:.*]] = arith.constant 3 : index
+! CHECK:           %[[C1:.*]] = arith.constant 1 : index
+! CHECK:           %[[C9:.*]] = arith.constant 9 : index
+! CHECK:           %[[DUMMY_SCOPE_0:.*]] = fir.dummy_scope : !fir.dscope
+! CHECK:           %[[ADDRESS_OF_0:.*]] = fir.address_of(@_QMtest_show_descriptorFtest_charEc) : !fir.ref<!fir.char<1,9>>
+! CHECK:           %[[DECLARE_0:.*]] = fir.declare %[[ADDRESS_OF_0]] typeparams %[[C9]] {uniq_name = "_QMtest_show_descriptorFtest_charEc"} : (!fir.ref<!fir.char<1,9>>, index) -> !fir.ref<!fir.char<1,9>>
+! CHECK:           %[[EMBOX_0:.*]] = fir.embox %[[DECLARE_0]] : (!fir.ref<!fir.char<1,9>>) -> !fir.box<!fir.char<1,9>>
+! CHECK:           fir.call @_FortranAShowDescriptor(%[[EMBOX_0]]) fastmath<contract> : (!fir.box<!fir.char<1,9>>) -> ()
+
+  call show_descriptor(c(1:3))
+! CHECK:           %[[C1_0:.*]] = arith.constant 1 : index
+! CHECK:           %[[SUBI_0:.*]] = arith.subi %[[C1]], %[[C1_0]] : index
+! CHECK:           %[[CONVERT_0:.*]] = fir.convert %[[DECLARE_0]] : (!fir.ref<!fir.char<1,9>>) -> !fir.ref<!fir.array<9x!fir.char<1>>>
+! CHECK:           %[[COORDINATE_OF_0:.*]] = fir.coordinate_of %[[CONVERT_0]], %[[SUBI_0]] : (!fir.ref<!fir.array<9x!fir.char<1>>>, index) -> !fir.ref<!fir.char<1>>
+! CHECK:           %[[CONVERT_1:.*]] = fir.convert %[[COORDINATE_OF_0]] : (!fir.ref<!fir.char<1>>) -> !fir.ref<!fir.char<1,3>>
+! CHECK:           %[[EMBOX_1:.*]] = fir.embox %[[CONVERT_1]] : (!fir.ref<!fir.char<1,3>>) -> !fir.box<!fir.char<1,3>>
+! CHECK:           fir.call @_FortranAShowDescriptor(%[[EMBOX_1]]) fastmath<contract> : (!fir.box<!fir.char<1,3>>) -> ()
+! CHECK:           return
+end subroutine test_char
+
+subroutine test_logical
+! CHECK-LABEL:   func.func @_QMtest_show_descriptorPtest_logical() {
+  implicit none
+  logical(kind=1) :: l1 = .false.
+  logical(kind=2) :: l2 = .true.
+  logical(kind=2), dimension(2), target :: la2 = (/ .true., .false. /)
+  logical(kind=2), dimension(:), pointer :: pla2
+! CHECK:           %[[C0:.*]] = arith.constant 0 : index
+! CHECK:           %[[C2:.*]] = arith.constant 2 : index
+! CHECK:           %[[DUMMY_SCOPE_0:.*]] = fir.dummy_scope : !fir.dscope
+! CHECK:           %[[ADDRESS_OF_0:.*]] = fir.address_of(@_QMtest_show_descriptorFtest_logicalEl1) : !fir.ref<!fir.logical<1>>
+! CHECK:           %[[DECLARE_0:.*]] = fir.declare %[[ADDRESS_OF_0]] {uniq_name = "_QMtest_show_descriptorFtest_logicalEl1"} : (!fir.ref<!fir.logical<1>>) -> !fir.ref<!fir.logical<1>>
+! CHECK:           %[[ADDRESS_OF_1:.*]] = fir.address_of(@_QMtest_show_descriptorFtest_logicalEl2) : !fir.ref<!fir.logical<2>>
+! CHECK:           %[[DECLARE_1:.*]] = fir.declare %[[ADDRESS_OF_1]] {uniq_name = "_QMtest_show_descriptorFtest_logicalEl2"} : (!fir.ref<!fir.logical<2>>) -> !fir.ref<!fir.logical<2>>
+! CHECK:           %[[ADDRESS_OF_2:.*]] = fir.address_of(@_QMtest_show_descriptorFtest_logicalEla2) : !fir.ref<!fir.array<2x!fir.logical<2>>>
+! CHECK:           %[[SHAPE_0:.*]] = fir.shape %[[C2]] : (index) -> !fir.shape<1>
+! CHECK:           %[[DECLARE_2:.*]] = fir.declare %[[ADDRESS_OF_2]](%[[SHAPE_0]]) {fortran_attrs = #fir.var_attrs<target>, uniq_name = "_QMtest_show_descriptorFtest_logicalEla2"} : (!fir.ref<!fir.array<2x!fir.logical<2>>>, !fir.shape<1>) -> !fir.ref<!fir.array<2x!fir.logical<2>>>
+! CHECK:           %[[ALLOCA_0:.*]] = fir.alloca !fir.box<!fir.ptr<!fir.array<?x!fir.logical<2>>>> {bindc_name = "pla2", uniq_name = "_QMtest_show_descriptorFtest_logicalEpla2"}
+! CHECK:           %[[ZERO_BITS_0:.*]] = fir.zero_bits !fir.ptr<!fir.array<?x!fir.logical<2>>>
+! CHECK:           %[[SHAPE_1:.*]] = fir.shape %[[C0]] : (index) -> !fir.shape<1>
+! CHECK:           %[[EMBOX_0:.*]] = fir.embox %[[ZERO_BITS_0]](%[[SHAPE_1]]) : (!fir.ptr<!fir.array<?x!fir.logical<2>>>, !fir.shape<1>) -> !fir.box<!fir.ptr<!fir.array<?x!fir.logical<2>>>>
+! CHECK:           fir.store %[[EMBOX_0]] to %[[ALLOCA_0]] : !fir.ref<!fir.box<!fir.ptr<!fir.array<?x!fir.logical<2>>>>>
+
+  call show_descriptor(l1)
+  call show_descriptor(l2)
+  pla2 => la2
+! CHECK:           %[[DECLARE_3:.*]] = fir.declare %[[ALLOCA_0]] {fortran_attrs = #fir.var_attrs<pointer>, uniq_name = "_QMtest_show_descriptorFtest_logicalEpla2"} : (!fir.ref<!fir.box<!fir.ptr<!fir.array<?x!fir.logical<2>>>>>) -> !fir.ref<!fir.box<!fir.ptr<!fir.array<?x!fir.logical<2>>>>>
+! CHECK:           %[[EMBOX_1:.*]] = fir.embox %[[DECLARE_0]] : (!fir.ref<!fir.logical<1>>) -> !fir.box<!fir.logical<1>>
+! CHECK:           fir.call @_FortranAShowDescriptor(%[[EMBOX_1]]) fastmath<contract> : (!fir.box<!fir.logical<1>>) -> ()
+! CHECK:           %[[EMBOX_2:.*]] = fir.embox %[[DECLARE_1]] : (!fir.ref<!fir.logical<2>>) -> !fir.box<!fir.logical<2>>
+! CHECK:           fir.call @_FortranAShowDescriptor(%[[EMBOX_2]]) fastmath<contract> : (!fir.box<!fir.logical<2>>) -> ()
+
+  call show_descriptor(la2)
+  call show_descriptor(pla2)
+! CHECK:           %[[CONVERT_0:.*]] = fir.convert %[[DECLARE_2]] : (!fir.ref<!fir.array<2x!fir.logical<2>>>) -> !fir.ref<!fir.array<?x!fir.logical<2>>>
+! CHECK:           %[[EMBOX_3:.*]] = fir.embox %[[CONVERT_0]](%[[SHAPE_0]]) : (!fir.ref<!fir.array<?x!fir.logical<2>>>, !fir.shape<1>) -> !fir.box<!fir.ptr<!fir.array<?x!fir.logical<2>>>>
+! CHECK:           fir.store %[[EMBOX_3]] to %[[DECLARE_3]] : !fir.ref<!fir.box<!fir.ptr<!fir.array<?x!fir.logical<2>>>>>
+! CHECK:           %[[EMBOX_4:.*]] = fir.embox %[[DECLARE_2]](%[[SHAPE_0]]) : (!fir.ref<!fir.array<2x!fir.logical<2>>>, !fir.shape<1>) -> !fir.box<!fir.array<2x!fir.logical<2>>>
+! CHECK:           fir.call @_FortranAShowDescriptor(%[[EMBOX_4]]) fastmath<contract> : (!fir.box<!fir.array<2x!fir.logical<2>>>) -> ()
+! CHECK:           %[[LOAD_0:.*]] = fir.load %[[DECLARE_3]] : !fir.ref<!fir.box<!fir.ptr<!fir.array<?x!fir.logical<2>>>>>
+! CHECK:           fir.call @_FortranAShowDescriptor(%[[LOAD_0]]) fastmath<contract> : (!fir.box<!fir.ptr<!fir.array<?x!fir.logical<2>>>>) -> ()
+! CHECK:           return
+end subroutine test_logical
+
+subroutine test_real
+! CHECK-LABEL:   func.func @_QMtest_show_descriptorPtest_real() {
+  implicit none
+  real :: half = 0.5
+  real :: row(3) = (/ 1 , 2, 3 /)
+  real(kind=8) :: w(4) = (/ .00011_8 , .00012_8, .00013_8, .00014_8 /)
+! CHECK:           %[[C2:.*]] = arith.constant 2 : index
+! CHECK:           %[[C1:.*]] = arith.constant 1 : index
+! CHECK:           %[[C4:.*]] = arith.constant 4 : index
+! CHECK:           %[[C3:.*]] = arith.constant 3 : index
+! CHECK:           %[[DUMMY_SCOPE_2:.*]] = fir.dummy_scope : !fir.dscope
+! CHECK:           %[[ADDRESS_OF_4:.*]] = fir.address_of(@_QMtest_show_descriptorFtest_realEhalf) : !fir.ref<f32>
+! CHECK:           %[[DECLARE_5:.*]] = fir.declare %[[ADDRESS_OF_4]] {uniq_name = "_QMtest_show_descriptorFtest_realEhalf"} : (!fir.ref<f32>) -> !fir.ref<f32>
+! CHECK:           %[[ADDRESS_OF_5:.*]] = fir.address_of(@_QMtest_show_descriptorFtest_realErow) : !fir.ref<!fir.array<3xf32>>
+! CHECK:           %[[SHAPE_2:.*]] = fir.shape %[[C3]] : (index) -> !fir.shape<1>
+! CHECK:           %[[DECLARE_6:.*]] = fir.declare %[[ADDRESS_OF_5]](%[[SHAPE_2]]) {uniq_name = "_QMtest_show_descriptorFtest_realErow"} : (!fir.ref<!fir.array<3xf32>>, !fir.shape<1>) -> !fir.ref<!fir.array<3xf32>>
+! CHECK:           %[[ADDRESS_OF_6:.*]] = fir.address_of(@_QMtest_show_descriptorFtest_realEw) : !fir.ref<!fir.array<4xf64>>
+! CHECK:           %[[SHAPE_3:.*]] = fir.shape %[[C4]] : (index) -> !fir.shape<1>
+! CHECK:           %[[DECLARE_7:.*]] = fir.declare %[[ADDRESS_OF_6]](%[[SHAPE_3]]) {uniq_name = "_QMtest_show_descriptorFtest_realEw"} : (!fir.ref<!fir.array<4xf64>>, !fir.shape<1>) -> !fir.ref<!fir.array<4xf64>>
+
+  call show_descriptor(half)
+  call show_descriptor(row)
+  call show_descriptor(w)
+  call show_descriptor(w(1:4:2))
+! CHECK:           %[[EMBOX_7:.*]] = fir.embox %[[DECLARE_5]] : (!fir.ref<f32>) -> !fir.box<f32>
+! CHECK:           fir.call @_FortranAShowDescriptor(%[[EMBOX_7]]) fastmath<contract> : (!fir.box<f32>) -> ()
+! CHECK:           %[[EMBOX_8:.*]] = fir.embox %[[DECLARE_6]](%[[SHAPE_2]]) : (!fir.ref<!fir.array<3xf32>>, !fir.shape<1>) -> !fir.box<!fir.array<3xf32>>
+! CHECK:           fir.call @_FortranAShowDescriptor(%[[EMBOX_8]]) fastmath<contract> : (!fir.box<!fir.array<3xf32>>) -> ()
+! CHECK:           %[[EMBOX_9:.*]] = fir.embox %[[DECLARE_7]](%[[SHAPE_3]]) : (!fir.ref<!fir.array<4xf64>>, !fir.shape<1>) -> !fir.box<!fir.array<4xf64>>
+! CHECK:           fir.call @_FortranAShowDescriptor(%[[EMBOX_9]]) fastmath<contract> : (!fir.box<!fir.array<4xf64>>) -> ()
+! CHECK:           %[[SHAPE_4:.*]] = fir.shape %[[C2]] : (index) -> !fir.shape<1>
+! CHECK:           %[[UNDEFINED_0:.*]] = fir.undefined index
+! CHECK:           %[[SLICE_0:.*]] = fir.slice %[[C1]], %[[C4]], %[[C2]] : (index, index, index) -> !fir.slice<1>
+! CHECK:           %[[EMBOX_10:.*]] = fir.embox %[[DECLARE_7]](%[[SHAPE_3]]) {{\[}}%[[SLICE_0]]] : (!fir.ref<!fir.array<4xf64>>, !fir.shape<1>, !fir.slice<1>) -> !fir.box<!fir.array<2xf64>>
+! CHECK:           fir.call @_FortranAShowDescriptor(%[[EMBOX_10]]) fastmath<contract> : (!fir.box<!fir.array<2xf64>>) -> ()
+! CHECK:           return
+end subroutine test_real
+
+subroutine test_complex
+! CHECK-LABEL:   func.func @_QMtest_show_descriptorPtest_complex() {
+  implicit none
+  complex, parameter :: hr = 0.5
+  complex, parameter :: hi = (0, 0.5)
+  complex :: c1 = hr
+  complex :: c2 = hi
+  complex :: a2(2) = (/ hr, hi /)
+! CHECK:           %[[CST_0:.*]] = arith.constant 0.000000e+00 : f32
+! CHECK:           %[[CST_1:.*]] = arith.constant 5.000000e-01 : f32
+! CHECK:           %[[C2:.*]] = arith.constant 2 : index
+! CHECK:           %[[ALLOCA_1:.*]] = fir.alloca complex<f32>
+! CHECK:           %[[ALLOCA_2:.*]] = fir.alloca complex<f32>
+! CHECK:           %[[DUMMY_SCOPE_3:.*]] = fir.dummy_scope : !fir.dscope
+! CHECK:           %[[ADDRESS_OF_7:.*]] = fir.address_of(@_QMtest_show_descriptorFtest_complexEa2) : !fir.ref<!fir.array<2xcomplex<f32>>>
+! CHECK:           %[[SHAPE_5:.*]] = fir.shape %[[C2]] : (index) -> !fir.shape<1>
+! CHECK:           %[[DECLARE_8:.*]] = fir.declare %[[ADDRESS_OF_7]](%[[SHAPE_5]]) {uniq_name = "_QMtest_show_descriptorFtest_complexEa2"} : (!fir.ref<!fir.array<2xcomplex<f32>>>, !fir.shape<1>) -> !fir.ref<!fir.array<2xcomplex<f32>>>
+! CHECK:           %[[ADDRESS_OF_8:.*]] = fir.address_of(@_QMtest_show_descriptorFtest_complexEc1) : !fir.ref<complex<f32>>
+! CHECK:           %[[DECLARE_9:.*]] = fir.declare %[[ADDRESS_OF_8]] {uniq_name = "_QMtest_show_descriptorFtest_complexEc1"} : (!fir.ref<complex<f32>>) -> !fir.ref<complex<f32>>
+! CHECK:           %[[ADDRESS_OF_9:.*]] = fir.address_of(@_QMtest_show_descriptorFtest_complexEc2) : !fir.ref<complex<f32>>
+! CHECK:           %[[DECLARE_10:.*]] = fir.declare %[[ADDRESS_OF_9]] {uniq_name = "_QMtest_show_descriptorFtest_complexEc2"} : (!fir.ref<complex<f32>>) -> !fir.ref<complex<f32>>
+! CHECK:           %[[ADDRESS_OF_10:.*]] = fir.address_of(@_QMtest_show_descriptorFtest_complexEChi) : !fir.ref<complex<f32>>
+! CHECK:           %[[DECLARE_11:.*]] = fir.declare %[[ADDRESS_OF_10]] {fortran_attrs = #fir.var_attrs<parameter>, uniq_name = "_QMtest_show_descriptorFtest_complexEChi"} : (!fir.ref<complex<f32>>) -> !fir.ref<complex<f32>>
+! CHECK:           %[[ADDRESS_OF_11:.*]] = fir.address_of(@_QMtest_show_descriptorFtest_complexEChr) : !fir.ref<complex<f32>>
+! CHECK:           %[[DECLARE_12:.*]] = fir.declare %[[ADDRESS_OF_11]] {fortran_attrs = #fir.var_attrs<parameter>, uniq_name = "_QMtest_show_descriptorFtest_complexEChr"} : (!fir.ref<complex<f32>>) -> !fir.ref<complex<f32>>
+! CHECK:           %[[UNDEFINED_1:.*]] = fir.undefined complex<f32>
+! CHECK:           %[[INSERT_VALUE_0:.*]] = fir.insert_value %[[UNDEFINED_1]], %[[CST_1]], [0 : index] : (complex<f32>, f32) -> complex<f32>
+! CHECK:           %[[INSERT_VALUE_1:.*]] = fir.insert_value %[[INSERT_VALUE_0]], %[[CST_0]], [1 : index] : (complex<f32>, f32) -> complex<f32>
+! CHECK:           fir.store %[[INSERT_VALUE_1]] to %[[ALLOCA_2]] : !fir.ref<complex<f32>>
+
+  call show_descriptor(hr)
+! CHECK:           %[[EMBOX_11:.*]] = fir.embox %[[ALLOCA_2]] : (!fir.ref<complex<f32>>) -> !fir.box<complex<f32>>
+! CHECK:           fir.call @_FortranAShowDescriptor(%[[EMBOX_11]]) fastmath<contract> : (!fir.box<complex<f32>>) -> ()
+
+  call show_descriptor(hi)
+! CHECK:           %[[INSERT_VALUE_2:.*]] = fir.insert_value %[[UNDEFINED_1]], %[[CST_0]], [0 : index] : (complex<f32>, f32) -> complex<f32>
+! CHECK:           %[[INSERT_VALUE_3:.*]] = fir.insert_value %[[INSERT_VALUE_2]], %[[CST_1]], [1 : index] : (complex<f32>, f32) -> complex<f32>
+! CHECK:           fir.store %[[INSERT_VALUE_3]] to %[[ALLOCA_1]] : !fir.ref<complex<f32>>
+! CHECK:           %[[EMBOX_12:.*]] = fir.embox %[[ALLOCA_1]] : (!fir.ref<complex<f32>>) -> !fir.box<complex<f32>>
+! CHECK:           fir.call @_FortranAShowDescriptor(%[[EMBOX_12]]) fastmath<contract> : (!fir.box<complex<f32>>) -> ()
+
+  call show_descriptor(a2)
+! CHECK:           %[[EMBOX_13:.*]] = fir.embox %[[DECLARE_8]](%[[SHAPE_5]]) : (!fir.ref<!fir.array<2xcomplex<f32>>>, !fir.shape<1>) -> !fir.box<!fir.array<2xcomplex<f32>>>
+! CHECK:           fir.call @_FortranAShowDescriptor(%[[EMBOX_13]]) fastmath<contract> : (!fir.box<!fir.array<2xcomplex<f32>>>) -> ()
+! CHECK:           return
+end subroutine test_complex
+
+subroutine test_derived
+! CHECK-LABEL:   func.func @_QMtest_show_descriptorPtest_derived() {
+  implicit none
+  type :: t1
+     integer :: a
+     integer :: b
+  end type t1
+  type, extends (t1) :: t2
+     integer :: c
+  end type t2
+  type(t2) :: vt2 = t2(7,5,3)
+! CHECK:           %[[C0:.*]] = arith.constant 0 : index
+! CHECK:           %[[C2:.*]] = arith.constant 2 : index
+! CHECK:           %[[C1:.*]] = arith.constant 1 : index
+! CHECK:           %[[DUMMY_SCOPE_4:.*]] = fir.dummy_scope : !fir.dscope
+! CHECK:           %[[ADDRESS_OF_12:.*]] = fir.address_of(@_QMtest_show_descriptorFtest_derivedE.n.a) : !fir.ref<!fir.char<1>>
+! CHECK:           %[[DECLARE_13:.*]] = fir.declare %[[ADDRESS_OF_12]] typeparams %[[C1]] {fortran_attrs = #fir.var_attrs<target>, uniq_name = "_QMtest_show_descriptorFtest_derivedE.n.a"} : (!fir.ref<!fir.char<1>>, index) -> !fir.ref<!fir.char<1>>
+! CHECK:           %[[ADDRESS_OF_13:.*]] = fir.address_of(@_QMtest_show_descriptorFtest_derivedE.n.b) : !fir.ref<!fir.char<1>>
+! CHECK:           %[[DECLARE_14:.*]] = fir.declare %[[ADDRESS_OF_13]] typeparams %[[C1]] {fortran_attrs = #fir.var_attrs<target>, uniq_name = "_QMtest_show_descriptorFtest_derivedE.n.b"} : (!fir.ref<!fir.char<1>>, index) -> !fir.ref<!fir.char<1>>
+! CHECK:           %[[ADDRESS_OF_14:.*]] = fir.address_of(@_QMtest_show_descriptorFtest_derivedE.n.t1) : !fir.ref<!fir.char<1,2>>
+! CHECK:           %[[DECLARE_15:.*]] = fir.declare %[[ADDRESS_OF_14]] typeparams %[[C2]] {fortran_attrs = #fir.var_attrs<target>, uniq_name = "_QMtest_show_descriptorFtest_derivedE.n.t1"} : (!fir.ref<!fir.char<1,2>>, index) -> !fir.ref<!fir.char<1,2>>
+! CHECK:           %[[ADDRESS_OF_15:.*]] = fir.address_of(@_QMtest_show_descriptorFtest_derivedE.n.c) : !fir.ref<!fir.char<1>>
+! CHECK:           %[[DECLARE_16:.*]] = fir.declare %[[ADDRESS_OF_15]] typeparams %[[C1]] {fortran_attrs = #fir.var_attrs<target>, uniq_name = "_QMtest_show_descriptorFtest_derivedE.n.c"} : (!fir.ref<!fir.char<1>>, index) -> !fir.ref<!fir.char<1>>
+! CHECK:           %[[ADDRESS_OF_16:.*]] = fir.address_of(@_QMtest_show_descriptorFtest_derivedE.n.t2) : !fir.ref<!fir.char<1,2>>
+! CHECK:           %[[DECLARE_17:.*]] = fir.declare %[[ADDRESS_OF_16]] typeparams %[[C2]] {fortran_attrs = #fir.var_attrs<target>, uniq_name = "_QMtest_show_descriptorFtest_derivedE.n.t2"} : (!fir.ref<!fir.char<1,2>>, index) -> !fir.ref<!fir.char<1,2>>
+! CHECK:           %[[ADDRESS_OF_17:.*]] = fir.address_of(@_QMtest_show_descriptorFtest_derivedEvt2) : !fir.ref<!fir.type<_QMtest_show_descriptorFtest_derivedTt2{t1:!fir.type<_QMtest_show_descriptorFtest_derivedTt1{a:i32,b:i32}>,c:i32}>>
+! CHECK:           %[[DECLARE_18:.*]] = fir.declare %[[ADDRESS_OF_17]] {uniq_name = "_QMtest_show_descriptorFtest_derivedEvt2"} : (!fir.ref<!fir.type<_QMtest_show_descriptorFtest_derivedTt2{t1:!fir.type<_QMtest_show_descriptorFtest_derivedTt1{a:i32,b:i32}>,c:i32}>>) -> !fir.ref<!fir.type<_QMtest_show_descriptorFtest_derivedTt2{t1:!fir.type<_QMtest_show_descriptorFtest_derivedTt1{a:i32,b:i32}>,c:i32}>>
+
+  call show_descriptor(vt2)
+! CHECK:           %[[EMBOX_16:.*]] = fir.embox %[[DECLARE_18]] : (!fir.ref<!fir.type<_QMtest_show_descriptorFtest_derivedTt2{t1:!fir.type<_QMtest_show_descriptorFtest_derivedTt1{a:i32,b:i32}>,c:i32}>>) -> !fir.box<!fir.type<_QMtest_show_descriptorFtest_derivedTt2{t1:!fir.type<_QMtest_show_descriptorFtest_derivedTt1{a:i32,b:i32}>,c:i32}>>
+! CHECK:           fir.call @_FortranAShowDescriptor(%[[EMBOX_16]]) fastmath<contract> : (!fir.box<!fir.type<_QMtest_show_descriptorFtest_derivedTt2{t1:!fir.type<_QMtest_show_descriptorFtest_derivedTt1{a:i32,b:i32}>,c:i32}>>) -> ()
+! CHECK:           return
+end subroutine test_derived
+end module test_show_descriptor
diff --git a/flang/tools/f18/CMakeLists.txt b/flang/tools/f18/CMakeLists.txt
index 715992c756c4b..58ea782ce213e 100644
--- a/flang/tools/f18/CMakeLists.txt
+++ b/flang/tools/f18/CMakeLists.txt
@@ -23,6 +23,7 @@ set(MODULES
   "iso_c_binding"
   "iso_fortran_env"
   "iso_fortran_env_impl"
+  "flang_debug"
 )
 
 # Check if 128-bit float computations can be done via long double.

>From 22f72dadfb3950c35dfa98ebdc8b5cb69c375df6 Mon Sep 17 00:00:00 2001
From: Valery Dmitriev <valeryd at nvidia.com>
Date: Tue, 2 Dec 2025 14:43:18 -0800
Subject: [PATCH 2/4] Limit descriptor dump flang-rt unit test with linux
 platform only

---
 flang-rt/unittests/Runtime/Descriptor.cpp | 58 +++++++++++++----------
 1 file changed, 34 insertions(+), 24 deletions(-)

diff --git a/flang-rt/unittests/Runtime/Descriptor.cpp b/flang-rt/unittests/Runtime/Descriptor.cpp
index f86ff4cf16a55..dc6bacfcba3f6 100644
--- a/flang-rt/unittests/Runtime/Descriptor.cpp
+++ b/flang-rt/unittests/Runtime/Descriptor.cpp
@@ -160,18 +160,10 @@ TEST(Descriptor, FixedStride) {
   EXPECT_EQ(descriptor.FixedStride().value_or(-666), 0);
 }
 
-static std::string getAddrFilteredContent(FILE *fin) {
-  rewind(fin);
-  std::ostringstream content;
-  char buffer[1024];
-  size_t bytes_read;
-  while ((bytes_read = fread(buffer, 1, sizeof(buffer), fin)) > 0) {
-    content.write(buffer, bytes_read);
-  }
-  return std::regex_replace(
-      content.str(), std::regex("(0x[0-9a-fA-F]*)"), "[address]");
-}
-
+// The test below uses file operations that have nuances across multiple
+// platforms. Hence limit coverage by linux only unless wider coverage
+// should be required.
+#if defined(__linux__) && !defined(__ANDROID__)
 TEST(Descriptor, Dump) {
   StaticDescriptor<4> staticDesc[2];
   Descriptor &descriptor{staticDesc[0].descriptor()};
@@ -181,20 +173,37 @@ TEST(Descriptor, Dump) {
   TypeCode integer{TypeCategory::Integer, four};
   // Scalar
   descriptor.Establish(integer, four, data, 0);
-  FILE *tmpf = tmpfile();
+  FILE *tmpf = nullptr;
+  tmpf = tmpfile();
   ASSERT_TRUE(tmpf) << "tmpfile returned NULL";
   auto resetTmpFile = [tmpf]() {
+    fflush(tmpf);
     rewind(tmpf);
     ftruncate(fileno(tmpf), 0);
   };
 
+  auto getAddrFilteredContent = [tmpf]() -> std::string {
+    rewind(tmpf);
+    std::ostringstream content;
+    char buffer[1024];
+    size_t bytes_read;
+    while ((bytes_read = fread(buffer, 1, sizeof(buffer), tmpf)) > 0) {
+      content.write(buffer, bytes_read);
+    }
+
+    return std::regex_replace(
+        std::regex_replace(content.str(), std::regex("Descriptor @.*:"),
+            "Descriptor @ [addr]:"),
+        std::regex("base_addr .*"), "base_addr [addr]");
+  };
+
   descriptor.Dump(tmpf, /*dumpRawType=*/false);
   // also dump as CFI type
   descriptor.Dump(tmpf, /*dumpRawType=*/true);
-  std::string output = getAddrFilteredContent(tmpf);
+  std::string output = getAddrFilteredContent();
   ASSERT_STREQ(output.c_str(),
-      "Descriptor @ [address]:\n"
-      "  base_addr [address]\n"
+      "Descriptor @ [addr]:\n"
+      "  base_addr [addr]\n"
       "  elem_len  4\n"
       "  version   20240719\n"
       "  scalar\n"
@@ -203,8 +212,8 @@ TEST(Descriptor, Dump) {
       "  extra     0\n"
       "    addendum  0\n"
       "    alloc_idx 0\n"
-      "Descriptor @ [address]:\n"
-      "  base_addr [address]\n"
+      "Descriptor @ [addr]:\n"
+      "  base_addr [addr]\n"
       "  elem_len  4\n"
       "  version   20240719\n"
       "  scalar\n"
@@ -219,10 +228,10 @@ TEST(Descriptor, Dump) {
   descriptor.Establish(integer, four, data, 2, extent);
   resetTmpFile();
   descriptor.Dump(tmpf, /*dumpRawType=*/false);
-  output = getAddrFilteredContent(tmpf);
+  output = getAddrFilteredContent();
   ASSERT_STREQ(output.c_str(),
-      "Descriptor @ [address]:\n"
-      "  base_addr [address]\n"
+      "Descriptor @ [addr]:\n"
+      "  base_addr [addr]\n"
       "  elem_len  4\n"
       "  version   20240719\n"
       "  rank      2\n"
@@ -248,10 +257,10 @@ TEST(Descriptor, Dump) {
 
   resetTmpFile();
   descriptor.Dump(tmpf, /*dumpRawType=*/false);
-  output = getAddrFilteredContent(tmpf);
+  output = getAddrFilteredContent();
   ASSERT_STREQ(output.c_str(),
-      "Descriptor @ [address]:\n"
-      "  base_addr [address]\n"
+      "Descriptor @ [addr]:\n"
+      "  base_addr [addr]\n"
       "  elem_len  4\n"
       "  version   20240719\n"
       "  rank      3\n"
@@ -271,3 +280,4 @@ TEST(Descriptor, Dump) {
       "         sm          512\n");
   fclose(tmpf);
 }
+#endif // defined(__linux__) && !defined(__ANDROID__)

>From 7fe9e887f5d1dc01deeb1211d713216098de18a4 Mon Sep 17 00:00:00 2001
From: Valery Dmitriev <valeryd at nvidia.com>
Date: Tue, 2 Dec 2025 14:57:34 -0800
Subject: [PATCH 3/4] Apply style fixes from Peter (#170227)

---
 flang-rt/lib/runtime/descriptor.cpp       | 33 +++++++++--------------
 flang-rt/unittests/Runtime/Descriptor.cpp |  4 +--
 2 files changed, 15 insertions(+), 22 deletions(-)

diff --git a/flang-rt/lib/runtime/descriptor.cpp b/flang-rt/lib/runtime/descriptor.cpp
index 066e94232c003..75bea976e2087 100644
--- a/flang-rt/lib/runtime/descriptor.cpp
+++ b/flang-rt/lib/runtime/descriptor.cpp
@@ -347,23 +347,21 @@ static const char *GetTypeStr(ISO::CFI_type_t type, bool dumpRawType) {
       CASE(CFI_type_uint32_t)
       CASE(CFI_type_uint64_t)
       CASE(CFI_type_uint128_t)
+    default:
+      return nullptr;
     }
 #undef CASE
-    return nullptr;
   }
   TypeCode code{type};
-
-  if (!code.IsValid())
+  if (!code.IsValid()) {
     return "invalid";
-
-  common::optional<std::pair<TypeCategory, int>> categoryAndKind =
-      code.GetCategoryAndKind();
-  if (!categoryAndKind)
+  }
+  auto categoryAndKind{code.GetCategoryAndKind()};
+  if (!categoryAndKind) {
     return nullptr;
-
-  TypeCategory tcat;
-  int kind;
-  std::tie(tcat, kind) = *categoryAndKind;
+  }
+  TypeCategory tcat{categoryAndKind->first};
+  int kind{categoryAndKind->second};
 
 #define CASE(cat, k) \
   case (k): \
@@ -434,18 +432,14 @@ void Descriptor::Dump(FILE *f, bool dumpRawType) const {
   std::fprintf(f, "  base_addr %p\n", raw_.base_addr);
   std::fprintf(f, "  elem_len  %zd\n", ElementBytes());
   std::fprintf(f, "  version   %d\n", static_cast<int>(raw_.version));
-  if (rank() > 0) {
-    std::fprintf(f, "  rank      %d\n", rank());
-  } else {
-    std::fprintf(f, "  scalar\n");
-  }
-  int ty = static_cast<int>(raw_.type);
-  if (const char *tyStr = GetTypeStr(raw_.type, dumpRawType)) {
+  std::fprintf(f, "  rank      %d%s\n", rank(), rank() ? "" : " (scalar)");
+  int ty{static_cast<int>(raw_.type)};
+  if (const char *tyStr{GetTypeStr(raw_.type, dumpRawType)}) {
     std::fprintf(f, "  type      %d \"%s\"\n", ty, tyStr);
   } else {
     std::fprintf(f, "  type      %d\n", ty);
   }
-  int attr = static_cast<int>(raw_.attribute);
+  int attr{static_cast<int>(raw_.attribute)};
   if (IsPointer()) {
     std::fprintf(f, "  attribute %d (pointer) \n", attr);
   } else if (IsAllocatable()) {
@@ -453,7 +447,6 @@ void Descriptor::Dump(FILE *f, bool dumpRawType) const {
   } else {
     std::fprintf(f, "  attribute %d\n", attr);
   }
-
   std::fprintf(f, "  extra     %d\n", static_cast<int>(raw_.extra));
   std::fprintf(f, "    addendum  %d\n", static_cast<int>(HasAddendum()));
   std::fprintf(f, "    alloc_idx %d\n", static_cast<int>(GetAllocIdx()));
diff --git a/flang-rt/unittests/Runtime/Descriptor.cpp b/flang-rt/unittests/Runtime/Descriptor.cpp
index dc6bacfcba3f6..0f6dd697e1e33 100644
--- a/flang-rt/unittests/Runtime/Descriptor.cpp
+++ b/flang-rt/unittests/Runtime/Descriptor.cpp
@@ -206,7 +206,7 @@ TEST(Descriptor, Dump) {
       "  base_addr [addr]\n"
       "  elem_len  4\n"
       "  version   20240719\n"
-      "  scalar\n"
+      "  rank      0 (scalar)\n"
       "  type      9 \"INTEGER(kind=4)\"\n"
       "  attribute 0\n"
       "  extra     0\n"
@@ -216,7 +216,7 @@ TEST(Descriptor, Dump) {
       "  base_addr [addr]\n"
       "  elem_len  4\n"
       "  version   20240719\n"
-      "  scalar\n"
+      "  rank      0 (scalar)\n"
       "  type      9 \"CFI_type_int32_t\"\n"
       "  attribute 0\n"
       "  extra     0\n"

>From 5067de22989645d8901f25ecd37a5ebf13238fa4 Mon Sep 17 00:00:00 2001
From: Valery Dmitriev <valeryd at nvidia.com>
Date: Tue, 2 Dec 2025 15:25:04 -0800
Subject: [PATCH 4/4] delete extra blank line

---
 flang-rt/lib/runtime/extensions.cpp | 1 -
 1 file changed, 1 deletion(-)

diff --git a/flang-rt/lib/runtime/extensions.cpp b/flang-rt/lib/runtime/extensions.cpp
index 108d7b1923b99..100046fc7bbf7 100644
--- a/flang-rt/lib/runtime/extensions.cpp
+++ b/flang-rt/lib/runtime/extensions.cpp
@@ -467,7 +467,6 @@ void FORTRAN_PROCEDURE_NAME(srand)(int *seed) {
   rand_seed_lock.Drop();
 }
 
-
 void RTNAME(ShowDescriptor)(const Fortran::runtime::Descriptor *descr) {
   if (descr) {
     descr->Dump(stderr, /*dumpRawType=*/false);



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