[flang-commits] [flang] [flang] Implement IERRNO intrinsic (PR #124281)

[Jean-Didier PAILLEUX via flang-commits]

https://github.com/JDPailleux updated https://github.com/llvm/llvm-project/pull/124281

>From bd26c05127d52322536fecbdbff2ff7d8330798b Mon Sep 17 00:00:00 2001
From: Jean-Didier Pailleux <jean-didier.pailleux at sipearl.com>
Date: Mon, 27 Jan 2025 13:47:24 +0100
Subject: [PATCH] [flang] Implement IERRNO intrinsic

---
 flang/docs/Intrinsics.md                 | 11 +++++++++++
 flang/include/flang/Runtime/extensions.h |  3 +++
 flang/runtime/extensions.cpp             |  2 ++
 flang/test/Lower/Intrinsics/ierrno.f90   | 12 ++++++++++++
 4 files changed, 28 insertions(+)
 create mode 100644 flang/test/Lower/Intrinsics/ierrno.f90

diff --git a/flang/docs/Intrinsics.md b/flang/docs/Intrinsics.md
index d0b7999fbd067e..946ac3680efe91 100644
--- a/flang/docs/Intrinsics.md
+++ b/flang/docs/Intrinsics.md
@@ -1064,3 +1064,14 @@ This intrinsic is an alias for `LEN_TRIM`, without the optional KIND argument.
 - **Arguments:** `TIME` - a REAL value into which the elapsed CPU time in
                           seconds is written
 - **RETURN value:** same as TIME argument
+
+### Non-Standard Intrinsics: IERRNO
+
+#### Description
+`IERRNO()` returns the last system error number, as given by the C `errno` variable.
+
+#### Usage and Info
+
+- **Standard:** GNU extension
+- **Class:** function
+- **Syntax:** `RESULT = IERRNO()`
diff --git a/flang/include/flang/Runtime/extensions.h b/flang/include/flang/Runtime/extensions.h
index a855c694e0090d..837966c80c0e55 100644
--- a/flang/include/flang/Runtime/extensions.h
+++ b/flang/include/flang/Runtime/extensions.h
@@ -69,5 +69,8 @@ std::int64_t FORTRAN_PROCEDURE_NAME(access)(const char *name,
     std::int64_t nameLength, const char *mode, std::int64_t modeLength);
 #endif
 
+// GNU extension function IERRNO()
+int FORTRAN_PROCEDURE_NAME(ierrno)();
+
 } // extern "C"
 #endif // FORTRAN_RUNTIME_EXTENSIONS_H_
diff --git a/flang/runtime/extensions.cpp b/flang/runtime/extensions.cpp
index 50d3c72fe650d0..49cf9ec476a22d 100644
--- a/flang/runtime/extensions.cpp
+++ b/flang/runtime/extensions.cpp
@@ -248,5 +248,7 @@ std::int64_t FORTRAN_PROCEDURE_NAME(access)(const char *name,
 }
 #endif
 
+int FORTRAN_PROCEDURE_NAME(ierrno)() { return errno; }
+
 } // namespace Fortran::runtime
 } // extern "C"
diff --git a/flang/test/Lower/Intrinsics/ierrno.f90 b/flang/test/Lower/Intrinsics/ierrno.f90
new file mode 100644
index 00000000000000..26ab895959a5bd
--- /dev/null
+++ b/flang/test/Lower/Intrinsics/ierrno.f90
@@ -0,0 +1,12 @@
+! RUN: bbc -emit-fir -hlfir=false %s -o - | FileCheck --check-prefixes=CHECK %s
+! RUN: %flang_fc1 -emit-fir -flang-deprecated-no-hlfir %s -o - | FileCheck --check-prefixes=CHECK %s
+
+! CHECK-LABEL: func @_QPtest_ierrno(
+subroutine test_ierrno()
+    integer :: i
+    i = ierrno()
+! CHECK: %[[VAL_0:.*]] = fir.alloca i32 {bindc_name = "i", uniq_name = "_QFtest_ierrnoEi"}
+! CHECK: %[[VAL_1:.*]] = fir.call @_QPierrno() fastmath<contract> : () -> i32
+! CHECK: fir.store %[[VAL_1]] to %[[VAL_0]] : !fir.ref<i32>
+! CHECK: return
+end subroutine test_ierrno