forked from OSchip/llvm-project
Fix a fixme: allow memdep to see past read-only calls when doing
load dependence queries. This allows GVN to eliminate a few more instructions on 403.gcc: 152598 gvn - Number of instructions deleted 49240 gvn - Number of loads deleted after: 153986 gvn - Number of instructions deleted 50069 gvn - Number of loads deleted llvm-svn: 60786
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@ -213,11 +213,20 @@ getPointerDependencyFrom(Value *MemPtr, uint64_t MemSize, bool isLoad,
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// See if this instruction (e.g. a call or vaarg) mod/ref's the pointer.
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// See if this instruction (e.g. a call or vaarg) mod/ref's the pointer.
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// FIXME: If this is a load, we should ignore readonly calls!
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// FIXME: If this is a load, we should ignore readonly calls!
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if (AA->getModRefInfo(Inst, MemPtr, MemSize) == AliasAnalysis::NoModRef)
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switch (AA->getModRefInfo(Inst, MemPtr, MemSize)) {
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case AliasAnalysis::NoModRef:
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// If the call has no effect on the queried pointer, just ignore it.
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continue;
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continue;
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case AliasAnalysis::Ref:
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// Otherwise, there is a dependence.
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// If the call is known to never store to the pointer, and if this is a
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return MemDepResult::getClobber(Inst);
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// load query, we can safely ignore it (scan past it).
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if (isLoad)
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continue;
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// FALL THROUGH.
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default:
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// Otherwise, there is a potential dependence. Return a clobber.
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return MemDepResult::getClobber(Inst);
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}
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}
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}
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// No dependence found. If this is the entry block of the function, it is a
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// No dependence found. If this is the entry block of the function, it is a
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