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| author | Christopher Lamb <christopher.lamb@gmail.com> | 2008-03-19 08:30:06 +0000 |
|---|---|---|
| committer | Christopher Lamb <christopher.lamb@gmail.com> | 2008-03-19 08:30:06 +0000 |
| commit | fc5c164b753c9ca42901514c645c70e5b61c5c11 (patch) | |
| tree | 323a51a31cb8a7c4e37df464dd13c8708c085f7b /lib/CodeGen/SelectionDAG | |
| parent | 9792837e758478bbdc7e1df3d1f1d304eee59011 (diff) | |
| download | external_llvm-fc5c164b753c9ca42901514c645c70e5b61c5c11.zip external_llvm-fc5c164b753c9ca42901514c645c70e5b61c5c11.tar.gz external_llvm-fc5c164b753c9ca42901514c645c70e5b61c5c11.tar.bz2 | |
Fix X86's isTruncateFree to not claim that truncate to i1 is free. This fixes Bill's testcase that failed for r48491.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48542 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/CodeGen/SelectionDAG')
| -rw-r--r-- | lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index acc00fd..f33946c 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -2383,6 +2383,31 @@ SDOperand DAGCombiner::visitSRA(SDNode *N) { DAG.getConstant(Sum, N1C->getValueType(0))); } } + + // fold sra (shl X, m), result_size - n + // -> (sign_extend (trunc (shl X, result_size - n - m))) for + // result_size - n != m. If truncate is free for the target sext(shl) is + // likely to result in better code. + if (N0.getOpcode() == ISD::SHL) { + // Get the two constanst of the shifts, CN0 = m, CN = n. + const ConstantSDNode *N01C = dyn_cast<ConstantSDNode>(N0.getOperand(1)); + if (N01C && N1C) { + // Determine if the truncate type's bitsize would correspond to + // an integer type for this target. + unsigned VTValSize = MVT::getSizeInBits(VT); + MVT::ValueType TruncVT = MVT::getIntegerType(VTValSize - N1C->getValue()); + unsigned ShiftAmt = N1C->getValue() - N01C->getValue(); + + // If the shift wouldn't be a noop, the truncated type is an actual type, + // and the truncate is free, then proceed with the transform. + if (ShiftAmt != 0 && TLI.isTruncateFree(VT, TruncVT)) { + SDOperand Amt = DAG.getConstant(ShiftAmt, TLI.getShiftAmountTy()); + SDOperand Shift = DAG.getNode(ISD::SRL, VT, N0.getOperand(0), Amt); + SDOperand Trunc = DAG.getNode(ISD::TRUNCATE, TruncVT, Shift); + return DAG.getNode(ISD::SIGN_EXTEND, N->getValueType(0), Trunc); + } + } + } // Simplify, based on bits shifted out of the LHS. if (N1C && SimplifyDemandedBits(SDOperand(N, 0))) |