[llvm-commits] [llvm] r128140 - in /llvm/trunk: lib/Analysis/BasicAliasAnalysis.cpp test/Analysis/BasicAA/non-escaping-local-object.ll
Anders Carlsson
andersca at mac.com
Tue Mar 22 19:19:48 PDT 2011
Author: andersca
Date: Tue Mar 22 21:19:48 2011
New Revision: 128140
URL: http://llvm.org/viewvc/llvm-project?rev=128140&view=rev
Log:
A global variable with internal linkage where all uses are in one function and whose address is never taken is a non-escaping local object and can't alias anything else.
Added:
llvm/trunk/test/Analysis/BasicAA/non-escaping-local-object.ll
Modified:
llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
Modified: llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp?rev=128140&r1=128139&r2=128140&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp (original)
+++ llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp Tue Mar 22 21:19:48 2011
@@ -57,6 +57,29 @@
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 @@
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;
}
Added: llvm/trunk/test/Analysis/BasicAA/non-escaping-local-object.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/BasicAA/non-escaping-local-object.ll?rev=128140&view=auto
==============================================================================
--- llvm/trunk/test/Analysis/BasicAA/non-escaping-local-object.ll (added)
+++ llvm/trunk/test/Analysis/BasicAA/non-escaping-local-object.ll Tue Mar 22 21:19:48 2011
@@ -0,0 +1,19 @@
+; RUN: opt -basicaa -aa-eval -print-all-alias-modref-info -disable-output < %s |& FileCheck %s
+
+ at 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
+}
+
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