[llvm-commits] CVS: llvm/lib/Analysis/BasicAliasAnalysis.cpp
Chris Lattner
lattner at cs.uiuc.edu
Fri Nov 26 11:20:13 PST 2004
Changes in directory llvm/lib/Analysis:
BasicAliasAnalysis.cpp updated: 1.55 -> 1.56
---
Log message:
A store or load cannot alias a global if the accessed amount is larger then
the global.
This implements Regression/Analysis/BasicAA/global-size.ll
---
Diffs of the changes: (+49 -20)
Index: llvm/lib/Analysis/BasicAliasAnalysis.cpp
diff -u llvm/lib/Analysis/BasicAliasAnalysis.cpp:1.55 llvm/lib/Analysis/BasicAliasAnalysis.cpp:1.56
--- llvm/lib/Analysis/BasicAliasAnalysis.cpp:1.55 Wed Nov 17 11:39:39 2004
+++ llvm/lib/Analysis/BasicAliasAnalysis.cpp Fri Nov 26 13:20:01 2004
@@ -265,28 +265,57 @@
const Value *O2 = getUnderlyingObject(V2);
// Pointing at a discernible object?
- if (O1 && O2) {
- if (isa<Argument>(O1)) {
- // Incoming argument cannot alias locally allocated object!
- if (isa<AllocationInst>(O2)) return NoAlias;
- // Otherwise, nothing is known...
- } else if (isa<Argument>(O2)) {
- // Incoming argument cannot alias locally allocated object!
- if (isa<AllocationInst>(O1)) return NoAlias;
- // Otherwise, nothing is known...
- } else {
- // If they are two different objects, we know that we have no alias...
- if (O1 != O2) return NoAlias;
+ if (O1) {
+ if (O2) {
+ if (isa<Argument>(O1)) {
+ // Incoming argument cannot alias locally allocated object!
+ if (isa<AllocationInst>(O2)) return NoAlias;
+ // Otherwise, nothing is known...
+ } else if (isa<Argument>(O2)) {
+ // Incoming argument cannot alias locally allocated object!
+ if (isa<AllocationInst>(O1)) return NoAlias;
+ // Otherwise, nothing is known...
+ } else if (O1 != O2) {
+ // If they are two different objects, we know that we have no alias...
+ return NoAlias;
+ }
+
+ // If they are the same object, they we can look at the indexes. If they
+ // index off of the object is the same for both pointers, they must alias.
+ // If they are provably different, they must not alias. Otherwise, we
+ // can't tell anything.
}
- // If they are the same object, they we can look at the indexes. If they
- // index off of the object is the same for both pointers, they must alias.
- // If they are provably different, they must not alias. Otherwise, we can't
- // tell anything.
- } else if (O1 && !isa<Argument>(O1) && isa<ConstantPointerNull>(V2)) {
- return NoAlias; // Unique values don't alias null
- } else if (O2 && !isa<Argument>(O2) && isa<ConstantPointerNull>(V1)) {
- return NoAlias; // Unique values don't alias null
+
+ if (!isa<Argument>(O1) && isa<ConstantPointerNull>(V2))
+ return NoAlias; // Unique values don't alias null
+
+ if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(O1))
+ if (GV->getType()->getElementType()->isSized()) {
+ // If the size of the other access is larger than the total size of the
+ // global, it cannot be accessing the global (it's undefined to load or
+ // store bytes after the global).
+ unsigned GlobalSize =
+ getTargetData().getTypeSize(GV->getType()->getElementType());
+ if (GlobalSize < V2Size)
+ return NoAlias;
+ }
+ }
+
+ if (O2) {
+ if (!isa<Argument>(O2) && isa<ConstantPointerNull>(V1))
+ return NoAlias; // Unique values don't alias null
+
+ if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(O2))
+ if (GV->getType()->getElementType()->isSized()) {
+ // If the size of the other access is larger than the total size of the
+ // global, it cannot be accessing the global (it's undefined to load or
+ // store bytes after the global).
+ unsigned GlobalSize =
+ getTargetData().getTypeSize(GV->getType()->getElementType());
+ if (GlobalSize < V1Size)
+ return NoAlias;
+ }
}
// If we have two gep instructions with must-alias'ing base pointers, figure
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