[PATCH] D53390: [DebugInfo][Dexter] Unreachable line stepped onto after SimplifyCFG.

[Carlos Alberto Enciso via Phabricator via llvm-commits]

CarlosAlbertoEnciso added inline comments.


================
Comment at: lib/Transforms/Utils/SimplifyCFG.cpp:1379
+  Instruction *InsertPt = BIParent->size() > 1
+                              ? BIParent->getTerminator()->getPrevNode()
+                              : BIParent->getTerminator();
----------------
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.




https://reviews.llvm.org/D53390