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[DebugInfo][LICM] Salvage dbg_values for the dead instructions to erase #138796

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Merged
merged 2 commits into from
May 12, 2025
Merged

[DebugInfo][LICM] Salvage dbg_values for the dead instructions to erase #138796

merged 2 commits into from
May 12, 2025

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Apochens
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@Apochens Apochens commented May 7, 2025

fix #138684 .

@Apochens Apochens requested review from SLTozer and OCHyams May 7, 2025 02:04
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llvmbot commented May 7, 2025

@llvm/pr-subscribers-debuginfo

Author: Shan Huang (Apochens)

Changes

fix #138684 .

Full diff: https://github.com/llvm/llvm-project/pull/138796.diff

5 Files Affected:

  • (modified) llvm/lib/Transforms/Scalar/LICM.cpp (+12-3)
  • (added) llvm/test/Transforms/LICM/salvage-hoisted-add.ll (+70)
  • (added) llvm/test/Transforms/LICM/salvage-hoisted-binop.ll (+45)
  • (added) llvm/test/Transforms/LICM/salvage-hoisted-gep.ll (+58)
  • (added) llvm/test/Transforms/LICM/salvage-hoisted-sub.ll (+70)
diff --git a/llvm/lib/Transforms/Scalar/LICM.cpp b/llvm/lib/Transforms/Scalar/LICM.cpp
index 42bccc858cdaa..62ef40c686874 100644
--- a/llvm/lib/Transforms/Scalar/LICM.cpp
+++ b/llvm/lib/Transforms/Scalar/LICM.cpp
@@ -2538,6 +2538,7 @@ static bool hoistGEP(Instruction &I, Loop &L, ICFLoopSafetyInfo &SafetyInfo,
                                     IsInBounds);
   GEP->replaceAllUsesWith(NewGEP);
   eraseInstruction(*GEP, SafetyInfo, MSSAU);
+  salvageDebugInfo(*Src);
   eraseInstruction(*Src, SafetyInfo, MSSAU);
   return true;
 }
@@ -2592,7 +2593,10 @@ static bool hoistAdd(ICmpInst::Predicate Pred, Value *VariantLHS,
   ICmp.setPredicate(Pred);
   ICmp.setOperand(0, VariantOp);
   ICmp.setOperand(1, NewCmpOp);
-  eraseInstruction(cast<Instruction>(*VariantLHS), SafetyInfo, MSSAU);
+
+  Instruction &DeadI = cast<Instruction>(*VariantLHS);
+  salvageDebugInfo(DeadI);
+  eraseInstruction(DeadI, SafetyInfo, MSSAU);
   return true;
 }
 
@@ -2670,7 +2674,10 @@ static bool hoistSub(ICmpInst::Predicate Pred, Value *VariantLHS,
   ICmp.setPredicate(Pred);
   ICmp.setOperand(0, VariantOp);
   ICmp.setOperand(1, NewCmpOp);
-  eraseInstruction(cast<Instruction>(*VariantLHS), SafetyInfo, MSSAU);
+
+  Instruction &DeadI = cast<Instruction>(*VariantLHS);
+  salvageDebugInfo(DeadI);
+  eraseInstruction(DeadI, SafetyInfo, MSSAU);
   return true;
 }
 
@@ -2877,8 +2884,10 @@ static bool hoistBOAssociation(Instruction &I, Loop &L,
 
   // (LV op C1) might not be erased if it has more uses than the one we just
   // replaced.
-  if (BO0->use_empty())
+  if (BO0->use_empty()) {
+    salvageDebugInfo(*BO0);
     eraseInstruction(*BO0, SafetyInfo, MSSAU);
+  }
 
   return true;
 }
diff --git a/llvm/test/Transforms/LICM/salvage-hoisted-add.ll b/llvm/test/Transforms/LICM/salvage-hoisted-add.ll
new file mode 100644
index 0000000000000..1bc5802d5997c
--- /dev/null
+++ b/llvm/test/Transforms/LICM/salvage-hoisted-add.ll
@@ -0,0 +1,70 @@
+; RUN: opt -S -passes=licm %s | FileCheck %s
+
+; Check that hoistAdd() in LICM salvages the dbg_value for the hoisted add
+; instruction.
+
+define i32 @hoist_add(ptr %p, ptr %x_p, ptr %length_p) !dbg !5 {
+; CHECK-LABEL: define i32 @hoist_add(
+; CHECK-LABEL: loop:
+; CHECK:           #dbg_value(!DIArgList(i32 [[X:%.*]], i32 [[IV:%.*]]), [[META9:![0-9]+]], !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_arg, 1, DW_OP_plus, DW_OP_stack_value), [[META16:![0-9]+]])
+;
+entry:
+  %x = load i32, ptr %x_p, align 4, !dbg !20, !range !21
+  %length = load i32, ptr %length_p, align 4, !dbg !22, !range !21
+  br label %loop, !dbg !23
+
+loop:                                             ; preds = %backedge, %entry
+  %iv = phi i32 [ 0, %entry ], [ %iv.next, %backedge ], !dbg !24
+  %arith = add nsw i32 %x, %iv, !dbg !25
+    #dbg_value(i32 %arith, !13, !DIExpression(), !25)
+  %x_check = icmp slt i32 %arith, 4, !dbg !26
+  br i1 %x_check, label %out_of_bounds, label %backedge, !dbg !27
+
+backedge:                                         ; preds = %loop
+  %el.ptr = getelementptr i32, ptr %p, i32 %iv, !dbg !28
+  store i32 1, ptr %el.ptr, align 4, !dbg !29
+  %iv.next = add nuw nsw i32 %iv, 4, !dbg !30
+  %loop_cond = icmp slt i32 %iv.next, %length, !dbg !31
+  br i1 %loop_cond, label %loop, label %exit, !dbg !32
+
+exit:                                             ; preds = %backedge
+  ret i32 %iv.next, !dbg !33
+
+out_of_bounds:                                    ; preds = %loop
+  ret i32 -1, !dbg !34
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.debugify = !{!2, !3}
+!llvm.module.flags = !{!4}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug)
+!1 = !DIFile(filename: "salvage-hoisted-add", directory: "/")
+!2 = !{i32 14}
+!3 = !{i32 8}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = distinct !DISubprogram(name: "hoist_add", linkageName: "hoist_add", scope: null, file: !1, line: 1, type: !6, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !8)
+!6 = !DISubroutineType(types: !7)
+!7 = !{}
+!8 = !{!13}
+!10 = !DIBasicType(name: "ty32", size: 32, encoding: DW_ATE_unsigned)
+!13 = !DILocalVariable(name: "4", scope: !5, file: !1, line: 5, type: !10)
+!20 = !DILocation(line: 1, column: 1, scope: !5)
+!21 = !{i32 0, i32 -2147483648}
+!22 = !DILocation(line: 2, column: 1, scope: !5)
+!23 = !DILocation(line: 3, column: 1, scope: !5)
+!24 = !DILocation(line: 4, column: 1, scope: !5)
+!25 = !DILocation(line: 5, column: 1, scope: !5)
+!26 = !DILocation(line: 6, column: 1, scope: !5)
+!27 = !DILocation(line: 7, column: 1, scope: !5)
+!28 = !DILocation(line: 8, column: 1, scope: !5)
+!29 = !DILocation(line: 9, column: 1, scope: !5)
+!30 = !DILocation(line: 10, column: 1, scope: !5)
+!31 = !DILocation(line: 11, column: 1, scope: !5)
+!32 = !DILocation(line: 12, column: 1, scope: !5)
+!33 = !DILocation(line: 13, column: 1, scope: !5)
+!34 = !DILocation(line: 14, column: 1, scope: !5)
+;.
+; CHECK: [[META9]] = !DILocalVariable(name: "4",
+; CHECK: [[META16]] = !DILocation(line: 5, column: 1,
+;.
diff --git a/llvm/test/Transforms/LICM/salvage-hoisted-binop.ll b/llvm/test/Transforms/LICM/salvage-hoisted-binop.ll
new file mode 100644
index 0000000000000..97461865c4d79
--- /dev/null
+++ b/llvm/test/Transforms/LICM/salvage-hoisted-binop.ll
@@ -0,0 +1,45 @@
+; RUN: opt -S -passes=licm %s | FileCheck %s
+
+; Check that hoistBOAssociation() in LICM salvages the dbg_value for the
+; hoisted binary operation.
+
+define void @hoist_binop(i64 %c1, i64 %c2) !dbg !5 {
+; CHECK-LABEL: define void @hoist_binop(
+; CHECK-LABEL: loop:
+; CHECK:           #dbg_value(!DIArgList(i64 [[INDEX:%.*]], i64 [[C1:%.*]]), [[META9:![0-9]+]], !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_arg, 1, DW_OP_plus, DW_OP_stack_value), [[META13:![0-9]+]])
+;
+entry:
+  br label %loop, !dbg !13
+
+loop:                                             ; preds = %loop, %entry
+  %index = phi i64 [ 0, %entry ], [ %index.next, %loop ], !dbg !14
+  %step.add = add i64 %index, %c1, !dbg !15
+  #dbg_value(i64 %step.add, !11, !DIExpression(), !15)
+  %index.next = add i64 %step.add, %c2, !dbg !16
+  br label %loop, !dbg !17
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.debugify = !{!2, !3}
+!llvm.module.flags = !{!4}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug)
+!1 = !DIFile(filename: "salvage-hoist-binop.ll", directory: "/")
+!2 = !{i32 5}
+!3 = !{i32 3}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = distinct !DISubprogram(name: "hoist_binop", linkageName: "hoist_binop", scope: null, file: !1, line: 1, type: !6, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !8)
+!6 = !DISubroutineType(types: !7)
+!7 = !{}
+!8 = !{!11}
+!10 = !DIBasicType(name: "ty64", size: 64, encoding: DW_ATE_unsigned)
+!11 = !DILocalVariable(name: "2", scope: !5, file: !1, line: 3, type: !10)
+!13 = !DILocation(line: 1, column: 1, scope: !5)
+!14 = !DILocation(line: 2, column: 1, scope: !5)
+!15 = !DILocation(line: 3, column: 1, scope: !5)
+!16 = !DILocation(line: 4, column: 1, scope: !5)
+!17 = !DILocation(line: 5, column: 1, scope: !5)
+;.
+; CHECK: [[META9]] = !DILocalVariable(name: "2",
+; CHECK: [[META13]] = !DILocation(line: 3, column: 1,
+;.
diff --git a/llvm/test/Transforms/LICM/salvage-hoisted-gep.ll b/llvm/test/Transforms/LICM/salvage-hoisted-gep.ll
new file mode 100644
index 0000000000000..828a92765b6f3
--- /dev/null
+++ b/llvm/test/Transforms/LICM/salvage-hoisted-gep.ll
@@ -0,0 +1,58 @@
+; RUN: opt -S -passes=licm %s | FileCheck %s
+
+; Check that hoistGEP() in LICM salvages the dbg_value for the hoisted
+; getelementptr instruction.
+
+define void @hoist_gep(ptr %ptr, i1 %c, i32 %arg) !dbg !5 {
+; CHECK-LABEL: define void @hoist_gep(
+; CHECK-LABEL: loop:
+; CHECK:           #dbg_value(!DIArgList(ptr [[PTR:%.*]], i64 [[VAL_EXT:%.*]]), [[META9:![0-9]+]], !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_arg, 1, DW_OP_plus, DW_OP_stack_value), [[META15:![0-9]+]])
+;
+entry:
+  %arg.ext = zext i32 %arg to i64, !dbg !16
+  br label %loop, !dbg !17
+
+loop:                                             ; preds = %loop, %entry
+  %val = call i32 @get.i32(), !dbg !18
+  %val.ext = zext i32 %val to i64, !dbg !19
+  %ptr2 = getelementptr inbounds i8, ptr %ptr, i64 %val.ext, !dbg !20
+  #dbg_value(ptr %ptr2, !14, !DIExpression(), !20)
+  %ptr3 = getelementptr i8, ptr %ptr2, i64 %arg.ext, !dbg !21
+  call void @use(ptr %ptr3), !dbg !22
+  br i1 %c, label %loop, label %exit, !dbg !23
+
+exit:                                             ; preds = %loop
+  ret void, !dbg !24
+}
+
+declare i32 @get.i32()
+declare void @use(ptr)
+
+!llvm.dbg.cu = !{!0}
+!llvm.debugify = !{!2, !3}
+!llvm.module.flags = !{!4}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug)
+!1 = !DIFile(filename: "salvage-hoisted-gep.ll", directory: "/")
+!2 = !{i32 9}
+!3 = !{i32 5}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = distinct !DISubprogram(name: "hoist_gep", linkageName: "hoist_gep", scope: null, file: !1, line: 1, type: !6, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !8)
+!6 = !DISubroutineType(types: !7)
+!7 = !{}
+!8 = !{!14}
+!10 = !DIBasicType(name: "ty64", size: 64, encoding: DW_ATE_unsigned)
+!14 = !DILocalVariable(name: "4", scope: !5, file: !1, line: 5, type: !10)
+!16 = !DILocation(line: 1, column: 1, scope: !5)
+!17 = !DILocation(line: 2, column: 1, scope: !5)
+!18 = !DILocation(line: 3, column: 1, scope: !5)
+!19 = !DILocation(line: 4, column: 1, scope: !5)
+!20 = !DILocation(line: 5, column: 1, scope: !5)
+!21 = !DILocation(line: 6, column: 1, scope: !5)
+!22 = !DILocation(line: 7, column: 1, scope: !5)
+!23 = !DILocation(line: 8, column: 1, scope: !5)
+!24 = !DILocation(line: 9, column: 1, scope: !5)
+;.
+; CHECK: [[META9]] = !DILocalVariable(name: "4",
+; CHECK: [[META15]] = !DILocation(line: 5,
+;.
diff --git a/llvm/test/Transforms/LICM/salvage-hoisted-sub.ll b/llvm/test/Transforms/LICM/salvage-hoisted-sub.ll
new file mode 100644
index 0000000000000..854fd102fdf56
--- /dev/null
+++ b/llvm/test/Transforms/LICM/salvage-hoisted-sub.ll
@@ -0,0 +1,70 @@
+; RUN: opt -S -passes=licm %s | FileCheck %s
+
+; Check that hoistSub() in LICM salvages the dbg_value for the hoisted sub
+; instruction.
+
+define i32 @hoist_sub(ptr %p, ptr %x_p, ptr %length_p) !dbg !5 {
+; CHECK-LABEL: define i32 @hoist_sub(
+; CHECK-LABEL: loop:
+; CHECK:           #dbg_value(!DIArgList(i32 [[X:%.*]], i32 [[IV:%.*]]), [[META9:![0-9]+]], !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_arg, 1, DW_OP_minus, DW_OP_stack_value), [[META16:![0-9]+]])
+;
+entry:
+  %x = load i32, ptr %x_p, align 4, !dbg !20, !range !21
+  %length = load i32, ptr %length_p, align 4, !dbg !22, !range !21
+  br label %loop, !dbg !23
+
+loop:                                             ; preds = %backedge, %entry
+  %iv = phi i32 [ 0, %entry ], [ %iv.next, %backedge ], !dbg !24
+  %arith = sub nsw i32 %x, %iv, !dbg !25
+  #dbg_value(i32 %arith, !13, !DIExpression(), !25)
+  %x_check = icmp slt i32 %arith, 4, !dbg !26
+  br i1 %x_check, label %out_of_bounds, label %backedge, !dbg !27
+
+backedge:                                         ; preds = %loop
+  %el.ptr = getelementptr i32, ptr %p, i32 %iv, !dbg !28
+  store i32 1, ptr %el.ptr, align 4, !dbg !29
+  %iv.next = add nuw nsw i32 %iv, 4, !dbg !30
+  %loop_cond = icmp slt i32 %iv.next, %length, !dbg !31
+  br i1 %loop_cond, label %loop, label %exit, !dbg !32
+
+exit:                                             ; preds = %backedge
+  ret i32 %iv.next, !dbg !33
+
+out_of_bounds:                                    ; preds = %loop
+  ret i32 -1, !dbg !34
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.debugify = !{!2, !3}
+!llvm.module.flags = !{!4}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug)
+!1 = !DIFile(filename: "salvage-hoisted-sub.ll", directory: "/")
+!2 = !{i32 14}
+!3 = !{i32 8}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = distinct !DISubprogram(name: "hoist_sub", linkageName: "hoist_sub", scope: null, file: !1, line: 1, type: !6, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !8)
+!6 = !DISubroutineType(types: !7)
+!7 = !{}
+!8 = !{!13}
+!10 = !DIBasicType(name: "ty32", size: 32, encoding: DW_ATE_unsigned)
+!13 = !DILocalVariable(name: "4", scope: !5, file: !1, line: 5, type: !10)
+!20 = !DILocation(line: 1, column: 1, scope: !5)
+!21 = !{i32 0, i32 -2147483648}
+!22 = !DILocation(line: 2, column: 1, scope: !5)
+!23 = !DILocation(line: 3, column: 1, scope: !5)
+!24 = !DILocation(line: 4, column: 1, scope: !5)
+!25 = !DILocation(line: 5, column: 1, scope: !5)
+!26 = !DILocation(line: 6, column: 1, scope: !5)
+!27 = !DILocation(line: 7, column: 1, scope: !5)
+!28 = !DILocation(line: 8, column: 1, scope: !5)
+!29 = !DILocation(line: 9, column: 1, scope: !5)
+!30 = !DILocation(line: 10, column: 1, scope: !5)
+!31 = !DILocation(line: 11, column: 1, scope: !5)
+!32 = !DILocation(line: 12, column: 1, scope: !5)
+!33 = !DILocation(line: 13, column: 1, scope: !5)
+!34 = !DILocation(line: 14, column: 1, scope: !5)
+;.
+; CHECK: [[META9]] = !DILocalVariable(name: "4",
+; CHECK: [[META16]] = !DILocation(line: 5, column: 1,
+;.

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llvmbot commented May 7, 2025

@llvm/pr-subscribers-llvm-transforms

Author: Shan Huang (Apochens)

Changes

fix #138684 .

Full diff: https://github.com/llvm/llvm-project/pull/138796.diff

5 Files Affected:

  • (modified) llvm/lib/Transforms/Scalar/LICM.cpp (+12-3)
  • (added) llvm/test/Transforms/LICM/salvage-hoisted-add.ll (+70)
  • (added) llvm/test/Transforms/LICM/salvage-hoisted-binop.ll (+45)
  • (added) llvm/test/Transforms/LICM/salvage-hoisted-gep.ll (+58)
  • (added) llvm/test/Transforms/LICM/salvage-hoisted-sub.ll (+70)
diff --git a/llvm/lib/Transforms/Scalar/LICM.cpp b/llvm/lib/Transforms/Scalar/LICM.cpp
index 42bccc858cdaa..62ef40c686874 100644
--- a/llvm/lib/Transforms/Scalar/LICM.cpp
+++ b/llvm/lib/Transforms/Scalar/LICM.cpp
@@ -2538,6 +2538,7 @@ static bool hoistGEP(Instruction &I, Loop &L, ICFLoopSafetyInfo &SafetyInfo,
                                     IsInBounds);
   GEP->replaceAllUsesWith(NewGEP);
   eraseInstruction(*GEP, SafetyInfo, MSSAU);
+  salvageDebugInfo(*Src);
   eraseInstruction(*Src, SafetyInfo, MSSAU);
   return true;
 }
@@ -2592,7 +2593,10 @@ static bool hoistAdd(ICmpInst::Predicate Pred, Value *VariantLHS,
   ICmp.setPredicate(Pred);
   ICmp.setOperand(0, VariantOp);
   ICmp.setOperand(1, NewCmpOp);
-  eraseInstruction(cast<Instruction>(*VariantLHS), SafetyInfo, MSSAU);
+
+  Instruction &DeadI = cast<Instruction>(*VariantLHS);
+  salvageDebugInfo(DeadI);
+  eraseInstruction(DeadI, SafetyInfo, MSSAU);
   return true;
 }
 
@@ -2670,7 +2674,10 @@ static bool hoistSub(ICmpInst::Predicate Pred, Value *VariantLHS,
   ICmp.setPredicate(Pred);
   ICmp.setOperand(0, VariantOp);
   ICmp.setOperand(1, NewCmpOp);
-  eraseInstruction(cast<Instruction>(*VariantLHS), SafetyInfo, MSSAU);
+
+  Instruction &DeadI = cast<Instruction>(*VariantLHS);
+  salvageDebugInfo(DeadI);
+  eraseInstruction(DeadI, SafetyInfo, MSSAU);
   return true;
 }
 
@@ -2877,8 +2884,10 @@ static bool hoistBOAssociation(Instruction &I, Loop &L,
 
   // (LV op C1) might not be erased if it has more uses than the one we just
   // replaced.
-  if (BO0->use_empty())
+  if (BO0->use_empty()) {
+    salvageDebugInfo(*BO0);
     eraseInstruction(*BO0, SafetyInfo, MSSAU);
+  }
 
   return true;
 }
diff --git a/llvm/test/Transforms/LICM/salvage-hoisted-add.ll b/llvm/test/Transforms/LICM/salvage-hoisted-add.ll
new file mode 100644
index 0000000000000..1bc5802d5997c
--- /dev/null
+++ b/llvm/test/Transforms/LICM/salvage-hoisted-add.ll
@@ -0,0 +1,70 @@
+; RUN: opt -S -passes=licm %s | FileCheck %s
+
+; Check that hoistAdd() in LICM salvages the dbg_value for the hoisted add
+; instruction.
+
+define i32 @hoist_add(ptr %p, ptr %x_p, ptr %length_p) !dbg !5 {
+; CHECK-LABEL: define i32 @hoist_add(
+; CHECK-LABEL: loop:
+; CHECK:           #dbg_value(!DIArgList(i32 [[X:%.*]], i32 [[IV:%.*]]), [[META9:![0-9]+]], !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_arg, 1, DW_OP_plus, DW_OP_stack_value), [[META16:![0-9]+]])
+;
+entry:
+  %x = load i32, ptr %x_p, align 4, !dbg !20, !range !21
+  %length = load i32, ptr %length_p, align 4, !dbg !22, !range !21
+  br label %loop, !dbg !23
+
+loop:                                             ; preds = %backedge, %entry
+  %iv = phi i32 [ 0, %entry ], [ %iv.next, %backedge ], !dbg !24
+  %arith = add nsw i32 %x, %iv, !dbg !25
+    #dbg_value(i32 %arith, !13, !DIExpression(), !25)
+  %x_check = icmp slt i32 %arith, 4, !dbg !26
+  br i1 %x_check, label %out_of_bounds, label %backedge, !dbg !27
+
+backedge:                                         ; preds = %loop
+  %el.ptr = getelementptr i32, ptr %p, i32 %iv, !dbg !28
+  store i32 1, ptr %el.ptr, align 4, !dbg !29
+  %iv.next = add nuw nsw i32 %iv, 4, !dbg !30
+  %loop_cond = icmp slt i32 %iv.next, %length, !dbg !31
+  br i1 %loop_cond, label %loop, label %exit, !dbg !32
+
+exit:                                             ; preds = %backedge
+  ret i32 %iv.next, !dbg !33
+
+out_of_bounds:                                    ; preds = %loop
+  ret i32 -1, !dbg !34
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.debugify = !{!2, !3}
+!llvm.module.flags = !{!4}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug)
+!1 = !DIFile(filename: "salvage-hoisted-add", directory: "/")
+!2 = !{i32 14}
+!3 = !{i32 8}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = distinct !DISubprogram(name: "hoist_add", linkageName: "hoist_add", scope: null, file: !1, line: 1, type: !6, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !8)
+!6 = !DISubroutineType(types: !7)
+!7 = !{}
+!8 = !{!13}
+!10 = !DIBasicType(name: "ty32", size: 32, encoding: DW_ATE_unsigned)
+!13 = !DILocalVariable(name: "4", scope: !5, file: !1, line: 5, type: !10)
+!20 = !DILocation(line: 1, column: 1, scope: !5)
+!21 = !{i32 0, i32 -2147483648}
+!22 = !DILocation(line: 2, column: 1, scope: !5)
+!23 = !DILocation(line: 3, column: 1, scope: !5)
+!24 = !DILocation(line: 4, column: 1, scope: !5)
+!25 = !DILocation(line: 5, column: 1, scope: !5)
+!26 = !DILocation(line: 6, column: 1, scope: !5)
+!27 = !DILocation(line: 7, column: 1, scope: !5)
+!28 = !DILocation(line: 8, column: 1, scope: !5)
+!29 = !DILocation(line: 9, column: 1, scope: !5)
+!30 = !DILocation(line: 10, column: 1, scope: !5)
+!31 = !DILocation(line: 11, column: 1, scope: !5)
+!32 = !DILocation(line: 12, column: 1, scope: !5)
+!33 = !DILocation(line: 13, column: 1, scope: !5)
+!34 = !DILocation(line: 14, column: 1, scope: !5)
+;.
+; CHECK: [[META9]] = !DILocalVariable(name: "4",
+; CHECK: [[META16]] = !DILocation(line: 5, column: 1,
+;.
diff --git a/llvm/test/Transforms/LICM/salvage-hoisted-binop.ll b/llvm/test/Transforms/LICM/salvage-hoisted-binop.ll
new file mode 100644
index 0000000000000..97461865c4d79
--- /dev/null
+++ b/llvm/test/Transforms/LICM/salvage-hoisted-binop.ll
@@ -0,0 +1,45 @@
+; RUN: opt -S -passes=licm %s | FileCheck %s
+
+; Check that hoistBOAssociation() in LICM salvages the dbg_value for the
+; hoisted binary operation.
+
+define void @hoist_binop(i64 %c1, i64 %c2) !dbg !5 {
+; CHECK-LABEL: define void @hoist_binop(
+; CHECK-LABEL: loop:
+; CHECK:           #dbg_value(!DIArgList(i64 [[INDEX:%.*]], i64 [[C1:%.*]]), [[META9:![0-9]+]], !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_arg, 1, DW_OP_plus, DW_OP_stack_value), [[META13:![0-9]+]])
+;
+entry:
+  br label %loop, !dbg !13
+
+loop:                                             ; preds = %loop, %entry
+  %index = phi i64 [ 0, %entry ], [ %index.next, %loop ], !dbg !14
+  %step.add = add i64 %index, %c1, !dbg !15
+  #dbg_value(i64 %step.add, !11, !DIExpression(), !15)
+  %index.next = add i64 %step.add, %c2, !dbg !16
+  br label %loop, !dbg !17
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.debugify = !{!2, !3}
+!llvm.module.flags = !{!4}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug)
+!1 = !DIFile(filename: "salvage-hoist-binop.ll", directory: "/")
+!2 = !{i32 5}
+!3 = !{i32 3}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = distinct !DISubprogram(name: "hoist_binop", linkageName: "hoist_binop", scope: null, file: !1, line: 1, type: !6, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !8)
+!6 = !DISubroutineType(types: !7)
+!7 = !{}
+!8 = !{!11}
+!10 = !DIBasicType(name: "ty64", size: 64, encoding: DW_ATE_unsigned)
+!11 = !DILocalVariable(name: "2", scope: !5, file: !1, line: 3, type: !10)
+!13 = !DILocation(line: 1, column: 1, scope: !5)
+!14 = !DILocation(line: 2, column: 1, scope: !5)
+!15 = !DILocation(line: 3, column: 1, scope: !5)
+!16 = !DILocation(line: 4, column: 1, scope: !5)
+!17 = !DILocation(line: 5, column: 1, scope: !5)
+;.
+; CHECK: [[META9]] = !DILocalVariable(name: "2",
+; CHECK: [[META13]] = !DILocation(line: 3, column: 1,
+;.
diff --git a/llvm/test/Transforms/LICM/salvage-hoisted-gep.ll b/llvm/test/Transforms/LICM/salvage-hoisted-gep.ll
new file mode 100644
index 0000000000000..828a92765b6f3
--- /dev/null
+++ b/llvm/test/Transforms/LICM/salvage-hoisted-gep.ll
@@ -0,0 +1,58 @@
+; RUN: opt -S -passes=licm %s | FileCheck %s
+
+; Check that hoistGEP() in LICM salvages the dbg_value for the hoisted
+; getelementptr instruction.
+
+define void @hoist_gep(ptr %ptr, i1 %c, i32 %arg) !dbg !5 {
+; CHECK-LABEL: define void @hoist_gep(
+; CHECK-LABEL: loop:
+; CHECK:           #dbg_value(!DIArgList(ptr [[PTR:%.*]], i64 [[VAL_EXT:%.*]]), [[META9:![0-9]+]], !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_arg, 1, DW_OP_plus, DW_OP_stack_value), [[META15:![0-9]+]])
+;
+entry:
+  %arg.ext = zext i32 %arg to i64, !dbg !16
+  br label %loop, !dbg !17
+
+loop:                                             ; preds = %loop, %entry
+  %val = call i32 @get.i32(), !dbg !18
+  %val.ext = zext i32 %val to i64, !dbg !19
+  %ptr2 = getelementptr inbounds i8, ptr %ptr, i64 %val.ext, !dbg !20
+  #dbg_value(ptr %ptr2, !14, !DIExpression(), !20)
+  %ptr3 = getelementptr i8, ptr %ptr2, i64 %arg.ext, !dbg !21
+  call void @use(ptr %ptr3), !dbg !22
+  br i1 %c, label %loop, label %exit, !dbg !23
+
+exit:                                             ; preds = %loop
+  ret void, !dbg !24
+}
+
+declare i32 @get.i32()
+declare void @use(ptr)
+
+!llvm.dbg.cu = !{!0}
+!llvm.debugify = !{!2, !3}
+!llvm.module.flags = !{!4}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug)
+!1 = !DIFile(filename: "salvage-hoisted-gep.ll", directory: "/")
+!2 = !{i32 9}
+!3 = !{i32 5}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = distinct !DISubprogram(name: "hoist_gep", linkageName: "hoist_gep", scope: null, file: !1, line: 1, type: !6, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !8)
+!6 = !DISubroutineType(types: !7)
+!7 = !{}
+!8 = !{!14}
+!10 = !DIBasicType(name: "ty64", size: 64, encoding: DW_ATE_unsigned)
+!14 = !DILocalVariable(name: "4", scope: !5, file: !1, line: 5, type: !10)
+!16 = !DILocation(line: 1, column: 1, scope: !5)
+!17 = !DILocation(line: 2, column: 1, scope: !5)
+!18 = !DILocation(line: 3, column: 1, scope: !5)
+!19 = !DILocation(line: 4, column: 1, scope: !5)
+!20 = !DILocation(line: 5, column: 1, scope: !5)
+!21 = !DILocation(line: 6, column: 1, scope: !5)
+!22 = !DILocation(line: 7, column: 1, scope: !5)
+!23 = !DILocation(line: 8, column: 1, scope: !5)
+!24 = !DILocation(line: 9, column: 1, scope: !5)
+;.
+; CHECK: [[META9]] = !DILocalVariable(name: "4",
+; CHECK: [[META15]] = !DILocation(line: 5,
+;.
diff --git a/llvm/test/Transforms/LICM/salvage-hoisted-sub.ll b/llvm/test/Transforms/LICM/salvage-hoisted-sub.ll
new file mode 100644
index 0000000000000..854fd102fdf56
--- /dev/null
+++ b/llvm/test/Transforms/LICM/salvage-hoisted-sub.ll
@@ -0,0 +1,70 @@
+; RUN: opt -S -passes=licm %s | FileCheck %s
+
+; Check that hoistSub() in LICM salvages the dbg_value for the hoisted sub
+; instruction.
+
+define i32 @hoist_sub(ptr %p, ptr %x_p, ptr %length_p) !dbg !5 {
+; CHECK-LABEL: define i32 @hoist_sub(
+; CHECK-LABEL: loop:
+; CHECK:           #dbg_value(!DIArgList(i32 [[X:%.*]], i32 [[IV:%.*]]), [[META9:![0-9]+]], !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_arg, 1, DW_OP_minus, DW_OP_stack_value), [[META16:![0-9]+]])
+;
+entry:
+  %x = load i32, ptr %x_p, align 4, !dbg !20, !range !21
+  %length = load i32, ptr %length_p, align 4, !dbg !22, !range !21
+  br label %loop, !dbg !23
+
+loop:                                             ; preds = %backedge, %entry
+  %iv = phi i32 [ 0, %entry ], [ %iv.next, %backedge ], !dbg !24
+  %arith = sub nsw i32 %x, %iv, !dbg !25
+  #dbg_value(i32 %arith, !13, !DIExpression(), !25)
+  %x_check = icmp slt i32 %arith, 4, !dbg !26
+  br i1 %x_check, label %out_of_bounds, label %backedge, !dbg !27
+
+backedge:                                         ; preds = %loop
+  %el.ptr = getelementptr i32, ptr %p, i32 %iv, !dbg !28
+  store i32 1, ptr %el.ptr, align 4, !dbg !29
+  %iv.next = add nuw nsw i32 %iv, 4, !dbg !30
+  %loop_cond = icmp slt i32 %iv.next, %length, !dbg !31
+  br i1 %loop_cond, label %loop, label %exit, !dbg !32
+
+exit:                                             ; preds = %backedge
+  ret i32 %iv.next, !dbg !33
+
+out_of_bounds:                                    ; preds = %loop
+  ret i32 -1, !dbg !34
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.debugify = !{!2, !3}
+!llvm.module.flags = !{!4}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug)
+!1 = !DIFile(filename: "salvage-hoisted-sub.ll", directory: "/")
+!2 = !{i32 14}
+!3 = !{i32 8}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = distinct !DISubprogram(name: "hoist_sub", linkageName: "hoist_sub", scope: null, file: !1, line: 1, type: !6, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !8)
+!6 = !DISubroutineType(types: !7)
+!7 = !{}
+!8 = !{!13}
+!10 = !DIBasicType(name: "ty32", size: 32, encoding: DW_ATE_unsigned)
+!13 = !DILocalVariable(name: "4", scope: !5, file: !1, line: 5, type: !10)
+!20 = !DILocation(line: 1, column: 1, scope: !5)
+!21 = !{i32 0, i32 -2147483648}
+!22 = !DILocation(line: 2, column: 1, scope: !5)
+!23 = !DILocation(line: 3, column: 1, scope: !5)
+!24 = !DILocation(line: 4, column: 1, scope: !5)
+!25 = !DILocation(line: 5, column: 1, scope: !5)
+!26 = !DILocation(line: 6, column: 1, scope: !5)
+!27 = !DILocation(line: 7, column: 1, scope: !5)
+!28 = !DILocation(line: 8, column: 1, scope: !5)
+!29 = !DILocation(line: 9, column: 1, scope: !5)
+!30 = !DILocation(line: 10, column: 1, scope: !5)
+!31 = !DILocation(line: 11, column: 1, scope: !5)
+!32 = !DILocation(line: 12, column: 1, scope: !5)
+!33 = !DILocation(line: 13, column: 1, scope: !5)
+!34 = !DILocation(line: 14, column: 1, scope: !5)
+;.
+; CHECK: [[META9]] = !DILocalVariable(name: "4",
+; CHECK: [[META16]] = !DILocation(line: 5, column: 1,
+;.

OCHyams
OCHyams approved these changes May 9, 2025
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LGTM!

llvm/test/Transforms/LICM/salvage-hoisted-binop.ll Outdated
loop: ; preds = %loop, %entry
%index = phi i64 [ 0, %entry ], [ %index.next, %loop ], !dbg !14
%step.add = add i64 %index, %c1, !dbg !15
#dbg_value(i64 %step.add, !11, !DIExpression(), !15)
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nit: please can you indent the #dbg_value, same in the other tests below (sorry to be annoying).

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Sorry 😢 I found out that the #dbg_values without the indentations are generated after using the helper script update_test_checks.py. I'll fix them now.

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Oh, that's annoying for it to do that. I'm not very familiar with the script but I'll try and fix that (#139230).

(Patch still LGTM, ty)

@Apochens Apochens merged commit 5971b41 into llvm:main May 12, 2025
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@Apochens Apochens deleted the #138684-licm-salvage-dbg-value branch May 12, 2025 01:54
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@OCHyams OCHyams OCHyams approved these changes

@SLTozer SLTozer Awaiting requested review from SLTozer

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[DebugInfo][LICM] Debug value info loss caused by removing dead instructions without salvaging
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@Apochens @llvmbot @OCHyams