diff options
Diffstat (limited to 'llvm/lib')
| -rw-r--r-- | llvm/lib/Transforms/Scalar/NewGVN.cpp | 17 |
1 files changed, 9 insertions, 8 deletions
diff --git a/llvm/lib/Transforms/Scalar/NewGVN.cpp b/llvm/lib/Transforms/Scalar/NewGVN.cpp index 6f147d74bbd..8989d5cc2cc 100644 --- a/llvm/lib/Transforms/Scalar/NewGVN.cpp +++ b/llvm/lib/Transforms/Scalar/NewGVN.cpp @@ -2402,16 +2402,19 @@ bool NewGVN::eliminateInstructions(Function &F) { // we will simplify an operation with all constants so that it doesn't matter // what order they appear in. unsigned int NewGVN::getRank(const Value *V) const { - if (isa<Constant>(V)) + // Prefer undef to anything else + if (isa<UndefValue>(V)) return 0; + if (isa<Constant>(V)) + return 1; else if (auto *A = dyn_cast<Argument>(V)) - return 1 + A->getArgNo(); + return 2 + A->getArgNo(); - // Need to shift the instruction DFS by number of arguments + 2 to account for + // Need to shift the instruction DFS by number of arguments + 3 to account for // the constant and argument ranking above. unsigned Result = InstrDFS.lookup(V); if (Result > 0) - return 2 + NumFuncArgs + Result; + return 3 + NumFuncArgs + Result; // Unreachable or something else, just return a really large number. return ~0; } @@ -2421,8 +2424,6 @@ unsigned int NewGVN::getRank(const Value *V) const { bool NewGVN::shouldSwapOperands(const Value *A, const Value *B) const { // Because we only care about a total ordering, and don't rewrite expressions // in this order, we order by rank, which will give a strict weak ordering to - // everything but constants, and then we order by pointer address. This is - // not deterministic for constants, but it should not matter because any - // operation with only constants will be folded (except, usually, for undef). - return std::make_pair(getRank(B), B) > std::make_pair(getRank(A), A); + // everything but constants, and then we order by pointer address. + return std::make_pair(getRank(A), A) > std::make_pair(getRank(B), B); } |
