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[X86] Add X86ISD::CMOV to computeKnownBitsForTargetNode and ComputeNumSignBitsForTargetNode. 

Summary: Implementations based on ISD::SELECT.

Reviewers: RKSimon, spatel

Reviewed By: RKSimon

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D38663

llvm-svn: 315153
This commit is contained in:
Craig Topper 2017-10-07 16:51:19 +00:00
parent 865e6c852b
commit 2f60295364
3 changed files with 22 additions and 5 deletions
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20
llvm/lib/Target/X86/X86ISelLowering.cpp
View File

@ -27165,6 +27165,19 @@ void X86TargetLowering::computeKnownBitsForTargetNode(const SDValue Op,
Known.Zero.setBitsFrom(InBitWidth);
break;
}
case X86ISD::CMOV: {
DAG.computeKnownBits(Op.getOperand(1), Known, Depth+1);
// If we don't know any bits, early out.
if (Known.isUnknown())
break;
KnownBits Known2;
DAG.computeKnownBits(Op.getOperand(0), Known2, Depth+1);
// Only known if known in both the LHS and RHS.
Known.One &= Known2.One;
Known.Zero &= Known2.Zero;
break;
}
}
}
@ -27227,6 +27240,13 @@ unsigned X86TargetLowering::ComputeNumSignBitsForTargetNode(
case X86ISD::VPCOMU:
// Vector compares return zero/all-bits result values.
return VTBits;
case X86ISD::CMOV: {
unsigned Tmp0 = DAG.ComputeNumSignBits(Op.getOperand(0), Depth+1);
if (Tmp0 == 1) return 1; // Early out.
unsigned Tmp1 = DAG.ComputeNumSignBits(Op.getOperand(1), Depth+1);
return std::min(Tmp0, Tmp1);
}
}
// Fallback case.

6
llvm/test/CodeGen/X86/cmovcmov.ll
View File

@ -53,8 +53,7 @@ entry:
; NOCMOV-NEXT: leal 12(%esp), %ecx
; NOCMOV-NEXT: [[TBB]]:
; NOCMOV-NEXT: movl (%ecx), %eax
; NOCMOV-NEXT: orl $4, %ecx
; NOCMOV-NEXT: movl (%ecx), %edx
; NOCMOV-NEXT: movl 4(%ecx), %edx
; NOCMOV-NEXT: retl
define i64 @test_select_fcmp_oeq_i64(float %a, float %b, i64 %c, i64 %d) #0 {
entry:
@ -82,8 +81,7 @@ entry:
; NOCMOV-NEXT: leal 20(%esp), %ecx
; NOCMOV-NEXT: [[TBB]]:
; NOCMOV-NEXT: movl (%ecx), %eax
; NOCMOV-NEXT: orl $4, %ecx
; NOCMOV-NEXT: movl (%ecx), %edx
; NOCMOV-NEXT: movl 4(%ecx), %edx
; NOCMOV-NEXT: retl
define i64 @test_select_fcmp_une_i64(float %a, float %b, i64 %c, i64 %d) #0 {
entry:

1
llvm/test/CodeGen/X86/pr32282.ll
View File

@ -28,7 +28,6 @@ define void @foo() {
; X86-NEXT: cmovnel %ecx, %edx
; X86-NEXT: cmovnel %eax, %ecx
; X86-NEXT: andl $-2, %edx
; X86-NEXT: andl $2147483647, %ecx # imm = 0x7FFFFFFF
; X86-NEXT: addl $7, %edx
; X86-NEXT: adcxl %eax, %ecx
; X86-NEXT: pushl %ecx