[llvm] [DebugInfo][X86] Use merged DebugLoc in replaceBranchWithTailCall (PR #189509)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-x86

Author: Zequan Wu (ZequanWu)

<details>
<summary>Changes</summary>

Originally, the conditional tail call instruction uses the condition's debug location. 
```
if (b)

---
Full diff: https://github.com/llvm/llvm-project/pull/189509.diff


2 Files Affected:

- (modified) llvm/lib/Target/X86/X86InstrInfo.cpp (+5-1) 
- (added) llvm/test/CodeGen/X86/tailcall-debugloc.ll (+43) 


``````````diff
diff --git a/llvm/lib/Target/X86/X86InstrInfo.cpp b/llvm/lib/Target/X86/X86InstrInfo.cpp
index 3b48a333147b5..15d0923e0657b 100644
--- a/llvm/lib/Target/X86/X86InstrInfo.cpp
+++ b/llvm/lib/Target/X86/X86InstrInfo.cpp
@@ -3772,7 +3772,11 @@ void X86InstrInfo::replaceBranchWithTailCall(
   unsigned Opc = TailCall.getOpcode() == X86::TCRETURNdi ? X86::TCRETURNdicc
                                                          : X86::TCRETURNdi64cc;
 
-  auto MIB = BuildMI(MBB, I, MBB.findDebugLoc(I), get(Opc));
+  DebugLoc BranchDL = MBB.findDebugLoc(I);
+  DebugLoc TailCallDL = TailCall.getDebugLoc();
+  auto MIB = BuildMI(
+      MBB, I, DILocation::getMergedLocation(BranchDL.get(), TailCallDL.get()),
+      get(Opc));
   MIB->addOperand(TailCall.getOperand(0)); // Destination.
   MIB.addImm(0);                           // Stack offset (not used).
   MIB->addOperand(BranchCond[0]);          // Condition.
diff --git a/llvm/test/CodeGen/X86/tailcall-debugloc.ll b/llvm/test/CodeGen/X86/tailcall-debugloc.ll
new file mode 100644
index 0000000000000..524f61cd7fa1c
--- /dev/null
+++ b/llvm/test/CodeGen/X86/tailcall-debugloc.ll
@@ -0,0 +1,43 @@
+; RUN: llc -mtriple=x86_64-unknown-linux-gnu -stop-after=branch-folder -o - %s | FileCheck %s
+
+; CHECK: TCRETURNdi64cc {{.*}} debug-location !DILocation(line: 0, scope:
+
+define dso_local void @_Z3fooi(i32 noundef %x) !dbg !13 {
+entry:
+    #dbg_value(i32 %x, !18, !DIExpression(), !19)
+  %cmp = icmp eq i32 %x, 42, !dbg !20
+  br i1 %cmp, label %if.then, label %if.end, !dbg !22
+
+if.then:                                          ; preds = %entry
+  tail call void @_Z3barv(), !dbg !23
+  br label %if.end, !dbg !25
+
+if.end:                                           ; preds = %if.then, %entry
+  ret void, !dbg !26
+}
+
+declare !dbg !27 void @_Z3barv() 
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1)
+!1 = !DIFile(filename: "test.cpp", directory: "/tmp", checksumkind: CSK_MD5, checksum: "bcd632cd2764dd78c5bf358224f7e3ba")
+!2 = !{i32 7, !"Dwarf Version", i32 5}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!13 = distinct !DISubprogram(name: "foo", linkageName: "_Z3fooi", scope: !1, file: !1, line: 3, type: !14, scopeLine: 3, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !17, keyInstructions: true)
+!14 = !DISubroutineType(types: !15)
+!15 = !{null, !16}
+!16 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!17 = !{!18}
+!18 = !DILocalVariable(name: "x", arg: 1, scope: !13, file: !1, line: 3, type: !16)
+!19 = !DILocation(line: 0, scope: !13)
+!20 = !DILocation(line: 4, column: 9, scope: !21, atomGroup: 1, atomRank: 2)
+!21 = distinct !DILexicalBlock(scope: !13, file: !1, line: 4, column: 7)
+!22 = !DILocation(line: 4, column: 9, scope: !21, atomGroup: 1, atomRank: 1)
+!23 = !DILocation(line: 5, column: 5, scope: !24)
+!24 = distinct !DILexicalBlock(scope: !21, file: !1, line: 4, column: 16)
+!25 = !DILocation(line: 6, column: 3, scope: !24)
+!26 = !DILocation(line: 7, column: 1, scope: !13, atomGroup: 2, atomRank: 1)
+!27 = !DISubprogram(name: "bar", linkageName: "_Z3barv", scope: !1, file: !1, line: 1, type: !28, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized)
+!28 = !DISubroutineType(types: !29)
+!29 = !{null}

``````````

</details>


https://github.com/llvm/llvm-project/pull/189509