forked from OSchip/llvm-project
Teach BasicAA about noalias function parameters. Passes all of DejaGNU and test-suite.
llvm-svn: 40624
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fc1bd87814
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@ -18,6 +18,7 @@
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Function.h"
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#include "llvm/ParameterAttributes.h"
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#include "llvm/GlobalVariable.h"
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#include "llvm/Instructions.h"
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#include "llvm/Pass.h"
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@ -294,6 +295,21 @@ BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size,
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// Pointing at a discernible object?
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if (O1) {
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// Check for noalias attribute
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if (isa<Argument>(O1)) {
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const Argument *Arg = cast<Argument>(O1);
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const Function *Func = Arg->getParent();
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const ParamAttrsList *Attr = Func->getFunctionType()->getParamAttrs();
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if (Attr) {
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unsigned Idx = 1;
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for (Function::const_arg_iterator I = Func->arg_begin(),
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E = Func->arg_end(); I != E; ++I, ++Idx) {
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if (&(*I) == Arg &&
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Attr->paramHasAttr(Idx, ParamAttr::NoAlias))
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return NoAlias;
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}
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}
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}
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if (O2) {
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if (isa<Argument>(O1)) {
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// Incoming argument cannot alias locally allocated object!
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@ -307,7 +323,22 @@ BasicAliasAnalysis::alias(const Value *V1, unsigned V1Size,
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// If they are two different objects, we know that we have no alias...
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return NoAlias;
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}
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// Check for noalias atrribute independently from above logic
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if (isa<Argument>(O2)) {
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const Argument *Arg = cast<Argument>(O2);
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const Function *Func = Arg->getParent();
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const ParamAttrsList *Attr = Func->getFunctionType()->getParamAttrs();
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if (Attr) {
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unsigned Idx = 1;
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for (Function::const_arg_iterator I = Func->arg_begin(),
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E = Func->arg_end(); I != E; ++I, ++Idx) {
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if (&(*I) == Arg &&
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Attr->paramHasAttr(Idx, ParamAttr::NoAlias))
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return NoAlias;
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}
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}
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}
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// If they are the same object, they we can look at the indexes. If they
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// index off of the object is the same for both pointers, they must alias.
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// If they are provably different, they must not alias. Otherwise, we
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@ -0,0 +1,12 @@
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; RUN: llvm-as %s -o - | opt -aa-eval -print-may-aliases -disable-output |& grep '1 may alias'
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; RUN: llvm-as %s -o - | opt -aa-eval -print-may-aliases -disable-output |& grep '5 no alias'
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; RUN: llvm-as %s -o - | opt -aa-eval -print-may-aliases -disable-output |& grep 'MayAlias: i32* %ptr4, i32* %ptr2'
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define void @_Z3fooPiS_RiS_(i32* noalias %ptr1, i32* %ptr2, i32* noalias %ptr3, i32* %ptr4) {
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entry:
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store i32 0, i32* %ptr1
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store i32 0, i32* %ptr2
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store i32 0, i32* %ptr3
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store i32 0, i32* %ptr4
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ret void
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}
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