[llvm] r204829 - Revert "X86 memcpy lowering: use "rep movs" even when esi is used as base pointer" (r204174)
Hans Wennborg
hans at hanshq.net
Wed Mar 26 09:30:55 PDT 2014
Author: hans
Date: Wed Mar 26 11:30:54 2014
New Revision: 204829
URL: http://llvm.org/viewvc/llvm-project?rev=204829&view=rev
Log:
Revert "X86 memcpy lowering: use "rep movs" even when esi is used as base pointer" (r204174)
> For functions where esi is used as base pointer, we would previously fall ba
> from lowering memcpy with "rep movs" because that clobbers esi.
>
> With this patch, we just store esi in another physical register, and restore
> it afterwards. This adds a little bit of register preassure, but the more
> efficient memcpy should be worth it.
>
> Differential Revision: http://llvm-reviews.chandlerc.com/D2968
This didn't work. I was ending up with code like this:
lea edi,[esi+38h]
mov ecx,0Fh
mov edx,esi
mov esi,ebx
rep movs dword ptr es:[edi],dword ptr [esi]
lea ecx,[esi+74h] <-- Ooops, we're now using esi before restoring it from edx.
add ebx,3Ch
mov esi,edx
I guess if we want to do this we need stronger glue or something, or doing the expansion
much later.
Modified:
llvm/trunk/lib/Target/X86/X86SelectionDAGInfo.cpp
llvm/trunk/test/CodeGen/X86/inline-asm-sp-clobber-memcpy.ll
llvm/trunk/test/CodeGen/X86/stack-align-memcpy.ll
Modified: llvm/trunk/lib/Target/X86/X86SelectionDAGInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86SelectionDAGInfo.cpp?rev=204829&r1=204828&r2=204829&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86SelectionDAGInfo.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86SelectionDAGInfo.cpp Wed Mar 26 11:30:54 2014
@@ -200,11 +200,13 @@ X86SelectionDAGInfo::EmitTargetCodeForMe
SrcPtrInfo.getAddrSpace() >= 256)
return SDValue();
- // If ESI is used as a base pointer, we must preserve it when doing rep movs.
+ // ESI might be used as a base pointer, in that case we can't simply overwrite
+ // the register. Fall back to generic code.
const X86RegisterInfo *TRI =
static_cast<const X86RegisterInfo *>(DAG.getTarget().getRegisterInfo());
- bool PreserveESI = TRI->hasBasePointer(DAG.getMachineFunction()) &&
- TRI->getBaseRegister() == X86::ESI;
+ if (TRI->hasBasePointer(DAG.getMachineFunction()) &&
+ TRI->getBaseRegister() == X86::ESI)
+ return SDValue();
MVT AVT;
if (Align & 1)
@@ -223,45 +225,27 @@ X86SelectionDAGInfo::EmitTargetCodeForMe
SDValue Count = DAG.getIntPtrConstant(CountVal);
unsigned BytesLeft = SizeVal % UBytes;
-
- if (PreserveESI) {
- // Save ESI to a physical register. (We cannot use a virtual register
- // because if it is spilled we wouldn't be able to reload it.)
- // We don't glue this because the register dependencies are explicit.
- Chain = DAG.getCopyToReg(Chain, dl, X86::EDX,
- DAG.getRegister(X86::ESI, MVT::i32));
- }
-
- SDValue InGlue(0, 0);
+ SDValue InFlag(0, 0);
Chain = DAG.getCopyToReg(Chain, dl, Subtarget->is64Bit() ? X86::RCX :
X86::ECX,
- Count, InGlue);
- InGlue = Chain.getValue(1);
+ Count, InFlag);
+ InFlag = Chain.getValue(1);
Chain = DAG.getCopyToReg(Chain, dl, Subtarget->is64Bit() ? X86::RDI :
X86::EDI,
- Dst, InGlue);
- InGlue = Chain.getValue(1);
+ Dst, InFlag);
+ InFlag = Chain.getValue(1);
Chain = DAG.getCopyToReg(Chain, dl, Subtarget->is64Bit() ? X86::RSI :
X86::ESI,
- Src, InGlue);
- InGlue = Chain.getValue(1);
+ Src, InFlag);
+ InFlag = Chain.getValue(1);
SDVTList Tys = DAG.getVTList(MVT::Other, MVT::Glue);
- SDValue Ops[] = { Chain, DAG.getValueType(AVT), InGlue };
- // FIXME: Make X86rep_movs explicitly use FCX, RDI, RSI instead of glue.
+ SDValue Ops[] = { Chain, DAG.getValueType(AVT), InFlag };
SDValue RepMovs = DAG.getNode(X86ISD::REP_MOVS, dl, Tys, Ops,
array_lengthof(Ops));
- if (PreserveESI) {
- InGlue = RepMovs.getValue(1);
- RepMovs = DAG.getCopyToReg(RepMovs, dl, X86::ESI,
- DAG.getRegister(X86::EDX, MVT::i32), InGlue);
- }
-
SmallVector<SDValue, 4> Results;
Results.push_back(RepMovs);
-
-
if (BytesLeft) {
// Handle the last 1 - 7 bytes.
unsigned Offset = SizeVal - BytesLeft;
Modified: llvm/trunk/test/CodeGen/X86/inline-asm-sp-clobber-memcpy.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/inline-asm-sp-clobber-memcpy.ll?rev=204829&r1=204828&r2=204829&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/inline-asm-sp-clobber-memcpy.ll (original)
+++ llvm/trunk/test/CodeGen/X86/inline-asm-sp-clobber-memcpy.ll Wed Mar 26 11:30:54 2014
@@ -13,7 +13,5 @@ define void @test1(%struct.foo* nocaptur
; CHECK-LABEL: test1:
; CHECK: movl %esp, %esi
-; CHECK: movl %esi, %edx
-; CHECK: rep;movsl
-; CHECK: movl %edx, %esi
+; CHECK-NOT: rep;movsl
}
Modified: llvm/trunk/test/CodeGen/X86/stack-align-memcpy.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/stack-align-memcpy.ll?rev=204829&r1=204828&r2=204829&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/stack-align-memcpy.ll (original)
+++ llvm/trunk/test/CodeGen/X86/stack-align-memcpy.ll Wed Mar 26 11:30:54 2014
@@ -15,9 +15,7 @@ define void @test1(%struct.foo* nocaptur
; CHECK-LABEL: test1:
; CHECK: andl $-16, %esp
; CHECK: movl %esp, %esi
-; CHECK: movl %esi, %edx
-; CHECK: rep;movsl
-; CHECK: movl %edx, %esi
+; CHECK-NOT: rep;movsl
}
; PR19012
@@ -30,9 +28,7 @@ define void @test2(%struct.foo* nocaptur
; CHECK-LABEL: test2:
; CHECK: movl %esp, %esi
-; CHECK: movl %esi, %edx
-; CHECK: rep;movsl
-; CHECK: movl %edx, %esi
+; CHECK-NOT: rep;movsl
}
; Check that we do use rep movs if we make the alloca static.
@@ -43,6 +39,5 @@ define void @test3(%struct.foo* nocaptur
ret void
; CHECK-LABEL: test3:
-; CHECK-NOT: movl %esi, %edx
; CHECK: rep;movsl
}
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