[RemoveDIs] Add DPLabels support [3a/3] (#82633)

Patch 2 of 3 to add llvm.dbg.label support to the RemoveDIs project. The
patch stack adds the DPLabel class, which is the RemoveDIs llvm.dbg.label
equivalent.

   1. Add DbgRecord base class for DPValue and the not-yet-added
       DPLabel class.
   2. Add the DPLabel class.
-> 3. Add support to passes.

The next patch, #82639, will enable conversion between dbg.labels and DPLabels.

AssignemntTrackingAnalysis support could have gone two ways:

1. Have the analysis store a DPLabel representation in its results -
   SelectionDAGBuilder reads the analysis results and ignores all DbgRecord
   kinds.
2. Ignore DPLabels in the analysis - SelectionDAGBuilder reads the analysis
   results but still needs to iterate over DPLabels from the IR.

I went with option 2 because it's less work and is no less correct than 1. It's
worth noting that causes labels to sink to the bottom of packs of debug records.
e.g., [value, label, value] becomes [value, value, label]. This shouldn't be a
problem because labels and variable locations don't have an ordering requirement.
The ordering between variable locations is maintained and the label movement is
deterministic

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/test/Transforms/SpeculativeExecution/PR46267.ll b/llvm/test/Transforms/SpeculativeExecution/PR46267.ll
index c27b492..d940ee6 100644
--- a/llvm/test/Transforms/SpeculativeExecution/PR46267.ll
+++ b/llvm/test/Transforms/SpeculativeExecution/PR46267.ll
@@ -41,12 +41,16 @@ land.rhs:                                         ; preds = %entry
 ; CHECK-NEXT: call void @llvm.dbg.declare(metadata ptr %y
 ; CHECK-NEXT: %a0 = load i32, ptr undef, align 1
 ; CHECK-NEXT: call void @llvm.dbg.value(metadata i32 %a0
+; CHECK-NEXT: call void @llvm.dbg.label
   call void @llvm.dbg.label(metadata !11), !dbg !10
   %y = alloca i32, align 4
   call void @llvm.dbg.declare(metadata ptr %y, metadata !14, metadata !DIExpression()), !dbg !10
 
   %a0 = load i32, ptr undef, align 1
   call void @llvm.dbg.value(metadata i32 %a0, metadata !9, metadata !DIExpression()), !dbg !10
+  ;; RemoveDIs: Check a label that is attached to a hoisted instruction
+  ;; gets left behind (match intrinsic-style debug info behaviour).
+  call void @llvm.dbg.label(metadata !15), !dbg !10
 
   %a2 = add i32 %i, 0
   call void @llvm.dbg.value(metadata i32 %a2, metadata !13, metadata !DIExpression()), !dbg !10
@@ -82,3 +86,4 @@ attributes #1 = { nounwind readnone speculatable willreturn }
 !12 = !DILocalVariable(name: "x", scope: !6, file: !1, line: 3, type: !4)
 !13 = !DILocalVariable(name: "a2", scope: !6, file: !1, line: 3, type: !4)
 !14 = !DILocalVariable(name: "y", scope: !6, file: !1, line: 3, type: !4)
+!15 = !DILabel(scope: !6, name: "label2", file: !1, line: 2)