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Add a doesAccessArgPointees helper function, and update code to use 

it, and to be consistent.

llvm-svn: 118692
This commit is contained in:
Dan Gohman 2010-11-10 18:17:28 +00:00
parent 08feef8861
commit 066c1bb1e9
3 changed files with 33 additions and 23 deletions
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8
llvm/include/llvm/Analysis/AliasAnalysis.h
View File

@ -283,6 +283,14 @@ public:
return !(MRB & Anywhere & ~ArgumentPointees);
}
/// doesAccessArgPointees - Return true if functions with the specified
/// behavior are known to potentially read or write from objects pointed
/// to be their pointer-typed arguments (with arbitrary offsets).
///
static bool doesAccessArgPointees(ModRefBehavior MRB) {
return (MRB & ModRef) && (MRB & ArgumentPointees);
}
/// getModRefInfo - Return information about whether or not an instruction may
/// read or write the specified memory location. An instruction
/// that doesn't read or write memory may be trivially LICM'd for example.

46
llvm/lib/Analysis/AliasAnalysis.cpp
View File

@ -78,15 +78,15 @@ AliasAnalysis::getModRefInfo(ImmutableCallSite CS,
if (onlyReadsMemory(MRB))
Mask = Ref;
if (MRB == AccessesArguments ||
MRB == AccessesArgumentsReadonly) {
if (onlyAccessesArgPointees(MRB)) {
bool doesAlias = false;
for (ImmutableCallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
AI != AE; ++AI)
if (!isNoAlias(Location(*AI), Loc)) {
doesAlias = true;
break;
}
if (doesAccessArgPointees(MRB))
for (ImmutableCallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
AI != AE; ++AI)
if (!isNoAlias(Location(*AI), Loc)) {
doesAlias = true;
break;
}
if (!doesAlias)
return NoModRef;
@ -130,27 +130,29 @@ AliasAnalysis::getModRefInfo(ImmutableCallSite CS1, ImmutableCallSite CS2) {
// If CS2 only access memory through arguments, accumulate the mod/ref
// information from CS1's references to the memory referenced by
// CS2's arguments.
if (CS2B == AccessesArguments || CS2B == AccessesArgumentsReadonly) {
if (onlyAccessesArgPointees(CS2B)) {
AliasAnalysis::ModRefResult R = NoModRef;
for (ImmutableCallSite::arg_iterator
I = CS2.arg_begin(), E = CS2.arg_end(); I != E; ++I) {
R = ModRefResult((R | getModRefInfo(CS1, *I, UnknownSize)) & Mask);
if (R == Mask)
break;
}
if (doesAccessArgPointees(CS2B))
for (ImmutableCallSite::arg_iterator
I = CS2.arg_begin(), E = CS2.arg_end(); I != E; ++I) {
R = ModRefResult((R | getModRefInfo(CS1, *I, UnknownSize)) & Mask);
if (R == Mask)
break;
}
return R;
}
// If CS1 only accesses memory through arguments, check if CS2 references
// any of the memory referenced by CS1's arguments. If not, return NoModRef.
if (CS1B == AccessesArguments || CS1B == AccessesArgumentsReadonly) {
if (onlyAccessesArgPointees(CS1B)) {
AliasAnalysis::ModRefResult R = NoModRef;
for (ImmutableCallSite::arg_iterator
I = CS1.arg_begin(), E = CS1.arg_end(); I != E; ++I)
if (getModRefInfo(CS2, *I, UnknownSize) != NoModRef) {
R = Mask;
break;
}
if (doesAccessArgPointees(CS1B))
for (ImmutableCallSite::arg_iterator
I = CS1.arg_begin(), E = CS1.arg_end(); I != E; ++I)
if (getModRefInfo(CS2, *I, UnknownSize) != NoModRef) {
R = Mask;
break;
}
if (R == NoModRef)
return R;
}

2
llvm/lib/Transforms/IPO/FunctionAttrs.cpp
View File

@ -133,7 +133,7 @@ bool FunctionAttrs::AddReadAttrs(const CallGraphSCC &SCC) {
// figure out something.
if (AliasAnalysis::onlyAccessesArgPointees(MRB)) {
// If the call does access argument pointees, check each argument.
if (MRB & AliasAnalysis::AccessesArguments)
if (AliasAnalysis::doesAccessArgPointees(MRB))
// Check whether all pointer arguments point to local memory, and
// ignore calls that only access local memory.
for (CallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();