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[InstCombineCalls] Use isKnownNonNullAt() to check nullness of passing arguments at callsite

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Summary: This patch replaces isKnownNonNull() with isKnownNonNullAt() when checking nullness of passing arguments at callsite. In this way it can handle cases where the argument does not have nonnull attribute but has a dominating null check from the CFG. It also adds assertions in isKnownNonNull() and isKnownNonNullFromDominatingCondition() to make sure the value checked is pointer type (as defined in LLVM document). These assertions might trip failures in things which are not  covered under llvm/test, but fixes should be pretty obvious. 

Reviewers: reames

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D12779

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@247587 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chen Li 2015-09-14 18:10:43 +00:00
parent 2d35348660
commit ecc1d153b7
3 changed files with 26 additions and 2 deletions
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4
lib/Analysis/ValueTracking.cpp
View File

@ -3220,6 +3220,8 @@ bool llvm::mayBeMemoryDependent(const Instruction &I) {
/// Return true if we know that the specified value is never null.
bool llvm::isKnownNonNull(const Value *V, const TargetLibraryInfo *TLI) {
assert(V->getType()->isPointerTy() && "V must be pointer type");
// Alloca never returns null, malloc might.
if (isa<AllocaInst>(V)) return true;
@ -3252,6 +3254,8 @@ bool llvm::isKnownNonNull(const Value *V, const TargetLibraryInfo *TLI) {
static bool isKnownNonNullFromDominatingCondition(const Value *V,
const Instruction *CtxI,
const DominatorTree *DT) {
assert(V->getType()->isPointerTy() && "V must be pointer type");
unsigned NumUsesExplored = 0;
for (auto U : V->users()) {
// Avoid massive lists

4
lib/Transforms/InstCombine/InstCombineCalls.cpp
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@ -1583,8 +1583,8 @@ Instruction *InstCombiner::visitCallSite(CallSite CS) {
// checks on their arguments.
unsigned ArgNo = 0;
for (Value *V : CS.args()) {
if (!CS.paramHasAttr(ArgNo+1, Attribute::NonNull) &&
isKnownNonNull(V)) {
if (V->getType()->isPointerTy() && !CS.paramHasAttr(ArgNo+1, Attribute::NonNull) &&
isKnownNonNullAt(V, CS.getInstruction(), DT, TLI)) {
AttributeSet AS = CS.getAttributes();
AS = AS.addAttribute(CS.getInstruction()->getContext(), ArgNo+1,
Attribute::NonNull);

20
test/Transforms/InstCombine/call_nonnull_arg.ll Normal file
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@ -0,0 +1,20 @@
; RUN: opt < %s -instcombine -S | FileCheck %s
; InstCombine should mark null-checked argument as nonnull at callsite
declare void @dummy(i32*, i32)
define void @test(i32* %a, i32 %b) {
; CHECK-LABEL: @test
; CHECK: call void @dummy(i32* nonnull %a, i32 %b)
entry:
%cond1 = icmp eq i32* %a, null
br i1 %cond1, label %dead, label %not_null
not_null:
%cond2 = icmp eq i32 %b, 0
br i1 %cond2, label %dead, label %not_zero
not_zero:
call void @dummy(i32* %a, i32 %b)
ret void
dead:
unreachable
}