[llvm] [LV] Fix MinBWs in WidenIntrinsic case (PR #137005)

[Florian Hahn via llvm-commits]

================
@@ -0,0 +1,45 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -passes=loop-vectorize -S %s | FileCheck %s
+
+define void @pr87407(ptr %dst, i64 %n) {
+; CHECK-LABEL: define void @pr87407(
+; CHECK-SAME: ptr [[DST:%.*]], i64 [[N:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*]]:
+; CHECK-NEXT:    [[ZEXT_0:%.*]] = zext i8 0 to i64
+; CHECK-NEXT:    br label %[[LOOP:.*]]
+; CHECK:       [[LOOP]]:
+; CHECK-NEXT:    [[IV:%.*]] = phi i64 [ [[IV_NEXT:%.*]], %[[LOOP]] ], [ 0, %[[ENTRY]] ]
+; CHECK-NEXT:    [[MAX:%.*]] = tail call i64 @llvm.umax.i64(i64 [[ZEXT_0]], i64 0)
+; CHECK-NEXT:    [[CMP_MAX_0:%.*]] = icmp ne i64 [[MAX]], 0
+; CHECK-NEXT:    [[ZEXT_CMP:%.*]] = zext i1 [[CMP_MAX_0]] to i64
+; CHECK-NEXT:    [[TRUNC:%.*]] = trunc i64 [[ZEXT_CMP]] to i32
+; CHECK-NEXT:    [[SHL:%.*]] = shl i32 [[TRUNC]], 8
+; CHECK-NEXT:    [[RES:%.*]] = trunc i32 [[SHL]] to i8
+; CHECK-NEXT:    [[IV_NEXT]] = add i64 [[IV]], 1
+; CHECK-NEXT:    [[EXIT_COND:%.*]] = icmp ne i64 [[IV_NEXT]], [[N]]
+; CHECK-NEXT:    br i1 [[EXIT_COND]], label %[[LOOP]], label %[[EXIT:.*]]
+; CHECK:       [[EXIT]]:
+; CHECK-NEXT:    [[RES_LCSSA:%.*]] = phi i8 [ [[RES]], %[[LOOP]] ]
+; CHECK-NEXT:    store i8 [[RES_LCSSA]], ptr [[DST]], align 1
+; CHECK-NEXT:    ret void
+;
+entry:
+  %zext.0 = zext i8 0 to i64
----------------
fhahn wrote:

can we make this `zext` not fold-able?

https://github.com/llvm/llvm-project/pull/137005