[clang] [LoongArch] Fix ABI mismatch with gcc/g++ about empty structs passing (PR #70320)
https://github.com/SixWeining created https://github.com/llvm/llvm-project/pull/70320 How empty structs (not as fields of container struct) are passed in C++ is not explicitly documented in psABI. However, this patch fixes the mismatch with g++. Note that the unnamed bitfield case `struct { int : 1; }` in C is also fixed. Previously clang regards it as an empty struct and then ignores it when passing. Now size of the struct is counted; since it's size is not 0, clang will not ignore it even in C. While https://reviews.llvm.org/D156116 fixed the handling of empty struct when considering eligibility of the container struct for the FP calling convention ('flattening'), this patch fixes the handling of passing the empty struct itself. Fix https://github.com/llvm/llvm-project/issues/70319 >From 3ed0605126e2cfd94e58dd38c2f58764e32e2057 Mon Sep 17 00:00:00 2001 From: Weining Lu Date: Thu, 26 Oct 2023 13:40:27 +0800 Subject: [PATCH] [LoongArch] Fix ABI mismatch with gcc/g++ about empty structs passing How empty structs (not as fields of container struct) are passed in C++ is not explicitly documented in psABI. However, this patch fixes the mismatch with g++. Note that the unnamed bitfield case `struct { int : 1; }` in C is also fixed. Previously clang regards it as an empty struct and then ignores it when passing. Now size of the struct is counted; since it's size is not 0, clang will not ignore it even in C. While https://reviews.llvm.org/D156116 fixed the handling of empty struct when considering eligibility of the container struct for the FP calling convention ('flattening'), this patch fixes the handling of passing the empty struct itself. Fix https://github.com/llvm/llvm-project/issues/70319 --- clang/lib/CodeGen/Targets/LoongArch.cpp| 10 ++ clang/test/CodeGen/LoongArch/abi-lp64d-empty-structs.c | 8 2 files changed, 10 insertions(+), 8 deletions(-) diff --git a/clang/lib/CodeGen/Targets/LoongArch.cpp b/clang/lib/CodeGen/Targets/LoongArch.cpp index 7483bf6d6d1e8e2..bc508a99da9cedf 100644 --- a/clang/lib/CodeGen/Targets/LoongArch.cpp +++ b/clang/lib/CodeGen/Targets/LoongArch.cpp @@ -308,12 +308,14 @@ ABIArgInfo LoongArchABIInfo::classifyArgumentType(QualType Ty, bool IsFixed, CGCXXABI::RAA_DirectInMemory); } - // Ignore empty structs/unions. - if (isEmptyRecord(getContext(), Ty, true)) -return ABIArgInfo::getIgnore(); - uint64_t Size = getContext().getTypeSize(Ty); + // Ignore empty struct or union whose size is zero, e.g. `struct { }` in C or + // `struct { int a[0]; }` in C++. In C++, `struct { }` is empty but it's size + // is 1 byte and g++ doesn't ignore it; clang++ matches this behaviour. + if (isEmptyRecord(getContext(), Ty, true) && Size == 0) +return ABIArgInfo::getIgnore(); + // Pass floating point values via FARs if possible. if (IsFixed && Ty->isFloatingType() && !Ty->isComplexType() && FRLen >= Size && FARsLeft) { diff --git a/clang/test/CodeGen/LoongArch/abi-lp64d-empty-structs.c b/clang/test/CodeGen/LoongArch/abi-lp64d-empty-structs.c index d0daafac336ec0c..281b7b15841a999 100644 --- a/clang/test/CodeGen/LoongArch/abi-lp64d-empty-structs.c +++ b/clang/test/CodeGen/LoongArch/abi-lp64d-empty-structs.c @@ -93,7 +93,7 @@ struct s9 test_s9(struct s9 a) { } // CHECK-C: define{{.*}} void @test_s10() -// CHECK-CXX: define{{.*}} void @_Z8test_s103s10() +// CHECK-CXX: define{{.*}} i64 @_Z8test_s103s10(i64 {{.*}}) struct s10 { }; struct s10 test_s10(struct s10 a) { return a; @@ -128,14 +128,14 @@ struct s14 test_s14(struct s14 a) { } // CHECK-C: define{{.*}} void @test_s15() -// CHECK-CXX: define{{.*}} void @_Z8test_s153s15() +// CHECK-CXX: define{{.*}} i64 @_Z8test_s153s15(i64 {{.*}}) struct s15 { int : 0; }; struct s15 test_s15(struct s15 a) { return a; } -// CHECK-C: define{{.*}} void @test_s16() -// CHECK-CXX: define{{.*}} void @_Z8test_s163s16() +// CHECK-C: define{{.*}} i64 @test_s16(i64 {{.*}}) +// CHECK-CXX: define{{.*}} i64 @_Z8test_s163s16(i64 {{.*}}) struct s16 { int : 1; }; struct s16 test_s16(struct s16 a) { return a; ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [LoongArch] Fix ABI mismatch with gcc/g++ about empty structs passing (PR #70320)
llvmbot wrote: @llvm/pr-subscribers-clang-codegen Author: Lu Weining (SixWeining) Changes How empty structs (not as fields of container struct) are passed in C++ is not explicitly documented in psABI. However, this patch fixes the mismatch with g++. Note that the unnamed bitfield case `struct { int : 1; }` in C is also fixed. Previously clang regards it as an empty struct and then ignores it when passing. Now size of the struct is counted; since it's size is not 0, clang will not ignore it even in C. While https://reviews.llvm.org/D156116 fixed the handling of empty struct when considering eligibility of the container struct for the FP calling convention ('flattening'), this patch fixes the handling of passing the empty struct itself. Fix https://github.com/llvm/llvm-project/issues/70319 --- Full diff: https://github.com/llvm/llvm-project/pull/70320.diff 2 Files Affected: - (modified) clang/lib/CodeGen/Targets/LoongArch.cpp (+6-4) - (modified) clang/test/CodeGen/LoongArch/abi-lp64d-empty-structs.c (+4-4) ``diff diff --git a/clang/lib/CodeGen/Targets/LoongArch.cpp b/clang/lib/CodeGen/Targets/LoongArch.cpp index 7483bf6d6d1e8e2..bc508a99da9cedf 100644 --- a/clang/lib/CodeGen/Targets/LoongArch.cpp +++ b/clang/lib/CodeGen/Targets/LoongArch.cpp @@ -308,12 +308,14 @@ ABIArgInfo LoongArchABIInfo::classifyArgumentType(QualType Ty, bool IsFixed, CGCXXABI::RAA_DirectInMemory); } - // Ignore empty structs/unions. - if (isEmptyRecord(getContext(), Ty, true)) -return ABIArgInfo::getIgnore(); - uint64_t Size = getContext().getTypeSize(Ty); + // Ignore empty struct or union whose size is zero, e.g. `struct { }` in C or + // `struct { int a[0]; }` in C++. In C++, `struct { }` is empty but it's size + // is 1 byte and g++ doesn't ignore it; clang++ matches this behaviour. + if (isEmptyRecord(getContext(), Ty, true) && Size == 0) +return ABIArgInfo::getIgnore(); + // Pass floating point values via FARs if possible. if (IsFixed && Ty->isFloatingType() && !Ty->isComplexType() && FRLen >= Size && FARsLeft) { diff --git a/clang/test/CodeGen/LoongArch/abi-lp64d-empty-structs.c b/clang/test/CodeGen/LoongArch/abi-lp64d-empty-structs.c index d0daafac336ec0c..281b7b15841a999 100644 --- a/clang/test/CodeGen/LoongArch/abi-lp64d-empty-structs.c +++ b/clang/test/CodeGen/LoongArch/abi-lp64d-empty-structs.c @@ -93,7 +93,7 @@ struct s9 test_s9(struct s9 a) { } // CHECK-C: define{{.*}} void @test_s10() -// CHECK-CXX: define{{.*}} void @_Z8test_s103s10() +// CHECK-CXX: define{{.*}} i64 @_Z8test_s103s10(i64 {{.*}}) struct s10 { }; struct s10 test_s10(struct s10 a) { return a; @@ -128,14 +128,14 @@ struct s14 test_s14(struct s14 a) { } // CHECK-C: define{{.*}} void @test_s15() -// CHECK-CXX: define{{.*}} void @_Z8test_s153s15() +// CHECK-CXX: define{{.*}} i64 @_Z8test_s153s15(i64 {{.*}}) struct s15 { int : 0; }; struct s15 test_s15(struct s15 a) { return a; } -// CHECK-C: define{{.*}} void @test_s16() -// CHECK-CXX: define{{.*}} void @_Z8test_s163s16() +// CHECK-C: define{{.*}} i64 @test_s16(i64 {{.*}}) +// CHECK-CXX: define{{.*}} i64 @_Z8test_s163s16(i64 {{.*}}) struct s16 { int : 1; }; struct s16 test_s16(struct s16 a) { return a; `` https://github.com/llvm/llvm-project/pull/70320 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [LoongArch] Fix ABI mismatch with gcc/g++ about empty structs passing (PR #70320)
SixWeining wrote: Hi @xen0n @xry111, what do you think about this change? If it is ok, I'd like to checrry-pick to release/17.x (hope it's not too late...). https://github.com/llvm/llvm-project/pull/70320 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [LoongArch] Fix ABI mismatch with gcc/g++ about empty structs passing (PR #70320)
https://github.com/heiher approved this pull request. https://github.com/llvm/llvm-project/pull/70320 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [LoongArch] Fix ABI mismatch with gcc/g++ about empty structs passing (PR #70320)
xry111 wrote: LGTM. I've no permission to make a formal ("GitHub style") approval. https://github.com/llvm/llvm-project/pull/70320 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [LoongArch] Fix ABI mismatch with gcc/g++ about empty structs passing (PR #70320)
SixWeining wrote: > LGTM. I've no permission to make a formal ("GitHub style") approval. Thanks. You can request to join the llvm organization via https://llvm.org/docs/DeveloperPolicy.html#obtaining-commit-access firstly. Then you can make formal ("Github style") approval. https://github.com/llvm/llvm-project/pull/70320 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [LoongArch] Fix ABI mismatch with gcc/g++ about empty structs passing (PR #70320)
https://github.com/SixWeining closed https://github.com/llvm/llvm-project/pull/70320 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits