[PATCH] D53390: [DebugInfo][Dexter] Unreachable line stepped onto after SimplifyCFG.
Carlos Alberto Enciso via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Mon Nov 5 06:56:35 PST 2018
CarlosAlbertoEnciso added inline comments.
================
Comment at: lib/Transforms/Utils/SimplifyCFG.cpp:1379
+ Instruction *InsertPt = BIParent->size() > 1
+ ? BIParent->getTerminator()->getPrevNode()
+ : BIParent->getTerminator();
----------------
CarlosAlbertoEnciso wrote:
> vsk wrote:
> > A bit nitty-gritty, but: Can the instruction before the terminator be a debug info intrinsic?
> >
> > If so, I think the line location you pick be different if you switch from -gline-tables-only versus -g.
> Thanks for your review.
>
> Changing the test case to:
>
> ```
> int main() {
> volatile int foo = 0;
>
> int beards = 0;
> bool cond = foo == 4;
> if (cond)
> beards = 8;
> else
> beards = 4;
>
> volatile bool tmp;
> volatile bool *face = &tmp;
> *face = cond;
>
> return beards;
> }
> ```
>
> The IR will look like:
>
> ```
> ...
> %foo.0. = load volatile i32, i32* %foo, align 4, !dbg !28, !tbaa !23
> %cmp = icmp eq i32 %foo.0., 4, !dbg !28
> %frombool = zext i1 %cmp to i8, !dbg !28
> call void @llvm.dbg.value(metadata i8 %frombool, metadata !16, metadata !DIExpression()), !dbg !28
> br i1 %cmp, label %if.then, label %if.else, !dbg !29
>
> if.then: ; preds = %entry
> call void @llvm.dbg.value(metadata i32 8, metadata !15, metadata !DIExpression()), !dbg !27
> br label %if.end, !dbg !30
>
> if.else: ; preds = %entry
> call void @llvm.dbg.value(metadata i32 4, metadata !15, metadata !DIExpression()), !dbg !27
> br label %if.end
>
> if.end: ; preds = %if.else, %if.then
> ...
> ```
>
> The instruction before the terminator is a debug info intrinsic.
>
>
> If so, I think the line location you pick be different if you switch from -gline-tables-only versus -g.
IR for '-g'
```
...
%cmp = icmp eq i32 %foo.0., 4, !dbg !26
%frombool = zext i1 %cmp to i8, !dbg !26
call void @llvm.dbg.value(metadata i8 %frombool, metadata !16, metadata !DIExpression()), !dbg !26
br i1 %cmp, label %if.then, label %if.else, !dbg !27
...
!26 = !DILocation(line: 5, scope: !8)
```
IR for '-gline-tables-only'
```
...
%cmp = icmp eq i32 %foo.0., 4, !dbg !15
%frombool = zext i1 %cmp to i8, !dbg !15
br i1 %cmp, label %if.then, label %if.else, !dbg !16
...
!15 = !DILocation(line: 5, scope: !8)
...
```
InsertPts
```
call void @llvm.dbg.value(metadata i8 %frombool, metadata !16, metadata !DIExpression()), !dbg !26
&&
%frombool = zext i1 %cmp to i8, !dbg !15
```
For both options, the line location of the insertion point is the same, debug location `!DILocation(line: 5, scope: !8)`.
https://reviews.llvm.org/D53390
More information about the llvm-commits
mailing list