[llvm] [InstCombine] Retain debug information on store to null instruction (PR #86105)

[Abinaya Saravanan via llvm-commits]

https://github.com/quic-asaravan updated https://github.com/llvm/llvm-project/pull/86105

>From 4a8657baf6669ebb419e70554337b848749bba8d Mon Sep 17 00:00:00 2001
From: quic-asaravan <quic_asaravan at quicinc.com>
Date: Thu, 21 Mar 2024 03:02:18 -0700
Subject: [PATCH 1/2] [InstCombine] Retain debug information on store to null
 instruction

---
 llvm/lib/Transforms/InstCombine/InstCombineInternal.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
index b9ad3a7400792..c998c727eba48 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
+++ b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
@@ -461,7 +461,7 @@ class LLVM_LIBRARY_VISIBILITY InstCombinerImpl final
     auto *SI = new StoreInst(ConstantInt::getTrue(Ctx),
                              PoisonValue::get(PointerType::getUnqual(Ctx)),
                              /*isVolatile*/ false, Align(1));
-    InsertNewInstBefore(SI, InsertAt->getIterator());
+    InsertNewInstWith(SI, InsertAt->getIterator());
   }
 
   /// Combiner aware instruction erasure.

>From e10ce4787b466bf5ed9b26f4d4422bdc548323f1 Mon Sep 17 00:00:00 2001
From: quic-asaravan <quic_asaravan at quicinc.com>
Date: Mon, 3 Jun 2024 02:12:43 -0700
Subject: [PATCH 2/2] [InstCombine] Lit test added for "Retain debug
 information on store to null instruction"

---
 .../InstCombine/StoreToNull-DbgCheck.ll       | 30 +++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100644 llvm/test/Transforms/InstCombine/StoreToNull-DbgCheck.ll

diff --git a/llvm/test/Transforms/InstCombine/StoreToNull-DbgCheck.ll b/llvm/test/Transforms/InstCombine/StoreToNull-DbgCheck.ll
new file mode 100644
index 0000000000000..19638a7a44ae1
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/StoreToNull-DbgCheck.ll
@@ -0,0 +1,30 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
+; Verify whether debug information is attached to the store to null/undef instruction
+; !dbg should be present at the end of "store to null" instruction
+; RUN: opt -S -passes='instcombine' < %s | FileCheck %s > /dev/null
+
+source_filename = "test.ll"
+target triple = "hexagon"
+
+define void @_Z3foov() {
+; CHECK-LABEL: define void @_Z3foov() {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    store i1 true, ptr poison, align 1, !dbg
+; CHECK-NEXT:    ret void
+
+entry:
+  tail call void null(), !dbg !4
+  ret void
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "Clang", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, globals: !2, splitDebugInlining: false, debugInfoForProfiling: true, nameTableKind: None)
+!1 = !DIFile(filename: "test_sym_mod.cpp", directory: "/workspace/asaravan/test_bugpoint")
+!2 = !{}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = !DILocation(line: 83, column: 3, scope: !5)
+!5 = distinct !DISubprogram(name: "foo", linkageName: "_Z3foov", scope: !1, file: !1, line: 77, type: !6, scopeLine: 78, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !2)
+!6 = !DISubroutineType(types: !7)
+!7 = !{null}