[DebugInfo][LICM] Fix missing debug location updates (#91729)

Author: Apochens

llvm/lib/Transforms/Scalar/LICM.cpp

@@ -933,12 +933,14 @@ bool llvm::hoistRegion(DomTreeNode *N, AAResults *AA, LoopInfo *LI,
         ReciprocalDivisor->setFastMathFlags(I.getFastMathFlags());
         SafetyInfo->insertInstructionTo(ReciprocalDivisor, I.getParent());
         ReciprocalDivisor->insertBefore(&I);
+        ReciprocalDivisor->setDebugLoc(I.getDebugLoc());
 
         auto Product =
             BinaryOperator::CreateFMul(I.getOperand(0), ReciprocalDivisor);
         Product->setFastMathFlags(I.getFastMathFlags());
         SafetyInfo->insertInstructionTo(Product, I.getParent());
         Product->insertAfter(&I);
+        Product->setDebugLoc(I.getDebugLoc());
         I.replaceAllUsesWith(Product);
         eraseInstruction(I, *SafetyInfo, MSSAU);
 

llvm/test/Transforms/LICM/debugloc-preserve-fmul-drop-fdiv.ll

@@ -0,0 +1,66 @@
+; RUN: opt -passes=licm -verify-memoryssa -S < %s | FileCheck %s
+
+; JumpThreading's hoistRegion() replaces the `fdiv` (%v6), of which the second
+; operand (%v) is a loop invariant, with a loop invariant `fdiv` and a `fmul`.
+; This test checks that the debug location propagates to the new `fmul` from
+; the old `fdiv` it replaces in block `loop` and the debug location drop of new
+; `fdiv`, which is hoisted to block `entry` after being created.
+
+define zeroext i1 @invariant_denom(double %v) !dbg !5 {
+; CHECK:       entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = fdiv fast double 1.000000e+00, [[V:%.*]]{{$}}
+; CHECK:       loop:
+; CHECK:         [[TMP1:%.*]] = fmul fast double {{.*}}, !dbg [[DBG12:![0-9]+]]
+; CHECK:       [[DBG12]] = !DILocation(line: 5,
+;
+entry:
+  br label %loop, !dbg !8
+
+loop:                                             ; preds = %loop, %entry
+  %v3 = phi i32 [ 0, %entry ], [ %v11, %loop ], !dbg !9
+  %v4 = phi i32 [ 0, %entry ], [ %v12, %loop ], !dbg !10
+  %v5 = uitofp i32 %v4 to double, !dbg !11
+  %v6 = fdiv fast double %v5, %v, !dbg !12
+  %v7 = fptoui double %v6 to i64, !dbg !13
+  %v8 = and i64 %v7, 1, !dbg !14
+  %v9 = xor i64 %v8, 1, !dbg !15
+  %v10 = trunc i64 %v9 to i32, !dbg !16
+  %v11 = add i32 %v10, %v3, !dbg !17
+  %v12 = add nuw i32 %v4, 1, !dbg !18
+  %v13 = icmp eq i32 %v12, -1, !dbg !19
+  br i1 %v13, label %end, label %loop, !dbg !20
+
+end:                                              ; preds = %loop
+  %v15 = phi i32 [ %v11, %loop ], !dbg !21
+  %v16 = icmp ne i32 %v15, 0, !dbg !22
+  ret i1 %v16, !dbg !23
+}
+
+!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: "test.ll", directory: "/")
+!2 = !{i32 16}
+!3 = !{i32 0}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = distinct !DISubprogram(name: "invariant_denom", linkageName: "invariant_denom", scope: null, file: !1, line: 1, type: !6, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0)
+!6 = !DISubroutineType(types: !7)
+!7 = !{}
+!8 = !DILocation(line: 1, column: 1, scope: !5)
+!9 = !DILocation(line: 2, column: 1, scope: !5)
+!10 = !DILocation(line: 3, column: 1, scope: !5)
+!11 = !DILocation(line: 4, column: 1, scope: !5)
+!12 = !DILocation(line: 5, column: 1, scope: !5)
+!13 = !DILocation(line: 6, column: 1, scope: !5)
+!14 = !DILocation(line: 7, column: 1, scope: !5)
+!15 = !DILocation(line: 8, column: 1, scope: !5)
+!16 = !DILocation(line: 9, column: 1, scope: !5)
+!17 = !DILocation(line: 10, column: 1, scope: !5)
+!18 = !DILocation(line: 11, column: 1, scope: !5)
+!19 = !DILocation(line: 12, column: 1, scope: !5)
+!20 = !DILocation(line: 13, column: 1, scope: !5)
+!21 = !DILocation(line: 14, column: 1, scope: !5)
+!22 = !DILocation(line: 15, column: 1, scope: !5)
+!23 = !DILocation(line: 16, column: 1, scope: !5)