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[x86] check for commuted add pattern to find ADC/SBB

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llvm-svn: 296933
This commit is contained in:
Sanjay Patel 2017-03-04 00:18:31 +00:00
parent f1aa1056d9
commit 5dae0360af
2 changed files with 14 additions and 8 deletions
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15
lib/Target/X86/X86ISelLowering.cpp
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@ -34106,7 +34106,15 @@ static SDValue combineADC(SDNode *N, SelectionDAG &DAG,
static SDValue combineAddOrSubToADCOrSBB(SDNode *N, SelectionDAG &DAG) {
// Look through ZExts.
bool IsSub = N->getOpcode() == ISD::SUB;
SDValue Ext = N->getOperand(IsSub ? 1 : 0);
SDValue Y = N->getOperand(0);
SDValue Ext = N->getOperand(1);
// If this is an add, canonicalize a zext to the RHS.
// TODO: Incomplete? What if both sides are zexts?
if (!IsSub && Ext.getOpcode() != ISD::ZERO_EXTEND &&
Y.getOpcode() == ISD::ZERO_EXTEND)
std::swap(Ext, Y);
if (Ext.getOpcode() != ISD::ZERO_EXTEND || !Ext.hasOneUse())
return SDValue();
@ -34130,17 +34138,16 @@ static SDValue combineAddOrSubToADCOrSBB(SDNode *N, SelectionDAG &DAG) {
SDValue NewCmp = DAG.getNode(X86ISD::CMP, DL, MVT::i32, X,
DAG.getConstant(1, DL, X.getValueType()));
SDValue Y = N->getOperand(IsSub ? 0 : 1);
EVT VT = Y.getValueType();
// Y - (X != 0) --> sub Y, (zext(setne X, 0)) --> adc Y, -1, (cmp X, 1)
// (X != 0) + Y --> add (zext(setne X, 0)), Y --> sbb Y, -1, (cmp X, 1)
// Y + (X != 0) --> add Y, (zext(setne X, 0)) --> sbb Y, -1, (cmp X, 1)
if (CC == X86::COND_NE)
return DAG.getNode(IsSub ? X86ISD::ADC : X86ISD::SBB, DL, VT, Y,
DAG.getConstant(-1ULL, DL, VT), NewCmp);
// Y - (X == 0) --> sub Y, (zext(sete X, 0)) --> sbb Y, 0, (cmp X, 1)
// (X == 0) + Y --> add (zext(sete X, 0)), Y --> adc Y, 0, (cmp X, 1)
// Y + (X == 0) --> add Y, (zext(sete X, 0)) --> adc Y, 0, (cmp X, 1)
return DAG.getNode(IsSub ? X86ISD::SBB : X86ISD::ADC, DL, VT, Y,
DAG.getConstant(0, DL, VT), NewCmp);
}

7
test/CodeGen/X86/conditional-indecrement.ll
View File

@ -17,10 +17,9 @@ define i32 @test1(i32 %a, i32 %b) nounwind readnone {
define i32 @test1_commute(i32 %a, i32 %b) nounwind readnone {
; CHECK-LABEL: test1_commute:
; CHECK: # BB#0:
; CHECK-NEXT: xorl %eax, %eax
; CHECK-NEXT: testl %edi, %edi
; CHECK-NEXT: setne %al
; CHECK-NEXT: addl %esi, %eax
; CHECK-NEXT: cmpl $1, %edi
; CHECK-NEXT: sbbl $-1, %esi
; CHECK-NEXT: movl %esi, %eax
; CHECK-NEXT: retq
%cmp = icmp ne i32 %a, 0
%inc = zext i1 %cmp to i32