[llvm] [LV][EVL] Add test case for checking debug info when tail folding by EVL. nfc (PR #172429)

[Mel Chen via llvm-commits]

================
@@ -0,0 +1,94 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6
+; RUN: opt -passes=loop-vectorize \
+; RUN: -prefer-predicate-over-epilogue=predicate-else-scalar-epilogue \
+; RUN: -mtriple=riscv64 -mattr=+v -S < %s | FileCheck %s
+
+define void @reverse_store(ptr %a, i64 %n) !dbg !4 {
+; CHECK-LABEL: define void @reverse_store(
+; CHECK-SAME: ptr [[A:%.*]], i64 [[N:%.*]]) #[[ATTR0:[0-9]+]] !dbg [[DBG4:![0-9]+]] {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[TMP0:%.*]] = add i64 [[N]], 1
+; CHECK-NEXT:    [[UMIN:%.*]] = call i64 @llvm.umin.i64(i64 [[N]], i64 1)
+; CHECK-NEXT:    [[TMP1:%.*]] = sub i64 [[TMP0]], [[UMIN]]
+; CHECK-NEXT:    br label %[[VECTOR_PH:.*]]
+; CHECK:       [[VECTOR_PH]]:
+; CHECK-NEXT:    [[TMP2:%.*]] = call <vscale x 2 x i64> @llvm.stepvector.nxv2i64()
+; CHECK-NEXT:    [[BROADCAST_SPLATINSERT:%.*]] = insertelement <vscale x 2 x i64> poison, i64 [[N]], i64 0
+; CHECK-NEXT:    [[BROADCAST_SPLAT:%.*]] = shufflevector <vscale x 2 x i64> [[BROADCAST_SPLATINSERT]], <vscale x 2 x i64> poison, <vscale x 2 x i32> zeroinitializer
+; CHECK-NEXT:    [[TMP3:%.*]] = mul nsw <vscale x 2 x i64> [[TMP2]], splat (i64 -1)
+; CHECK-NEXT:    [[INDUCTION:%.*]] = add nsw <vscale x 2 x i64> [[BROADCAST_SPLAT]], [[TMP3]]
+; CHECK-NEXT:    br label %[[VECTOR_BODY:.*]]
+; CHECK:       [[VECTOR_BODY]]:
+; CHECK-NEXT:    [[VEC_IND:%.*]] = phi <vscale x 2 x i64> [ [[INDUCTION]], %[[VECTOR_PH]] ], [ [[VEC_IND_NEXT:%.*]], %[[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[AVL:%.*]] = phi i64 [ [[TMP1]], %[[VECTOR_PH]] ], [ [[AVL_NEXT:%.*]], %[[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[TMP4:%.*]] = call i32 @llvm.experimental.get.vector.length.i64(i64 [[AVL]], i32 2, i1 true)
+; CHECK-NEXT:    [[TMP5:%.*]] = zext i32 [[TMP4]] to i64
+; CHECK-NEXT:    [[TMP6:%.*]] = mul nsw i64 -1, [[TMP5]]
+; CHECK-NEXT:    [[BROADCAST_SPLATINSERT1:%.*]] = insertelement <vscale x 2 x i64> poison, i64 [[TMP6]], i64 0
+; CHECK-NEXT:    [[BROADCAST_SPLAT2:%.*]] = shufflevector <vscale x 2 x i64> [[BROADCAST_SPLATINSERT1]], <vscale x 2 x i64> poison, <vscale x 2 x i32> zeroinitializer
+; CHECK-NEXT:    [[TMP7:%.*]] = add nsw <vscale x 2 x i64> [[VEC_IND]], splat (i64 -1), !dbg [[DBG7:![0-9]+]]
+; CHECK-NEXT:    [[TMP8:%.*]] = extractelement <vscale x 2 x i64> [[TMP7]], i32 0
+; CHECK-NEXT:    [[TMP9:%.*]] = getelementptr inbounds nuw i64, ptr [[A]], i64 [[TMP8]], !dbg [[DBG8:![0-9]+]]
+; CHECK-NEXT:    [[TMP10:%.*]] = zext i32 [[TMP4]] to i64, !dbg [[DBG9:![0-9]+]]
+; CHECK-NEXT:    [[TMP11:%.*]] = mul i64 0, [[TMP10]], !dbg [[DBG9]]
+; CHECK-NEXT:    [[TMP12:%.*]] = sub i64 [[TMP10]], 1, !dbg [[DBG9]]
+; CHECK-NEXT:    [[TMP13:%.*]] = mul i64 -1, [[TMP12]], !dbg [[DBG9]]
+; CHECK-NEXT:    [[TMP14:%.*]] = getelementptr i64, ptr [[TMP9]], i64 [[TMP11]], !dbg [[DBG9]]
+; CHECK-NEXT:    [[TMP15:%.*]] = getelementptr i64, ptr [[TMP14]], i64 [[TMP13]], !dbg [[DBG9]]
+; CHECK-NEXT:    [[VP_REVERSE:%.*]] = call <vscale x 2 x i64> @llvm.experimental.vp.reverse.nxv2i64(<vscale x 2 x i64> [[TMP7]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP4]]), !dbg [[DBG9]]
+; CHECK-NEXT:    call void @llvm.vp.store.nxv2i64.p0(<vscale x 2 x i64> [[VP_REVERSE]], ptr align 8 [[TMP15]], <vscale x 2 x i1> splat (i1 true), i32 [[TMP4]]), !dbg [[DBG9]]
+; CHECK-NEXT:    [[AVL_NEXT]] = sub nuw i64 [[AVL]], [[TMP5]]
+; CHECK-NEXT:    [[VEC_IND_NEXT]] = add nsw <vscale x 2 x i64> [[VEC_IND]], [[BROADCAST_SPLAT2]]
+; CHECK-NEXT:    [[TMP17:%.*]] = icmp eq i64 [[AVL_NEXT]], 0
+; CHECK-NEXT:    br i1 [[TMP17]], label %[[MIDDLE_BLOCK:.*]], label %[[VECTOR_BODY]], !dbg [[DBG10:![0-9]+]], !llvm.loop [[LOOP11:![0-9]+]]
+; CHECK:       [[MIDDLE_BLOCK]]:
+; CHECK-NEXT:    br label %[[FOR_COND_CLEANUP:.*]], !dbg [[DBG10]]
+; CHECK:       [[FOR_COND_CLEANUP]]:
+; CHECK-NEXT:    ret void
+;
+entry:
+  br label %for.body
+
+for.cond.cleanup:                                 ; preds = %for.body
+  ret void
+
+for.body:                                         ; preds = %entry, %for.body
+  %indvars.iv = phi i64 [ %n, %entry ], [ %indvars.iv.next, %for.body ]
+  %indvars.iv.next = add nsw i64 %indvars.iv, -1, !dbg !7
+  %arrayidx = getelementptr inbounds nuw i64, ptr %a, i64 %indvars.iv.next, !dbg !8
+  store i64 %indvars.iv.next, ptr %arrayidx, align 8, !dbg !9
+  %cmp = icmp samesign ugt i64 %indvars.iv, 1, !dbg !10
+  br i1 %cmp, label %for.body, label %for.cond.cleanup, !dbg !11, !llvm.loop !12
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "dbg-tail-folding-by-evl.cpp", directory: "/test/file/path")
+!2 = !{i32 2, !"Debug Info Version", i32 3}
+!3 = !{i32 7, !"debug-info-assignment-tracking", i1 true}
----------------
Mel-Chen wrote:

8dee92e6da7aa9d77c0c8200f24bd1f1979b3830
We can only remove `debug-info-assignment-tracking`. Removing the `Debug Info Version` causes all debug info to be ignored and dropped, and results in the warning:
```
warning: ignoring debug info with an invalid version (0) in <stdin>
```

https://github.com/llvm/llvm-project/pull/172429