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Give the Reassociate pass a bit more flexibility and autonomy when optimizing expressions.

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Particularly, it addresses cases where Reassociate breaks Subtracts but then fails to optimize combinations like I1 + -I2 where I1 and I2 have the same rank and are identical.

Patch by Dmitri Shtilman.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219092 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson
2014-10-05 23:41:26 +00:00
parent 1d02acb7a0
commit eb2be34094
2 changed files with 27 additions and 2 deletions
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14
lib/Transforms/Scalar/Reassociate.cpp
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@ -1034,13 +1034,23 @@ static unsigned FindInOperandList(SmallVectorImpl<ValueEntry> &Ops, unsigned i,
Value *X) {
unsigned XRank = Ops[i].Rank;
unsigned e = Ops.size();
for (unsigned j = i+1; j != e && Ops[j].Rank == XRank; ++j)
for (unsigned j = i+1; j != e && Ops[j].Rank == XRank; ++j) {
if (Ops[j].Op == X)
return j;
if (Instruction *I1 = dyn_cast<Instruction>(Ops[j].Op))
if (Instruction *I2 = dyn_cast<Instruction>(X))
if (I1->isIdenticalTo(I2))
return j;
}
// Scan backwards.
for (unsigned j = i-1; j != ~0U && Ops[j].Rank == XRank; --j)
for (unsigned j = i-1; j != ~0U && Ops[j].Rank == XRank; --j) {
if (Ops[j].Op == X)
return j;
if (Instruction *I1 = dyn_cast<Instruction>(Ops[j].Op))
if (Instruction *I2 = dyn_cast<Instruction>(X))
if (I1->isIdenticalTo(I2))
return j;
}
return i;
}