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[X86] Don't zero_extend cmov up to i64, stop at i32. 

Zero extend from i32 to i64 is free. So extend from i16 to i32, and then use a free zero extend to finish.

llvm-svn: 325317
This commit is contained in:
Craig Topper 2018-02-16 06:52:43 +00:00
parent 6de1e858a1
commit 5d9e301042
2 changed files with 28 additions and 13 deletions
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39
llvm/lib/Target/X86/X86ISelLowering.cpp
View File

@ -36028,7 +36028,7 @@ static SDValue getDivRem8(SDNode *N, SelectionDAG &DAG) {
// promotion).
static SDValue combineToExtendCMOV(SDNode *Extend, SelectionDAG &DAG) {
SDValue CMovN = Extend->getOperand(0);
if (CMovN.getOpcode() != X86ISD::CMOV)
if (CMovN.getOpcode() != X86ISD::CMOV || !CMovN.hasOneUse())
return SDValue();
EVT TargetVT = Extend->getValueType(0);
@ -36039,20 +36039,35 @@ static SDValue combineToExtendCMOV(SDNode *Extend, SelectionDAG &DAG) {
SDValue CMovOp0 = CMovN.getOperand(0);
SDValue CMovOp1 = CMovN.getOperand(1);
bool DoPromoteCMOV =
(VT == MVT::i16 && (TargetVT == MVT::i32 || TargetVT == MVT::i64)) &&
CMovN.hasOneUse() &&
(isa<ConstantSDNode>(CMovOp0.getNode()) &&
isa<ConstantSDNode>(CMovOp1.getNode()));
if (!DoPromoteCMOV)
if (!isa<ConstantSDNode>(CMovOp0.getNode()) ||
!isa<ConstantSDNode>(CMovOp0.getNode()))
return SDValue();
CMovOp0 = DAG.getNode(ExtendOpcode, DL, TargetVT, CMovOp0);
CMovOp1 = DAG.getNode(ExtendOpcode, DL, TargetVT, CMovOp1);
// Only extend to i32 or i64.
if (TargetVT != MVT::i32 && TargetVT != MVT::i64)
return SDValue();
return DAG.getNode(X86ISD::CMOV, DL, TargetVT, CMovOp0, CMovOp1,
CMovN.getOperand(2), CMovN.getOperand(3));
// Only extend from i16.
if (VT != MVT::i16)
return SDValue();
// If this a zero extend to i64, we should only extend to i32 and use a free
// zero extend to finish.
EVT ExtendVT = TargetVT;
if (TargetVT == MVT::i64 && ExtendOpcode == ISD::ZERO_EXTEND)
ExtendVT = MVT::i32;
CMovOp0 = DAG.getNode(ExtendOpcode, DL, ExtendVT, CMovOp0);
CMovOp1 = DAG.getNode(ExtendOpcode, DL, ExtendVT, CMovOp1);
SDValue Res = DAG.getNode(X86ISD::CMOV, DL, ExtendVT, CMovOp0, CMovOp1,
CMovN.getOperand(2), CMovN.getOperand(3));
// Finish extending if needed.
if (ExtendVT != TargetVT)
Res = DAG.getNode(ISD::ZERO_EXTEND, DL, TargetVT, Res);
return Res;
}
// Convert (vXiY *ext(vXi1 bitcast(iX))) to extend_in_reg(broadcast(iX)).

2
llvm/test/CodeGen/X86/cmov-promotion.ll
View File

@ -115,7 +115,7 @@ define i64 @cmov_zpromotion_16_to_64(i1 %c) {
; CMOV-NEXT: testb $1, %dil
; CMOV-NEXT: movl $12414, %ecx # imm = 0x307E
; CMOV-NEXT: movl $65535, %eax # imm = 0xFFFF
; CMOV-NEXT: cmovneq %rcx, %rax
; CMOV-NEXT: cmovnel %ecx, %eax
; CMOV-NEXT: retq
;
; NO_CMOV-LABEL: cmov_zpromotion_16_to_64: