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| author | Shuxin Yang <shuxin.llvm@gmail.com> | 2013-03-25 22:52:29 +0000 |
|---|---|---|
| committer | Shuxin Yang <shuxin.llvm@gmail.com> | 2013-03-25 22:52:29 +0000 |
| commit | 1cd1d02141788b212e185d190b4c358e47cc74b4 (patch) | |
| tree | fa0982071c8d36376f6fa7a562c247805d826b60 /lib/CodeGen/SelectionDAG/DAGCombiner.cpp | |
| parent | 3800f5748ffdb55d8838eac9300d84276c3dd2c1 (diff) | |
| download | llvm-1cd1d02141788b212e185d190b4c358e47cc74b4.tar.gz llvm-1cd1d02141788b212e185d190b4c358e47cc74b4.tar.bz2 llvm-1cd1d02141788b212e185d190b4c358e47cc74b4.tar.xz | |
Disable some unsafe-fp-math DAG-combine transformation after legalization.
For instance, following transformation will be disabled:
x + x + x => 3.0f * x;
The problem of these transformations is that it introduces a FP constant, which
following Instruction-Selection pass cannot handle.
Reviewed by Nadav, thanks a lot!
rdar://13445387
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177933 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/CodeGen/SelectionDAG/DAGCombiner.cpp')
| -rw-r--r-- | lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 22 |
1 files changed, 17 insertions, 5 deletions
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 61603e18f5..b2f970b447 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -5835,14 +5835,25 @@ SDValue DAGCombiner::visitFADD(SDNode *N) { DAG.getNode(ISD::FADD, N->getDebugLoc(), VT, N0.getOperand(1), N1)); + // No FP constant should be created after legalization as Instruction + // Selection pass has hard time in dealing with FP constant. + // + // We don't need test this condition for transformation like following, as + // the DAG being transformed implies it is legal to take FP constant as + // operand. + // + // (fadd (fmul c, x), x) -> (fmul c+1, x) + // + bool AllowNewFpConst = (Level < AfterLegalizeDAG); + // If allow, fold (fadd (fneg x), x) -> 0.0 - if (DAG.getTarget().Options.UnsafeFPMath && + if (AllowNewFpConst && DAG.getTarget().Options.UnsafeFPMath && N0.getOpcode() == ISD::FNEG && N0.getOperand(0) == N1) { return DAG.getConstantFP(0.0, VT); } // If allow, fold (fadd x, (fneg x)) -> 0.0 - if (DAG.getTarget().Options.UnsafeFPMath && + if (AllowNewFpConst && DAG.getTarget().Options.UnsafeFPMath && N1.getOpcode() == ISD::FNEG && N1.getOperand(0) == N0) { return DAG.getConstantFP(0.0, VT); } @@ -5944,7 +5955,7 @@ SDValue DAGCombiner::visitFADD(SDNode *N) { } } - if (N0.getOpcode() == ISD::FADD) { + if (N0.getOpcode() == ISD::FADD && AllowNewFpConst) { ConstantFPSDNode *CFP = dyn_cast<ConstantFPSDNode>(N0.getOperand(0)); // (fadd (fadd x, x), x) -> (fmul 3.0, x) if (!CFP && N0.getOperand(0) == N0.getOperand(1) && @@ -5954,7 +5965,7 @@ SDValue DAGCombiner::visitFADD(SDNode *N) { } } - if (N1.getOpcode() == ISD::FADD) { + if (N1.getOpcode() == ISD::FADD && AllowNewFpConst) { ConstantFPSDNode *CFP10 = dyn_cast<ConstantFPSDNode>(N1.getOperand(0)); // (fadd x, (fadd x, x)) -> (fmul 3.0, x) if (!CFP10 && N1.getOperand(0) == N1.getOperand(1) && @@ -5965,7 +5976,8 @@ SDValue DAGCombiner::visitFADD(SDNode *N) { } // (fadd (fadd x, x), (fadd x, x)) -> (fmul 4.0, x) - if (N0.getOpcode() == ISD::FADD && N1.getOpcode() == ISD::FADD && + if (AllowNewFpConst && + N0.getOpcode() == ISD::FADD && N1.getOpcode() == ISD::FADD && N0.getOperand(0) == N0.getOperand(1) && N1.getOperand(0) == N1.getOperand(1) && N0.getOperand(0) == N1.getOperand(0)) { |