llvm-reduce: Reduce nuw/nsw flags from trunc

Author: arsenm

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

@@ -232,3 +232,35 @@ define i32 @or_disjoint_keep(i32 %a, i32 %b) {
   %op = or disjoint i32 %a, %b
   ret i32 %op
 }
+
+; CHECK-LABEL: @trunc_nuw_drop(
+; INTERESTING: = trunc
+; RESULT: trunc i64
+define i32 @trunc_nuw_drop(i64 %a) {
+  %op = trunc nuw i64 %a to i32
+  ret i32 %op
+}
+
+; CHECK-LABEL: @trunc_nuw_keep(
+; INTERESTING: = trunc nuw
+; RESULT: trunc nuw i64
+define i32 @trunc_nuw_keep(i64 %a) {
+  %op = trunc nuw i64 %a to i32
+  ret i32 %op
+}
+
+; CHECK-LABEL: @trunc_nsw_drop(
+; INTERESTING: = trunc
+; RESULT: trunc i64
+define i32 @trunc_nsw_drop(i64 %a) {
+  %op = trunc nsw i64 %a to i32
+  ret i32 %op
+}
+
+; CHECK-LABEL: @trunc_nsw_keep(
+; INTERESTING: = trunc nsw
+; RESULT: trunc nsw i64
+define i32 @trunc_nsw_keep(i64 %a) {
+  %op = trunc nsw i64 %a to i32
+  ret i32 %op
+}

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

@@ -27,6 +27,11 @@ static void reduceFlagsInModule(Oracle &O, ReducerWorkItem &WorkItem) {
           I.setHasNoSignedWrap(false);
         if (OBO->hasNoUnsignedWrap() && !O.shouldKeep())
           I.setHasNoUnsignedWrap(false);
+      } else if (auto *Trunc = dyn_cast<TruncInst>(&I)) {
+        if (Trunc->hasNoSignedWrap() && !O.shouldKeep())
+          Trunc->setHasNoSignedWrap(false);
+        if (Trunc->hasNoUnsignedWrap() && !O.shouldKeep())
+          Trunc->setHasNoUnsignedWrap(false);
       } else if (auto *PE = dyn_cast<PossiblyExactOperator>(&I)) {
         if (PE->isExact() && !O.shouldKeep())
           I.setIsExact(false);