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| author | Benjamin Kramer <benny.kra@googlemail.com> | 2013-09-19 13:28:20 +0000 |
|---|---|---|
| committer | Benjamin Kramer <benny.kra@googlemail.com> | 2013-09-19 13:28:20 +0000 |
| commit | d443e4a080ae07b3cf2dcf2c59cf756111b721ec (patch) | |
| tree | 71bdde6e7323933d17c68825eac2b4d65891915b /llvm/lib/CodeGen/SelectionDAG | |
| parent | 58078d0103fa9cab73f5a3b79dbb97c9f92a097e (diff) | |
| download | bcm5719-llvm-d443e4a080ae07b3cf2dcf2c59cf756111b721ec.tar.gz bcm5719-llvm-d443e4a080ae07b3cf2dcf2c59cf756111b721ec.zip | |
DAGCombiner: Don't fold vector muls with constants that look like a splat of a power of 2 but differ in bit width.
PR17283.
llvm-svn: 191000
Diffstat (limited to 'llvm/lib/CodeGen/SelectionDAG')
| -rw-r--r-- | llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 67f3f0643e4..0eecd39d247 100644 --- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -1824,20 +1824,24 @@ SDValue DAGCombiner::visitMUL(SDNode *N) { // fold (mul x, 0) -> 0 if (N1IsConst && ConstValue1 == 0) return N1; + // We require a splat of the entire scalar bit width for non-contiguous + // bit patterns. + bool IsFullSplat = + ConstValue1.getBitWidth() == VT.getScalarType().getSizeInBits(); // fold (mul x, 1) -> x - if (N1IsConst && ConstValue1 == 1) + if (N1IsConst && ConstValue1 == 1 && IsFullSplat) return N0; // fold (mul x, -1) -> 0-x if (N1IsConst && ConstValue1.isAllOnesValue()) return DAG.getNode(ISD::SUB, SDLoc(N), VT, DAG.getConstant(0, VT), N0); // fold (mul x, (1 << c)) -> x << c - if (N1IsConst && ConstValue1.isPowerOf2()) + if (N1IsConst && ConstValue1.isPowerOf2() && IsFullSplat) return DAG.getNode(ISD::SHL, SDLoc(N), VT, N0, DAG.getConstant(ConstValue1.logBase2(), getShiftAmountTy(N0.getValueType()))); // fold (mul x, -(1 << c)) -> -(x << c) or (-x) << c - if (N1IsConst && (-ConstValue1).isPowerOf2()) { + if (N1IsConst && (-ConstValue1).isPowerOf2() && IsFullSplat) { unsigned Log2Val = (-ConstValue1).logBase2(); // FIXME: If the input is something that is easily negated (e.g. a // single-use add), we should put the negate there. |
