[llvm] [ValueTracking] Infer NonEqual from dominating conditions/assumptions (PR #117442)
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Sat Nov 23 08:32:57 PST 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-transforms
Author: Yingwei Zheng (dtcxzyw)
<details>
<summary>Changes</summary>
This patch adds context-sensitive analysis support for `isKnownNonEqual`. It is required for https://github.com/llvm/llvm-project/issues/117436.
---
Full diff: https://github.com/llvm/llvm-project/pull/117442.diff
2 Files Affected:
- (modified) llvm/lib/Analysis/ValueTracking.cpp (+47-2)
- (modified) llvm/test/Transforms/InstCombine/icmp-dom.ll (+200)
``````````diff
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index c48068afc04816..b45bfa2fd3d964 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -3748,6 +3748,50 @@ static bool isKnownNonEqual(const Value *V1, const Value *V2,
match(V2, m_PtrToIntSameSize(Q.DL, m_Value(B))))
return isKnownNonEqual(A, B, DemandedElts, Depth + 1, Q);
+ if (!Q.CxtI)
+ return false;
+
+ // Try to infer NonEqual based on information from dominating conditions.
+ if (Q.DC && Q.DT) {
+ for (BranchInst *BI : Q.DC->conditionsFor(V1)) {
+ Value *Cond = BI->getCondition();
+ BasicBlockEdge Edge0(BI->getParent(), BI->getSuccessor(0));
+ if (Q.DT->dominates(Edge0, Q.CxtI->getParent()) &&
+ isImpliedCondition(Cond, ICmpInst::ICMP_NE, V1, V2, Q.DL,
+ /*LHSIsTrue=*/true, Depth)
+ .value_or(false))
+ return true;
+
+ BasicBlockEdge Edge1(BI->getParent(), BI->getSuccessor(1));
+ if (Q.DT->dominates(Edge1, Q.CxtI->getParent()) &&
+ isImpliedCondition(Cond, ICmpInst::ICMP_NE, V1, V2, Q.DL,
+ /*LHSIsTrue=*/false, Depth)
+ .value_or(false))
+ return true;
+ }
+ }
+
+ if (!Q.AC)
+ return false;
+
+ // Try to infer NonEqual based on information from assumptions.
+ for (auto &AssumeVH : Q.AC->assumptionsFor(V1)) {
+ if (!AssumeVH)
+ continue;
+ CallInst *I = cast<CallInst>(AssumeVH);
+
+ assert(I->getFunction() == Q.CxtI->getFunction() &&
+ "Got assumption for the wrong function!");
+ assert(I->getIntrinsicID() == Intrinsic::assume &&
+ "must be an assume intrinsic");
+
+ if (isImpliedCondition(I->getArgOperand(0), ICmpInst::ICMP_NE, V1, V2, Q.DL,
+ /*LHSIsTrue=*/true, Depth)
+ .value_or(false) &&
+ isValidAssumeForContext(I, Q.CxtI, Q.DT))
+ return true;
+ }
+
return false;
}
@@ -10037,10 +10081,10 @@ void llvm::findValuesAffectedByCondition(
Worklist.push_back(B);
}
} else if (match(V, m_ICmp(Pred, m_Value(A), m_Value(B)))) {
- AddCmpOperands(A, B);
-
bool HasRHSC = match(B, m_ConstantInt());
if (ICmpInst::isEquality(Pred)) {
+ AddAffected(A);
+ AddAffected(B);
if (HasRHSC) {
Value *Y;
// (X & C) or (X | C) or (X ^ C).
@@ -10055,6 +10099,7 @@ void llvm::findValuesAffectedByCondition(
}
}
} else {
+ AddCmpOperands(A, B);
if (HasRHSC) {
// Handle (A + C1) u< C2, which is the canonical form of
// A > C3 && A < C4.
diff --git a/llvm/test/Transforms/InstCombine/icmp-dom.ll b/llvm/test/Transforms/InstCombine/icmp-dom.ll
index 3cf3a7af77041c..07793e8951de59 100644
--- a/llvm/test/Transforms/InstCombine/icmp-dom.ll
+++ b/llvm/test/Transforms/InstCombine/icmp-dom.ll
@@ -534,3 +534,203 @@ else:
%cmp1 = icmp eq i32 %and1, 0
ret i1 %cmp1
}
+
+; TODO: X != Y implies X | Y != 0
+define i1 @or_nonzero_from_nonequal(i8 %x, i8 %y) {
+; CHECK-LABEL: @or_nonzero_from_nonequal(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[COND:%.*]] = icmp eq i8 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT: br i1 [[COND]], label [[IF_ELSE:%.*]], label [[IF_THEN:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: [[OR:%.*]] = or i8 [[X]], [[Y]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[OR]], 0
+; CHECK-NEXT: ret i1 [[CMP]]
+; CHECK: if.else:
+; CHECK-NEXT: ret i1 false
+;
+entry:
+ %cond = icmp eq i8 %x, %y
+ br i1 %cond, label %if.else, label %if.then
+
+if.then:
+ %or = or i8 %x, %y
+ %cmp = icmp eq i8 %or, 0
+ ret i1 %cmp
+
+if.else:
+ ret i1 false
+}
+
+define i1 @test_nonequal_domcond1(i64 %x, i64 %y, i64 %z, i64 %w) {
+; CHECK-LABEL: @test_nonequal_domcond1(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[COND1:%.*]] = icmp eq i64 [[Y:%.*]], [[X:%.*]]
+; CHECK-NEXT: [[COND2:%.*]] = icmp eq i64 [[W:%.*]], [[Z:%.*]]
+; CHECK-NEXT: [[OR_COND:%.*]] = select i1 [[COND1]], i1 true, i1 [[COND2]]
+; CHECK-NEXT: br i1 [[OR_COND]], label [[IF_END:%.*]], label [[IF_THEN:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: ret i1 false
+; CHECK: if.end:
+; CHECK-NEXT: ret i1 false
+;
+entry:
+ %cond1 = icmp eq i64 %y, %x
+ %cond2 = icmp eq i64 %w, %z
+ %or.cond = select i1 %cond1, i1 true, i1 %cond2
+ br i1 %or.cond, label %if.end, label %if.then
+
+if.then:
+ %sub1 = sub i64 %w, %z
+ %sub2 = sub i64 %y, %x
+ %umin = call i64 @llvm.umin.i64(i64 %sub1, i64 %sub2)
+ %cmp = icmp eq i64 %umin, 0
+ ret i1 %cmp
+
+if.end:
+ ret i1 false
+}
+
+define i1 @test_nonequal_domcond2(i64 %x, i64 %y, i64 %z, i64 %w) {
+; CHECK-LABEL: @test_nonequal_domcond2(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[COND1:%.*]] = icmp ne i64 [[Y:%.*]], [[X:%.*]]
+; CHECK-NEXT: [[COND2:%.*]] = icmp ne i64 [[W:%.*]], [[Z:%.*]]
+; CHECK-NEXT: [[OR_COND:%.*]] = select i1 [[COND1]], i1 [[COND2]], i1 false
+; CHECK-NEXT: br i1 [[OR_COND]], label [[IF_THEN:%.*]], label [[IF_END:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: ret i1 false
+; CHECK: if.end:
+; CHECK-NEXT: ret i1 false
+;
+entry:
+ %cond1 = icmp ne i64 %y, %x
+ %cond2 = icmp ne i64 %w, %z
+ %or.cond = select i1 %cond1, i1 %cond2, i1 false
+ br i1 %or.cond, label %if.then, label %if.end
+
+if.then:
+ %sub1 = sub i64 %w, %z
+ %sub2 = sub i64 %y, %x
+ %umin = call i64 @llvm.umin.i64(i64 %sub1, i64 %sub2)
+ %cmp = icmp eq i64 %umin, 0
+ ret i1 %cmp
+
+if.end:
+ ret i1 false
+}
+
+define i1 @test_nonequal_assume(i64 %x, i64 %y, i64 %z, i64 %w) {
+; CHECK-LABEL: @test_nonequal_assume(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[COND1:%.*]] = icmp ne i64 [[Y:%.*]], [[X:%.*]]
+; CHECK-NEXT: call void @llvm.assume(i1 [[COND1]])
+; CHECK-NEXT: [[COND2:%.*]] = icmp ne i64 [[W:%.*]], [[Z:%.*]]
+; CHECK-NEXT: call void @llvm.assume(i1 [[COND2]])
+; CHECK-NEXT: ret i1 false
+;
+entry:
+ %cond1 = icmp ne i64 %y, %x
+ call void @llvm.assume(i1 %cond1)
+ %cond2 = icmp ne i64 %w, %z
+ call void @llvm.assume(i1 %cond2)
+
+ %sub1 = sub i64 %w, %z
+ %sub2 = sub i64 %y, %x
+ %umin = call i64 @llvm.umin.i64(i64 %sub1, i64 %sub2)
+ %cmp = icmp eq i64 %umin, 0
+ ret i1 %cmp
+}
+
+; Negative tests
+
+define i1 @test_nonequal_invalid_domcond1(i64 %x, i64 %y, i64 %z, i64 %w) {
+; CHECK-LABEL: @test_nonequal_invalid_domcond1(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[COND1:%.*]] = icmp ne i64 [[Y:%.*]], [[X:%.*]]
+; CHECK-NEXT: [[COND2:%.*]] = icmp eq i64 [[W:%.*]], [[Z:%.*]]
+; CHECK-NEXT: [[OR_COND:%.*]] = select i1 [[COND1]], i1 true, i1 [[COND2]]
+; CHECK-NEXT: br i1 [[OR_COND]], label [[IF_END:%.*]], label [[IF_THEN:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: ret i1 true
+; CHECK: if.end:
+; CHECK-NEXT: ret i1 false
+;
+entry:
+ %cond1 = icmp ne i64 %y, %x
+ %cond2 = icmp eq i64 %w, %z
+ %or.cond = select i1 %cond1, i1 true, i1 %cond2
+ br i1 %or.cond, label %if.end, label %if.then
+
+if.then:
+ %sub1 = sub i64 %w, %z
+ %sub2 = sub i64 %y, %x
+ %umin = call i64 @llvm.umin.i64(i64 %sub1, i64 %sub2)
+ %cmp = icmp eq i64 %umin, 0
+ ret i1 %cmp
+
+if.end:
+ ret i1 false
+}
+
+define i1 @test_nonequal_invalid_domcond2(i64 %x, i64 %y, i64 %z, i64 %w) {
+; CHECK-LABEL: @test_nonequal_invalid_domcond2(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[COND1:%.*]] = icmp eq i64 [[Y:%.*]], [[X:%.*]]
+; CHECK-NEXT: [[COND2:%.*]] = icmp eq i64 [[W:%.*]], [[Z:%.*]]
+; CHECK-NEXT: [[OR_COND:%.*]] = select i1 [[COND1]], i1 true, i1 [[COND2]]
+; CHECK-NEXT: br i1 [[OR_COND]], label [[IF_THEN:%.*]], label [[IF_END:%.*]]
+; CHECK: if.then:
+; CHECK-NEXT: br label [[IF_END]]
+; CHECK: if.end:
+; CHECK-NEXT: [[SUB1:%.*]] = sub i64 [[W]], [[Z]]
+; CHECK-NEXT: [[SUB2:%.*]] = sub i64 [[Y]], [[X]]
+; CHECK-NEXT: [[UMIN:%.*]] = call i64 @llvm.umin.i64(i64 [[SUB1]], i64 [[SUB2]])
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i64 [[UMIN]], 0
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+entry:
+ %cond1 = icmp eq i64 %y, %x
+ %cond2 = icmp eq i64 %w, %z
+ %or.cond = select i1 %cond1, i1 true, i1 %cond2
+ br i1 %or.cond, label %if.then, label %if.end
+
+if.then:
+ br label %if.end
+
+if.end:
+ %sub1 = sub i64 %w, %z
+ %sub2 = sub i64 %y, %x
+ %umin = call i64 @llvm.umin.i64(i64 %sub1, i64 %sub2)
+ %cmp = icmp eq i64 %umin, 0
+ ret i1 %cmp
+}
+
+define i1 @test_nonequal_invalid_assume(i64 %x, i64 %y, i64 %z, i64 %w) {
+; CHECK-LABEL: @test_nonequal_invalid_assume(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[SUB1:%.*]] = sub i64 [[W:%.*]], [[Z:%.*]]
+; CHECK-NEXT: [[SUB2:%.*]] = sub i64 [[Y:%.*]], [[X:%.*]]
+; CHECK-NEXT: [[UMIN:%.*]] = call i64 @llvm.umin.i64(i64 [[SUB1]], i64 [[SUB2]])
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i64 [[UMIN]], 0
+; CHECK-NEXT: call void @side_effect()
+; CHECK-NEXT: [[COND1:%.*]] = icmp ne i64 [[Y]], [[X]]
+; CHECK-NEXT: call void @llvm.assume(i1 [[COND1]])
+; CHECK-NEXT: [[COND2:%.*]] = icmp ne i64 [[W]], [[Z]]
+; CHECK-NEXT: call void @llvm.assume(i1 [[COND2]])
+; CHECK-NEXT: ret i1 [[CMP]]
+;
+entry:
+ %sub1 = sub i64 %w, %z
+ %sub2 = sub i64 %y, %x
+ %umin = call i64 @llvm.umin.i64(i64 %sub1, i64 %sub2)
+ %cmp = icmp eq i64 %umin, 0
+
+ call void @side_effect()
+ %cond1 = icmp ne i64 %y, %x
+ call void @llvm.assume(i1 %cond1)
+ %cond2 = icmp ne i64 %w, %z
+ call void @llvm.assume(i1 %cond2)
+ ret i1 %cmp
+}
+
+declare void @side_effect()
``````````
</details>
https://github.com/llvm/llvm-project/pull/117442
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