forked from OSchip/llvm-project
06a2128cfa
Summary:
Currently MachineBasicBlock::updateTerminator simply drops DebugLoc for newly created branch instructions, which may cause incorrect stepping and/or imprecise sample profile data. Below is an example:
```
1 extern int bar(int x);
2
3 int foo(int *begin, int *end) {
4 int *i;
5 int ret = 0;
6 for (
7 i = begin ;
8 i != end ;
9 i++)
10 {
11 ret += bar(*i);
12 }
13 return ret;
14 }
```
Below is a bitcode of 'foo' at the end of LLVM-IR level optimizations with -O3:
```
define i32 @foo(i32* readonly %begin, i32* readnone %end) !dbg !4 {
entry:
%cmp6 = icmp eq i32* %begin, %end, !dbg !9
br i1 %cmp6, label %for.end, label %for.body.preheader, !dbg !12
for.body.preheader: ; preds = %entry
br label %for.body, !dbg !13
for.body: ; preds = %for.body.preheader, %for.body
%ret.08 = phi i32 [ %add, %for.body ], [ 0, %for.body.preheader ]
%i.07 = phi i32* [ %incdec.ptr, %for.body ], [ %begin, %for.body.preheader ]
%0 = load i32, i32* %i.07, align 4, !dbg !13, !tbaa !15
%call = tail call i32 @bar(i32 %0), !dbg !19
%add = add nsw i32 %call, %ret.08, !dbg !20
%incdec.ptr = getelementptr inbounds i32, i32* %i.07, i64 1, !dbg !21
%cmp = icmp eq i32* %incdec.ptr, %end, !dbg !9
br i1 %cmp, label %for.end.loopexit, label %for.body, !dbg !12, !llvm.loop !22
for.end.loopexit: ; preds = %for.body
br label %for.end, !dbg !24
for.end: ; preds = %for.end.loopexit, %entry
%ret.0.lcssa = phi i32 [ 0, %entry ], [ %add, %for.end.loopexit ]
ret i32 %ret.0.lcssa, !dbg !24
}
```
where
```
!12 = !DILocation(line: 6, column: 3, scope: !11)
```
. As you can see, the terminator of 'entry' block, which is a loop control branch, has a DebugLoc of line 6, column 3. Howerver, after the execution of 'MachineBlock::updateTerminator' function, which is triggered by MachineSinking pass, the DebugLoc info is dropped as below (see there's no debug-location for JNE_1):
```
bb.0.entry:
successors: %bb.4(0x30000000), %bb.1.for.body.preheader(0x50000000)
liveins: %rdi, %rsi
%6 = COPY %rsi
%5 = COPY %rdi
%8 = SUB64rr %5, %6, implicit-def %eflags, debug-location !9
JNE_1 %bb.1.for.body.preheader, implicit %eflags
```
This patch addresses this issue and make newly created branch instructions to keep debug-location info.
Reviewers: aprantl, MatzeB, craig.topper, qcolombet
Reviewed By: qcolombet
Subscribers: qcolombet, llvm-commits
Differential Revision: https://reviews.llvm.org/D29596
llvm-svn: 294976
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| .. | ||
| bindings | ||
| cmake | ||
| docs | ||
| examples | ||
| include | ||
| lib | ||
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| resources | ||
| runtimes | ||
| test | ||
| tools | ||
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| utils | ||
| .arcconfig | ||
| .clang-format | ||
| .clang-tidy | ||
| .gitignore | ||
| CMakeLists.txt | ||
| CODE_OWNERS.TXT | ||
| CREDITS.TXT | ||
| LICENSE.TXT | ||
| LLVMBuild.txt | ||
| README.txt | ||
| RELEASE_TESTERS.TXT | ||
| configure | ||
| llvm.spec.in | ||
README.txt
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