[Mangler] Calculate the argument list byte count suffix correctly when returning...

`__stdcall`, `__fastcall` and `__vectorcall` return large values via a
hidden pointer argument. However, the size of that argument should not
be included in the argument list byte count suffix added to the
function's decorated name.

This patch fixes that issue so that LLVM generates the same decorated
name as MSVC does.

MSVC example: https://godbolt.org/z/nc35MKPhr

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D110719

diff --git a/llvm/lib/IR/Mangler.cpp b/llvm/lib/IR/Mangler.cpp
index db833e3c668ff99e0d211109825ebb67a163a821..2399ea27ee9d474b387ce8f828f37edce7dbd349 100644 (file)
--- a/llvm/lib/IR/Mangler.cpp
+++ b/llvm/lib/IR/Mangler.cpp
@@ -99,6 +99,11 @@ static void addByteCountSuffix(raw_ostream &OS, const Function *F,
   const unsigned PtrSize = DL.getPointerSize();
 
   for (const Argument &A : F->args()) {
+    // For the purposes of the byte count suffix, structs returned by pointer
+    // do not count as function arguments.
+    if (A.hasStructRetAttr())
+      continue;
+
     // 'Dereference' type in case of byval or inalloca parameter attribute.
     uint64_t AllocSize = A.hasPassPointeeByValueCopyAttr() ?
       A.getPassPointeeByValueCopySize(DL) :

diff --git a/llvm/test/CodeGen/X86/stdcall.ll b/llvm/test/CodeGen/X86/stdcall.ll
index 3cefe14fe0d57095c2cb112a95f75ae4e3819582..25107c5d93f25a8a943d6afc81ae7badd1e407e1 100644 (file)
--- a/llvm/test/CodeGen/X86/stdcall.ll
+++ b/llvm/test/CodeGen/X86/stdcall.ll
@@ -18,6 +18,21 @@ entry:
   ret i32 %a
 }
 
+%struct.large_type = type { i64, i64, i64 }
+
+define x86_stdcallcc void @ReturnLargeType(%struct.large_type* noalias nocapture sret(%struct.large_type) align 8 %agg.result) {
+; CHECK: ReturnLargeType@0:
+; CHECK: retl
+entry:
+  %a = getelementptr inbounds %struct.large_type, %struct.large_type* %agg.result, i32 0, i32 0
+  store i64 123, i64* %a, align 8
+  %b = getelementptr inbounds %struct.large_type, %struct.large_type* %agg.result, i32 0, i32 1
+  store i64 456, i64* %b, align 8
+  %c = getelementptr inbounds %struct.large_type, %struct.large_type* %agg.result, i32 0, i32 2
+  store i64 789, i64* %c, align 8
+  ret void
+}
+
 @B = global %0 { void (...)* bitcast (void ()* @MyFunc to void (...)*) }, align 4
 ; CHECK: _B:
 ; CHECK: .long _MyFunc@0

diff --git a/llvm/test/CodeGen/X86/vectorcall.ll b/llvm/test/CodeGen/X86/vectorcall.ll
index d3d44f6bdd7a6c1a675054712b8a718c3e38f89d..b8d53eaf0bba2e89d86c2d100ed3ca5070c16ef8 100644 (file)
--- a/llvm/test/CodeGen/X86/vectorcall.ll
+++ b/llvm/test/CodeGen/X86/vectorcall.ll
@@ -172,8 +172,7 @@ declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture writeonly, i8* nocapture r
 declare void @llvm.memcpy.p0i8.p0i8.i32(i8* nocapture writeonly, i8* nocapture readonly, i32, i1)
 
 define x86_vectorcallcc void @test_mixed_7(%struct.HVA5* noalias sret(%struct.HVA5) %agg.result) {
-; X86-LABEL: test_mixed_7@@4
-; X64-LABEL: test_mixed_7@@8
+; CHECK-LABEL: test_mixed_7@@0
 ; X64:         mov{{[ql]}}     %rcx, %rax
 ; CHECK:       movaps  %xmm{{[0-9]}}, 64(%{{rcx|eax}})
 ; CHECK:       movaps  %xmm{{[0-9]}}, 48(%{{rcx|eax}})