<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Issue</th>
<td>
<a href=https://github.com/llvm/llvm-project/issues/95731>95731</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>
[DebugInfo][TailCallElim] Cloned AccRecInstrNew should drop its debugloc when being inserted into other blocks
</td>
</tr>
<tr>
<th>Labels</th>
<td>
new issue
</td>
</tr>
<tr>
<th>Assignees</th>
<td>
</td>
</tr>
<tr>
<th>Reporter</th>
<td>
Apochens
</td>
</tr>
</table>
<pre>
TailCallElimination-[L805](https://github.com/llvm/llvm-project/blob/15bb02650e26875c48889053d6a9697444583721/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp#L805): In optimized `@test^_multiple_returns`, `%accumulator.ret.tr` (in block `%case99`) and `%accumulator.ret.tr2` (in block `%case0`) have the same debug location of `%accumulate` (in block `%default`). However, they are all in different switch cases, the debug location of `% accumulate` should not be propagated to the two `*.ret.tr*`.
Before TailCallElim optimization:
```LLVM IR
define i32 @test6_multiple_returns(i32 %x, i32 %y) local_unnamed_addr !dbg !5 {
entry:
switch i32 %x, label %default [
i32 0, label %case0
i32 99, label %case99
], !dbg !8
case0: ; preds = %entry
%helper = call i32 @test6_helper(), !dbg !9
ret i32 %helper, !dbg !10
case99: ; preds = %entry
%sub1 = add i32 %x, -1, !dbg !11
%recurse1 = call i32 @test6_multiple_returns(i32 %sub1, i32 %y), !dbg !12
ret i32 18, !dbg !13
default: ; preds = %entry
%sub2 = add i32 %x, -1, !dbg !14
%recurse2 = call i32 @test6_multiple_returns(i32 %sub2, i32 %y), !dbg !15
->%accumulate = add i32 %recurse2, %y, !dbg !16
ret i32 %accumulate, !dbg !17
}
!16 = !DILocation(line: 9, column: 1, scope: !5)
```
After TailCallElim optimization:
```LLVM IR
define i32 @test6_multiple_returns(i32 %x, i32 %y) local_unnamed_addr !dbg !5 {
entry:
br label %tailrecurse
tailrecurse: ; preds = %default, %case99, %entry
%accumulator.tr = phi i32 [ %accumulator.tr, %case99 ], [ 0, %entry ], [ %accumulate, %default ]
%x.tr = phi i32 [ %x, %entry ], [ %sub1, %case99 ], [ %sub2, %default ]
%ret.tr = phi i32 [ poison, %entry ], [ %current.ret.tr, %case99 ], [ %ret.tr, %default ]
%ret.known.tr = phi i1 [ false, %entry ], [ true, %case99 ], [ %ret.known.tr, %default ]
switch i32 %x.tr, label %default [
i32 0, label %case0
i32 99, label %case99
], !dbg !8
case0: ; preds = %tailrecurse
%helper = tail call i32 @test6_helper(), !dbg !9
->%accumulator.ret.tr2 = add i32 %accumulator.tr, %helper, !dbg !10
%current.ret.tr1 = select i1 %ret.known.tr, i32 %ret.tr, i32 %accumulator.ret.tr2
ret i32 %current.ret.tr1, !dbg !11
case99: ; preds = %tailrecurse
%sub1 = add i32 %x.tr, -1, !dbg !12
->%accumulator.ret.tr = add i32 %accumulator.tr, 18, !dbg !10
%current.ret.tr = select i1 %ret.known.tr, i32 %ret.tr, i32 %accumulator.ret.tr
br label %tailrecurse, !dbg !13
default: ; preds = %tailrecurse
%sub2 = add i32 %x.tr, -1, !dbg !14
%accumulate = add i32 %accumulator.tr, %y, !dbg !10
br label %tailrecurse, !dbg !15
}
!10 = !DILocation(line: 9, column: 1, scope: !5)
```
TailCallElimination-[L777](https://github.com/llvm/llvm-project/blob/15bb02650e26875c48889053d6a9697444583721/llvm/lib/Transforms/Scalar/TailRecursionElimination.cpp#L777): The same as the above error. When either `%accumulator.ret.tr` or `%accumulator.ret.tr1` is executed, block `%if.then2` would be considered being executed.
Before TailCallElim optimization:
```LLVM IR
define i32 @test7_multiple_accumulators(i32 %a) local_unnamed_addr !dbg !18 {
entry:
%tobool = icmp eq i32 %a, 0, !dbg !19
br i1 %tobool, label %return, label %if.end, !dbg !20
if.end: ; preds = %entry
%and = and i32 %a, 1, !dbg !21
%tobool1 = icmp eq i32 %and, 0, !dbg !22
%sub = add nsw i32 %a, -1, !dbg !23
br i1 %tobool1, label %if.end3, label %if.then2, !dbg !24
if.then2: ; preds = %if.end
%recurse1 = tail call i32 @test7_multiple_accumulators(i32 %sub), !dbg !25
->%accumulate1 = add nsw i32 %recurse1, 1, !dbg !26
br label %return, !dbg !27
if.end3: ; preds = %if.end
%recurse2 = tail call i32 @test7_multiple_accumulators(i32 %sub), !dbg !28
%accumulate2 = mul nsw i32 %recurse2, 2, !dbg !29
br label %return, !dbg !30
return: ; preds = %if.end3, %if.then2, %entry
%retval.0 = phi i32 [ %accumulate1, %if.then2 ], [ %accumulate2, %if.end3 ], [ 0, %entry ], !dbg !31
ret i32 %retval.0, !dbg !32
}
!26 = !DILocation(line: 18, column: 1, scope: !18)
```
After TailCallElim optimization:
```LLVM IR
define i32 @test7_multiple_accumulators(i32 %a) local_unnamed_addr !dbg !16 {
entry:
br label %tailrecurse
tailrecurse: ; preds = %if.then2, %entry
%accumulator.tr = phi i32 [ 0, %entry ], [ %accumulate1, %if.then2 ]
%a.tr = phi i32 [ %a, %entry ], [ %sub, %if.then2 ]
%tobool = icmp eq i32 %a.tr, 0, !dbg !17
br i1 %tobool, label %return, label %if.end, !dbg !18
if.end: ; preds = %tailrecurse
%and = and i32 %a.tr, 1, !dbg !19
%tobool1 = icmp eq i32 %and, 0, !dbg !20
%sub = add nsw i32 %a.tr, -1, !dbg !21
br i1 %tobool1, label %if.end3, label %if.then2, !dbg !22
if.then2: ; preds = %if.end
%accumulate1 = add nsw i32 %accumulator.tr, 1, !dbg !23
br label %tailrecurse, !dbg !24
if.end3: ; preds = %if.end
%recurse2 = tail call i32 @test7_multiple_accumulators(i32 %sub), !dbg !25
%accumulate2 = mul nsw i32 %recurse2, 2, !dbg !26
->%accumulator.ret.tr = add nsw i32 %accumulator.tr, %accumulate2, !dbg !23
ret i32 %accumulator.ret.tr, !dbg !27
return: ; preds = %tailrecurse
->%accumulator.ret.tr1 = add nsw i32 %accumulator.tr, 0, !dbg !23
ret i32 %accumulator.ret.tr1, !dbg !27
}
!23 = !DILocation(line: 18, column: 1, scope: !16)
```
The two test case are in llvm/test/Transforms/TailCallElim/accum_recursion.ll.
</pre>
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