Fix for PR 19261:

llc doesn't generate nodes for unconditional fall-through branches for targets
without FastISel implementation (X86 has it, but can be disabled by
"-fast-isel=false") in SelectionDAGBuilder::visitBr().

So for line 4 in the following testcase

1: void foo(int i){
2:   switch(i){
3:   default:
4:     break;
5:   }
6:   return;
7: }

there is no corresponding line in .debug_line section, and a debugger
cannot set a breakpoint at line 4.

Fix this by always emitting a branch when we're not optimizing and add a
testcase to ensure that there's code on every line we'd want to break.

Patch by Daniil Fukalov.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205529 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 604ff70f92397d8985e8164c4b0b388697ef3157..4a6e5cf0361eaf1b7a6e23ee1ed9b9143945b500 100644 (file)
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -1571,8 +1571,9 @@ void SelectionDAGBuilder::visitBr(const BranchInst &I) {
     // Update machine-CFG edges.
     BrMBB->addSuccessor(Succ0MBB);
 
-    // If this is not a fall-through branch, emit the branch.
-    if (Succ0MBB != NextBlock)
+    // If this is not a fall-through branch or optimizations are switched off,
+    // emit the branch.
+    if (Succ0MBB != NextBlock || TM.getOptLevel() == CodeGenOpt::None)
       DAG.setRoot(DAG.getNode(ISD::BR, getCurSDLoc(),
                               MVT::Other, getControlRoot(),
                               DAG.getBasicBlock(Succ0MBB)));

diff --git a/test/DebugInfo/unconditional-branch.ll b/test/DebugInfo/unconditional-branch.ll
new file mode 100644 (file)
index 0000000..1e5dac6
--- /dev/null
+++ b/test/DebugInfo/unconditional-branch.ll
@@ -0,0 +1,64 @@
+; REQUIRES: object-emission
+; PR 19261
+
+; RUN: %llc_dwarf -fast-isel=false -O0 -filetype=obj < %s > %t
+; RUN: llvm-dwarfdump %t | FileCheck %s
+
+; CHECK: {{0x[0-9a-f]+}}      1      0      1   0             0  is_stmt
+; CHECK-NEXT: {{0x[0-9a-f]+}}      2      0      1   0             0  is_stmt
+; CHECK-NEXT: {{0x[0-9a-f]+}}      4      0      1   0             0  is_stmt
+
+; IR generated from clang -O0 -g with the following source:
+;void foo(int i){
+;  switch(i){
+;  default:
+;    break;
+;  }
+;  return;
+;}
+
+; Function Attrs: nounwind
+define void @foo(i32 %i) #0 {
+entry:
+  %i.addr = alloca i32, align 4
+  store i32 %i, i32* %i.addr, align 4
+  call void @llvm.dbg.declare(metadata !{i32* %i.addr}, metadata !12), !dbg !13
+  %0 = load i32* %i.addr, align 4, !dbg !14
+  switch i32 %0, label %sw.default [
+  ], !dbg !14
+
+sw.default:                                       ; preds = %entry
+  br label %sw.epilog, !dbg !15
+
+sw.epilog:                                        ; preds = %sw.default
+  ret void, !dbg !17
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.declare(metadata, metadata) #1
+
+attributes #0 = { nounwind "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" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind readnone }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!9, !10}
+!llvm.ident = !{!11}
+
+!0 = metadata !{i32 786449, metadata !1, i32 12, metadata !"clang version 3.5.0 (204712)", i1 false, metadata !"", i32 0, metadata !2, metadata !2, metadata !3, metadata !2, metadata !2, metadata !"", i32 1} ; [ DW_TAG_compile_unit ] [D:\work\EPRs\396363/test.c] [DW_LANG_C99]
+!1 = metadata !{metadata !"test.c", metadata !"D:\5Cwork\5CEPRs\5C396363"}
+!2 = metadata !{}
+!3 = metadata !{metadata !4}
+!4 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"foo", metadata !"foo", metadata !"", i32 1, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 false, void (i32)* @foo, null, null, metadata !2, i32 1} ; [ DW_TAG_subprogram ] [line 1] [def] [foo]
+!5 = metadata !{i32 786473, metadata !1}          ; [ DW_TAG_file_type ] [D:\work\EPRs\396363/test.c]
+!6 = metadata !{i32 786453, i32 0, null, metadata !"", i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !7, i32 0, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!7 = metadata !{null, metadata !8}
+!8 = metadata !{i32 786468, null, null, metadata !"int", i32 0, i64 32, i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ] [int] [line 0, size 32, align 32, offset 0, enc DW_ATE_signed]
+!9 = metadata !{i32 2, metadata !"Dwarf Version", i32 4}
+!10 = metadata !{i32 1, metadata !"Debug Info Version", i32 1}
+!11 = metadata !{metadata !"clang version 3.5.0 (204712)"}
+!12 = metadata !{i32 786689, metadata !4, metadata !"i", metadata !5, i32 16777217, metadata !8, i32 0, i32 0} ; [ DW_TAG_arg_variable ] [i] [line 1]
+!13 = metadata !{i32 1, i32 0, metadata !4, null}
+!14 = metadata !{i32 2, i32 0, metadata !4, null}
+!15 = metadata !{i32 4, i32 0, metadata !16, null}
+!16 = metadata !{i32 786443, metadata !1, metadata !4, i32 2, i32 0, i32 0, i32 0} ; [ DW_TAG_lexical_block ] [D:\work\EPRs\396363/test.c]
+!17 = metadata !{i32 6, i32 0, metadata !4, null}