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Introduce a 'nonnull' metadata on Load instructions.

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The newly introduced 'nonnull' metadata is analogous to existing 'nonnull' attributes, but applies to load instructions rather than call arguments or returns.  Long term, it would be nice to combine these into a single construct.   The value of the load is allowed to vary between successive loads, but null is not a valid value to be loaded by any load marked nonnull.

Reviewed by: Hal Finkel
Differential Revision:  http://reviews.llvm.org/D5220




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220240 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Philip Reames
2014-10-20 22:40:55 +00:00
parent 0d1978b813
commit 90f3f15da5
3 changed files with 36 additions and 1 deletions
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4
lib/Analysis/ValueTracking.cpp
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@ -2622,6 +2622,10 @@ bool llvm::isKnownNonNull(const Value *V, const TargetLibraryInfo *TLI) {
if (const GlobalValue *GV = dyn_cast<GlobalValue>(V))
return !GV->hasExternalWeakLinkage();
// A Load tagged w/nonnull metadata is never null.
if (const LoadInst *LI = dyn_cast<LoadInst>(V))
return LI->getMetadata("nonnull");
if (ImmutableCallSite CS = V)
if (CS.isReturnNonNull())
return true;