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Co-authored-by: Nikita Popov <[email protected]>

Author: gaynor-anthropic

llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp

@@ -1791,8 +1791,8 @@ Instruction *InstCombinerImpl::visitAdd(BinaryOperator &I) {
   // (X >> log2(N)) + zext(X & (N-1) != 0) --> (X + (N-1)) >> log2(N)
   // This is valid when adding (N-1) to X doesn't overflow.
   {
-    Value *X = nullptr;
-    const APInt *ShiftAmt = nullptr, *Mask = nullptr;
+    Value *X;
+    const APInt *ShiftAmt, *Mask;
     CmpPredicate Pred;
 
     // Match: (X >> C) + zext((X & Mask) != 0)
@@ -1806,9 +1806,7 @@ Instruction *InstCombinerImpl::visitAdd(BinaryOperator &I) {
 
       // Check if X + Mask doesn't overflow
       Constant *MaskC = ConstantInt::get(X->getType(), *Mask);
-      bool WillNotOverflowUnsigned = willNotOverflowUnsignedAdd(X, MaskC, I);
-
-      if (WillNotOverflowUnsigned) {
+      if (willNotOverflowUnsignedAdd(X, MaskC, I)) {
         // (X + Mask) >> ShiftAmt
         Value *Add = Builder.CreateNUWAdd(X, MaskC);
         return BinaryOperator::CreateLShr(

llvm/test/Transforms/InstCombine/add.ll

@@ -4279,7 +4279,7 @@ declare i32 @llvm.ctlz.i32(i32, i1)
 ; This is only valid when x + (N-1) doesn't overflow
 
 ; Test with known range that prevents overflow
-define noundef range(i32 0, 100) i32 @ceil_div_by_8_known_range(i32 noundef range(i32 0, 100) %x) {
+define i32 @ceil_div_by_8_known_range(i32 range(i32 0, 100) %x) {
 ; CHECK-LABEL: @ceil_div_by_8_known_range(
 ; CHECK-NEXT:    [[TMP1:%.*]] = add nuw nsw i32 [[X:%.*]], 7
 ; CHECK-NEXT:    [[R:%.*]] = lshr i32 [[TMP1]], 3
@@ -4294,7 +4294,7 @@ define noundef range(i32 0, 100) i32 @ceil_div_by_8_known_range(i32 noundef rang
 }
 
 ; Test with the exact IR from the original testcase
-define noundef range(i32 0, 6) i32 @ceil_div_from_clz(i32 noundef %v) {
+define i32 @ceil_div_from_clz(i32 %v) {
 ; CHECK-LABEL: @ceil_div_from_clz(
 ; CHECK-NEXT:    [[CTLZ:%.*]] = tail call range(i32 0, 33) i32 @llvm.ctlz.i32(i32 [[V:%.*]], i1 false)
 ; CHECK-NEXT:    [[TMP1:%.*]] = sub nuw nsw i32 39, [[CTLZ]]