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[ValueTracking] Improve isKnowNonZero for Ints

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Improve isKnownNonZero for integers in order to improve cttz
optimizations.

Differential Revision: https://reviews.llvm.org/D60846

llvm-svn: 360222
This commit is contained in:
Dan Robertson 2019-05-08 02:25:08 +00:00
parent 5a6a2a5321
commit 525c17ceb3
4 changed files with 19 additions and 25 deletions
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26
lib/Analysis/ValueTracking.cpp
View File

@ -1893,10 +1893,9 @@ static bool isGEPKnownNonNull(const GEPOperator *GEP, unsigned Depth,
return false;
}
static bool isKnownNonNullFromDominatingCondition(const Value *V,
static bool isKnownNonZeroFromDominatingCondition(const Value *V,
const Instruction *CtxI,
const DominatorTree *DT) {
assert(V->getType()->isPointerTy() && "V must be pointer type");
assert(!isa<ConstantData>(V) && "Did not expect ConstantPointerNull");
if (!CtxI || !DT)
@ -1909,14 +1908,15 @@ static bool isKnownNonNullFromDominatingCondition(const Value *V,
break;
NumUsesExplored++;
// If the value is used as an argument to a call or invoke, then argument
// attributes may provide an answer about null-ness.
if (auto CS = ImmutableCallSite(U))
if (auto *CalledFunc = CS.getCalledFunction())
for (const Argument &Arg : CalledFunc->args())
if (CS.getArgOperand(Arg.getArgNo()) == V &&
Arg.hasNonNullAttr() && DT->dominates(CS.getInstruction(), CtxI))
return true;
// If the value is a pointer and used as an argument to a call or invoke,
// then argument attributes may provide an answer about null-ness.
if (V->getType()->isPointerTy())
if (auto CS = ImmutableCallSite(U))
if (auto *CalledFunc = CS.getCalledFunction())
for (const Argument &Arg : CalledFunc->args())
if (CS.getArgOperand(Arg.getArgNo()) == V &&
Arg.hasNonNullAttr() && DT->dominates(CS.getInstruction(), CtxI))
return true;
// Consider only compare instructions uniquely controlling a branch
CmpInst::Predicate Pred;
@ -2064,11 +2064,11 @@ bool isKnownNonZero(const Value *V, unsigned Depth, const Query &Q) {
}
if (isKnownNonZeroFromDominatingCondition(V, Q.CxtI, Q.DT))
return true;
// Check for recursive pointer simplifications.
if (V->getType()->isPointerTy()) {
if (isKnownNonNullFromDominatingCondition(V, Q.CxtI, Q.DT))
return true;
// Look through bitcast operations, GEPs, and int2ptr instructions as they
// do not alter the value, or at least not the nullness property of the
// value, e.g., int2ptr is allowed to zero/sign extend the value.

4
test/Transforms/InstCombine/known-non-zero.ll
View File

@ -13,7 +13,7 @@ define i32 @test0(i64 %x) {
; CHECK-NEXT: [[C:%.*]] = icmp eq i64 [[X:%.*]], 0
; CHECK-NEXT: br i1 [[C]], label [[EXIT:%.*]], label [[NON_ZERO:%.*]]
; CHECK: non_zero:
; CHECK-NEXT: [[CTZ:%.*]] = call i64 @llvm.cttz.i64(i64 [[X]], i1 false), !range !0
; CHECK-NEXT: [[CTZ:%.*]] = call i64 @llvm.cttz.i64(i64 [[X]], i1 true), !range !0
; CHECK-NEXT: [[CTZ32:%.*]] = trunc i64 [[CTZ]] to i32
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
@ -40,7 +40,7 @@ define i32 @test1(i64 %x) {
; CHECK-NEXT: [[C:%.*]] = icmp eq i64 [[X:%.*]], 0
; CHECK-NEXT: br i1 [[C]], label [[EXIT:%.*]], label [[NON_ZERO:%.*]]
; CHECK: non_zero:
; CHECK-NEXT: [[CTZ:%.*]] = call i64 @llvm.ctlz.i64(i64 [[X]], i1 false), !range !0
; CHECK-NEXT: [[CTZ:%.*]] = call i64 @llvm.ctlz.i64(i64 [[X]], i1 true), !range !0
; CHECK-NEXT: [[CTZ32:%.*]] = trunc i64 [[CTZ]] to i32
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:

10
test/Transforms/InstSimplify/known-non-zero.ll
View File

@ -7,8 +7,7 @@ define i64 @test0(i64 %x) {
; CHECK-NEXT: [[A:%.*]] = icmp eq i64 [[X:%.*]], 0
; CHECK-NEXT: br i1 [[A]], label [[EXIT:%.*]], label [[NON_ZERO:%.*]]
; CHECK: non_zero:
; CHECK-NEXT: [[B:%.*]] = icmp eq i64 [[X]], 0
; CHECK-NEXT: br i1 [[B]], label [[UNREACHABLE:%.*]], label [[EXIT]]
; CHECK-NEXT: br i1 false, label [[UNREACHABLE:%.*]], label [[EXIT]]
; CHECK: unreachable:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
@ -37,8 +36,7 @@ define i64 @test1(i64 %x) {
; CHECK-NEXT: [[A:%.*]] = icmp eq i64 [[X:%.*]], 0
; CHECK-NEXT: br i1 [[A]], label [[EXIT:%.*]], label [[NON_ZERO:%.*]]
; CHECK: non_zero:
; CHECK-NEXT: [[B:%.*]] = icmp ugt i64 [[X]], 0
; CHECK-NEXT: br i1 [[B]], label [[EXIT]], label [[UNREACHABLE:%.*]]
; CHECK-NEXT: br i1 true, label [[EXIT]], label [[UNREACHABLE:%.*]]
; CHECK: unreachable:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
@ -73,11 +71,9 @@ define i1 @test2(i64 %x, i1 %y) {
; CHECK: two:
; CHECK-NEXT: br label [[MAINBLOCK]]
; CHECK: mainblock:
; CHECK-NEXT: [[P:%.*]] = phi i64 [ [[X]], [[ONE]] ], [ 42, [[TWO]] ]
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i64 [[P]], 0
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: [[RES:%.*]] = phi i1 [ [[CMP]], [[MAINBLOCK]] ], [ true, [[START:%.*]] ]
; CHECK-NEXT: [[RES:%.*]] = phi i1 [ false, [[MAINBLOCK]] ], [ true, [[START:%.*]] ]
; CHECK-NEXT: ret i1 [[RES]]
;
start:

4
test/Transforms/LICM/hoist-mustexec.ll
View File

@ -129,8 +129,6 @@ fail:
}
; requires fact length is non-zero
; TODO: IsKnownNonNullFromDominatingConditions is currently only be done for
; pointers; should handle integers too
define i32 @test4(i32* noalias nocapture readonly %a) nounwind uwtable {
; CHECK-LABEL: @test4(
; CHECK-NEXT: entry:
@ -138,6 +136,7 @@ define i32 @test4(i32* noalias nocapture readonly %a) nounwind uwtable {
; CHECK-NEXT: [[IS_ZERO:%.*]] = icmp eq i32 [[LEN]], 0
; CHECK-NEXT: br i1 [[IS_ZERO]], label [[FAIL:%.*]], label [[PREHEADER:%.*]]
; CHECK: preheader:
; CHECK-NEXT: [[I1:%.*]] = load i32, i32* [[A]], align 4
; CHECK-NEXT: br label [[FOR_BODY:%.*]]
; CHECK: for.body:
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, [[PREHEADER]] ], [ [[INC:%.*]], [[CONTINUE:%.*]] ]
@ -145,7 +144,6 @@ define i32 @test4(i32* noalias nocapture readonly %a) nounwind uwtable {
; CHECK-NEXT: [[R_CHK:%.*]] = icmp ult i32 [[IV]], [[LEN]]
; CHECK-NEXT: br i1 [[R_CHK]], label [[CONTINUE]], label [[FAIL_LOOPEXIT:%.*]]
; CHECK: continue:
; CHECK-NEXT: [[I1:%.*]] = load i32, i32* [[A]], align 4
; CHECK-NEXT: [[ADD]] = add nsw i32 [[I1]], [[ACC]]
; CHECK-NEXT: [[INC]] = add nuw nsw i32 [[IV]], 1
; CHECK-NEXT: [[EXITCOND:%.*]] = icmp eq i32 [[INC]], 1000