[InstCombine] Drop range attributes in foldIsPowerOf2OrZero (llvm#1…

…12178) Closes llvm#112078.
DanielCChen · Oct 16, 2024 · 5aa39a6 · 5aa39a6
1 parent a180562
commit 5aa39a6
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Showing 2 changed files with 43 additions and 7 deletions.
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -935,21 +935,31 @@ static Value *foldSignedTruncationCheck(ICmpInst *ICmp0, ICmpInst *ICmp1,
 
 /// Fold (icmp eq ctpop(X) 1) | (icmp eq X 0) into (icmp ult ctpop(X) 2) and
 /// fold (icmp ne ctpop(X) 1) & (icmp ne X 0) into (icmp ugt ctpop(X) 1).
-/// Also used for logical and/or, must be poison safe.
+/// Also used for logical and/or, must be poison safe if range attributes are
+/// dropped.
 static Value *foldIsPowerOf2OrZero(ICmpInst *Cmp0, ICmpInst *Cmp1, bool IsAnd,
-                                   InstCombiner::BuilderTy &Builder) {
+                                   InstCombiner::BuilderTy &Builder,
+                                   InstCombinerImpl &IC) {
   CmpInst::Predicate Pred0, Pred1;
   Value *X;
   if (!match(Cmp0, m_ICmp(Pred0, m_Intrinsic<Intrinsic::ctpop>(m_Value(X)),
                           m_SpecificInt(1))) ||
       !match(Cmp1, m_ICmp(Pred1, m_Specific(X), m_ZeroInt())))
     return nullptr;
 
-  Value *CtPop = Cmp0->getOperand(0);
-  if (IsAnd && Pred0 == ICmpInst::ICMP_NE && Pred1 == ICmpInst::ICMP_NE)
+  auto *CtPop = cast<Instruction>(Cmp0->getOperand(0));
+  if (IsAnd && Pred0 == ICmpInst::ICMP_NE && Pred1 == ICmpInst::ICMP_NE) {
+    // Drop range attributes and re-infer them in the next iteration.
+    CtPop->dropPoisonGeneratingAnnotations();
+    IC.addToWorklist(CtPop);
     return Builder.CreateICmpUGT(CtPop, ConstantInt::get(CtPop->getType(), 1));
-  if (!IsAnd && Pred0 == ICmpInst::ICMP_EQ && Pred1 == ICmpInst::ICMP_EQ)
+  }
+  if (!IsAnd && Pred0 == ICmpInst::ICMP_EQ && Pred1 == ICmpInst::ICMP_EQ) {
+    // Drop range attributes and re-infer them in the next iteration.
+    CtPop->dropPoisonGeneratingAnnotations();
+    IC.addToWorklist(CtPop);
     return Builder.CreateICmpULT(CtPop, ConstantInt::get(CtPop->getType(), 2));
+  }
 
   return nullptr;
 }
@@ -3362,9 +3372,9 @@ Value *InstCombinerImpl::foldAndOrOfICmps(ICmpInst *LHS, ICmpInst *RHS,
                                              /*IsLogical*/ false, Builder, Q))
     return V;
 
-  if (Value *V = foldIsPowerOf2OrZero(LHS, RHS, IsAnd, Builder))
+  if (Value *V = foldIsPowerOf2OrZero(LHS, RHS, IsAnd, Builder, *this))
     return V;
-  if (Value *V = foldIsPowerOf2OrZero(RHS, LHS, IsAnd, Builder))
+  if (Value *V = foldIsPowerOf2OrZero(RHS, LHS, IsAnd, Builder, *this))
     return V;
 
   // TODO: One of these directions is fine with logical and/or, the other could

diff --git a/llvm/test/Transforms/InstCombine/ispow2.ll b/llvm/test/Transforms/InstCombine/ispow2.ll
@@ -1546,3 +1546,29 @@ entry:
   %sel = select i1 %cmp1, i1 true, i1 %cmp2
   ret i1 %sel
 }
+
+define i1 @is_power2_or_zero_with_range(i32 %x) {
+; CHECK-LABEL: @is_power2_or_zero_with_range(
+; CHECK-NEXT:    [[CTPOP:%.*]] = call range(i32 0, 33) i32 @llvm.ctpop.i32(i32 [[X:%.*]])
+; CHECK-NEXT:    [[RES:%.*]] = icmp ult i32 [[CTPOP]], 2
+; CHECK-NEXT:    ret i1 [[RES]]
+;
+  %ctpop = call range(i32 1, 33) i32 @llvm.ctpop.i32(i32 %x)
+  %cmp = icmp eq i32 %ctpop, 1
+  %notzero = icmp eq i32 %x, 0
+  %res = select i1 %notzero, i1 true, i1 %cmp
+  ret i1 %res
+}
+
+define i1 @is_power2_or_zero_inv_with_range(i32 %x) {
+; CHECK-LABEL: @is_power2_or_zero_inv_with_range(
+; CHECK-NEXT:    [[CTPOP:%.*]] = call range(i32 0, 33) i32 @llvm.ctpop.i32(i32 [[X:%.*]])
+; CHECK-NEXT:    [[RES:%.*]] = icmp ugt i32 [[CTPOP]], 1
+; CHECK-NEXT:    ret i1 [[RES]]
+;
+  %ctpop = call range(i32 1, 33) i32 @llvm.ctpop.i32(i32 %x)
+  %cmp = icmp ne i32 %ctpop, 1
+  %notzero = icmp ne i32 %x, 0
+  %res = select i1 %notzero, i1 %cmp, i1 false
+  ret i1 %res
+}