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Allow isDereferenceablePointer to look through some bitcasts

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isDereferenceablePointer should not give up upon encountering any bitcast. If
we're casting from a pointer to a larger type to a pointer to a small type, we
can continue by examining the bitcast's operand. This missing capability
was noted in a comment in the function.

In order for this to work, isDereferenceablePointer now takes an optional
DataLayout pointer (essentially all callers already had such a pointer
available). Most code uses isDereferenceablePointer though
isSafeToSpeculativelyExecute (which already took an optional DataLayout
pointer), and to enable the LICM test case, LICM needs to actually provide its DL
pointer to isSafeToSpeculativelyExecute (which it was not doing previously).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212686 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Hal Finkel
2014-07-10 05:27:53 +00:00
parent 344517923c
commit a739834446
8 changed files with 202 additions and 21 deletions
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6
lib/Transforms/Scalar/SROA.cpp
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@@ -1130,7 +1130,7 @@ static bool isSafePHIToSpeculate(PHINode &PN,
// If this pointer is always safe to load, or if we can prove that there
// is already a load in the block, then we can move the load to the pred
// block.
if (InVal->isDereferenceablePointer() ||
if (InVal->isDereferenceablePointer(DL) ||
isSafeToLoadUnconditionally(InVal, TI, MaxAlign, DL))
continue;
@@ -1198,8 +1198,8 @@ static bool isSafeSelectToSpeculate(SelectInst &SI,
const DataLayout *DL = nullptr) {
Value *TValue = SI.getTrueValue();
Value *FValue = SI.getFalseValue();
bool TDerefable = TValue->isDereferenceablePointer();
bool FDerefable = FValue->isDereferenceablePointer();
bool TDerefable = TValue->isDereferenceablePointer(DL);
bool FDerefable = FValue->isDereferenceablePointer(DL);
for (User *U : SI.users()) {
LoadInst *LI = dyn_cast<LoadInst>(U);