[DebugInfo] Fix pr41180 : Loop Vectorization Debugify Failure

Bug: https://bugs.llvm.org/show_bug.cgi?id=41180

In the bug test case the debug location was missing for the cmp instruction in
the "middle block" BB. This patch fixes the bug by copying the debug location
from the cmp of the scalar loop's terminator branch, if it exists.

The patch also fixes the debug location on the subsequent branch instruction.
It was previously using the location of the of the original loop's pre-header
block terminator. Both of these instructions will now map to the source line of
the conditional branch in the original loop.

A regression test has been added that covers these issues.

Patch by Orlando Cazalet-Hyams!

Differential Revision: https://reviews.llvm.org/D59944

llvm-svn: 357499

1 files changed, 110 insertions, 0 deletions

diff --git a/llvm/test/Transforms/LoopVectorize/middle-block-dbg.ll b/llvm/test/Transforms/LoopVectorize/middle-block-dbg.ll
new file mode 100644
index 00000000000..662d8ed7499
--- /dev/null
+++ b/llvm/test/Transforms/LoopVectorize/middle-block-dbg.ll
@@ -0,0 +1,110 @@
+; RUN: opt -loop-vectorize -force-vector-width=2 -S < %s | FileCheck %s
+;
+; Confirm that the DebugLoc info for the instructions in the middle block of a
+; vectorized loop are correct. The Cmp and Br instructions should map to the
+; same source lines as the Cmp and Br of the scalar loop.
+
+; CHECK-LABEL: middle.block:
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq {{.*}}!dbg ![[DL:[0-9]+]]
+; CHECK-NEXT: br i1 [[CMP]]{{.*}} !dbg ![[DL]]
+; CHECK: ![[DL]] = !DILocation(line: 6,
+
+; This IR can be generated by running:
+; clang -g -O2 -emit-llvm -S -mllvm -opt-bisect-limit=68 vec.cpp -o - | opt -loop-vectorize -force-vector-width=2 -S -o vec.ll
+;
+; Where vec.cpp contains:
+;
+; extern int x;
+; extern int y;
+; void a() {
+;     const int len = x;
+;     int b[len];
+;     for(int i = 0; i< len; ++i)
+;         b[i] = x;
+;
+;     y = b[x] + b[x-5];
+; }
+
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+
+@"?x@@3HA" = external dso_local local_unnamed_addr global i32, align 4
+@"?y@@3HA" = external dso_local local_unnamed_addr global i32, align 4
+
+define dso_local void @"?a@@YAXXZ"() local_unnamed_addr #0 !dbg !8 {
+entry:
+  %0 = load i32, i32* @"?x@@3HA", align 4, !dbg !23, !tbaa !24
+  %1 = zext i32 %0 to i64, !dbg !28
+  %vla = alloca i32, i64 %1, align 16, !dbg !28
+  %cmp10 = icmp sgt i32 %0, 0, !dbg !30
+  br i1 %cmp10, label %for.body.preheader, label %for.cond.cleanup, !dbg !30
+
+for.body.preheader:
+  br label %for.body, !dbg !31
+
+for.cond.cleanup.loopexit:
+  %idxprom1.phi.trans.insert = sext i32 %0 to i64
+  %arrayidx2.phi.trans.insert = getelementptr inbounds i32, i32* %vla, i64 %idxprom1.phi.trans.insert
+  %.pre = load i32, i32* %arrayidx2.phi.trans.insert, align 4, !dbg !33, !tbaa !24
+  br label %for.cond.cleanup, !dbg !33
+
+for.cond.cleanup:
+  %2 = phi i32 [ %.pre, %for.cond.cleanup.loopexit ], [ undef, %entry ], !dbg !33
+  %sub = add nsw i32 %0, -5, !dbg !33
+  %idxprom3 = sext i32 %sub to i64, !dbg !33
+  %arrayidx4 = getelementptr inbounds i32, i32* %vla, i64 %idxprom3, !dbg !33
+  %3 = load i32, i32* %arrayidx4, align 4, !dbg !33, !tbaa !24
+  %add = add nsw i32 %3, %2, !dbg !33
+  store i32 %add, i32* @"?y@@3HA", align 4, !dbg !33, !tbaa !24
+  ret void, !dbg !34
+
+for.body:
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %for.body.preheader ]
+  %arrayidx = getelementptr inbounds i32, i32* %vla, i64 %indvars.iv, !dbg !31
+  store i32 %0, i32* %arrayidx, align 4, !dbg !31, !tbaa !24
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1, !dbg !35
+  %exitcond = icmp eq i64 %indvars.iv.next, %1, !dbg !30
+  br i1 %exitcond, label %for.cond.cleanup.loopexit, label %for.body, !dbg !30, !llvm.loop !36
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5, !6}
+!llvm.ident = !{!7}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 9.0.0 (https://github.com/llvm/llvm-project.git 045b8544fd2c4e14f7e72e0df2bc681d823b0838)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, nameTableKind: None)
+!1 = !DIFile(filename: "vec.cpp", directory: "C:\5CUsers\5Cgbhyamso\5Cdev\5Cllvm\5Csamples", checksumkind: CSK_MD5, checksum: "fed997f50117f5514a69caf1c2fb2c49")
+!2 = !{}
+!3 = !{i32 2, !"CodeView", i32 1}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 2}
+!6 = !{i32 7, !"PIC Level", i32 2}
+!7 = !{!"clang version 9.0.0 (https://github.com/llvm/llvm-project.git 045b8544fd2c4e14f7e72e0df2bc681d823b0838)"}
+!8 = distinct !DISubprogram(name: "a", linkageName: "?a@@YAXXZ", scope: !1, file: !1, line: 3, type: !9, scopeLine: 3, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !11)
+!9 = !DISubroutineType(types: !10)
+!10 = !{null}
+!11 = !{!12, !15, !17, !21}
+!12 = !DILocalVariable(name: "len", scope: !8, file: !1, line: 4, type: !13)
+!13 = !DIDerivedType(tag: DW_TAG_const_type, baseType: !14)
+!14 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!15 = !DILocalVariable(name: "__vla_expr0", scope: !8, type: !16, flags: DIFlagArtificial)
+!16 = !DIBasicType(name: "long long unsigned int", size: 64, encoding: DW_ATE_unsigned)
+!17 = !DILocalVariable(name: "b", scope: !8, file: !1, line: 5, type: !18)
+!18 = !DICompositeType(tag: DW_TAG_array_type, baseType: !14, elements: !19)
+!19 = !{!20}
+!20 = !DISubrange(count: !15)
+!21 = !DILocalVariable(name: "i", scope: !22, file: !1, line: 6, type: !14)
+!22 = distinct !DILexicalBlock(scope: !8, file: !1, line: 6)
+!23 = !DILocation(line: 4, scope: !8)
+!24 = !{!25, !25, i64 0}
+!25 = !{!"int", !26, i64 0}
+!26 = !{!"omnipotent char", !27, i64 0}
+!27 = !{!"Simple C++ TBAA"}
+!28 = !DILocation(line: 5, scope: !8)
+!29 = !DILocation(line: 0, scope: !8)
+!30 = !DILocation(line: 6, scope: !22)
+!31 = !DILocation(line: 7, scope: !32)
+!32 = distinct !DILexicalBlock(scope: !22, file: !1, line: 6)
+!33 = !DILocation(line: 9, scope: !8)
+!34 = !DILocation(line: 10, scope: !8)
+!35 = !DILocation(line: 6, scope: !32)
+!36 = distinct !{!36, !30, !37}
+!37 = !DILocation(line: 7, scope: !22)