llvm-reduce: Handle nneg flag

Author: arsenm

llvm/test/tools/llvm-reduce/reduce-flags.ll

@@ -200,3 +200,19 @@ define float @fadd_nnan_ninf_keep_nnan(float %a, float %b) {
   %op = fadd nnan ninf float %a, %b
   ret float %op
 }
+
+; CHECK-LABEL: @zext_nneg_drop(
+; INTERESTING: = zext
+; RESULT: zext i32
+define i64 @zext_nneg_drop(i32 %a) {
+  %op = zext nneg i32 %a to i64
+  ret i64 %op
+}
+
+; CHECK-LABEL: @zext_nneg_keep(
+; INTERESTING: = zext nneg
+; RESULT: zext nneg i32
+define i64 @zext_nneg_keep(i32 %a) {
+  %op = zext nneg i32 %a to i64
+  ret i64 %op
+}

llvm/tools/llvm-reduce/deltas/ReduceInstructionFlags.cpp

@@ -30,6 +30,9 @@ static void reduceFlagsInModule(Oracle &O, ReducerWorkItem &WorkItem) {
       } else if (auto *PE = dyn_cast<PossiblyExactOperator>(&I)) {
         if (PE->isExact() && !O.shouldKeep())
           I.setIsExact(false);
+      } else if (auto *NNI = dyn_cast<PossiblyNonNegInst>(&I)) {
+        if (NNI->hasNonNeg() && !O.shouldKeep())
+          NNI->setNonNeg(false);
       } else if (auto *GEP = dyn_cast<GetElementPtrInst>(&I)) {
         if (GEP->isInBounds() && !O.shouldKeep())
           GEP->setIsInBounds(false);