[LTO][Veclib] Fix vector library handling with LTO

[usha1830]

Commit #167996 moved VecLib into TargetOptions and ensured clang properly sets it. However, some LTO backend code paths were still creating TargetLibraryInfoImpl without passing the VecLib parameter from TargetMachine::Options.

This PR completes the fix by ensuring that:

LTOBackend.cpp, ThinLTOCodeGenerator.cpp, UpdateCompilerUsed.cpp all pass TM->Options.VecLib when constructing TargetLibraryInfoImpl.

Without this fix, vector library information (e.g., -fveclib=ArmPL) would not be properly recognized during LTO optimization and code generation, potentially causing incorrect optimizations or linker errors when vector library functions are referenced.

[llvmbot]

@llvm/pr-subscribers-lto

Author: Usha Gupta (usha1830)

Changes

Commit #167996 moved VecLib into TargetOptions and ensured clang properly sets it. However, some LTO backend code paths were still creating TargetLibraryInfoImpl without passing the VecLib parameter from TargetMachine::Options.

This PR completes the fix by ensuring that:

LTOBackend.cpp, ThinLTOCodeGenerator.cpp, UpdateCompilerUsed.cpp all pass TM->Options.VecLib when constructing TargetLibraryInfoImpl.

Without this fix, vector library information (e.g., -fveclib=ArmPL) would not be properly recognized during LTO optimization and code generation, potentially causing incorrect optimizations or linker errors when vector library functions are referenced.

---

Full diff: https://github.com/llvm/llvm-project/pull/170638.diff

3 Files Affected:

• (modified) llvm/lib/LTO/LTOBackend.cpp (+2-2)
• (modified) llvm/lib/LTO/ThinLTOCodeGenerator.cpp (+1-1)
• (modified) llvm/lib/LTO/UpdateCompilerUsed.cpp (+1-1)

diff --git a/llvm/lib/LTO/LTOBackend.cpp b/llvm/lib/LTO/LTOBackend.cpp
index 93118becedbac..705bdbae4acf7 100644
--- a/llvm/lib/LTO/LTOBackend.cpp
+++ b/llvm/lib/LTO/LTOBackend.cpp
@@ -278,7 +278,7 @@ static void runNewPMPasses(const Config &Conf, Module &Mod, TargetMachine *TM,
   RegisterPassPlugins(Conf.PassPlugins, PB);
 
   std::unique_ptr<TargetLibraryInfoImpl> TLII(
-      new TargetLibraryInfoImpl(TM->getTargetTriple()));
+      new TargetLibraryInfoImpl(TM->getTargetTriple(), TM->Options.VecLib));
   if (Conf.Freestanding)
     TLII->disableAllFunctions();
   FAM.registerPass([&] { return TargetLibraryAnalysis(*TLII); });
@@ -444,7 +444,7 @@ static void codegen(const Config &Conf, TargetMachine *TM,
   // keep the pointer and may use it until their destruction. See #138194.
   {
     legacy::PassManager CodeGenPasses;
-    TargetLibraryInfoImpl TLII(Mod.getTargetTriple());
+    TargetLibraryInfoImpl TLII(Mod.getTargetTriple(), TM->Options.VecLib);
     CodeGenPasses.add(new TargetLibraryInfoWrapperPass(TLII));
     // No need to make index available if the module is empty.
     // In theory these passes should not use the index for an empty
diff --git a/llvm/lib/LTO/ThinLTOCodeGenerator.cpp b/llvm/lib/LTO/ThinLTOCodeGenerator.cpp
index ff94c54ab3e6e..ed26c931d0629 100644
--- a/llvm/lib/LTO/ThinLTOCodeGenerator.cpp
+++ b/llvm/lib/LTO/ThinLTOCodeGenerator.cpp
@@ -249,7 +249,7 @@ static void optimizeModule(Module &TheModule, TargetMachine &TM,
   PassBuilder PB(&TM, PTO, PGOOpt, &PIC);
 
   std::unique_ptr<TargetLibraryInfoImpl> TLII(
-      new TargetLibraryInfoImpl(TM.getTargetTriple()));
+      new TargetLibraryInfoImpl(TM.getTargetTriple(), TM.Options.VecLib));
   if (Freestanding)
     TLII->disableAllFunctions();
   FAM.registerPass([&] { return TargetLibraryAnalysis(*TLII); });
diff --git a/llvm/lib/LTO/UpdateCompilerUsed.cpp b/llvm/lib/LTO/UpdateCompilerUsed.cpp
index 1889c2b762ff7..f79a3744afad3 100644
--- a/llvm/lib/LTO/UpdateCompilerUsed.cpp
+++ b/llvm/lib/LTO/UpdateCompilerUsed.cpp
@@ -57,7 +57,7 @@ class PreserveLibCallsAndAsmUsed {
   // same names are added to llvm.compiler.used to prevent them from being
   // deleted by optimizations.
   void initializeLibCalls(const Module &TheModule) {
-    TargetLibraryInfoImpl TLII(TM.getTargetTriple());
+    TargetLibraryInfoImpl TLII(TM.getTargetTriple(), TM.Options.VecLib);
     TargetLibraryInfo TLI(TLII);
 
     // TargetLibraryInfo has info on C runtime library calls on the current

[teresajohnson]

The changes seem straightforward, but it needs tests (probably in llvm/test/LTO/ARM?). Since you are modifying both the old and new LTO APIs, you'd want one using llvm-lto (old LTO API) and one using llvm-lto2 (new LTO API). As examples, there are some llvm-lto tests already in that directory, and some llvm-lto2 tests under the X86 directory.