[llvm-bugs] [Bug 46267] New: opt -speculative-execution moves dbg.value(%0 before definition of %0

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=46267

            Bug ID: 46267
           Summary: opt -speculative-execution moves dbg.value(%0 before
                    definition of %0
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: mikael.holmen at ericsson.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 23595
  --> https://bugs.llvm.org/attachment.cgi?id=23595&action=edit
bbi-43737.ll reproducer

Repriduce with:
 opt -speculative-execution -S -o - bbi-43737.ll

Input:

define void @f() {
entry:
  br i1 undef, label %land.rhs, label %land.end

land.rhs:                                         ; preds = %entry
  %0 = load i16, i16* undef, align 1
  call void @llvm.dbg.value(metadata i16 %0, metadata !9, metadata
!DIExpression()), !dbg !10
  br label %land.end

land.end:                                         ; preds = %land.rhs, %entry
  ret void
}

Output:

define dso_local void @f() {
entry:
  call void @llvm.dbg.value(metadata i16 %0, metadata !6, metadata
!DIExpression()), !dbg !10
  br i1 undef, label %land.rhs, label %land.end

land.rhs:                                         ; preds = %entry
  %0 = load i16, i16* undef, align 1
  br label %land.end

land.end:                                         ; preds = %land.rhs, %entry
  ret void
}

So the dbg.value is hoisted to the entry block, before the definition of the
value it uses.

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