[ValueTracking] Improve isKnowNonZero for Ints

Improve isKnownNonZero for integers in order to improve cttz
optimizations.

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

llvm-svn: 360222

llvm/lib/Analysis/ValueTracking.cpp

@@ -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.

llvm/test/Transforms/InstCombine/known-non-zero.ll

@@ -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:

llvm/test/Transforms/InstSimplify/known-non-zero.ll

@@ -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:

llvm/test/Transforms/LICM/hoist-mustexec.ll

@@ -129,23 +129,21 @@ 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:
 ; CHECK-NEXT:    [[LEN:%.*]] = load i32, i32* [[A:%.*]], align 4, !range !0
 ; 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:%.*]] ]
 ; CHECK-NEXT:    [[ACC:%.*]] = phi i32 [ 0, [[PREHEADER]] ], [ [[ADD:%.*]], [[CONTINUE]] ]
 ; 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