llvm-context: remove the linear memory pointer indirection (#211)

CHANGELOG.md

@@ -6,6 +6,10 @@ This is a development pre-release.
 
 Supported `polkadot-sdk` rev: `274a781e8ca1a9432c7ec87593bd93214abbff50`
 
+### Fixed
+- A bug causing incorrect loads from the emulated EVM linear memory.
+- A missing integer truncate after switching to 64bit.
+
 ## v0.1.0-dev.10
 
 This is a development pre-release.

crates/integration/contracts/MLoad.sol

@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.28;
+
+/* runner.json
+{
+    "differential": true,
+    "actions": [
+        {
+            "Instantiate": {
+                "code": {
+                    "Solidity": {
+                        "contract": "MLoad"
+                    }
+                }
+            }
+        },
+        {
+            "Call": {
+                "dest": {
+                    "Instantiated": 0
+                },
+                "data": "e2179b8e"
+            }
+        }
+    ]
+}
+*/
+
+contract MLoad {
+    constructor() payable {
+        assert(g() == 0);
+    }
+
+    function g() public payable returns (uint m) {
+        assembly {
+            m := mload(0)
+        }
+    }
+}

crates/integration/src/tests.rs

@@ -55,6 +55,7 @@ test_spec!(create2, "CreateB", "Create2.sol");
 test_spec!(transfer, "Transfer", "Transfer.sol");
 test_spec!(send, "Send", "Send.sol");
 test_spec!(function_pointer, "FunctionPointer", "FunctionPointer.sol");
+test_spec!(mload, "MLoad", "MLoad.sol");
 
 fn instantiate(path: &str, contract: &str) -> Vec<SpecsAction> {
     vec![Instantiate {

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

@@ -6,15 +6,9 @@ pub const LLVM_VERSION: semver::Version = semver::Version::new(18, 1, 4);
 /// The pointer width sized type.
 pub static XLEN: usize = revive_common::BIT_LENGTH_X32;
 
-/// The heap memory pointer pointer global variable name.
-pub static GLOBAL_HEAP_MEMORY_POINTER: &str = "memory_pointer";
-
 /// The calldata size global variable name.
 pub static GLOBAL_CALLDATA_SIZE: &str = "calldatasize";
 
-/// The call flags global variable name.
-pub static GLOBAL_CALL_FLAGS: &str = "call_flags";
-
 /// The deployer call header size that consists of:
 /// - bytecode hash (32 bytes)
 pub const DEPLOYER_CALL_HEADER_SIZE: usize = revive_common::BYTE_LENGTH_WORD;

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

@@ -24,22 +24,6 @@ impl Entry {
     where
         D: Dependency + Clone,
     {
-        context.set_global(
-            crate::polkavm::GLOBAL_HEAP_MEMORY_POINTER,
-            context.llvm().ptr_type(AddressSpace::Heap.into()),
-            AddressSpace::Stack,
-            context.xlen_type().get_undef(),
-        );
-        context.build_store(
-            context
-                .get_global(crate::polkavm::GLOBAL_HEAP_MEMORY_POINTER)?
-                .into(),
-            context.build_sbrk(
-                context.xlen_type().const_zero(),
-                context.xlen_type().const_zero(),
-            )?,
-        )?;
-
         context.set_global(
             crate::polkavm::GLOBAL_CALLDATA_SIZE,
             context.xlen_type(),
@@ -47,13 +31,6 @@ impl Entry {
             context.xlen_type().get_undef(),
         );
 
-        context.set_global(
-            crate::polkavm::GLOBAL_CALL_FLAGS,
-            context.word_type(),
-            AddressSpace::Stack,
-            context.word_const(0),
-        );
-
         Ok(())
     }
 
@@ -70,6 +47,11 @@ impl Entry {
             .build_runtime_call(revive_runtime_api::polkavm_imports::CALL_DATA_SIZE, &[])
             .expect("the call_data_size syscall method should return a value")
             .into_int_value();
+        let call_data_size_value = context.builder().build_int_truncate(
+            call_data_size_value,
+            context.xlen_type(),
+            "call_data_size_truncated",
+        )?;
         context
             .builder()
             .build_store(call_data_size_pointer, call_data_size_value)?;
@@ -90,13 +72,6 @@ impl Entry {
             .borrow()
             .get_nth_param(Self::ARGUMENT_INDEX_CALL_FLAGS);
 
-        context.set_global(
-            crate::polkavm::GLOBAL_CALL_FLAGS,
-            is_deploy.get_type(),
-            AddressSpace::Stack,
-            is_deploy.into_int_value(),
-        );
-
         let deploy_code_call_block = context.append_basic_block("deploy_code_call_block");
         let runtime_code_call_block = context.append_basic_block("runtime_code_call_block");
 

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

@@ -1209,17 +1209,17 @@ where
 
     /// Build a call to PolkaVM `msize` for querying the linear memory size.
     pub fn build_msize(&self) -> anyhow::Result<inkwell::values::IntValue<'ctx>> {
-        Ok(self
-            .builder()
-            .build_call(
-                self.runtime_api_method(revive_runtime_api::polkavm_imports::MEMORY_SIZE),
-                &[],
-                "call_msize",
-            )?
-            .try_as_basic_value()
-            .left()
-            .expect("sbrk returns an int")
-            .into_int_value())
+        let memory_size_pointer = self
+            .module()
+            .get_global(revive_runtime_api::polkavm_imports::MEMORY_SIZE)
+            .expect("the memory size symbol should have been declared")
+            .as_pointer_value();
+        let memory_size_value = self.builder().build_load(
+            self.xlen_type(),
+            memory_size_pointer,
+            "memory_size_value",
+        )?;
+        Ok(memory_size_value.into_int_value())
     }
 
     /// Call PolkaVM `sbrk` for extending the heap by `offset` + `size`,
@@ -1265,8 +1265,9 @@ where
         self.build_heap_alloc(offset, length)?;
 
         let heap_start = self
-            .get_global(crate::polkavm::GLOBAL_HEAP_MEMORY_POINTER)?
-            .value
+            .module()
+            .get_global(revive_runtime_api::polkavm_imports::MEMORY)
+            .expect("the memory symbol should have been declared")
             .as_pointer_value();
         Ok(self.build_gep(
             Pointer::new(self.byte_type(), AddressSpace::Stack, heap_start),

crates/runtime-api/src/polkavm_imports.c

@@ -8,10 +8,10 @@
 #define EVM_WORD_SIZE 32
 #define ALIGN(size) ((size + EVM_WORD_SIZE - 1) & ~(EVM_WORD_SIZE - 1))
 #define MAX_MEMORY_SIZE (64 * 1024)
-static char __memory[MAX_MEMORY_SIZE];
-static uint32_t __memory_size = 0;
+char __memory[MAX_MEMORY_SIZE];
+uint32_t __memory_size = 0;
 
-void *  __sbrk_internal(uint32_t offset, uint32_t size) {
+void * __sbrk_internal(uint32_t offset, uint32_t size) {
     if (offset >= MAX_MEMORY_SIZE || size > MAX_MEMORY_SIZE) {
         return NULL;
     }
@@ -27,10 +27,6 @@ void *  __sbrk_internal(uint32_t offset, uint32_t size) {
     return (void *)&__memory[__memory_size];
 }
 
-uint32_t __msize() {
-    return __memory_size;
-}
-
 void * memset(void *b, int c, size_t len) {
     uint8_t *dest = b;
     while (len-- > 0) *dest++ = c;

crates/runtime-api/src/polkavm_imports.rs

@@ -1,18 +1,14 @@
-//! This crate vendors the [PolkaVM][0] C API and provides a LLVM module for interacting
-//! with the `pallet-revive` runtime API.
-//! At present, the revive pallet requires blobs to export `call` and `deploy`,
-//! and offers a bunch of [runtime API methods][1]. The provided [module] implements
-//! those exports and imports.
-//! [0]: [https://crates.io/crates/polkavm]
-//! [1]: [https://docs.rs/pallet-contracts/26.0.0/pallet_contracts/api_doc/index.html]
-
 use inkwell::{context::Context, memory_buffer::MemoryBuffer, module::Module, support::LLVMString};
 
 include!(concat!(env!("OUT_DIR"), "/polkavm_imports.rs"));
 
-pub static SBRK: &str = "__sbrk_internal";
+/// The emulated EVM heap memory global symbol.
+pub static MEMORY: &str = "__memory";
 
-pub static MEMORY_SIZE: &str = "__msize";
+/// The emulated EVM heap memory size global symbol.
+pub static MEMORY_SIZE: &str = "__memory_size";
+
+pub static SBRK: &str = "__sbrk_internal";
 
 pub static ADDRESS: &str = "address";
 
@@ -82,9 +78,8 @@ pub static WEIGHT_TO_FEE: &str = "weight_to_fee";
 
 /// All imported runtime API symbols.
 /// Useful for configuring common attributes and linkage.
-pub static IMPORTS: [&str; 35] = [
+pub static IMPORTS: [&str; 34] = [
     SBRK,
-    MEMORY_SIZE,
     ADDRESS,
     BALANCE,
     BALANCE_OF,