[DebugInfo][InstCombine] When replacing bswap idiom, add DebugLoc to new insts

llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

@@ -2879,8 +2879,10 @@ Instruction *InstCombinerImpl::matchBSwapOrBitReverse(Instruction &I,
   Instruction *LastInst = Insts.pop_back_val();
   LastInst->removeFromParent();
 
-  for (auto *Inst : Insts)
+  for (auto *Inst : Insts) {
+    Inst->setDebugLoc(I.getDebugLoc());
     Worklist.push(Inst);
+  }
   return LastInst;
 }
 

llvm/test/Transforms/InstCombine/debugloc-bswap.ll

@@ -0,0 +1,52 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -passes=instcombine -S %s -o - | FileCheck %s
+;; Tests that when InstCombine replaces a bswap idiom with an intrinsic, the
+;; !dbg attachment from the replaced instruction is applied to all generated
+;; instructions, not just the last.
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define i32 @inflate(ptr %strm) {
+; CHECK-LABEL: define i32 @inflate(
+; CHECK-SAME: ptr [[STRM:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[TMP0:%.*]] = load i64, ptr [[STRM]], align 8
+; CHECK-NEXT:    [[TRUNC:%.*]] = trunc i64 [[TMP0]] to i32, !dbg [[DBG3:![0-9]+]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[TRUNC]], 65535, !dbg [[DBG3]]
+; CHECK-NEXT:    [[MASK:%.*]] = call i32 @llvm.bswap.i32(i32 [[TMP1]]), !dbg [[DBG3]]
+; CHECK-NEXT:    [[ADD665:%.*]] = zext i32 [[MASK]] to i64, !dbg [[DBG3]]
+; CHECK-NEXT:    store i64 [[ADD665]], ptr [[STRM]], align 8
+; CHECK-NEXT:    ret i32 0
+;
+entry:
+  %0 = load i64, ptr %strm, align 8
+  %and660 = and i64 %0, 65280
+  %shl661 = shl i64 %and660, 8
+  %and663 = and i64 %0, 255
+  %shl664 = shl i64 %and663, 24
+  %add665 = or i64 %shl661, %shl664, !dbg !4
+  store i64 %add665, ptr %strm, align 8
+  ret i32 0
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang version 20.0.0git")
+!1 = !DIFile(filename: "/tmp/zlib_inflate.c", directory: "/tmp")
+!2 = !{}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = !DILocation(line: 8, column: 42, scope: !6)
+!5 = !DIFile(filename: "zlib_inflate.c", directory: "/tmp")
+!6 = distinct !DISubprogram(name: "inflate", scope: !5, file: !5, line: 622, type: !7, scopeLine: 625, unit: !0, retainedNodes: !2)
+!7 = distinct !DISubroutineType(types: !2)
+;.
+; CHECK: [[META0:![0-9]+]] = distinct !DICompileUnit(language: DW_LANG_C11, file: [[META1:![0-9]+]], producer: "{{.*}}clang version {{.*}}", isOptimized: false, runtimeVersion: 0, emissionKind: NoDebug)
+; CHECK: [[META1]] = !DIFile(filename: "/tmp/zlib_inflate.c", directory: {{.*}})
+; CHECK: [[DBG3]] = !DILocation(line: 8, column: 42, scope: [[META4:![0-9]+]])
+; CHECK: [[META4]] = distinct !DISubprogram(name: "inflate", scope: [[META5:![0-9]+]], file: [[META5]], line: 622, type: [[META6:![0-9]+]], scopeLine: 625, spFlags: DISPFlagDefinition, unit: [[META0]], retainedNodes: [[META7:![0-9]+]])
+; CHECK: [[META5]] = !DIFile(filename: "zlib_inflate.c", directory: {{.*}})
+; CHECK: [[META6]] = distinct !DISubroutineType(types: [[META7]])
+; CHECK: [[META7]] = !{}
+;.