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[Alias Analysis] handle casts in projection path.

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We ignore casts when generating projection paths for alias analysis. When
comparing two paths, we say no alias when accessing different fields of
the same Decl Context.


Swift SVN r20353
This commit is contained in:
Manman Ren
2014-07-23 00:02:28 +00:00
parent 12e598a4f3
commit bea41c0bd3
4 changed files with 42 additions and 5 deletions
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21
lib/SILAnalysis/AliasAnalysis.cpp
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@@ -235,6 +235,16 @@ static bool projectionListsEqual(llvm::SmallVectorImpl<Projection> &V1Path,
return true;
}
/// Returns true if we are accessing different fields.
static bool areProjectionsToDifferentFields(Projection &P1, Projection &P2) {
// If operands have the same type and we are accessing different fields,
// returns true. Operand's type is not saved in Projection. Instead we check
// Decl's context.
return P1.getDecl() && P2.getDecl() &&
P1.getDecl()->getDeclContext() == P2.getDecl()->getDeclContext() &&
P1 != P2;
}
/// Returns true if we are accessing different fields of the same object.
static bool projectionListsNoAlias(llvm::SmallVectorImpl<Projection> &V1Path,
llvm::SmallVectorImpl<Projection> &V2Path) {
@@ -248,10 +258,13 @@ static bool projectionListsNoAlias(llvm::SmallVectorImpl<Projection> &V1Path,
unsigned e = V1Path.size() > V2Path.size() ? V2Path.size() : V1Path.size();
for (unsigned i = 0; i != e; ++i) {
// If we are accessing different fields of a common object, return true.
if (V1Path[i] != V2Path[i]) {
if (areProjectionsToDifferentFields(V1Path[i], V2Path[i])) {
DEBUG(llvm::dbgs() << " Path different at index: " << i << '\n');
return true;
}
if (V1Path[i] != V2Path[i])
return false;
// Continue if we are accessing the same field.
}
return false;
}
@@ -280,8 +293,10 @@ aliasAddressProjection(AliasAnalysis &AA, SILValue V1, SILValue V2, SILValue O1,
// other exactly, see if computing offsets from the common pointer tells us
// about the relation of the resulting pointer.
llvm::SmallVector<Projection, 4> V1Path, V2Path;
bool Result = findAddressProjectionPathBetweenValues(O1, V1, V1Path);
Result &= findAddressProjectionPathBetweenValues(O1, V2, V2Path);
bool Result = findAddressProjectionPathBetweenValues(O1, V1, V1Path,
true/*IgnoreCasts*/);
Result &= findAddressProjectionPathBetweenValues(O1, V2, V2Path,
true/*IgnoreCasts*/);
// getUnderlyingPath and findAddressProjectionPathBetweenValues disagree on
// what the base pointer of the two values are. Be conservative and return