From 926d101640f128a0bd32be2039c795d4b3b2fb96 Mon Sep 17 00:00:00 2001 From: Duncan Sands Date: Fri, 24 Feb 2012 15:16:31 +0000 Subject: Teach GVN that x+y is the same as y+x and that xx. llvm-svn: 151365 --- llvm/lib/Transforms/Scalar/GVN.cpp | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) (limited to 'llvm/lib/Transforms/Scalar/GVN.cpp') diff --git a/llvm/lib/Transforms/Scalar/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp index 5b95f5b86fb..162ee2b5cea 100644 --- a/llvm/lib/Transforms/Scalar/GVN.cpp +++ b/llvm/lib/Transforms/Scalar/GVN.cpp @@ -154,9 +154,24 @@ Expression ValueTable::create_expression(Instruction *I) { for (Instruction::op_iterator OI = I->op_begin(), OE = I->op_end(); OI != OE; ++OI) e.varargs.push_back(lookup_or_add(*OI)); + if (I->isCommutative()) { + // Ensure that commutative instructions that only differ by a permutation + // of their operands get the same value number by sorting the operand value + // numbers. Since all commutative instructions have two operands it is more + // efficient to sort by hand rather than using, say, std::sort. + assert(I->getNumOperands() == 2 && "Unsupported commutative instruction!"); + if (e.varargs[0] > e.varargs[1]) + std::swap(e.varargs[0], e.varargs[1]); + } if (CmpInst *C = dyn_cast(I)) { - e.opcode = (C->getOpcode() << 8) | C->getPredicate(); + // Sort the operand value numbers so xx get the same value number. + CmpInst::Predicate Predicate = C->getPredicate(); + if (e.varargs[0] > e.varargs[1]) { + std::swap(e.varargs[0], e.varargs[1]); + Predicate = CmpInst::getSwappedPredicate(Predicate); + } + e.opcode = (C->getOpcode() << 8) | Predicate; } else if (InsertValueInst *E = dyn_cast(I)) { for (InsertValueInst::idx_iterator II = E->idx_begin(), IE = E->idx_end(); II != IE; ++II) -- cgit v1.2.3