[clang] 983f248 - Revert "[Clang][LoongArch] Fix ABI handling of empty structs in C++ to match GCC behaviour"

[Weining Lu via cfe-commits]

Author: Weining Lu
Date: 2023-07-25T09:18:06+08:00
New Revision: 983f2488326e1f8034f3b0686cd44221d8697bdc

URL: https://github.com/llvm/llvm-project/commit/983f2488326e1f8034f3b0686cd44221d8697bdc
DIFF: https://github.com/llvm/llvm-project/commit/983f2488326e1f8034f3b0686cd44221d8697bdc.diff

LOG: Revert "[Clang][LoongArch] Fix ABI handling of empty structs in C++ to match GCC behaviour"

This reverts commit c299efbf284fae92bb8d7d29110f76912f089daf.

Reason to revert: D142327 has been reverted which is depended by this
change.

Added: 
    

Modified: 
    clang/docs/ReleaseNotes.rst
    clang/lib/CodeGen/Targets/LoongArch.cpp
    clang/test/CodeGen/LoongArch/abi-lp64d-empty-structs.c

Removed: 
    


################################################################################
diff  --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 45753a651e723a..13fb95b8767c3b 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -891,8 +891,6 @@ LoongArch Support
   on LoongArch.
 - Unaligned memory accesses can be toggled by ``-m[no-]unaligned-access`` or the
   aliases ``-m[no-]strict-align``.
-- An ABI mismatch between GCC and Clang related to the handling of empty structs
-  in C++ parameter passing under ``lp64d`` ABI was fixed.
 
 RISC-V Support
 ^^^^^^^^^^^^^^

diff  --git a/clang/lib/CodeGen/Targets/LoongArch.cpp b/clang/lib/CodeGen/Targets/LoongArch.cpp
index 056b3946d1b33f..6391a8aeaa67cd 100644
--- a/clang/lib/CodeGen/Targets/LoongArch.cpp
+++ b/clang/lib/CodeGen/Targets/LoongArch.cpp
@@ -148,13 +148,6 @@ bool LoongArchABIInfo::detectFARsEligibleStructHelper(
   if (const ConstantArrayType *ATy = getContext().getAsConstantArrayType(Ty)) {
     uint64_t ArraySize = ATy->getSize().getZExtValue();
     QualType EltTy = ATy->getElementType();
-    // Non-zero-length arrays of empty records make the struct ineligible to be
-    // passed via FARs in C++.
-    if (const auto *RTy = EltTy->getAs<RecordType>()) {
-      if (ArraySize != 0 && isa<CXXRecordDecl>(RTy->getDecl()) &&
-          isEmptyRecord(getContext(), EltTy, true, true))
-        return false;
-    }
     CharUnits EltSize = getContext().getTypeSizeInChars(EltTy);
     for (uint64_t i = 0; i < ArraySize; ++i) {
       if (!detectFARsEligibleStructHelper(EltTy, CurOff, Field1Ty, Field1Off,
@@ -170,7 +163,7 @@ bool LoongArchABIInfo::detectFARsEligibleStructHelper(
     // copy constructor are not eligible for the FP calling convention.
     if (getRecordArgABI(Ty, CGT.getCXXABI()))
       return false;
-    if (isEmptyRecord(getContext(), Ty, true, true))
+    if (isEmptyRecord(getContext(), Ty, true))
       return true;
     const RecordDecl *RD = RTy->getDecl();
     // Unions aren't eligible unless they're empty (which is caught above).

diff  --git a/clang/test/CodeGen/LoongArch/abi-lp64d-empty-structs.c b/clang/test/CodeGen/LoongArch/abi-lp64d-empty-structs.c
index b5c7916f57cd99..3a65b90e48e0e0 100644
--- a/clang/test/CodeGen/LoongArch/abi-lp64d-empty-structs.c
+++ b/clang/test/CodeGen/LoongArch/abi-lp64d-empty-structs.c
@@ -3,6 +3,7 @@
 // RUN: %clang_cc1 -triple loongarch64 -target-feature +f -target-feature +d -target-abi lp64d -emit-llvm %s -o - -x c++ | \
 // RUN:   FileCheck --check-prefix=CHECK-CXX %s
 
+// FIXME: This isn't currently respected.
 // Fields containing empty structs or unions are ignored when flattening
 // structs to examine whether the structs can be passed via FARs, even in C++.
 // But there is an exception that non-zero-length array of empty structures are
@@ -15,7 +16,7 @@ struct empty { struct { struct { } e; }; };
 struct s1 { struct empty e; float f; };
 
 // CHECK-C: define{{.*}} float @test_s1(float {{.*}})
-// CHECK-CXX: define{{.*}} float @_Z7test_s12s1(float {{.*}})
+// CHECK-CXX: define{{.*}} i64 @_Z7test_s12s1(i64 {{.*}})
 struct s1 test_s1(struct s1 a) {
   return a;
 }
@@ -23,7 +24,7 @@ struct s1 test_s1(struct s1 a) {
 struct s2 { struct empty e; int32_t i; float f; };
 
 // CHECK-C: define{{.*}} { i32, float } @test_s2(i32 {{.*}}, float {{.*}})
-// CHECK-CXX: define{{.*}} { i32, float } @_Z7test_s22s2(i32 {{.*}}, float {{.*}})
+// CHECK-CXX: define{{.*}} [2 x i64] @_Z7test_s22s2([2 x i64] {{.*}})
 struct s2 test_s2(struct s2 a) {
   return a;
 }
@@ -31,7 +32,7 @@ struct s2 test_s2(struct s2 a) {
 struct s3 { struct empty e; float f; float g; };
 
 // CHECK-C: define{{.*}} { float, float } @test_s3(float {{.*}}, float {{.*}})
-// CHECK-CXX: define{{.*}} { float, float } @_Z7test_s32s3(float {{.*}}, float {{.*}})
+// CHECK-CXX: define{{.*}} [2 x i64] @_Z7test_s32s3([2 x i64] {{.*}})
 struct s3 test_s3(struct s3 a) {
   return a;
 }
@@ -39,7 +40,7 @@ struct s3 test_s3(struct s3 a) {
 struct s4 { struct empty e; float __complex__ c; };
 
 // CHECK-C: define{{.*}} { float, float } @test_s4(float {{.*}}, float {{.*}})
-// CHECK-CXX: define{{.*}} { float, float } @_Z7test_s42s4(float {{.*}}, float {{.*}})
+// CHECK-CXX: define{{.*}} [2 x i64] @_Z7test_s42s4([2 x i64] {{.*}})
 struct s4 test_s4(struct s4 a) {
   return a;
 }
@@ -76,7 +77,7 @@ struct empty_arr0 { struct { struct { } e[0]; }; };
 struct s8 { struct empty_arr0 e; float f; };
 
 // CHECK-C: define{{.*}} float @test_s8(float {{.*}})
-// CHECK-CXX: define{{.*}} float @_Z7test_s82s8(float {{.*}})
+// CHECK-CXX: define{{.*}} i64 @_Z7test_s82s8(i64 {{.*}})
 struct s8 test_s8(struct s8 a) {
   return a;
 }