diff options
Diffstat (limited to 'lib/Transforms/Scalar/GVN.cpp')
-rw-r--r-- | lib/Transforms/Scalar/GVN.cpp | 18 |
1 files changed, 12 insertions, 6 deletions
diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp index 915871e..09aff1b 100644 --- a/lib/Transforms/Scalar/GVN.cpp +++ b/lib/Transforms/Scalar/GVN.cpp @@ -557,12 +557,12 @@ namespace { } /// removeFromLeaderTable - Scan the list of values corresponding to a given - /// value number, and remove the given value if encountered. - void removeFromLeaderTable(uint32_t N, Value *V, BasicBlock *BB) { + /// value number, and remove the given instruction if encountered. + void removeFromLeaderTable(uint32_t N, Instruction *I, BasicBlock *BB) { LeaderTableEntry* Prev = 0; LeaderTableEntry* Curr = &LeaderTable[N]; - while (Curr->Val != V || Curr->BB != BB) { + while (Curr->Val != I || Curr->BB != BB) { Prev = Curr; Curr = Curr->Next; } @@ -2021,9 +2021,15 @@ bool GVN::propagateEquality(Value *LHS, Value *RHS, BasicBlock *Root) { DT->properlyDominates(cast<Instruction>(RHS)->getParent(), Root)) && "Instruction doesn't dominate scope!"); - // If value numbering later deduces that an instruction in the scope is equal - // to 'LHS' then ensure it will be turned into 'RHS'. - addToLeaderTable(LVN, RHS, Root); + // If value numbering later sees that an instruction in the scope is equal + // to 'LHS' then ensure it will be turned into 'RHS'. In order to preserve + // the invariant that instructions only occur in the leader table for their + // own value number (this is used by removeFromLeaderTable), do not do this + // if RHS is an instruction (if an instruction in the scope is morphed into + // LHS then it will be turned into RHS by the next GVN iteration anyway, so + // using the leader table is about compiling faster, not optimizing better). + if (!isa<Instruction>(RHS)) + addToLeaderTable(LVN, RHS, Root); // Replace all occurrences of 'LHS' with 'RHS' everywhere in the scope. As // LHS always has at least one use that is not dominated by Root, this will |