[llvm] 2dd8834 - [Mangler] Calculate the argument list byte count suffix correctly when returning large values

[Reid Kleckner via llvm-commits]

Author: Wesley Wiser
Date: 2021-09-29T11:42:28-07:00
New Revision: 2dd883439c7886182902c0aa17b34c0a8ed88b66

URL: https://github.com/llvm/llvm-project/commit/2dd883439c7886182902c0aa17b34c0a8ed88b66
DIFF: https://github.com/llvm/llvm-project/commit/2dd883439c7886182902c0aa17b34c0a8ed88b66.diff

LOG: [Mangler] Calculate the argument list byte count suffix correctly when returning large values

`__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

Added: 
    

Modified: 
    llvm/lib/IR/Mangler.cpp
    llvm/test/CodeGen/X86/stdcall.ll
    llvm/test/CodeGen/X86/vectorcall.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/IR/Mangler.cpp b/llvm/lib/IR/Mangler.cpp
index db833e3c668ff..2399ea27ee9d4 100644
--- 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 3cefe14fe0d57..25107c5d93f25 100644
--- 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 at 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 at 0

diff  --git a/llvm/test/CodeGen/X86/vectorcall.ll b/llvm/test/CodeGen/X86/vectorcall.ll
index d3d44f6bdd7a6..b8d53eaf0bba2 100644
--- 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}})