From 391bf068f2c124e98e18bbc027f4cfc6f0b413d6 Mon Sep 17 00:00:00 2001
From: AdityaK <hiraditya@msn.com>
Date: Thu, 21 Nov 2024 10:07:39 -0800
Subject: [PATCH] [LTO] Print conflicting operands between Src and Dest modules
 (#115104)

The current error message doesn't give sufficient details to help with
debugging. This patch will log the operand values that are conflicting.

After this patch the output is of the form:
```
'Large Data Threshold': IDs have conflicting values: 'i32 101' from /usr/local/home/llvm-project/build/test/LTO/X86/Output/largedatathreshold-3.ll.tmp1.o, and 'i32 100' from ld-temp.o
```
---
 llvm/lib/Linker/IRMover.cpp                        | 14 +++++++++-----
 llvm/test/LTO/X86/codemodel-3.ll                   |  2 +-
 llvm/test/LTO/X86/largedatathreshold-3.ll          |  2 +-
 llvm/test/Linker/module-flags-6-a.ll               |  2 +-
 .../test/Transforms/FunctionImport/module-flags.ll |  2 +-
 5 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/llvm/lib/Linker/IRMover.cpp b/llvm/lib/Linker/IRMover.cpp
index 4bb0ddf89174..a0c3f2c5b0ba 100644
--- a/llvm/lib/Linker/IRMover.cpp
+++ b/llvm/lib/Linker/IRMover.cpp
@@ -1430,11 +1430,15 @@ Error IRLinker::linkModuleFlagsMetadata() {
       llvm_unreachable("not possible");
     case Module::Error: {
       // Emit an error if the values differ.
-      if (SrcOp->getOperand(2) != DstOp->getOperand(2))
-        return stringErr("linking module flags '" + ID->getString() +
-                         "': IDs have conflicting values in '" +
-                         SrcM->getModuleIdentifier() + "' and '" +
-                         DstM.getModuleIdentifier() + "'");
+      if (SrcOp->getOperand(2) != DstOp->getOperand(2)) {
+        std::string Str;
+        raw_string_ostream(Str)
+            << "linking module flags '" << ID->getString()
+            << "': IDs have conflicting values: '" << *SrcOp->getOperand(2)
+            << "' from " << SrcM->getModuleIdentifier() << ", and '"
+            << *DstOp->getOperand(2) << "' from " + DstM.getModuleIdentifier();
+        return stringErr(Str);
+      }
       continue;
     }
     case Module::Warning: {
diff --git a/llvm/test/LTO/X86/codemodel-3.ll b/llvm/test/LTO/X86/codemodel-3.ll
index 13702dfbca2d..8ae601c43cb2 100644
--- a/llvm/test/LTO/X86/codemodel-3.ll
+++ b/llvm/test/LTO/X86/codemodel-3.ll
@@ -18,4 +18,4 @@ entry:
     ret ptr @data
 }
 
-; CHECK: 'Code Model': IDs have conflicting values
+; CHECK: 'Code Model': IDs have conflicting values: 'i32 1' from {{.*}}, and 'i32 4' from {{.*}}
diff --git a/llvm/test/LTO/X86/largedatathreshold-3.ll b/llvm/test/LTO/X86/largedatathreshold-3.ll
index fea7987ff155..496b71ea0ca0 100644
--- a/llvm/test/LTO/X86/largedatathreshold-3.ll
+++ b/llvm/test/LTO/X86/largedatathreshold-3.ll
@@ -3,7 +3,7 @@
 ; RUN: not llvm-lto2 run -r %t0.o,_start,px -r %t1.o,bar,px -r %t0.o,_GLOBAL_OFFSET_TABLE_, \
 ; RUN:   -r %t1.o,_GLOBAL_OFFSET_TABLE_, %t0.o %t1.o -o %t2.s 2>&1 | FileCheck %s
 
-; CHECK: 'Large Data Threshold': IDs have conflicting values
+; CHECK: 'Large Data Threshold': IDs have conflicting values: 'i32 101' from {{.*}}, and 'i32 100' from {{.*}}
 
 target triple = "x86_64-unknown-linux-gnu"
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
diff --git a/llvm/test/Linker/module-flags-6-a.ll b/llvm/test/Linker/module-flags-6-a.ll
index dd6519727f24..47f46d4d1889 100644
--- a/llvm/test/Linker/module-flags-6-a.ll
+++ b/llvm/test/Linker/module-flags-6-a.ll
@@ -2,7 +2,7 @@
 
 ; Test module flags error messages.
 
-; CHECK: linking module flags 'foo': IDs have conflicting values in '{{.*}}module-flags-6-b.ll' and 'llvm-link'
+; CHECK: linking module flags 'foo': IDs have conflicting values: 'i32 38' from {{.*}}module-flags-6-b.ll, and 'i32 37' from llvm-link
 
 !0 = !{ i32 1, !"foo", i32 37 }
 
diff --git a/llvm/test/Transforms/FunctionImport/module-flags.ll b/llvm/test/Transforms/FunctionImport/module-flags.ll
index 662df3065b30..2fc2b8ea9727 100644
--- a/llvm/test/Transforms/FunctionImport/module-flags.ll
+++ b/llvm/test/Transforms/FunctionImport/module-flags.ll
@@ -4,7 +4,7 @@
 ; RUN: llvm-lto -thinlto -o 3 1.bc 2.bc
 ; RUN: opt -S -passes=function-import -summary-file 3.thinlto.bc 1.bc 2>&1 | FileCheck %s
 
-; CHECK: Function Import: link error: linking module flags 'Error': IDs have conflicting values in '2.bc' and '1.bc'
+; CHECK: Function Import: link error: linking module flags 'Error': IDs have conflicting values: 'i32 1' from 2.bc, and 'i32 0' from 1.bc
 
 ;--- 1.ll
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"