[RISCV] Allow mismatched SmallDataLimit and use Min for conflicting values

Authored By: joshua-arch1 (Jun Sha)
Reviewed By: shiva0217, apazos, luismarques, asb, jrtc27, MaskRay
Reviewers: MaskRay, jrtc27

Differential Revision: https://reviews.llvm.org/D131230

This patch is to fix an issue about module linking with LTO.

When compiling with PIE, the small data limitation needs to be consistent with that in PIC, otherwise there will be linking errors due to conflicting values.

bar.c

int bar() { return 1; }
foo.c

int foo() { return 1; }
clang --target=riscv64-unknown-linux-gnu -flto -c foo.c -o foo.o -fPIE
clang --target=riscv64-unknown-linux-gnu -flto -c bar.c -o bar.o -fPIC

clang --target=riscv64-unknown-linux-gnu -flto foo.o bar.o -flto -nostdlib -v -fuse-ld=lld
ld.lld: error: linking module flags 'SmallDataLimit': IDs have conflicting values in 'bar.o' and 'ld-temp.o'
clang-15: error: linker command failed with exit code 1 (use -v to see invocation)
What we are trying to do here is to use Min instead of Error for conflicting SmallDataLimit when combining -fno-PIC code with -fPIC code.

Signed-off-by: xiaojing.zhang <xiaojing.zhang@xcalibyte.com>
Signed-off-by: jianxin.lai <jianxin.lai@xcalibyte.com>

clang/lib/CodeGen/CodeGenModule.cpp

@@ -980,7 +980,7 @@ void CodeGenModule::EmitOpenCLMetadata() {
 void CodeGenModule::EmitBackendOptionsMetadata(
     const CodeGenOptions CodeGenOpts) {
   if (getTriple().isRISCV()) {
-    getModule().addModuleFlag(llvm::Module::Error, "SmallDataLimit",
+    getModule().addModuleFlag(llvm::Module::Min, "SmallDataLimit",
                               CodeGenOpts.SmallDataLimit);
   }
 }