Suport passing arbitrary llvm arguments (#271)

- Support for passing LLVM command line options via the prcoess input or
providing one or more `--llvm-arg='..'` resolc CLI flag. This allows
more fine-grained control over the LLVM backend configuration.
- Make LLVM initialization idempotent.

---------

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

crates/llvm-context/src/polkavm/context/mod.rs

@@ -83,6 +83,8 @@ where
     current_function: Option<Rc<RefCell<Function<'ctx>>>>,
     /// The loop context stack.
     loop_stack: Vec<Loop<'ctx>>,
+    /// The extra LLVM arguments that were used during target initialization.
+    llvm_arguments: &'ctx [String],
 
     /// The project dependency manager. It can be any entity implementing the trait.
     /// The manager is used to get information about contracts and their dependencies during
@@ -223,6 +225,7 @@ where
         dependency_manager: Option<D>,
         include_metadata_hash: bool,
         debug_config: DebugConfig,
+        llvm_arguments: &'ctx [String],
     ) -> Self {
         Self::set_data_layout(llvm, &module);
         Self::link_stdlib_module(llvm, &module);
@@ -250,6 +253,7 @@ where
             functions: HashMap::with_capacity(Self::FUNCTIONS_HASHMAP_INITIAL_CAPACITY),
             current_function: None,
             loop_stack: Vec::with_capacity(Self::LOOP_STACK_INITIAL_CAPACITY),
+            llvm_arguments,
 
             dependency_manager,
             include_metadata_hash,
@@ -639,6 +643,7 @@ where
                     self.optimizer.settings().to_owned(),
                     self.include_metadata_hash,
                     self.debug_config.clone(),
+                    self.llvm_arguments,
                 )
             })
     }

crates/llvm-context/src/polkavm/context/tests.rs

@@ -10,12 +10,20 @@ pub fn create_context(
     llvm: &inkwell::context::Context,
     optimizer_settings: OptimizerSettings,
 ) -> Context<DummyDependency> {
-    crate::polkavm::initialize_target();
+    crate::initialize_llvm(crate::Target::PVM, "resolc", Default::default());
 
     let module = llvm.create_module("test");
     let optimizer = Optimizer::new(optimizer_settings);
 
-    Context::<DummyDependency>::new(llvm, module, optimizer, None, true, Default::default())
+    Context::<DummyDependency>::new(
+        llvm,
+        module,
+        optimizer,
+        None,
+        true,
+        Default::default(),
+        Default::default(),
+    )
 }
 
 #[test]

crates/llvm-context/src/polkavm/mod.rs

@@ -17,11 +17,6 @@ use sha3::Digest;
 use self::context::build::Build;
 use self::context::Context;
 
-/// Initializes the PolkaVM target machine.
-pub fn initialize_target() {
-    inkwell::targets::Target::initialize_riscv(&Default::default());
-}
-
 /// Builds PolkaVM assembly text.
 pub fn build_assembly_text(
     contract_path: &str,
@@ -94,6 +89,7 @@ pub trait Dependency {
         optimizer_settings: OptimizerSettings,
         include_metadata_hash: bool,
         debug_config: DebugConfig,
+        llvm_arguments: &[String],
     ) -> anyhow::Result<String>;
 
     /// Resolves a full contract path.
@@ -114,6 +110,7 @@ impl Dependency for DummyDependency {
         _optimizer_settings: OptimizerSettings,
         _include_metadata_hash: bool,
         _debug_config: DebugConfig,
+        _llvm_arguments: &[String],
     ) -> anyhow::Result<String> {
         Ok(String::new())
     }