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

[Tibor Győri via llvm-commits]

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@@ -0,0 +1,101 @@
+; TEST 1
+; This test checks that we emit only the correct debug messages and
+; optimization remark when the loop vectorizer is disabled by loop metadata.
+
+; 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:     < %s 2>&1 | FileCheck --check-prefix=METADATA %s
+; METADATA-NOT: LV: We can vectorize this loop
+; METADATA-NOT: LV: Not vectorizing: loop hasDisableAllTransformsHint
+; METADATA-NOT: LV: Not vectorizing: VectorizeOnlyWhenForced is set
+; METADATA-NOT: LV: Not vectorizing: Disabled/already vectorized
+; METADATA-NOT: LV: Not vectorizing: Cannot prove legality
+; METADATA: LV: Loop hints: force=disabled
+; METADATA: LV: Not vectorizing: #pragma vectorize disable.
+; METADATA: remark:
+; METADATA-SAME: loop not vectorized: vectorization is explicitly disabled
+; METADATA: LV: Loop hints prevent vectorization
+
+; TEST 2
+; This test checks that we emit only the correct debug messages and
+; optimization remark when the loop is not vectorized due to the 
+; vectorize-forced-only pass option being set.
+
+; Strip metadata for FORCEDONLY run, keep it for METADATA run
+; RUN: sed 's/,[[:space:]]*!llvm\.loop[[:space:]]*!0//' %s | \
+; RUN: opt -passes='loop-vectorize<vectorize-forced-only>' \
+; RUN:   -pass-remarks=loop-vectorize \
+; RUN:   -pass-remarks-missed=loop-vectorize \
+; RUN:   -pass-remarks-analysis=loop-vectorize -debug -disable-output \
+; RUN:   2>&1 | FileCheck --check-prefix=FORCEDONLY %s
+; FORCEDONLY-NOT: LV: We can vectorize this loop
+; FORCEDONLY-NOT: LV: Not vectorizing: loop hasDisableAllTransformsHint
+; FORCEDONLY-NOT: LV: Not vectorizing: #pragma vectorize disable
+; FORCEDONLY-NOT: LV: Not vectorizing: Disabled/already vectorized
+; FORCEDONLY-NOT: LV: Not vectorizing: Cannot prove legality
+; FORCEDONLY: LV: Loop hints: force=?
+; FORCEDONLY: LV: Not vectorizing: VectorizeOnlyWhenForced is set, and no #pragma vectorize enable
+; FORCEDONLY: remark:
+; FORCEDONLY-SAME: loop not vectorized: only vectorizing loops that explicitly request it
+; FORCEDONLY: LV: Loop hints prevent vectorization
+
+define i64 @disabled_loop_vectorization(ptr %src) {
+entry:
+  br label %loop
+
+loop:
+  %iv = phi i64 [ 0, %entry ], [ %inc, %loop ]
+  %arrayidx = getelementptr inbounds nuw double, ptr %src, i64 %iv
+  store double 1.234e+0, ptr %arrayidx, align 8
+  %inc = add nuw nsw i64 %iv, 1
+  %exitcond.not = icmp eq i64 %inc, 15
+  br i1 %exitcond.not, label %exit, label %loop, !llvm.loop !0
+
+exit:
+  ret i64 0
+}
+
+!0 = distinct !{!0, !1}
+!1 = !{!"llvm.loop.vectorize.enable", i1 false}
+
+; TEST 3
+; 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.
+
+; 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
----------------
TiborGY wrote:

Since opt seems to always output all of the remarks and debug messages first, before any of the IR, I could not get CHECK-LABEL to match on the actual function name. As a workaround I made it match a message that contains the function name in question. This is less elegant than I would like, but I cannot see a better solution without putting the two functions into separate files.

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