[DebugInfo][IndVarSimplify] Fix missing debug location updates (#91443)

Adds debug location updates for the newly created `phi`, `add`, `icmp` and `sitofp` instructions in `IndVarSimplify`.

Fixes #91436

Author: Apochens

llvm/lib/Transforms/Scalar/IndVarSimplify.cpp

@@ -359,15 +359,18 @@ bool IndVarSimplify::handleFloatingPointIV(Loop *L, PHINode *PN) {
       PHINode::Create(Int32Ty, 2, PN->getName() + ".int", PN->getIterator());
   NewPHI->addIncoming(ConstantInt::get(Int32Ty, InitValue),
                       PN->getIncomingBlock(IncomingEdge));
+  NewPHI->setDebugLoc(PN->getDebugLoc());
 
-  Value *NewAdd =
+  Instruction *NewAdd =
       BinaryOperator::CreateAdd(NewPHI, ConstantInt::get(Int32Ty, IncValue),
                                 Incr->getName() + ".int", Incr->getIterator());
+  NewAdd->setDebugLoc(Incr->getDebugLoc());
   NewPHI->addIncoming(NewAdd, PN->getIncomingBlock(BackEdge));
 
   ICmpInst *NewCompare =
       new ICmpInst(TheBr->getIterator(), NewPred, NewAdd,
                    ConstantInt::get(Int32Ty, ExitValue), Compare->getName());
+  NewCompare->setDebugLoc(Compare->getDebugLoc());
 
   // In the following deletions, PN may become dead and may be deleted.
   // Use a WeakTrackingVH to observe whether this happens.
@@ -391,8 +394,9 @@ bool IndVarSimplify::handleFloatingPointIV(Loop *L, PHINode *PN) {
   // We give preference to sitofp over uitofp because it is faster on most
   // platforms.
   if (WeakPH) {
-    Value *Conv = new SIToFPInst(NewPHI, PN->getType(), "indvar.conv",
-                                 PN->getParent()->getFirstInsertionPt());
+    Instruction *Conv = new SIToFPInst(NewPHI, PN->getType(), "indvar.conv",
+                                       PN->getParent()->getFirstInsertionPt());
+    Conv->setDebugLoc(PN->getDebugLoc());
     PN->replaceAllUsesWith(Conv);
     RecursivelyDeleteTriviallyDeadInstructions(PN, TLI, MSSAU.get());
   }

llvm/test/Transforms/IndVarSimplify/preserving-debugloc.ll

@@ -0,0 +1,61 @@
+; RUN: opt < %s -passes=indvars -S | FileCheck %s
+
+; This testcase checks the preservation of debug locations of newly created 
+; phi, sitofp, add and icmp instructions in IndVarSimplify Pass.
+
+define void @test1() !dbg !5 {
+; CHECK-LABEL: @test1(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[BB:%.*]], !dbg
+; CHECK:  bb:
+; CHECK:    [[IV_INT:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[DOTINT:%.*]], [[BB]] ], !dbg ![[DBG1:[0-9]+]]
+; CHECK:    [[INDVAR_CONV:%.*]] = sitofp i32 [[IV_INT]] to double, !dbg ![[DBG1]]
+; CHECK:    [[DOTINT]] = add nuw nsw i32 [[IV_INT]], 1, !dbg ![[DBG2:[0-9]+]]
+; CHECK:    [[TMP1:%.*]] = icmp ult i32 [[DOTINT]], 10000, !dbg ![[DBG3:[0-9]+]]
+; CHECK: ![[DBG1]] = !DILocation(line: 2
+; CHECK: ![[DBG2]] = !DILocation(line: 4
+; CHECK: ![[DBG3]] = !DILocation(line: 5
+;
+entry:
+  br label %bb, !dbg !16
+
+bb:                                               ; preds = %bb, %entry
+  %iv = phi double [ 0.000000e+00, %entry ], [ %1, %bb ], !dbg !17
+  %0 = tail call i32 @foo(double %iv), !dbg !18
+  %1 = fadd double %iv, 1.000000e+00, !dbg !19
+  %2 = fcmp olt double %1, 1.000000e+04, !dbg !20
+  br i1 %2, label %bb, label %return, !dbg !21
+
+return:                                           ; preds = %bb
+  ret void, !dbg !22
+}
+
+declare i32 @foo(double)
+
+!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: "indvars-preserving.ll", directory: "/")
+!2 = !{i32 7}
+!3 = !{i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = distinct !DISubprogram(name: "test1", linkageName: "test1", scope: null, file: !1, line: 1, type: !6, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !8)
+!6 = !DISubroutineType(types: !7)
+!7 = !{}
+!8 = !{!9, !11, !13, !14}
+!9 = !DILocalVariable(name: "1", scope: !5, file: !1, line: 2, type: !10)
+!10 = !DIBasicType(name: "ty64", size: 64, encoding: DW_ATE_unsigned)
+!11 = !DILocalVariable(name: "2", scope: !5, file: !1, line: 3, type: !12)
+!12 = !DIBasicType(name: "ty32", size: 32, encoding: DW_ATE_unsigned)
+!13 = !DILocalVariable(name: "3", scope: !5, file: !1, line: 4, type: !10)
+!14 = !DILocalVariable(name: "4", scope: !5, file: !1, line: 5, type: !15)
+!15 = !DIBasicType(name: "ty8", size: 8, encoding: DW_ATE_unsigned)
+!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)