mlir: Avoid SmallVector::set_size in SerializeToHsacoPass::loadLibraries

[dexonsmith]

Summary

Spotted this in a final grep of projects I don't usually build before
pushing https://reviews.llvm.org/D115380, which makes
SmallVector::set_size() private.

Update to truncate(), a new-ish variant of resize() that asserts the
new size is not bigger and that avoids pulling in the allocation and
initialization code for growing. Doesn't really look like the perf
impact of that would matter here, but since dirLength is known to be a
smaller size then we might as well.

Blocker for https://reviews.llvm.org/D115380.

[krzysz00]

LGTM as well!

[dexonsmith]

Pushed as b77d4d54f96a1110f1d83e19f773ac93537ca3f9. Thanks for the reviews!

mlir/lib/Dialect/GPU/Transforms/SerializeToHsaco.cpp

SerializeToHsacoPass::loadLibraries(SmallVectorImpl<char> &path,
   }
 
   for (const StringRef file : libraries) {
     llvm::SMDiagnostic error;
     llvm::sys::path::append(path, file);
     llvm::StringRef pathRef(path.data(), path.size());
     std::unique_ptr<llvm::Module> library =
         llvm::getLazyIRFileModule(pathRef, error, context);
-    path.set_size(dirLength);
+    path.truncate(dirLength);
     if (!library) {
       getOperation().emitError() << "Failed to load library " << file
                                  << " from " << path << error.getMessage();
       return llvm::None;
     }
     // Some ROCM builds don't strip this like they should
     if (auto *openclVersion = library->getNamedMetadata("opencl.ocl.version"))
       library->eraseNamedMetadata(openclVersion);