Revert r237175: [X86] Always return the sret parameter in eax/rax ...

This commit broke an x86 test and the bots have been broken for well
over an hour now so I'm just reverting.

llvm-svn: 237210

Author: chandlerc

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -2000,8 +2000,9 @@ X86TargetLowering::LowerReturn(SDValue Chain,
     RetOps.push_back(DAG.getRegister(VA.getLocReg(), VA.getLocVT()));
   }
 
-  // All x86 ABIs require that for returning structs by value we copy
+  // The x86-64 ABIs require that for returning structs by value we copy
   // the sret argument into %rax/%eax (depending on ABI) for the return.
+  // Win32 requires us to put the sret argument to %eax as well.
   // We saved the argument into a virtual register in the entry block,
   // so now we copy the value out and into %rax/%eax.
   //
@@ -2010,6 +2011,8 @@ X86TargetLowering::LowerReturn(SDValue Chain,
   // false, then an sret argument may be implicitly inserted in the SelDAG. In
   // either case FuncInfo->setSRetReturnReg() will have been called.
   if (unsigned SRetReg = FuncInfo->getSRetReturnReg()) {
+    assert((Subtarget->is64Bit() || Subtarget->isTargetKnownWindowsMSVC()) &&
+           "No need for an sret register");
     SDValue Val = DAG.getCopyFromReg(Chain, dl, SRetReg, getPointerTy());
 
     unsigned RetValReg
@@ -2431,21 +2434,24 @@ X86TargetLowering::LowerFormalArguments(SDValue Chain,
     InVals.push_back(ArgValue);
   }
 
-  for (unsigned i = 0, e = ArgLocs.size(); i != e; ++i) {
-    // All x86 ABIs require that for returning structs by value we copy the
-    // sret argument into %rax/%eax (depending on ABI) for the return. Save
-    // the argument into a virtual register so that we can access it from the
-    // return points.
-    if (Ins[i].Flags.isSRet()) {
-      unsigned Reg = FuncInfo->getSRetReturnReg();
-      if (!Reg) {
-        MVT PtrTy = getPointerTy();
-        Reg = MF.getRegInfo().createVirtualRegister(getRegClassFor(PtrTy));
-        FuncInfo->setSRetReturnReg(Reg);
+  if (Subtarget->is64Bit() || Subtarget->isTargetKnownWindowsMSVC()) {
+    for (unsigned i = 0, e = ArgLocs.size(); i != e; ++i) {
+      // The x86-64 ABIs require that for returning structs by value we copy
+      // the sret argument into %rax/%eax (depending on ABI) for the return.
+      // Win32 requires us to put the sret argument to %eax as well.
+      // Save the argument into a virtual register so that we can access it
+      // from the return points.
+      if (Ins[i].Flags.isSRet()) {
+        unsigned Reg = FuncInfo->getSRetReturnReg();
+        if (!Reg) {
+          MVT PtrTy = getPointerTy();
+          Reg = MF.getRegInfo().createVirtualRegister(getRegClassFor(PtrTy));
+          FuncInfo->setSRetReturnReg(Reg);
+        }
+        SDValue Copy = DAG.getCopyToReg(DAG.getEntryNode(), dl, Reg, InVals[i]);
+        Chain = DAG.getNode(ISD::TokenFactor, dl, MVT::Other, Copy, Chain);
+        break;
       }
-      SDValue Copy = DAG.getCopyToReg(DAG.getEntryNode(), dl, Reg, InVals[i]);
-      Chain = DAG.getNode(ISD::TokenFactor, dl, MVT::Other, Copy, Chain);
-      break;
     }
   }
 

llvm/test/CodeGen/X86/cmovcmov.ll

@@ -143,30 +143,30 @@ entry:
 ; NOCMOV-NEXT:   jp  [[TBB]]
 ; NOCMOV-NEXT:   leal  24(%esp), %eax
 ; NOCMOV-NEXT: [[TBB]]:
-; NOCMOV-NEXT:   movl  (%eax), %ecx
-; NOCMOV-NEXT:   leal  44(%esp), %edx
+; NOCMOV-NEXT:   movl  (%eax), %eax
+; NOCMOV-NEXT:   leal  44(%esp), %ecx
 ; NOCMOV-NEXT:   jne  [[TBB:.LBB[0-9_]+]]
 ; NOCMOV-NEXT:   jp  [[TBB]]
-; NOCMOV-NEXT:   leal  28(%esp), %edx
+; NOCMOV-NEXT:   leal  28(%esp), %ecx
 ; NOCMOV-NEXT: [[TBB]]:
-; NOCMOV-NEXT:   movl  12(%esp), %eax
-; NOCMOV-NEXT:   movl  (%edx), %edx
+; NOCMOV-NEXT:   movl  (%ecx), %ecx
 ; NOCMOV-NEXT:   leal  48(%esp), %esi
 ; NOCMOV-NEXT:   jne  [[TBB:.LBB[0-9_]+]]
 ; NOCMOV-NEXT:   jp  [[TBB]]
 ; NOCMOV-NEXT:   leal  32(%esp), %esi
 ; NOCMOV-NEXT: [[TBB]]:
+; NOCMOV-NEXT:   movl  12(%esp), %edx
 ; NOCMOV-NEXT:   movl  (%esi), %esi
 ; NOCMOV-NEXT:   leal  52(%esp), %edi
 ; NOCMOV-NEXT:   jne  [[TBB:.LBB[0-9_]+]]
 ; NOCMOV-NEXT:   jp  [[TBB]]
 ; NOCMOV-NEXT:   leal  36(%esp), %edi
 ; NOCMOV-NEXT: [[TBB]]:
 ; NOCMOV-NEXT:   movl  (%edi), %edi
-; NOCMOV-NEXT:   movl  %edi, 12(%eax)
-; NOCMOV-NEXT:   movl  %esi, 8(%eax)
-; NOCMOV-NEXT:   movl  %edx, 4(%eax)
-; NOCMOV-NEXT:   movl  %ecx, (%eax)
+; NOCMOV-NEXT:   movl  %edi, 12(%edx)
+; NOCMOV-NEXT:   movl  %esi, 8(%edx)
+; NOCMOV-NEXT:   movl  %ecx, 4(%edx)
+; NOCMOV-NEXT:   movl  %eax, (%edx)
 ; NOCMOV-NEXT:   popl  %esi
 ; NOCMOV-NEXT:   popl  %edi
 ; NOCMOV-NEXT:   retl  $4

llvm/test/CodeGen/X86/sret-implicit.ll

@@ -1,34 +1,12 @@
-; RUN: llc -mtriple=x86_64-apple-darwin8 < %s | FileCheck %s --check-prefix=X64
-; RUN: llc -mtriple=x86_64-pc-linux < %s | FileCheck %s --check-prefix=X64
-; RUN: llc -mtriple=i686-pc-linux < %s | FileCheck %s --check-prefix=X86
-; RUN: llc -mtriple=x86_64-apple-darwin8 -terminal-rule < %s | FileCheck %s --check-prefix=X64
-; RUN: llc -mtriple=x86_64-pc-linux -terminal-rule < %s | FileCheck %s --check-prefix=X64
-
-define void @sret_void(i32* sret %p) {
-  store i32 0, i32* %p
-  ret void
-}
-
-; X64-LABEL: sret_void
-; X64-DAG: movl $0, (%rdi)
-; X64-DAG: movq %rdi, %rax
-; X64: retq
-
-; X86-LABEL: sret_void
-; X86: movl 4(%esp), %eax
-; X86: movl $0, (%eax)
-; X86: retl
-
-define i256 @sret_demoted() {
+; RUN: llc -mtriple=x86_64-apple-darwin8 < %s | FileCheck %s
+; RUN: llc -mtriple=x86_64-pc-linux < %s | FileCheck %s
+; RUN: llc -mtriple=x86_64-apple-darwin8 -terminal-rule < %s | FileCheck %s
+; RUN: llc -mtriple=x86_64-pc-linux -terminal-rule < %s | FileCheck %s
+
+; CHECK-LABEL: return32
+; CHECK-DAG: movq	$0, (%rdi)
+; CHECK-DAG: movq	%rdi, %rax
+; CHECK: retq
+define i256 @return32() {
   ret i256 0
 }
-
-; X64-LABEL: sret_demoted
-; X64-DAG: movq $0, (%rdi)
-; X64-DAG: movq %rdi, %rax
-; X64: retq
-
-; X86-LABEL: sret_demoted
-; X86: movl 4(%esp), %eax
-; X86: movl $0, (%eax)
-; X86: retl