llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang
Author: Longsheng Mou (CoTinker)
<details>
<summary>Changes</summary>
struct SuperEmpty { struct{ int a[0];} b;};
Such 0 sized structs in c++ mode can not be ignored in i386 for that c++ fields
are never empty.But when EmitVAArg, its size is 0, so that va_list not
increase.Maybe we can use direct in this case.
https://github.com/llvm/llvm-project/blob/691b97c884a15a7eac641ddf67c9f2f30fb4e747/clang/lib/CodeGen/ABIInfoImpl.cpp#L202-L216
This case use indirect before and `DirectSize == 0`, now we use direct and
`DirectSize == 4`.
Or we can just Ignore this kind of arguments, like X86_64 did.
---
Full diff: https://github.com/llvm/llvm-project/pull/86388.diff
2 Files Affected:
- (modified) clang/lib/CodeGen/Targets/X86.cpp (+3)
- (modified) clang/test/CodeGenCXX/regparm.cpp (+1-1)
``````````diff
diff --git a/clang/lib/CodeGen/Targets/X86.cpp
b/clang/lib/CodeGen/Targets/X86.cpp
index 1ec0f159ebcb8a..8e6e7c17452048 100644
--- a/clang/lib/CodeGen/Targets/X86.cpp
+++ b/clang/lib/CodeGen/Targets/X86.cpp
@@ -805,6 +805,9 @@ ABIArgInfo X86_32ABIInfo::classifyArgumentType(QualType Ty,
CCState &State,
if (!IsWin32StructABI && isEmptyRecord(getContext(), Ty, true))
return ABIArgInfo::getIgnore();
+ if (TI.Width == 0 && getContext().getLangOpts().CPlusPlus)
+ return ABIArgInfo::getDirect();
+
llvm::LLVMContext &LLVMContext = getVMContext();
llvm::IntegerType *Int32 = llvm::Type::getInt32Ty(LLVMContext);
bool NeedsPadding = false;
diff --git a/clang/test/CodeGenCXX/regparm.cpp
b/clang/test/CodeGenCXX/regparm.cpp
index 1fd471c2d0727b..559702a84c99e1 100644
--- a/clang/test/CodeGenCXX/regparm.cpp
+++ b/clang/test/CodeGenCXX/regparm.cpp
@@ -32,7 +32,7 @@ struct S3 {
} a;
};
__attribute((regparm(2))) void foo4(S3 a, int b);
-// CHECK: declare void @_Z4foo42S3i(ptr noundef byval(%struct.S3) align 4, i32
inreg noundef)
+// CHECK: declare void @_Z4foo42S3i(%struct.anon, i32 inreg noundef)
void bar3(S3 a, int b) {
foo4(a, b);
}
``````````
</details>
https://github.com/llvm/llvm-project/pull/86388
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