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Implement review feedback from Devang: make use

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of mayReadFromMemory and mayWriteToMemory.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56387 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan Sands 2008-09-20 16:45:58 +00:00
parent 34d8f7559c
commit f95f945fb0
1 changed files with 12 additions and 27 deletions
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39
lib/Transforms/IPO/AddReadAttrs.cpp
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@ -54,7 +54,7 @@ bool AddReadAttrs::runOnSCC(const std::vector<CallGraphNode *> &SCC) {
Function *F = SCC[i]->getFunction();
if (F == 0)
// May write memory.
// External node - may write memory.
return false;
if (F->doesNotAccessMemory())
@ -72,34 +72,19 @@ bool AddReadAttrs::runOnSCC(const std::vector<CallGraphNode *> &SCC) {
continue;
}
// Scan the function body for explicit loads and stores, or calls to
// functions that may read or write memory.
// Scan the function body for instructions that may read or write memory.
for (inst_iterator II = inst_begin(F), E = inst_end(F); II != E; ++II) {
Instruction *I = &*II;
if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
if (LI->isVolatile())
// Volatile loads may have side-effects, so treat them as writing
// memory.
return false;
ReadsMemory = true;
} else if (isa<StoreInst>(I) || isa<MallocInst>(I) || isa<FreeInst>(I)) {
// Writes memory.
CallSite CS = CallSite::get(&*II);
// Ignore calls to functions in the same SCC.
if (CS.getInstruction() &&
std::find(SCC.begin(), SCC.end(), CG[CS.getCalledFunction()]) !=
SCC.end())
continue;
if (II->mayWriteToMemory())
return false;
} else if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
CallSite CS(I);
if (std::find(SCC.begin(), SCC.end(), CG[CS.getCalledFunction()]) !=
SCC.end())
// The callee is inside our current SCC - ignore it.
continue;
if (!CS.onlyReadsMemory())
// May write memory.
return false;
if (!CS.doesNotAccessMemory())
ReadsMemory = true;
}
ReadsMemory |= II->mayReadFromMemory();
}
}