[DebugInfo][LICM] Fix debug value loss caused by hoisting the cmp instructions (#146640)

fix #146621

Author: Apochens

llvm/lib/Transforms/Scalar/LICM.cpp

@@ -2490,8 +2490,12 @@ static bool hoistMinMax(Instruction &I, Loop &L, ICFLoopSafetyInfo &SafetyInfo,
   NewCond->takeName(&I);
   I.replaceAllUsesWith(NewCond);
   eraseInstruction(I, SafetyInfo, MSSAU);
-  eraseInstruction(*cast<Instruction>(Cond1), SafetyInfo, MSSAU);
-  eraseInstruction(*cast<Instruction>(Cond2), SafetyInfo, MSSAU);
+  Instruction &CondI1 = *cast<Instruction>(Cond1);
+  Instruction &CondI2 = *cast<Instruction>(Cond2);
+  salvageDebugInfo(CondI1);
+  salvageDebugInfo(CondI2);
+  eraseInstruction(CondI1, SafetyInfo, MSSAU);
+  eraseInstruction(CondI2, SafetyInfo, MSSAU);
   return true;
 }
 

llvm/test/Transforms/LICM/salvage-hoisted-minmax.ll

@@ -0,0 +1,59 @@
+; RUN: opt -S -passes=licm %s | FileCheck %s
+
+; Check that hoistMinMax() in LICM salvages the debug values for the hoisted
+; cmp instructions.
+
+define i32 @test_ult(i32 %start, i32 %inv_1, i32 %inv_2) !dbg !5 {
+; CHECK-LABEL: define i32 @test_ult(
+; CHECK-SAME: i32 [[START:%.*]], i32 [[INV_1:%.*]], i32 [[INV_2:%.*]])
+; CHECK:       [[LOOP:.*]]:
+; CHECK:           #dbg_value(!DIArgList(i32 [[IV:%.*]], i32 [[INV_1]]), [[META9:![0-9]+]], !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_arg, 1, DW_OP_lt, DW_OP_stack_value), [[META14:![0-9]+]])
+; CHECK-NEXT:      #dbg_value(!DIArgList(i32 [[IV]], i32 [[INV_2]]), [[META11:![0-9]+]], !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_arg, 1, DW_OP_lt, DW_OP_stack_value), [[META15:![0-9]+]])
+; CHECK-NEXT:    [[LOOP_COND:%.*]] = icmp ult i32 [[IV]], [[INVARIANT_UMIN:%.*]], !dbg [[DBG16:![0-9]+]]
+entry:
+  br label %loop, !dbg !16
+
+loop:                                             ; preds = %loop, %entry
+  %iv = phi i32 [ %start, %entry ], [ %iv.next, %loop ], !dbg !17
+  %cmp_1 = icmp ult i32 %iv, %inv_1, !dbg !18
+    #dbg_value(i1 %cmp_1, !11, !DIExpression(), !18)
+  %cmp_2 = icmp ult i32 %iv, %inv_2, !dbg !19
+    #dbg_value(i1 %cmp_2, !13, !DIExpression(), !19)
+  %loop_cond = and i1 %cmp_1, %cmp_2, !dbg !20
+  %iv.next = add i32 %iv, 1, !dbg !21
+  br i1 %loop_cond, label %loop, label %exit, !dbg !22
+
+exit:                                             ; preds = %loop
+  ret i32 %iv, !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: "temp.ll", directory: "/")
+!2 = !{i32 8}
+!3 = !{i32 5}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = distinct !DISubprogram(name: "test_ult", linkageName: "test_ult", scope: null, file: !1, line: 1, type: !6, scopeLine: 1, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !8)
+!6 = !DISubroutineType(types: !7)
+!7 = !{}
+!8 = !{!11, !13}
+!11 = !DILocalVariable(name: "2", scope: !5, file: !1, line: 3, type: !12)
+!12 = !DIBasicType(name: "ty8", size: 8, encoding: DW_ATE_unsigned)
+!13 = !DILocalVariable(name: "3", scope: !5, file: !1, line: 4, type: !12)
+!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)
+;.
+; CHECK: [[META9]] = !DILocalVariable(name: "2",
+; CHECK: [[META11]] = !DILocalVariable(name: "3",
+; CHECK: [[META14]] = !DILocation(line: 3,
+; CHECK: [[META15]] = !DILocation(line: 4,
+;.