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author | Duncan Sands <baldrick@free.fr> | 2012-02-24 15:16:31 +0000 |
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committer | Duncan Sands <baldrick@free.fr> | 2012-02-24 15:16:31 +0000 |
commit | e170c76ccdcf9b0343d2d5a2805010ff77b8b56e (patch) | |
tree | 2129356bb19d6704ae20679b6680c6f95ed6a942 /lib/Transforms/Scalar/GVN.cpp | |
parent | 8b93ff298cbaa8a16f950374e1be1f7e5114da8f (diff) | |
download | llvm-e170c76ccdcf9b0343d2d5a2805010ff77b8b56e.tar.gz llvm-e170c76ccdcf9b0343d2d5a2805010ff77b8b56e.tar.bz2 llvm-e170c76ccdcf9b0343d2d5a2805010ff77b8b56e.tar.xz |
Teach GVN that x+y is the same as y+x and that x<y is the same as y>x.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151365 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Transforms/Scalar/GVN.cpp')
-rw-r--r-- | lib/Transforms/Scalar/GVN.cpp | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp index 5b95f5b86f..162ee2b5ce 100644 --- a/lib/Transforms/Scalar/GVN.cpp +++ b/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<CmpInst>(I)) { - e.opcode = (C->getOpcode() << 8) | C->getPredicate(); + // Sort the operand value numbers so x<y and y>x 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<InsertValueInst>(I)) { for (InsertValueInst::idx_iterator II = E->idx_begin(), IE = E->idx_end(); II != IE; ++II) |