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authorJoel Jones <joel_k_jones@apple.com>2012-04-17 22:23:10 +0000
committerJoel Jones <joel_k_jones@apple.com>2012-04-17 22:23:10 +0000
commitd16ce17711e8e6231363fe1fd47800570b75d61d (patch)
tree64a54a49018988155fc54b5e3bb29515d427310f /lib/CodeGen
parent3f5966b85ea572002bfd0bb2f7c371ed087ae260 (diff)
Fixes a problem in instruction selection with testing whether or not the
transformation: (X op C1) ^ C2 --> (X op C1) & ~C2 iff (C1&C2) == C2 should be done. This change has been tested: Using a debug+asserts build: on the specific test case that brought this bug to light make check-all lnt nt using this clang to build a release version of clang Using the release+asserts clang-with-clang build: on the specific test case that brought this bug to light make check-all lnt nt Checking in because Evan wants it checked in. Test case forthcoming after scrubbing. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154955 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/CodeGen')
-rw-r--r--lib/CodeGen/SelectionDAG/TargetLowering.cpp5
1 files changed, 3 insertions, 2 deletions
diff --git a/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 09a2b1f3d7..e341e15e41 100644
--- a/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -1367,8 +1367,9 @@ bool TargetLowering::SimplifyDemandedBits(SDValue Op,
// bits on that side are also known to be set on the other side, turn this
// into an AND, as we know the bits will be cleared.
// e.g. (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
- if ((NewMask & (KnownZero|KnownOne)) == NewMask) { // all known
- if ((KnownOne & KnownOne2) == KnownOne) {
+ // NB: it is okay if more bits are known than are requested
+ if ((NewMask & (KnownZero|KnownOne)) == NewMask) { // all known on one side
+ if (KnownOne == KnownOne2) { // set bits are the same on both sides
EVT VT = Op.getValueType();
SDValue ANDC = TLO.DAG.getConstant(~KnownOne & NewMask, VT);
return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::AND, dl, VT,