[PATCH] D98422: [ValueTracking] Handle two PHIs in isKnownNonEqual()
JinGu Kang via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Thu Mar 25 10:16:38 PDT 2021
jaykang10 updated this revision to Diff 333336.
jaykang10 added a comment.
Following comment of @lebedev.ri, updated code.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D98422/new/
https://reviews.llvm.org/D98422
Files:
llvm/lib/Analysis/ValueTracking.cpp
llvm/test/Analysis/ValueTracking/monotonic-phi.ll
Index: llvm/test/Analysis/ValueTracking/monotonic-phi.ll
===================================================================
--- llvm/test/Analysis/ValueTracking/monotonic-phi.ll
+++ llvm/test/Analysis/ValueTracking/monotonic-phi.ll
@@ -278,3 +278,28 @@
%cmp = icmp eq i8 %A, 0
ret i1 %cmp
}
+
+define i1 @test12(i8 %p, i8* %pq, i8 %n, i8 %r) {
+; CHECK-LABEL: @test12(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: br label [[LOOP:%.*]]
+; CHECK: loop:
+; CHECK-NEXT: [[A:%.*]] = phi i8 [ 2, [[ENTRY:%.*]] ], [ [[NEXT:%.*]], [[LOOP]] ]
+; CHECK-NEXT: [[NEXT]] = mul nsw i8 [[A]], 2
+; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i8 [[A]], [[N:%.*]]
+; CHECK-NEXT: br i1 [[CMP1]], label [[EXIT:%.*]], label [[LOOP]]
+; CHECK: exit:
+; CHECK-NEXT: ret i1 true
+;
+entry:
+ br label %loop
+loop:
+ %A = phi i8 [ 2, %entry ], [ %next, %loop ]
+ %B = phi i8 [ 3, %entry ], [ %A, %loop ]
+ %next = mul nsw i8 %A, 2
+ %cmp1 = icmp eq i8 %A, %n
+ br i1 %cmp1, label %exit, label %loop
+exit:
+ %cmp = icmp ne i8 %A, %B
+ ret i1 %cmp
+}
Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -2542,6 +2542,26 @@
return false;
}
+static bool isNonEqualPHIs(const PHINode *PN1, const PHINode *PN2,
+ unsigned Depth, const Query &Q) {
+ // Check two PHIs are in same block.
+ if (PN1->getParent() != PN2->getParent())
+ return false;
+
+ SmallPtrSet<const BasicBlock *, 8> VisitedBBs;
+ for (const BasicBlock *IncomBB : PN1->blocks()) {
+ if (!VisitedBBs.insert(IncomBB).second)
+ continue; // Don't reprocess blocks that we have dealt with already.
+ const Value *IV1 = PN1->getIncomingValueForBlock(IncomBB);
+ const Value *IV2 = PN2->getIncomingValueForBlock(IncomBB);
+ Query RecQ = Q;
+ RecQ.CxtI = PN1;
+ if (!isKnownNonEqual(IV1, IV2, Depth + 1, RecQ))
+ return false;
+ }
+ return true;
+}
+
/// Return true if it is known that V1 != V2.
static bool isKnownNonEqual(const Value *V1, const Value *V2, unsigned Depth,
const Query &Q) {
@@ -2593,12 +2613,20 @@
case Instruction::SExt:
case Instruction::ZExt:
if (O1->getOperand(0)->getType() == O2->getOperand(0)->getType())
- return isKnownNonEqual(O1->getOperand(0), O2->getOperand(0),
- Depth + 1, Q);
+ return isKnownNonEqual(O1->getOperand(0), O2->getOperand(0), Depth + 1,
+ Q);
+ break;
+ case Instruction::PHI:
+ const PHINode *PN1 = cast<PHINode>(V1);
+ const PHINode *PN2 = cast<PHINode>(V2);
+ // FIXME: This is missing a generalization to handle the case where one is
+ // a PHI and another one isn't.
+ if (isNonEqualPHIs(PN1, PN2, Depth, Q))
+ return true;
break;
};
}
-
+
if (isAddOfNonZero(V1, V2, Depth, Q) || isAddOfNonZero(V2, V1, Depth, Q))
return true;
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