[Clang][Driver] Support linker relaxation options for LoongArch

[zhaoqi5]

This commit completed four tasks:

• Add -mrelax/-mno-relax options support for LoongArch in clang driver.
• Print error for -gsplit-dwarf with LoongArch linker relaxation (-mrelax).
• Pass -X to linker to discard a plethora of .L symbols due to linker relaxation.
• Forward --no-relax option to linker.

[llvmbot]

@llvm/pr-subscribers-backend-loongarch
@llvm/pr-subscribers-clang-driver

@llvm/pr-subscribers-clang

Author: ZhaoQi (zhaoqi5)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/123587.diff

1 Files Affected:

• (modified) clang/lib/Driver/ToolChains/Gnu.cpp (+1-1)

diff --git a/clang/lib/Driver/ToolChains/Gnu.cpp b/clang/lib/Driver/ToolChains/Gnu.cpp
index e5db1b2f1550b8..5557ca4bf4491f 100644
--- a/clang/lib/Driver/ToolChains/Gnu.cpp
+++ b/clang/lib/Driver/ToolChains/Gnu.cpp
@@ -422,7 +422,7 @@ void tools::gnutools::Linker::ConstructJob(Compilation &C, const JobAction &JA,
     return;
   }
 
-  if (Triple.isRISCV()) {
+  if (Triple.isRISCV() || Triple.isLoongArch()) {
     CmdArgs.push_back("-X");
     if (Args.hasArg(options::OPT_mno_relax))
       CmdArgs.push_back("--no-relax");

[SixWeining]

LGTM. What do you think about this? Clang doesn't pass +relax or -relax by default which means the default behavior is determined by LLVM and currently the relax target feature is not enabled by any LoongArch processor. @MaskRay