implement immutable variables codegen (#70)

crates/llvm-context/src/polkavm/context/function/runtime/entry.rs

@@ -31,6 +31,18 @@ impl Entry {
     where
         D: Dependency + Clone,
     {
+        context.declare_global(
+            revive_runtime_api::immutable_data::GLOBAL_IMMUTABLE_DATA_POINTER,
+            context.word_type().array_type(0),
+            AddressSpace::Stack,
+        );
+
+        context.declare_global(
+            revive_runtime_api::immutable_data::GLOBAL_IMMUTABLE_DATA_SIZE,
+            context.xlen_type(),
+            AddressSpace::Stack,
+        );
+
         let calldata_type = context.array_type(context.byte_type(), Self::MAX_CALLDATA_SIZE);
         context.set_global(
             crate::polkavm::GLOBAL_CALLDATA_POINTER,

crates/llvm-context/src/polkavm/context/function/runtime/immutable_data_load.rs

@@ -0,0 +1,116 @@
+//! The immutable data runtime function.
+
+use crate::polkavm::context::address_space::AddressSpace;
+use crate::polkavm::context::function::runtime;
+use crate::polkavm::context::pointer::Pointer;
+use crate::polkavm::context::Context;
+use crate::polkavm::WriteLLVM;
+use crate::polkavm::{runtime_api, Dependency};
+
+/// A function for requesting the immutable data from the runtime.
+/// This is a special function that is only used by the front-end generated code.
+///
+/// The runtime API is called lazily and subsequent calls are no-ops.
+///
+/// The bytes written is asserted to match the expected length.
+/// This should never fail; the length is known.
+/// However, this is a one time assertion, hence worth it.
+#[derive(Debug)]
+pub struct ImmutableDataLoad;
+
+impl<D> WriteLLVM<D> for ImmutableDataLoad
+where
+    D: Dependency + Clone,
+{
+    fn declare(&mut self, context: &mut Context<D>) -> anyhow::Result<()> {
+        context.add_function(
+            runtime::FUNCTION_LOAD_IMMUTABLE_DATA,
+            context.void_type().fn_type(Default::default(), false),
+            0,
+            Some(inkwell::module::Linkage::Private),
+        )?;
+
+        Ok(())
+    }
+
+    fn into_llvm(self, context: &mut Context<D>) -> anyhow::Result<()> {
+        context.set_current_function(runtime::FUNCTION_LOAD_IMMUTABLE_DATA)?;
+        context.set_basic_block(context.current_function().borrow().entry_block());
+
+        let immutable_data_size_pointer = context
+            .get_global(revive_runtime_api::immutable_data::GLOBAL_IMMUTABLE_DATA_SIZE)?
+            .value
+            .as_pointer_value();
+        let immutable_data_size = context.build_load(
+            Pointer::new(
+                context.xlen_type(),
+                AddressSpace::Stack,
+                immutable_data_size_pointer,
+            ),
+            "immutable_data_size_load",
+        )?;
+
+        let load_immutable_data_block = context.append_basic_block("load_immutables_block");
+        let return_block = context.current_function().borrow().return_block();
+        let immutable_data_size_is_zero = context.builder().build_int_compare(
+            inkwell::IntPredicate::EQ,
+            context.xlen_type().const_zero(),
+            immutable_data_size.into_int_value(),
+            "immutable_data_size_is_zero",
+        )?;
+        context.build_conditional_branch(
+            immutable_data_size_is_zero,
+            return_block,
+            load_immutable_data_block,
+        )?;
+
+        context.set_basic_block(load_immutable_data_block);
+        let output_pointer = context
+            .get_global(revive_runtime_api::immutable_data::GLOBAL_IMMUTABLE_DATA_POINTER)?
+            .value
+            .as_pointer_value();
+        context.build_runtime_call(
+            runtime_api::imports::GET_IMMUTABLE_DATA,
+            &[
+                context
+                    .builder()
+                    .build_ptr_to_int(output_pointer, context.xlen_type(), "ptr_to_xlen")?
+                    .into(),
+                context
+                    .builder()
+                    .build_ptr_to_int(
+                        immutable_data_size_pointer,
+                        context.xlen_type(),
+                        "ptr_to_xlen",
+                    )?
+                    .into(),
+            ],
+        );
+        let bytes_written = context.builder().build_load(
+            context.xlen_type(),
+            immutable_data_size_pointer,
+            "bytes_written",
+        )?;
+        context.builder().build_store(
+            immutable_data_size_pointer,
+            context.xlen_type().const_zero(),
+        )?;
+        let overflow_block = context.append_basic_block("immutable_data_overflow");
+        let is_overflow = context.builder().build_int_compare(
+            inkwell::IntPredicate::UGT,
+            immutable_data_size.into_int_value(),
+            bytes_written.into_int_value(),
+            "is_overflow",
+        )?;
+        context.build_conditional_branch(is_overflow, overflow_block, return_block)?;
+
+        context.set_basic_block(overflow_block);
+        context.build_call(context.intrinsics().trap, &[], "invalid_trap");
+        context.build_unreachable();
+
+        context.set_basic_block(return_block);
+        context.build_return(None);
+
+        Ok(())
+    }
+}

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

@@ -2,6 +2,7 @@
 
 pub mod deploy_code;
 pub mod entry;
+pub mod immutable_data_load;
 pub mod runtime_code;
 
 /// The main entry function name.
@@ -12,3 +13,6 @@ pub const FUNCTION_DEPLOY_CODE: &str = "__deploy";
 
 /// The runtime code function name.
 pub const FUNCTION_RUNTIME_CODE: &str = "__runtime";
+
+/// The immutable data load function name.
+pub const FUNCTION_LOAD_IMMUTABLE_DATA: &str = "__immutable_data_load";