Revert "Don't count inreg params when mangling fastcall functions"

This reverts commit r214981.

I'm not sure what I was thinking when I wrote this. Testing with MSVC
shows that this function is mangled to '@f@8':
  int __fastcall f(int a, int b);

llvm-svn: 220492

lib/IR/Mangler.cpp

@@ -72,9 +72,6 @@ static void AddFastCallStdCallSuffix(raw_ostream &OS, const Function *F,
   unsigned ArgWords = 0;
   for (Function::const_arg_iterator AI = F->arg_begin(), AE = F->arg_end();
        AI != AE; ++AI) {
-    // Skip arguments in registers to handle typical fastcall lowering.
-    if (F->getAttributes().hasAttribute(AI->getArgNo() + 1, Attribute::InReg))
-      continue;
     Type *Ty = AI->getType();
     // 'Dereference' type in case of byval or inalloca parameter attribute.
     if (AI->hasByValOrInAllocaAttr())

test/CodeGen/X86/byval-callee-cleanup.ll

@@ -23,5 +23,5 @@ define x86_thiscallcc void @g(i8* %this, %struct.Six* byval %a) {
 define x86_fastcallcc void @h(i32 inreg %x, i32 inreg %y, %struct.Six* byval %a) {
   ret void
 }
-; CHECK-LABEL: @h@8:
+; CHECK-LABEL: @h@16:
 ; CHECK: retl $8

test/CodeGen/X86/musttail-indirect.ll

@@ -109,7 +109,7 @@ entry:
   ret i32 %3
 }
 
-; CHECK-LABEL: @fastcall_thunk@4:
+; CHECK-LABEL: @fastcall_thunk@8:
 ; CHECK-NOT: mov %{{.*}}, {{.*(.*esp.*)}}
 ; CHECK: jmpl
 ; CHECK-NOT: ret