[LTO] Print conflicting operands between Src and Dest modules

[hiraditya]

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

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[llvmbot]

@llvm/pr-subscribers-llvm-transforms

@llvm/pr-subscribers-lto

Author: AdityaK (hiraditya)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/115104.diff

3 Files Affected:

• (modified) llvm/lib/Linker/IRMover.cpp (+9-5)
• (modified) llvm/test/LTO/X86/codemodel-3.ll (+1-1)
• (modified) llvm/test/LTO/X86/largedatathreshold-3.ll (+1-1)

diff --git a/llvm/lib/Linker/IRMover.cpp b/llvm/lib/Linker/IRMover.cpp
index 0d54c534590ca9..f94b30801ab142 100644
--- a/llvm/lib/Linker/IRMover.cpp
+++ b/llvm/lib/Linker/IRMover.cpp
@@ -1445,11 +1445,15 @@ 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 13702dfbca2da4..8ae601c43cb29f 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 fea7987ff15566..496b71ea0ca005 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"