diff options
Diffstat (limited to 'llvm/lib/Transforms/InstCombine/InstructionCombining.cpp')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstructionCombining.cpp | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp index 4cc81b9e50f..230a429a7b3 100644 --- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp +++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp @@ -1415,6 +1415,30 @@ Instruction *InstCombiner::foldVectorBinop(BinaryOperator &Inst) { return createBinOpShuffle(V1, V2, Mask); } + // If both arguments of a commutative binop are select-shuffles that use the + // same mask with commuted operands, the shuffles are unnecessary. + if (Inst.isCommutative() && + match(LHS, m_ShuffleVector(m_Value(V1), m_Value(V2), m_Constant(Mask))) && + match(RHS, m_ShuffleVector(m_Specific(V2), m_Specific(V1), + m_Specific(Mask)))) { + auto *LShuf = cast<ShuffleVectorInst>(LHS); + auto *RShuf = cast<ShuffleVectorInst>(RHS); + // TODO: Allow shuffles that contain undefs in the mask? + // That is legal, but it reduces undef knowledge. + // TODO: Allow arbitrary shuffles by shuffling after binop? + // That might be legal, but we have to deal with poison. + if (LShuf->isSelect() && !LShuf->getMask()->containsUndefElement() && + RShuf->isSelect() && !RShuf->getMask()->containsUndefElement()) { + // Example: + // LHS = shuffle V1, V2, <0, 5, 6, 3> + // RHS = shuffle V2, V1, <0, 5, 6, 3> + // LHS + RHS --> (V10+V20, V21+V11, V22+V12, V13+V23) --> V1 + V2 + Instruction *NewBO = BinaryOperator::Create(Opcode, V1, V2); + NewBO->copyIRFlags(&Inst); + return NewBO; + } + } + // If one argument is a shuffle within one vector and the other is a constant, // try moving the shuffle after the binary operation. This canonicalization // intends to move shuffles closer to other shuffles and binops closer to |
