diff options
| -rw-r--r-- | lib/Analysis/BasicAliasAnalysis.cpp | 22 | ||||
| -rw-r--r-- | test/Analysis/BasicAA/no-escape-call.ll | 23 |
2 files changed, 44 insertions, 1 deletions
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp index 7e096cd..6ab7d94 100644 --- a/lib/Analysis/BasicAliasAnalysis.cpp +++ b/lib/Analysis/BasicAliasAnalysis.cpp @@ -317,6 +317,18 @@ static bool isKnownNonNull(const Value *V) { return false; } +/// isNonEscapingLocalObject - Return true if the pointer is to a function-local +/// object that never escapes from the function. +static bool isNonEscapingLocalObject(const Value *V) { + // If this is a local allocation or byval argument, check to see if it + // escapes. + if (isa<AllocationInst>(V) || + (isa<Argument>(V) && cast<Argument>(V)->hasByValAttr())) + return !AddressMightEscape(V); + return false; +} + + /// isObjectSmallerThan - Return true if we can prove that the object specified /// by V is smaller than Size. static bool isObjectSmallerThan(const Value *V, unsigned Size, @@ -393,7 +405,15 @@ BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size, (V2Size != ~0U && isObjectSmallerThan(O1, V2Size, TD))) return NoAlias; - + // If one pointer is the result of a call/invoke and the other is a + // non-escaping local object, then we know the object couldn't escape to a + // point where the call could return it. + if ((isa<CallInst>(O1) || isa<InvokeInst>(O1)) && + isNonEscapingLocalObject(O2)) + return NoAlias; + if ((isa<CallInst>(O2) || isa<InvokeInst>(O2)) && + isNonEscapingLocalObject(O1)) + return NoAlias; // If we have two gep instructions with must-alias'ing base pointers, figure // out if the indexes to the GEP tell us anything about the derived pointer. diff --git a/test/Analysis/BasicAA/no-escape-call.ll b/test/Analysis/BasicAA/no-escape-call.ll new file mode 100644 index 0000000..ab1fea7 --- /dev/null +++ b/test/Analysis/BasicAA/no-escape-call.ll @@ -0,0 +1,23 @@ +; RUN: llvm-as < %s | opt -basicaa -gvn -instcombine | llvm-dis | grep {ret i1 true} +; PR2436 +target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128" +target triple = "i386-apple-darwin8" + +define i1 @foo(i32 %i) nounwind { +entry: + %arr = alloca [10 x i8*] ; <[10 x i8*]*> [#uses=1] + %tmp2 = call i8* @getPtr( ) nounwind ; <i8*> [#uses=2] + %tmp4 = getelementptr [10 x i8*]* %arr, i32 0, i32 %i ; <i8**> [#uses=2] + store i8* %tmp2, i8** %tmp4, align 4 + %tmp10 = getelementptr i8* %tmp2, i32 10 ; <i8*> [#uses=1] + store i8 42, i8* %tmp10, align 1 + %tmp14 = load i8** %tmp4, align 4 ; <i8*> [#uses=1] + %tmp16 = getelementptr i8* %tmp14, i32 10 ; <i8*> [#uses=1] + %tmp17 = load i8* %tmp16, align 1 ; <i8> [#uses=1] + %tmp19 = icmp eq i8 %tmp17, 42 ; <i1> [#uses=1] + ret i1 %tmp19 +} + +declare i8* @getPtr() + +declare void @abort() noreturn nounwind |