Do not clone debug instruction in code sinking

Move the debug instructions instead of cloning them in CodeSinking and
CodeLoopSinking passes.

Author: admitric

IGC/Compiler/CISACodeGen/CodeSinking.cpp

@@ -51,6 +51,7 @@ namespace IGC {
     // it is required for correct work of LiveVariables analysis and other
     static void ProcessDbgValueInst(BasicBlock& blk, DominatorTree *DT)
     {
+        llvm::DenseMap<Instruction *, Instruction *> PositionMap;
         for (auto I = blk.rbegin(), E = blk.rend(); I != E; ++I)
         {
             Instruction* inst = cast<Instruction>(&*I);
@@ -65,18 +66,15 @@ namespace IGC {
                     {
                         if (!DT->dominates(def, inst))
                         {
-                            auto* instClone = inst->clone();
                             if (isa<PHINode>(def)) {
                                 // If the instruction is a PHI node, insert the new instruction at the beginning of the block.
-                                instClone->insertBefore(&*def->getParent()->getFirstInsertionPt());
+                                PositionMap[inst] = &*def->getParent()->getFirstInsertionPt();
                             }
                             else {
                                 // Otherwise, insert the new instruction after the defining instruction.
-                                instClone->insertAfter(def);
+                                PositionMap[inst] = def->getNextNonDebugInstruction();
+                                IGC_ASSERT(!isa<BranchInst>(def));
                             }
-                            Value* undef = UndefValue::get(def->getType());
-                            MetadataAsValue* MAV = MetadataAsValue::get(inst->getContext(), ValueAsMetadata::get(undef));
-                            cast<CallInst>(inst)->setArgOperand(0, MAV);
                         }
                     }
                 }
@@ -89,6 +87,9 @@ namespace IGC {
                 }
             }
         }
+        for (auto &[I, Pos] : PositionMap) {
+            I->moveBefore(Pos);
+        }
     }
 
     // Check the instruction is a 2d block read

IGC/Compiler/tests/CodeSinking/LoopSinking/adds-sinking-debug.ll

@@ -0,0 +1,79 @@
+;=========================== begin_copyright_notice ============================
+;
+; Copyright (C) 2025 Intel Corporation
+;
+; SPDX-License-Identifier: MIT
+;
+;============================ end_copyright_notice =============================
+; REQUIRES: regkeys
+; RUN: igc_opt --regkey LoopSinkMinSave=0 --regkey ForceLoopSink=1 --regkey CodeLoopSinkingMinSize=10 --CheckInstrTypes -igc-update-instrtypes-on-run --basic-aa --igc-code-loop-sinking --verify -S %s | FileCheck %s --check-prefix=CHECK-SINK
+; RUN: igc_opt --regkey LoopSinkMinSave=0 --regkey ForceLoopSink=1 --regkey LoopSinkForceRollback=1 --regkey CodeLoopSinkingMinSize=10 --CheckInstrTypes -igc-update-instrtypes-on-run --basic-aa --igc-code-loop-sinking --verify -S %s | FileCheck %s --check-prefix=CHECK-ROLLBACK
+
+; CHECK-LABEL: @foo(
+
+; For sink we check there is only one debug value in the loop
+
+; CHECK-SINK: ph:
+; CHECK-SINK-NOT: call void @llvm.dbg.value
+; CHECK-SINK: loop:
+; CHECK-SINK:     call void @llvm.dbg.value
+; CHECK-SINK-NOT: call void @llvm.dbg.value
+
+
+; For rollback check the debug value is not duplicated
+; Also --verify pass checks that the IR is correct
+
+; CHECK-ROLLBACK:     call void @llvm.dbg.value
+; CHECK-ROLLBACK-NOT: call void @llvm.dbg.value
+
+
+define spir_kernel void @foo(i32 %t, i32 %count) {
+  br label %ph
+
+ph:
+  %1 = add i32 %t, 1
+  %2 = add i32 %1, 2
+  br label %loop
+
+loop:                                             ; preds = %loop, %ph
+  %index = phi i32 [ 0, %ph ], [ %inc, %loop ]
+  call void @llvm.dbg.value(metadata i32 %1, metadata !12, metadata !DIExpression(DW_OP_constu, 4, DW_OP_swap, DW_OP_xderef)), !dbg !13
+  %3 = add i32 %1, 3
+  %4 = add i32 %2, %3
+  %inc = add i32 %index, 1
+  %cmptmp = icmp ult i32 %index, %count
+  br i1 %cmptmp, label %loop, label %afterloop
+
+afterloop:                                        ; preds = %loop
+  ret void
+}
+
+; Function Attrs: nofree nosync nounwind readnone speculatable willreturn
+declare void @llvm.dbg.value(metadata, metadata, metadata) #0
+
+declare i32 @llvm.genx.GenISA.WavePrefix.i32(i32, i8, i1, i1, i32)
+
+attributes #0 = { nofree nosync nounwind readnone speculatable willreturn }
+
+!llvm.module.flags = !{!3, !4, !5}
+!llvm.dbg.cu = !{!0}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "hi.cpp", directory: "/test/")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!6 = !{!"clang"}
+!7 = distinct !DISubprogram(name: "test", scope: !1, file: !1, line: 3, type: !8, isLocal: false, isDefinition: true, scopeLine: 3, flags: DIFlagPrototyped, isOptimized: true, unit: !0, retainedNodes: !11)
+!8 = !DISubroutineType(types: !9)
+!9 = !{!10, !10}
+!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!11 = !{!12}
+!12 = !DILocalVariable(name: "t", arg: 1, scope: !7, file: !1, line: 3, type: !10)
+!13 = !DILocation(line: 3, column: 14, scope: !7)
+!14 = !DILocation(line: 4, column: 12, scope: !7)
+!15 = distinct !DISubprogram(name: "_start", scope: !1, file: !1, line: 7, type: !16, isLocal: false, isDefinition: true, scopeLine: 7, isOptimized: true, unit: !0, retainedNodes: !2)
+!16 = !DISubroutineType(types: !17)
+!17 = !{!10}
+!18 = !DILocalVariable(name: "a", arg: 1, scope: !7, file: !1, line: 3, type: !10)