[llvm] [LV] Emit better debug and opt-report messages when vectorization is disallowed in the LoopVectorizer (PR #158513)

[Florian Hahn via llvm-commits]

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@@ -0,0 +1,42 @@
+; This test checks that we emit only the correct debug messages and
+; optimization remark when the loop vectorizer is disabled by loop metadata
+; that requests no loop transformations.
+
+; REQUIRES: asserts
+; RUN: opt -passes=loop-vectorize -pass-remarks=loop-vectorize \
+; RUN:     -pass-remarks-missed=loop-vectorize \
+; RUN:     -pass-remarks-analysis=loop-vectorize -debug -disable-output \
+; RUN:     -force-vector-interleave=1 -force-vector-width=2 \
+; RUN:     < %s 2>&1 | FileCheck %s
+; CHECK-NOT: LV: We can vectorize this loop
+; CHECK-NOT: LV: Not vectorizing: #pragma vectorize disable.
+; CHECK-NOT: LV: [BUG] Not vectorizing: loop vect disabled for an unknown reason
+; CHECK-NOT: LV: Not vectorizing: VectorizeOnlyWhenForced is set
+; CHECK-NOT: LV: Not vectorizing: Disabled/already vectorized
+; CHECK-NOT: LV: Not vectorizing: Cannot prove legality
+; CHECK: LV: Loop hints: force=disabled
+; CHECK: LV: Not vectorizing: loop hasDisableAllTransformsHint.
+; CHECK: remark:
+; CHECK-SAME: loop not vectorized: loop transformations are disabled
+; CHECK: LV: Loop hints prevent vectorization
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
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fhahn wrote:

```suggestion

```

https://github.com/llvm/llvm-project/pull/158513