From 2d2520986ead1d49503cbef0394c843a7adcc2b2 Mon Sep 17 00:00:00 2001
From: "Duncan P. N. Exon Smith" <dexonsmith@apple.com>
Date: Fri, 3 Apr 2015 16:23:04 +0000
Subject: [PATCH] CodeGen: Fix MachineInstr::print() for DBG_VALUE

Grab the `MDLocalVariable` from the second-to-last argument; the last
argument is an `MDExpression`, and mixing them up will crash.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234019 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/MachineInstr.cpp   |  4 +--
 test/DebugInfo/X86/mi-print.ll | 56 ++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+), 2 deletions(-)
 create mode 100644 test/DebugInfo/X86/mi-print.ll

diff --git a/lib/CodeGen/MachineInstr.cpp b/lib/CodeGen/MachineInstr.cpp
index c2accbd1a2a..f1c0d8ef2ad 100644
--- a/lib/CodeGen/MachineInstr.cpp
+++ b/lib/CodeGen/MachineInstr.cpp
@@ -1711,9 +1711,9 @@ void MachineInstr::print(raw_ostream &OS, bool SkipOpers) const {
   }
 
   // Print debug location information.
-  if (isDebugValue() && getOperand(e - 1).isMetadata()) {
+  if (isDebugValue() && getOperand(e - 2).isMetadata()) {
     if (!HaveSemi) OS << ";";
-    DIVariable DV(getOperand(e - 1).getMetadata());
+    DIVariable DV(getOperand(e - 2).getMetadata());
     OS << " line no:" <<  DV.getLineNumber();
     if (auto *InlinedAt = DV.getInlinedAt()) {
       DebugLoc InlinedAtDL(InlinedAt);
diff --git a/test/DebugInfo/X86/mi-print.ll b/test/DebugInfo/X86/mi-print.ll
new file mode 100644
index 00000000000..49d9aa7c869
--- /dev/null
+++ b/test/DebugInfo/X86/mi-print.ll
@@ -0,0 +1,56 @@
+; RUN: llc -debug -mtriple x86_64-apple-darwin < %s -o /dev/null 2>&1 | FileCheck %s
+; REQUIRES: asserts
+; Check that llc -debug actually prints variables and locations, rather than
+; crashing.
+
+; CHECK: DBG_VALUE
+
+; Generated using `clang -g -O2 -S -emit-llvm -g` on the following source:
+;
+; static int foo(int x) { return x; }
+; int bar(int x) { return foo(x); }
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.10.0"
+
+; Function Attrs: nounwind readnone ssp uwtable
+define i32 @bar(i32 %x) #0 {
+entry:
+  tail call void @llvm.dbg.value(metadata i32 %x, i64 0, metadata !9, metadata !17), !dbg !18
+  tail call void @llvm.dbg.value(metadata i32 %x, i64 0, metadata !19, metadata !17), !dbg !21
+  ret i32 %x, !dbg !22
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.value(metadata, i64, metadata, metadata) #1
+
+attributes #0 = { nounwind readnone ssp uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="core2" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind readnone }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!13, !14, !15}
+!llvm.ident = !{!16}
+
+!0 = !MDCompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 3.7.0 (trunk 233919) (llvm/trunk 233920)", isOptimized: true, runtimeVersion: 0, emissionKind: 1, enums: !2, retainedTypes: !2, subprograms: !3, globals: !2, imports: !2)
+!1 = !MDFile(filename: "t.c", directory: "/Users/dexonsmith/data/llvm/debug-info/test/DebugInfo/X86")
+!2 = !{}
+!3 = !{!4, !10}
+!4 = !MDSubprogram(name: "bar", scope: !1, file: !1, line: 2, type: !5, isLocal: false, isDefinition: true, scopeLine: 2, flags: DIFlagPrototyped, isOptimized: true, function: i32 (i32)* @bar, variables: !8)
+!5 = !MDSubroutineType(types: !6)
+!6 = !{!7, !7}
+!7 = !MDBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!8 = !{!9}
+!9 = !MDLocalVariable(tag: DW_TAG_arg_variable, name: "x", arg: 1, scope: !4, file: !1, line: 2, type: !7)
+!10 = !MDSubprogram(name: "foo", scope: !1, file: !1, line: 1, type: !5, isLocal: true, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: true, variables: !11)
+!11 = !{!12}
+!12 = !MDLocalVariable(tag: DW_TAG_arg_variable, name: "x", arg: 1, scope: !10, file: !1, line: 1, type: !7)
+!13 = !{i32 2, !"Dwarf Version", i32 2}
+!14 = !{i32 2, !"Debug Info Version", i32 3}
+!15 = !{i32 1, !"PIC Level", i32 2}
+!16 = !{!"clang version 3.7.0 (trunk 233919) (llvm/trunk 233920)"}
+!17 = !MDExpression()
+!18 = !MDLocation(line: 2, column: 13, scope: !4)
+!19 = !MDLocalVariable(tag: DW_TAG_arg_variable, name: "x", arg: 1, scope: !10, file: !1, line: 1, type: !7, inlinedAt: !20)
+!20 = distinct !MDLocation(line: 2, column: 25, scope: !4)
+!21 = !MDLocation(line: 1, column: 20, scope: !10, inlinedAt: !20)
+!22 = !MDLocation(line: 2, column: 18, scope: !4)
-- 
2.34.1