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[X86] Don't use BZHI for short masks (>=32 bits). Thanks to Ben Kramer for the

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review.

llvm-svn: 206869
This commit is contained in:
Lang Hames 2014-04-22 07:40:34 +00:00
parent eb8b511a12
commit c6b233b58f
2 changed files with 14 additions and 13 deletions
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8
lib/Target/X86/X86ISelLowering.cpp
View File

@ -18507,13 +18507,15 @@ static SDValue PerformAndCombine(SDNode *N, SelectionDAG &DAG,
// Check for BZHI with contiguous mask: (and X, 0x0..0f..f)
// This should be checked after BEXTR - when X is a shift, a BEXTR is
// preferrable.
if (Subtarget->hasBMI2()) {
if (VT == MVT::i64 && Subtarget->hasBMI2()) {
if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(N1)) {
uint64_t Mask = C->getZExtValue();
if (isMask_64(Mask)) {
unsigned LZ = CountTrailingOnes_64(Mask);
return DAG.getNode(X86ISD::BZHI, DL, VT, N0,
DAG.getConstant(LZ, MVT::i8));
// Only use BZHI for immediates that are too large for an AND:
if (LZ > 32)
return DAG.getNode(X86ISD::BZHI, DL, VT, N0,
DAG.getConstant(LZ, MVT::i8));
}
}
}

19
test/CodeGen/X86/bmi.ll
View File

@ -216,22 +216,21 @@ entry:
; CHECK: bzhiq
}
define i32 @bzhi32_constant_mask(i32 %x) #0 {
entry:
%and = and i32 %x, 1073741823
ret i32 %and
; CHECK-LABEL: bzhi32_constant_mask:
; CHECK: movb $30, %al
; CHECK: bzhil %eax, %e[[ARG1:di|cx]], %eax
}
define i64 @bzhi64_constant_mask(i64 %x) #0 {
entry:
%and = and i64 %x, 4611686018427387903
ret i64 %and
; CHECK-LABEL: bzhi64_constant_mask:
; CHECK: movb $62, %al
; CHECK: bzhiq %rax, %r[[ARG1]], %rax
; CHECK: bzhiq %rax, %r[[ARG1:di|cx]], %rax
}
define i64 @bzhi64_small_constant_mask(i64 %x) #0 {
entry:
%and = and i64 %x, 2147483647
ret i64 %and
; CHECK-LABEL: bzhi64_small_constant_mask:
; CHECK: andq $2147483647, %r[[ARG1]]
}
define i32 @blsi32(i32 %x) nounwind readnone {