[ValueTracking] Handle not in dominating condition.

[andjo403]

General handling of not in dominating condition.
Split out from #126414

proof: https://alive2.llvm.org/ce/z/FjJN8q

[llvmbot]

@llvm/pr-subscribers-llvm-analysis

@llvm/pr-subscribers-llvm-transforms

Author: Andreas Jonson (andjo403)

Changes

General handling of not split out from #126414

proof: https://alive2.llvm.org/ce/z/FjJN8q

---

Full diff: https://github.com/llvm/llvm-project/pull/126423.diff

3 Files Affected:

• (modified) llvm/lib/Analysis/ValueTracking.cpp (+10)
• (modified) llvm/test/Transforms/InstCombine/fpclass-from-dom-cond.ll (+1-2)
• (modified) llvm/test/Transforms/InstCombine/known-bits.ll (+1-2)

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 8a9ad55366ee703..6163d6453db3514 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -801,6 +801,9 @@ static void computeKnownBitsFromCond(const Value *V, Value *Cond,
 
   if (auto *Cmp = dyn_cast<ICmpInst>(Cond))
     computeKnownBitsFromICmpCond(V, Cmp, Known, SQ, Invert);
+
+  if (Depth < MaxAnalysisRecursionDepth && match(Cond, m_Not(m_Value(A))))
+    computeKnownBitsFromCond(V, A, Known, Depth + 1, SQ, !Invert);
 }
 
 void llvm::computeKnownBitsFromContext(const Value *V, KnownBits &Known,
@@ -4934,6 +4937,11 @@ static void computeKnownFPClassFromCond(const Value *V, Value *Cond,
                                 KnownFromContext);
     return;
   }
+  if (Depth < MaxAnalysisRecursionDepth && match(Cond, m_Not(m_Value(A)))) {
+    computeKnownFPClassFromCond(V, A, Depth + 1, !CondIsTrue, CxtI,
+                                KnownFromContext);
+    return;
+  }
   CmpPredicate Pred;
   Value *LHS;
   uint64_t ClassVal = 0;
@@ -10272,6 +10280,8 @@ void llvm::findValuesAffectedByCondition(
                                                            m_Value()))) {
       // Handle patterns that computeKnownFPClass() support.
       AddAffected(A);
+    } else if (match(V, m_Not(m_Value(X)))) {
+      Worklist.push_back(X);
     }
   }
 }
diff --git a/llvm/test/Transforms/InstCombine/fpclass-from-dom-cond.ll b/llvm/test/Transforms/InstCombine/fpclass-from-dom-cond.ll
index e6df7fab356b4a5..934852d1ca8bc42 100644
--- a/llvm/test/Transforms/InstCombine/fpclass-from-dom-cond.ll
+++ b/llvm/test/Transforms/InstCombine/fpclass-from-dom-cond.ll
@@ -528,8 +528,7 @@ define i1 @test_inv_and(float %x, i1 %cond2) {
 ; CHECK-NEXT:    [[AND:%.*]] = and i1 [[COND2]], [[NOT]]
 ; CHECK-NEXT:    br i1 [[AND]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
 ; CHECK:       if.then:
-; CHECK-NEXT:    [[RET1:%.*]] = fcmp oeq float [[X]], 0x7FF0000000000000
-; CHECK-NEXT:    ret i1 [[RET1]]
+; CHECK-NEXT:    ret i1 false
 ; CHECK:       if.else:
 ; CHECK-NEXT:    ret i1 false
 ;
diff --git a/llvm/test/Transforms/InstCombine/known-bits.ll b/llvm/test/Transforms/InstCombine/known-bits.ll
index 7563a63f607f04d..b729cbd971accce 100644
--- a/llvm/test/Transforms/InstCombine/known-bits.ll
+++ b/llvm/test/Transforms/InstCombine/known-bits.ll
@@ -2374,8 +2374,7 @@ define i8 @test_inv_cond_and(i8 %x, i1 %c) {
 ; CHECK-NEXT:    [[COND:%.*]] = and i1 [[C:%.*]], [[NOT]]
 ; CHECK-NEXT:    br i1 [[COND]], label [[IF:%.*]], label [[EXIT:%.*]]
 ; CHECK:       if:
-; CHECK-NEXT:    [[OR1:%.*]] = or i8 [[X]], -4
-; CHECK-NEXT:    ret i8 [[OR1]]
+; CHECK-NEXT:    ret i8 -4
 ; CHECK:       exit:
 ; CHECK-NEXT:    [[OR2:%.*]] = or i8 [[X]], -4
 ; CHECK-NEXT:    ret i8 [[OR2]]

[nikic]

Can we drop the !IsAssume here and instead drop the m_Not special case for assumes above?

[andjo403]

to be able to do that isEphemeralValueOf need to be updated to handle that.
example of test that will fail as the assume is optimized away.

llvm-project/llvm/test/Transforms/GVN/assume.ll

Lines 48 to 61 in 3d14000

	define void @pr47496(i8 %x) {
	; CHECK-LABEL: @pr47496(
	; CHECK-NEXT: [[CMP:%.*]] = icmp slt i8 [[X:%.*]], 0
	; CHECK-NEXT: [[XOR:%.*]] = xor i1 [[CMP]], true
	; CHECK-NEXT: call void @llvm.assume(i1 [[XOR]])
	; CHECK-NEXT: call void @use(i1 false)
	; CHECK-NEXT: ret void
	;
	%cmp = icmp slt i8 %x, 0
	%xor = xor i1 %cmp, true
	call void @llvm.assume(i1 %xor)
	call void @use(i1 %cmp)
	ret void
	}

Maybe all instructions with boolean results building up the condition for the assume shall be Ephemeral.

[andjo403]

Have some follow up changes that update isEphemeralValueOf here main...andjo403:llvm-project:assumeNotCond but probably better as multiple PRs if that is something that we want

[nikic]

LGTM