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authorLang Hames <lhames@gmail.com>2014-04-21 08:18:53 +0000
committerLang Hames <lhames@gmail.com>2014-04-21 08:18:53 +0000
commitf69bb5e43c1427d23800e4e678a7c2f2088f0c88 (patch)
treed0ff7069c0da0d27b4acfaf87c300004cb00711d /lib
parenta21cd0433e7cde887b061ecac08c0de9f1cb8cb9 (diff)
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[X86] ISEL (and X, <constant mask>) to BZHI when BMI2 is available.
Generating BZHI in the variable mask case, i.e. (and X, (sub (shl 1, N), 1)), was already supported, but we were missing the constant-mask case. This patch fixes that. <rdar://problem/15480077> git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206738 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib')
-rw-r--r--lib/Target/X86/X86ISelLowering.cpp14
1 files changed, 14 insertions, 0 deletions
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 306fb7e199..d867414a98 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -18503,6 +18503,20 @@ static SDValue PerformAndCombine(SDNode *N, SelectionDAG &DAG,
}
} // BEXTR
+ // 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 (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));
+ }
+ }
+ }
+
return SDValue();
}