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Don't attempt load PRE when there is no real redundancy (i.e., the load is in

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a loop and is itself the only dependency).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97526 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bob Wilson 2010-03-02 00:09:29 +00:00
parent 6b30792d2d
commit 3bd19d753b
1 changed files with 6 additions and 4 deletions
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8
lib/Transforms/Scalar/GVN.cpp
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@ -1542,12 +1542,14 @@ bool GVN::processNonLocalLoad(LoadInst *LI,
// at least one of the values is LI. Since this means that we won't be able
// to eliminate LI even if we insert uses in the other predecessors, we will
// end up increasing code size. Reject this by scanning for LI.
if (!EnableFullLoadPRE) {
for (unsigned i = 0, e = ValuesPerBlock.size(); i != e; ++i)
for (unsigned i = 0, e = ValuesPerBlock.size(); i != e; ++i) {
if (ValuesPerBlock[i].isSimpleValue() &&
ValuesPerBlock[i].getSimpleValue() == LI)
ValuesPerBlock[i].getSimpleValue() == LI) {
// Skip cases where LI is the only definition, even for EnableFullLoadPRE.
if (!EnableFullLoadPRE || e == 1)
return false;
}
}
// FIXME: It is extremely unclear what this loop is doing, other than
// artificially restricting loadpre.