diff options
| -rw-r--r-- | lib/Transforms/IPO/FunctionAttrs.cpp | 30 | ||||
| -rw-r--r-- | test/Transforms/FunctionAttrs/2008-12-31-NoCapture.ll | 24 |
2 files changed, 50 insertions, 4 deletions
diff --git a/lib/Transforms/IPO/FunctionAttrs.cpp b/lib/Transforms/IPO/FunctionAttrs.cpp index fcdede2fa3..3c9570bd50 100644 --- a/lib/Transforms/IPO/FunctionAttrs.cpp +++ b/lib/Transforms/IPO/FunctionAttrs.cpp @@ -208,10 +208,20 @@ bool FunctionAttrs::isCaptured(Function &F, Value *V) { continue; } + if (isa<FreeInst>(I)) { + // Freeing a pointer does not cause it to escape. + continue; + } + CallSite CS = CallSite::get(I); if (CS.getInstruction()) { - // Does not escape if only passed via 'nocapture' arguments. Note - // that calling a function pointer does not in itself cause that + // Does not escape if the callee is readonly and doesn't return a + // copy through its own return value. + if (CS.onlyReadsMemory() && I->getType() == Type::VoidTy) + continue; + + // Does not escape if passed via 'nocapture' arguments. Note that + // calling a function pointer does not in itself cause that // function pointer to escape. This is a subtle point considering // that (for example) the callee might return its own address. It // is analogous to saying that loading a value from a pointer does @@ -264,6 +274,20 @@ bool FunctionAttrs::AddNoCaptureAttrs(const std::vector<CallGraphNode *> &SCC) { // External node - skip it; continue; + // If the function is readonly and doesn't return any value, we + // know that the pointer value can't escape. Mark all of its pointer + // arguments nocapture. + if (F->onlyReadsMemory() && F->getReturnType() == Type::VoidTy) { + for (Function::arg_iterator A = F->arg_begin(), E = F->arg_end(); + A != E; ++A) + if (isa<PointerType>(A->getType()) && !A->hasNoCaptureAttr()) { + A->addAttr(Attribute::NoCapture); + ++NumNoCapture; + Changed = true; + } + continue; + } + // Definitions with weak linkage may be overridden at linktime with // something that writes memory, so treat them like declarations. if (F->isDeclaration() || F->mayBeOverridden()) @@ -273,7 +297,7 @@ bool FunctionAttrs::AddNoCaptureAttrs(const std::vector<CallGraphNode *> &SCC) { if (isa<PointerType>(A->getType()) && !A->hasNoCaptureAttr() && !isCaptured(*F, A)) { A->addAttr(Attribute::NoCapture); - NumNoCapture++; + ++NumNoCapture; Changed = true; } } diff --git a/test/Transforms/FunctionAttrs/2008-12-31-NoCapture.ll b/test/Transforms/FunctionAttrs/2008-12-31-NoCapture.ll index 61c607dc00..758f0dd3ad 100644 --- a/test/Transforms/FunctionAttrs/2008-12-31-NoCapture.ll +++ b/test/Transforms/FunctionAttrs/2008-12-31-NoCapture.ll @@ -1,5 +1,5 @@ ; RUN: llvm-as < %s | opt -functionattrs | llvm-dis | not grep {nocapture *%%q} -; RUN: llvm-as < %s | opt -functionattrs | llvm-dis | grep {nocapture *%%p} | count 3 +; RUN: llvm-as < %s | opt -functionattrs | llvm-dis | grep {nocapture *%%p} | count 8 @g = global i32* null ; <i32**> [#uses=1] define i32* @c1(i32* %q) { @@ -62,3 +62,25 @@ define void @nc3(void ()* %p) { call void %p() ret void } + +declare void @external(i8*) readonly +define void @nc4(i8* %p) { + call void @external(i8* %p) + ret void +} + +define void @nc5(void (i8*)* %f, i8* %p) { + call void %f(i8* %p) readonly + call void %f(i8* nocapture %p) + ret void +} + +define void @nc6(i8* %p) { + call void @nc7(i8* %p) + ret void +} + +define void @nc7(i8* %p) { + call void @nc6(i8* %p) + ret void +} |