Index: lib/Transforms/IPO/FunctionAttrs.cpp =================================================================== --- lib/Transforms/IPO/FunctionAttrs.cpp +++ lib/Transforms/IPO/FunctionAttrs.cpp @@ -42,6 +42,7 @@ STATISTIC(NumReadNone, "Number of functions marked readnone"); STATISTIC(NumReadOnly, "Number of functions marked readonly"); STATISTIC(NumNoCapture, "Number of arguments marked nocapture"); +STATISTIC(NumReturned, "Number of arguments marked returned"); STATISTIC(NumReadNoneArg, "Number of arguments marked readnone"); STATISTIC(NumReadOnlyArg, "Number of arguments marked readonly"); STATISTIC(NumNoAlias, "Number of function returns marked noalias"); @@ -483,6 +484,46 @@ return IsRead ? Attribute::ReadOnly : Attribute::ReadNone; } +/// Deduce returned attributes for the SCC. +static bool addArgumentReturnedAttrs(const SCCNodeSet &SCCNodes) { + bool Changed = false; + + AttrBuilder B; + B.addAttribute(Attribute::Returned); + + // Check each function in turn, determining which pointer arguments are not + // captured. + for (Function *F : SCCNodes) { + // We can infer and propagate function attributes only when we know that the + // definition we'll get at link time is *exactly* the definition we see now. + // For more details, see GlobalValue::mayBeDerefined. + if (!F->hasExactDefinition()) + continue; + + if (F->getReturnType()->isVoidTy()) + continue; + + SmallPtrSet RetArgs; + for (BasicBlock &BB : *F) + if (ReturnInst *Ret = dyn_cast(BB.getTerminator())) { + // Note that stripPointerCasts should look through functions with + // returned arguments. + Value *RetVal = Ret->getReturnValue()->stripPointerCasts(); + if (RetVal->getType() == F->getReturnType() && isa(RetVal)) + RetArgs.insert(RetVal); + } + + if (RetArgs.size() == 1) { + auto *A = cast(*RetArgs.begin()); + A->addAttr(AttributeSet::get(F->getContext(), A->getArgNo() + 1, B)); + ++NumReturned; + Changed = true; + } + } + + return Changed; +} + /// Deduce nocapture attributes for the SCC. static bool addArgumentAttrs(const SCCNodeSet &SCCNodes) { bool Changed = false; @@ -1024,6 +1065,7 @@ } bool Changed = false; + Changed |= addArgumentReturnedAttrs(SCCNodes); Changed |= addReadAttrs(SCCNodes, AARGetter); Changed |= addArgumentAttrs(SCCNodes); @@ -1089,6 +1131,7 @@ SCCNodes.insert(F); } + Changed |= addArgumentReturnedAttrs(SCCNodes); Changed |= addReadAttrs(SCCNodes, AARGetter); Changed |= addArgumentAttrs(SCCNodes); Index: test/Transforms/FunctionAttrs/2009-01-02-LocalStores.ll =================================================================== --- test/Transforms/FunctionAttrs/2009-01-02-LocalStores.ll +++ test/Transforms/FunctionAttrs/2009-01-02-LocalStores.ll @@ -14,7 +14,7 @@ ret i32* %tmp } -; CHECK: define i32* @c(i32* readnone %r) +; CHECK: define i32* @c(i32* readnone returned %r) @g = global i32 0 define i32* @c(i32 *%r) { %a = icmp eq i32* %r, null Index: test/Transforms/FunctionAttrs/nocapture.ll =================================================================== --- test/Transforms/FunctionAttrs/nocapture.ll +++ test/Transforms/FunctionAttrs/nocapture.ll @@ -1,7 +1,7 @@ ; RUN: opt < %s -functionattrs -S | FileCheck %s @g = global i32* null ; [#uses=1] -; CHECK: define i32* @c1(i32* readnone %q) +; CHECK: define i32* @c1(i32* readnone returned %q) define i32* @c1(i32* %q) { ret i32* %q } @@ -140,7 +140,7 @@ ret void } -; CHECK: define i8* @test1_2(i8* nocapture readnone %x1_2, i8* %y1_2) +; CHECK: define i8* @test1_2(i8* nocapture readnone %x1_2, i8* returned %y1_2) define i8* @test1_2(i8* %x1_2, i8* %y1_2) { call void @test1_1(i8* %x1_2, i8* %y1_2) store i32* null, i32** @g @@ -168,7 +168,7 @@ ret void } -; CHECK: define i8* @test4_2(i8* nocapture readnone %x4_2, i8* readnone %y4_2, i8* nocapture readnone %z4_2) +; CHECK: define i8* @test4_2(i8* nocapture readnone %x4_2, i8* readnone returned %y4_2, i8* nocapture readnone %z4_2) define i8* @test4_2(i8* %x4_2, i8* %y4_2, i8* %z4_2) { call void @test4_1(i8* null) store i32* null, i32** @g Index: test/Transforms/FunctionAttrs/readattrs.ll =================================================================== --- test/Transforms/FunctionAttrs/readattrs.ll +++ test/Transforms/FunctionAttrs/readattrs.ll @@ -11,7 +11,7 @@ ret void } -; CHECK: define i8* @test2(i8* readnone %p) +; CHECK: define i8* @test2(i8* readnone returned %p) define i8* @test2(i8* %p) { store i32 0, i32* @x ret i8* %p @@ -53,7 +53,7 @@ ret void } -; CHECK: define i32* @test8_1(i32* readnone %p) +; CHECK: define i32* @test8_1(i32* readnone returned %p) define i32* @test8_1(i32* %p) { entry: ret i32* %p