diff options
| -rw-r--r-- | lib/Analysis/BasicAliasAnalysis.cpp | 33 | ||||
| -rw-r--r-- | test/Analysis/BasicAA/non-escaping-local-object.ll | 19 |
2 files changed, 52 insertions, 0 deletions
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp index f7bcd9ec44..e807933aaa 100644 --- a/lib/Analysis/BasicAliasAnalysis.cpp +++ b/lib/Analysis/BasicAliasAnalysis.cpp @@ -57,6 +57,29 @@ static bool isKnownNonNull(const Value *V) { return false; } +/// areAllUsesInOneFunction - Return true if all the uses of the given value +/// are in the same function. Note that this returns false if any of the uses +/// are from non-instruction values. +static bool areAllUsesInOneFunction(const Value *V) { + const llvm::Function *Fn = 0; + + for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); + UI != E; ++UI) { + if (const Instruction *I = dyn_cast<Instruction>(*UI)) { + if (!Fn) { + Fn = I->getParent()->getParent(); + continue; + } + + if (Fn != I->getParent()->getParent()) + return false; + } else + return false; + } + + return true; +} + /// isNonEscapingLocalObject - Return true if the pointer is to a function-local /// object that never escapes from the function. static bool isNonEscapingLocalObject(const Value *V) { @@ -79,6 +102,16 @@ static bool isNonEscapingLocalObject(const Value *V) { return true; return !PointerMayBeCaptured(V, false, /*StoreCaptures=*/true); } + + // If this is an internal global variable that's only used in this function, + // check if it escapes the function. + if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) { + if (GV->hasInternalLinkage() && areAllUsesInOneFunction(GV)) { + return !PointerMayBeCaptured(V, /*ReturnCaptures=*/true, + /*StoreCaptures=*/true); + } + } + return false; } diff --git a/test/Analysis/BasicAA/non-escaping-local-object.ll b/test/Analysis/BasicAA/non-escaping-local-object.ll new file mode 100644 index 0000000000..f5b73b6d26 --- /dev/null +++ b/test/Analysis/BasicAA/non-escaping-local-object.ll @@ -0,0 +1,19 @@ +; RUN: opt -basicaa -aa-eval -print-all-alias-modref-info -disable-output < %s |& FileCheck %s + +@global = internal global i32 0 + +declare void @should_not_be_called() +declare i32 @f() + +; CHECK: Function: g: 2 pointers, 0 call sites +define void @g(i32* nocapture %p) { + store i32 0, i32* @global + + ; @global is internal, is only used in this function, and never has its + ; address taken so it can't alias p. + ; CHECK: NoAlias: i32* %p, i32* @global + store i32 1, i32* %p + %1 = load i32* @global + ret void +} + |