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Fix bug in gather/scatter optimization passes.

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When flattening chains of insertelement instructions, we didn't
handle the case where the initial insertelement was to a constant
vector (with one value set and the other values undef).

Also generalized the "do all of the instances access the same location"
check to handle the case where some of them are accessing undef
locations; these are ignored in this check, as they should correspond to the
mask being off for that lane anyway.

Fixes issue #149.
This commit is contained in:
Matt Pharr
2012-01-06 09:19:18 -08:00
parent 1abaaee73e
commit 71317e6aa6
1 changed files with 26 additions and 10 deletions
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36
opt.cpp
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@@ -957,8 +957,16 @@ lFlattenInsertChain(llvm::InsertElementInst *ie, int vectorWidth,
llvm::Value *insertBase = ie->getOperand(0);
ie = llvm::dyn_cast<llvm::InsertElementInst>(insertBase);
if (ie == NULL)
Assert(llvm::isa<llvm::UndefValue>(insertBase));
if (ie == NULL) {
if (llvm::isa<llvm::UndefValue>(insertBase))
return;
llvm::ConstantVector *cv =
llvm::dyn_cast<llvm::ConstantVector>(insertBase);
Assert(cv != NULL);
Assert(iOffset < (int)cv->getNumOperands());
elements[iOffset] = cv->getOperand(iOffset);
}
}
}
@@ -1884,19 +1892,27 @@ lVectorValuesAllEqual(llvm::Value *v, int vectorLength,
llvm::Value *elements[ISPC_MAX_NVEC];
lFlattenInsertChain(ie, vectorLength, elements);
for (int i = 0; i < vectorLength-1; ++i) {
// TODO: It's not clear what to do in this case (which
// corresponds to elements of the vector being undef). It is
// probably to just ignore undef elements and return true if
// all of the other ones are equal, but it'd be nice to have
// some test cases to verify this.
Assert(elements[i] != NULL && elements[i+1] != NULL);
// We will ignore any values of elements[] that are NULL; as they
// correspond to undefined values--we just want to see if all of
// the defined values have the same value.
int lastNonNull = 0;
while (lastNonNull < vectorLength && elements[lastNonNull] == NULL)
++lastNonNull;
if (lastNonNull == vectorLength)
// all of them are undef!
return true;
for (int i = lastNonNull; i < vectorLength; ++i) {
if (elements[i] == NULL)
continue;
std::vector<llvm::PHINode *> seenPhi0;
std::vector<llvm::PHINode *> seenPhi1;
if (lValuesAreEqual(elements[i], elements[i+1], seenPhi0,
if (lValuesAreEqual(elements[lastNonNull], elements[i], seenPhi0,
seenPhi1) == false)
return false;
lastNonNull = i;
}
return true;
}