Fix fastcc structure return with fast-isel on x86-32

On x86-32, structure return via sret lets the callee pop the hidden
pointer argument off the stack, which the caller then re-pushes.
However if the calling convention is fastcc, then a register is used
instead, and the caller should not adjust the stack. This is
implemented with a check of IsTailCallConvention
X86TargetLowering::LowerCall but is now checked properly in
X86FastISel::DoSelectCall.

(this time, actually commit what was reviewed!)

llvm-svn: 155825

llvm/lib/Target/X86/X86FastISel.cpp

@@ -1858,6 +1858,8 @@ bool X86FastISel::DoSelectCall(const Instruction *I, const char *MemIntName) {
   unsigned AdjStackUp = TII.getCallFrameDestroyOpcode();
   unsigned NumBytesCallee = 0;
   if (!Subtarget->is64Bit() && !Subtarget->isTargetWindows() &&
+      !(CS.getCallingConv() == CallingConv::Fast ||
+        CS.getCallingConv() == CallingConv::GHC) &&
       CS.paramHasAttr(1, Attribute::StructRet))
     NumBytesCallee = 4;
   BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(AdjStackUp))

llvm/test/CodeGen/X86/fast-isel-x86.ll

@@ -46,3 +46,17 @@ entry:
 ; CHECK: addl $40
 }
 declare void @test3sret(%struct.a* sret)
+
+; Check that fast-isel sret works with fastcc (and does not callee-pop)
+define void @test4() nounwind ssp {
+entry:
+  %tmp = alloca %struct.a, align 8
+  call fastcc void @test4fastccsret(%struct.a* sret %tmp)
+  ret void
+; CHECK: test4:
+; CHECK: subl $28
+; CHECK: leal (%esp), %ecx
+; CHECK: calll _test4fastccsret
+; CHECK addl $28
+}
+declare fastcc void @test4fastccsret(%struct.a* sret)