[llvm] [DebugInfo][SpeculativeExecution] Drop the debug location of the hoisted instruction (PR #97384)

[Shan Huang via llvm-commits]

https://github.com/Apochens created https://github.com/llvm/llvm-project/pull/97384

Fix #97375 .

>From 1c03aa7fe843fa6d64048311980d2ba52b138951 Mon Sep 17 00:00:00 2001
From: Apochens <52285902006 at stu.ecnu.edu.cn>
Date: Tue, 2 Jul 2024 05:35:30 +0000
Subject: [PATCH] fix the missing debug location update

---
 .../Scalar/SpeculativeExecution.cpp           |  1 +
 .../dropping-debugloc-hoist.ll                | 36 +++++++++++++++++++
 2 files changed, 37 insertions(+)
 create mode 100644 llvm/test/Transforms/SpeculativeExecution/dropping-debugloc-hoist.ll

diff --git a/llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp b/llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp
index f921ee72a0a1c..ed9c1828ce06a 100644
--- a/llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp
+++ b/llvm/lib/Transforms/Scalar/SpeculativeExecution.cpp
@@ -328,6 +328,7 @@ bool SpeculativeExecutionPass::considerHoistingFromTo(
     ++I;
     if (!NotHoisted.count(&*Current)) {
       Current->moveBefore(ToBlock.getTerminator());
+      Current->dropLocation();
     }
   }
   return true;
diff --git a/llvm/test/Transforms/SpeculativeExecution/dropping-debugloc-hoist.ll b/llvm/test/Transforms/SpeculativeExecution/dropping-debugloc-hoist.ll
new file mode 100644
index 0000000000000..6355219699f6b
--- /dev/null
+++ b/llvm/test/Transforms/SpeculativeExecution/dropping-debugloc-hoist.ll
@@ -0,0 +1,36 @@
+; RUN: opt -S -passes=speculative-execution %s | FileCheck %s
+
+; Check that SpeculativeExecution's considerHoistingFromTo() drops
+; the debug location of the hoisted instructions in a certain branch.
+
+define void @ifThen() !dbg !5 {
+; CHECK-LABEL: define void @ifThen(
+; CHECK-SAME: ) !dbg [[DBG5:![0-9]+]] {
+; CHECK-NEXT:    [[X:%.*]] = add i32 2, 3{{$}}
+;
+  br i1 true, label %a, label %b, !dbg !8
+
+a:                                                ; preds = %0
+  %x = add i32 2, 3, !dbg !9
+  br label %b, !dbg !10
+
+b:                                                ; preds = %a, %0
+  ret void, !dbg !11
+}
+
+!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: "main.ll", directory: "/")
+!2 = !{i32 4}
+!3 = !{i32 0}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = distinct !DISubprogram(name: "ifThen", linkageName: "ifThen", 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)