From b0585893ccb78508e900754c4974b0e95aafd4bf Mon Sep 17 00:00:00 2001
From: Vedant Kumar <vsk@apple.com>
Date: Tue, 17 Apr 2018 22:03:08 +0000
Subject: [Mem2Reg] Create merged debug locations for inserted phis

Track the debug locations of the incoming values to newly-created phis,
and apply merged debug locations to the phis.

A merged location will be on line 0, but will have the correct scope
set. This improves crash reporting when an inlined instruction with a
merged location triggers a machine exception. A debugger will be able to
narrow down the crash to the correct inlined scope, instead of simply
pointing to the outer scope of the caller.

Taken together with a change allows generating merged line-0 locations
for  instructions which aren't calls, this results in a 0.5% increase in
the uncompressed size of the .debug_line section of a stage2+Release
build of clang (-O3 -g).

rdar://33858697

Differential Revision: https://reviews.llvm.org/D45397

llvm-svn: 330227
---
 .../Transforms/Mem2Reg/dbg-inline-scope-for-phi.ll | 110 +++++++++++++++++++++
 1 file changed, 110 insertions(+)
 create mode 100644 llvm/test/Transforms/Mem2Reg/dbg-inline-scope-for-phi.ll

(limited to 'llvm/test/Transforms/Mem2Reg')

diff --git a/llvm/test/Transforms/Mem2Reg/dbg-inline-scope-for-phi.ll b/llvm/test/Transforms/Mem2Reg/dbg-inline-scope-for-phi.ll
new file mode 100644
index 00000000000..680f2dd2833
--- /dev/null
+++ b/llvm/test/Transforms/Mem2Reg/dbg-inline-scope-for-phi.ll
@@ -0,0 +1,110 @@
+; RUN: opt -S < %s -mem2reg -verify | FileCheck %s
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.13.0"
+
+; Original source (with some whitespace removed):
+;
+;   extern int *getp();
+;   extern int cond();
+;   int get1() { return *getp(); }
+;   int get2(int *p) { return *p; }
+;   int bug(int *p) {
+;     if (cond()) return get1();
+;     else return get2(p);
+;   }
+
+define i32 @get1() !dbg !8 {
+  %1 = call i32* (...) @getp(), !dbg !12
+  %2 = load i32, i32* %1, align 4, !dbg !13
+  ret i32 %2, !dbg !14
+}
+
+declare i32* @getp(...)
+
+define i32 @get2(i32*) !dbg !15 {
+  %2 = alloca i32*, align 8
+  store i32* %0, i32** %2, align 8
+  call void @llvm.dbg.declare(metadata i32** %2, metadata !19, metadata !DIExpression()), !dbg !20
+  %3 = load i32*, i32** %2, align 8, !dbg !21
+  %4 = load i32, i32* %3, align 4, !dbg !22
+  ret i32 %4, !dbg !23
+}
+
+declare void @llvm.dbg.declare(metadata, metadata, metadata)
+
+; CHECK-LABEL: define i32 @bug
+define i32 @bug(i32*) !dbg !24 {
+  %2 = alloca i32, align 4
+  %3 = alloca i32*, align 8
+  store i32* %0, i32** %3, align 8
+  call void @llvm.dbg.declare(metadata i32** %3, metadata !25, metadata !DIExpression()), !dbg !26
+  %4 = call i32 (...) @cond(), !dbg !27
+  %5 = icmp ne i32 %4, 0, !dbg !27
+  br i1 %5, label %6, label %8, !dbg !29
+
+; <label>:6:                                      ; preds = %1
+  %7 = call i32 @get1(), !dbg !30
+  store i32 %7, i32* %2, align 4, !dbg !31
+  br label %11, !dbg !31
+
+; <label>:8:                                      ; preds = %1
+  %9 = load i32*, i32** %3, align 8, !dbg !32
+  %10 = call i32 @get2(i32* %9), !dbg !33
+  store i32 %10, i32* %2, align 4, !dbg !34
+  br label %11, !dbg !34
+
+; <label>:11:                                     ; preds = %8, %6
+  %12 = load i32, i32* %2, align 4, !dbg !35
+  ret i32 %12, !dbg !35
+
+  ; CHECK: [[phi:%.*]] = phi i32 [ {{.*}} ], [ {{.*}} ], !dbg [[mergedLoc:![0-9]+]]
+  ; CHECK-NEXT: ret i32 [[phi]], !dbg [[retLoc:![0-9]+]]
+}
+
+; CHECK: [[commonScope:![0-9]+]] = distinct !DILexicalBlock(scope: {{.*}}, file: !1, line: 15, column: 7)
+; CHECK: [[mergedLoc]] = !DILocation(line: 0, scope: [[commonScope]])
+; CHECK: [[retLoc]] = !DILocation(line: 23, column: 1
+
+declare i32 @cond(...)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5, !6}
+!llvm.ident = !{!7}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "Apple LLVM version 9.1.0 (clang-902.2.37.2)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "bug.c", directory: "/bug")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!6 = !{i32 7, !"PIC Level", i32 2}
+!7 = !{!"Apple LLVM version 9.1.0 (clang-902.2.37.2)"}
+!8 = distinct !DISubprogram(name: "get1", scope: !1, file: !1, line: 6, type: !9, isLocal: false, isDefinition: true, scopeLine: 6, isOptimized: false, unit: !0, variables: !2)
+!9 = !DISubroutineType(types: !10)
+!10 = !{!11}
+!11 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!12 = !DILocation(line: 7, column: 11, scope: !8)
+!13 = !DILocation(line: 7, column: 10, scope: !8)
+!14 = !DILocation(line: 7, column: 3, scope: !8)
+!15 = distinct !DISubprogram(name: "get2", scope: !1, file: !1, line: 10, type: !16, isLocal: false, isDefinition: true, scopeLine: 10, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!16 = !DISubroutineType(types: !17)
+!17 = !{!11, !18}
+!18 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !11, size: 64)
+!19 = !DILocalVariable(name: "p", arg: 1, scope: !15, file: !1, line: 10, type: !18)
+!20 = !DILocation(line: 10, column: 15, scope: !15)
+!21 = !DILocation(line: 11, column: 11, scope: !15)
+!22 = !DILocation(line: 11, column: 10, scope: !15)
+!23 = !DILocation(line: 11, column: 3, scope: !15)
+!24 = distinct !DISubprogram(name: "bug", scope: !1, file: !1, line: 14, type: !16, isLocal: false, isDefinition: true, scopeLine: 14, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!25 = !DILocalVariable(name: "p", arg: 1, scope: !24, file: !1, line: 14, type: !18)
+!26 = !DILocation(line: 14, column: 14, scope: !24)
+!27 = !DILocation(line: 15, column: 7, scope: !28)
+!28 = distinct !DILexicalBlock(scope: !24, file: !1, line: 15, column: 7)
+!29 = !DILocation(line: 15, column: 7, scope: !24)
+!30 = !DILocation(line: 16, column: 12, scope: !28)
+!31 = !DILocation(line: 16, column: 5, scope: !28)
+!32 = !DILocation(line: 18, column: 17, scope: !28)
+!33 = !DILocation(line: 18, column: 12, scope: !28)
+!34 = !DILocation(line: 18, column: 5, scope: !28)
+!35 = !DILocation(line: 23, column: 1, scope: !24)
-- 
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