Allow '@' to appear in x86 mingw symbols

Summary:
There is no reason to differ in assembler behavior here between -msvc
and -gnu targets. Without this setting, the text after the '@' is
interpreted as a symbol variable, like foo@IMGREL.

Reviewers: mstorsjo

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66974

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@370408 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/X86/MCTargetDesc/X86MCAsmInfo.cpp

@@ -163,5 +163,7 @@ X86MCAsmInfoGNUCOFF::X86MCAsmInfoGNUCOFF(const Triple &Triple) {
 
   TextAlignFillValue = 0x90;
 
+  AllowAtInName = true;
+
   UseIntegratedAssembler = true;
 }

test/MC/X86/stdcall.s

@@ -0,0 +1,19 @@
+# RUN: llvm-mc %s -filetype=obj -o - -triple i686-windows-msvc | llvm-nm - | FileCheck %s
+# RUN: llvm-mc %s -filetype=obj -o - -triple i686-windows-gnu | llvm-nm - | FileCheck %s
+
+# CHECK: T _mystdcall@8{{$}}
+# CHECK: T foo
+
+.text
+.global _mystdcall@8
+_mystdcall@8:
+	movl 4(%esp), %eax
+	addl 8(%esp), %eax
+	retl $8
+
+.global foo
+foo:
+	pushl $1
+	pushl $2
+	calll _mystdcall@8
+	retl