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[MemDep] Use BatchAA when computing pointer dependencies 

We're not changing IR while running a single MemDep query, so it's
safe to cache alias analysis results using BatchAA. This adds BatchAA
usage to getSimplePointerDependencyFrom(), which is non-intrusive --
covering larger parts (like a whole processNonLocalLoad query) is
also possible, but requires threading BatchAA through a bunch of APIs.

For the ThinLTO configuration, this is a 1% geomean improvement on CTMark.

Differential Revision: https://reviews.llvm.org/D85583
This commit is contained in:
Nikita Popov 2020-06-25 21:35:41 +02:00
parent 84fdc33f47
commit 3a54b6a4b7
1 changed files with 10 additions and 7 deletions
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17
llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
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@ -362,6 +362,8 @@ MemoryDependenceResults::getInvariantGroupPointerDependency(LoadInst *LI,
MemDepResult MemoryDependenceResults::getSimplePointerDependencyFrom(
const MemoryLocation &MemLoc, bool isLoad, BasicBlock::iterator ScanIt,
BasicBlock *BB, Instruction *QueryInst, unsigned *Limit) {
// We can batch AA queries, because IR does not change during a MemDep query.
BatchAAResults BatchAA(AA);
bool isInvariantLoad = false;
unsigned DefaultLimit = getDefaultBlockScanLimit();
@ -445,7 +447,7 @@ MemDepResult MemoryDependenceResults::getSimplePointerDependencyFrom(
// pointer, not on query pointers that are indexed off of them. It'd
// be nice to handle that at some point (the right approach is to use
// GetPointerBaseWithConstantOffset).
if (AA.isMustAlias(MemoryLocation(II->getArgOperand(1)), MemLoc))
if (BatchAA.isMustAlias(MemoryLocation(II->getArgOperand(1)), MemLoc))
return MemDepResult::getDef(II);
continue;
}
@ -485,7 +487,7 @@ MemDepResult MemoryDependenceResults::getSimplePointerDependencyFrom(
MemoryLocation LoadLoc = MemoryLocation::get(LI);
// If we found a pointer, check if it could be the same as our pointer.
AliasResult R = AA.alias(LoadLoc, MemLoc);
AliasResult R = BatchAA.alias(LoadLoc, MemLoc);
if (isLoad) {
if (R == NoAlias)
@ -516,7 +518,7 @@ MemDepResult MemoryDependenceResults::getSimplePointerDependencyFrom(
continue;
// Stores don't alias loads from read-only memory.
if (AA.pointsToConstantMemory(LoadLoc))
if (BatchAA.pointsToConstantMemory(LoadLoc))
continue;
// Stores depend on may/must aliased loads.
@ -547,7 +549,7 @@ MemDepResult MemoryDependenceResults::getSimplePointerDependencyFrom(
// If alias analysis can tell that this store is guaranteed to not modify
// the query pointer, ignore it. Use getModRefInfo to handle cases where
// the query pointer points to constant memory etc.
if (!isModOrRefSet(AA.getModRefInfo(SI, MemLoc)))
if (!isModOrRefSet(BatchAA.getModRefInfo(SI, MemLoc)))
continue;
// Ok, this store might clobber the query pointer. Check to see if it is
@ -556,7 +558,7 @@ MemDepResult MemoryDependenceResults::getSimplePointerDependencyFrom(
MemoryLocation StoreLoc = MemoryLocation::get(SI);
// If we found a pointer, check if it could be the same as our pointer.
AliasResult R = AA.alias(StoreLoc, MemLoc);
AliasResult R = BatchAA.alias(StoreLoc, MemLoc);
if (R == NoAlias)
continue;
@ -575,7 +577,7 @@ MemDepResult MemoryDependenceResults::getSimplePointerDependencyFrom(
// handled by BasicAA.
if (isa<AllocaInst>(Inst) || isNoAliasFn(Inst, &TLI)) {
const Value *AccessPtr = getUnderlyingObject(MemLoc.Ptr);
if (AccessPtr == Inst || AA.isMustAlias(Inst, AccessPtr))
if (AccessPtr == Inst || BatchAA.isMustAlias(Inst, AccessPtr))
return MemDepResult::getDef(Inst);
}
@ -592,9 +594,10 @@ MemDepResult MemoryDependenceResults::getSimplePointerDependencyFrom(
continue;
// See if this instruction (e.g. a call or vaarg) mod/ref's the pointer.
ModRefInfo MR = AA.getModRefInfo(Inst, MemLoc);
ModRefInfo MR = BatchAA.getModRefInfo(Inst, MemLoc);
// If necessary, perform additional analysis.
if (isModAndRefSet(MR))
// TODO: Support callCapturesBefore() on BatchAAResults.
MR = AA.callCapturesBefore(Inst, MemLoc, &DT);
switch (clearMust(MR)) {
case ModRefInfo::NoModRef: