[Win64] Only treat some functions as having the Win64 convention

All the usual X86 target-specific conventions are collapsed to the
normal Win64 convention, but the custom conventions like GHC and webkit
should not be.

Previously we would assume that the caller allocated 32 bytes of shadow
space for us, which is not how webkit_jscc or other custom conventions
are supposed to work.

Based on a patch by peavo@outlook.com.

Fixes PR24051.

llvm-svn: 241725

2 files changed, 38 insertions, 2 deletions

diff --git a/llvm/lib/Target/X86/X86Subtarget.h b/llvm/lib/Target/X86/X86Subtarget.h
index d420abbe143..f026d4295f7 100644
--- a/llvm/lib/Target/X86/X86Subtarget.h
+++ b/llvm/lib/Target/X86/X86Subtarget.h
@@ -447,8 +447,26 @@ public:
   }
 
   bool isCallingConvWin64(CallingConv::ID CC) const {
-    return (isTargetWin64() && CC != CallingConv::X86_64_SysV) ||
-           CC == CallingConv::X86_64_Win64;
+    switch (CC) {
+    // On Win64, all these conventions just use the default convention.
+    case CallingConv::C:
+    case CallingConv::Fast:
+    case CallingConv::X86_FastCall:
+    case CallingConv::X86_StdCall:
+    case CallingConv::X86_ThisCall:
+    case CallingConv::X86_VectorCall:
+    case CallingConv::Intel_OCL_BI:
+      return isTargetWin64();
+    // This convention allows using the Win64 convention on other targets.
+    case CallingConv::X86_64_Win64:
+      return true;
+    // This convention allows using the SysV convention on Windows targets.
+    case CallingConv::X86_64_SysV:
+      return false;
+    // Otherwise, who knows what this is.
+    default:
+      return false;
+    }
   }
 
   /// ClassifyGlobalReference - Classify a global variable reference for the
diff --git a/llvm/test/CodeGen/X86/webkit-jscc.ll b/llvm/test/CodeGen/X86/webkit-jscc.ll
new file mode 100644
index 00000000000..a58c53e024e
--- /dev/null
+++ b/llvm/test/CodeGen/X86/webkit-jscc.ll
@@ -0,0 +1,18 @@
+; RUN: llc -mtriple=x86_64-apple-darwin -mcpu=corei7 < %s | FileCheck %s
+; RUN: llc -mtriple=x86_64-linux-gnu -mcpu=corei7 < %s | FileCheck %s
+; RUN: llc -mtriple=x86_64-windows-gnu -mcpu=corei7 < %s | FileCheck %s
+; RUN: llc -mtriple=x86_64-windows-msvc -mcpu=corei7 < %s | FileCheck %s
+
+define webkit_jscc i32 @simple_jscall(i32 %a, i32 %b, i32 %c) {
+  %ab = add i32 %a, %b
+  %abc = add i32 %ab, %c
+  ret i32 %abc
+}
+
+; 32-bit integers are only aligned to 4 bytes, even on x64. They are *not*
+; promoted to i64.
+
+; CHECK: simple_jscall:
+; CHECK: addl 8(%rsp), %eax
+; CHECK-NEXT: addl 12(%rsp), %eax
+; CHECK-NEXT: retq