From 6a73128f15c5e7f41038bc432ad251659cba1ab2 Mon Sep 17 00:00:00 2001
From: Taewook Oh <twoh@fb.com>
Date: Mon, 27 Feb 2017 19:30:01 +0000
Subject: [PATCH] [TailDuplicator] Maintain DebugLoc for branch instructions

Summary: Existing implementation of duplicateSimpleBB function drops DebugLoc metadata of branch instructions during the transformation. This patch addresses this issue by making newly created branch instructions to keep the metadata of replaced branch instructions.

Reviewers: qcolombet, craig.topper, aprantl, MatzeB, sanjoy, dblaikie

Reviewed By: dblaikie

Subscribers: dblaikie, llvm-commits

Differential Revision: https://reviews.llvm.org/D30026

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296371 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/TailDuplicator.cpp        |  3 +-
 test/CodeGen/X86/tail-dup-debugloc.ll | 56 +++++++++++++++++++++++++++
 2 files changed, 58 insertions(+), 1 deletion(-)
 create mode 100644 test/CodeGen/X86/tail-dup-debugloc.ll

diff --git a/lib/CodeGen/TailDuplicator.cpp b/lib/CodeGen/TailDuplicator.cpp
index 7709236bbaa..d2414200e9d 100644
--- a/lib/CodeGen/TailDuplicator.cpp
+++ b/lib/CodeGen/TailDuplicator.cpp
@@ -725,6 +725,7 @@ bool TailDuplicator::duplicateSimpleBB(
     if (PredTBB == NextBB && PredFBB == nullptr)
       PredTBB = nullptr;
 
+    auto DL = PredBB->findBranchDebugLoc();
     TII->removeBranch(*PredBB);
 
     if (!PredBB->isSuccessor(NewTarget))
@@ -735,7 +736,7 @@ bool TailDuplicator::duplicateSimpleBB(
     }
 
     if (PredTBB)
-      TII->insertBranch(*PredBB, PredTBB, PredFBB, PredCond, DebugLoc());
+      TII->insertBranch(*PredBB, PredTBB, PredFBB, PredCond, DL);
 
     TDBBs.push_back(PredBB);
   }
diff --git a/test/CodeGen/X86/tail-dup-debugloc.ll b/test/CodeGen/X86/tail-dup-debugloc.ll
new file mode 100644
index 00000000000..c5ca6fc5750
--- /dev/null
+++ b/test/CodeGen/X86/tail-dup-debugloc.ll
@@ -0,0 +1,56 @@
+; RUN: llc -stop-after=tailduplication -march=x86-64 < %s | FileCheck %s
+;
+; Check that DebugLoc attached to the branch instruction of 
+; 'while.cond1.preheader.lr.ph' survives after tailduplication pass.
+;
+; CHECK: [[DLOC:![0-9]+]] = !DILocation(line: 9, column: 5, scope: !{{[0-9]+}})
+; CHECK: [[VREG:%[^ ]+]] = COPY %rdi
+; CHECK: TEST64rr [[VREG]], [[VREG]]
+; CHECK-NEXT: JE_1 {{.+}}, debug-location [[DLOC]]
+; CHECK-NEXT: JMP_1 {{.+}}, debug-location [[DLOC]]
+
+target triple = "x86_64-unknown-linux-gnu"
+
+%struct.Node = type { %struct.Node* }
+
+define i32 @foo(%struct.Node* readonly %node, %struct.Node* readnone %root) !dbg !6 {
+entry:
+  %cmp = icmp eq %struct.Node* %node, %root, !dbg !8
+  br i1 %cmp, label %while.end4, label %while.cond1.preheader.lr.ph, !dbg !10
+
+while.cond1.preheader.lr.ph:                      ; preds = %entry
+  %tobool = icmp eq %struct.Node* %node, null
+  br i1 %tobool, label %while.cond1.preheader.us.preheader, label %while.body2.preheader, !dbg !11
+
+while.body2.preheader:                            ; preds = %while.cond1.preheader.lr.ph
+  br label %while.body2, !dbg !11
+
+while.cond1.preheader.us.preheader:               ; preds = %while.cond1.preheader.lr.ph
+  br label %while.cond1.preheader.us, !dbg !10
+
+while.cond1.preheader.us:                         ; preds = %while.cond1.preheader.us.preheader, %while.cond1.preheader.us
+  br label %while.cond1.preheader.us, !dbg !10
+
+while.body2:                                      ; preds = %while.body2.preheader, %while.body2
+  br label %while.body2, !dbg !11
+
+while.end4:                                       ; preds = %entry
+  ret i32 0, !dbg !12
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, isOptimized: true, emissionKind: LineTablesOnly)
+!1 = !DIFile(filename: "foo.c", directory: "b/")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{}
+!6 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 5, type: !7, isLocal: false, isDefinition: true, scopeLine: 5, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !2)
+!7 = !DISubroutineType(types: !2)
+!8 = !DILocation(line: 7, column: 15, scope: !9)
+!9 = !DILexicalBlockFile(scope: !6, file: !1, discriminator: 2)
+!10 = !DILocation(line: 7, column: 3, scope: !9)
+!11 = !DILocation(line: 9, column: 5, scope: !9)
+!12 = !DILocation(line: 14, column: 3, scope: !6)
-- 
2.50.1