mark internal functions linker private (#381)

Prevents unused functions in the emitted ELF object. Drive-by add a
missing test case (which misses a relocation under `-Oz` when all
internal functions are marked as private).

---------

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

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

@@ -1,7 +1,5 @@
 //! The LLVM module build.
 
-use std::collections::BTreeMap;
-
 use revive_common::BYTE_LENGTH_WORD;
 use serde::Deserialize;
 use serde::Serialize;
@@ -17,8 +15,6 @@ pub struct Build {
     pub bytecode: Vec<u8>,
     /// The PolkaVM bytecode hash. Unlinked builds don't have a hash yet.
     pub bytecode_hash: Option<[u8; BYTE_LENGTH_WORD]>,
-    /// The hash-to-full-path mapping of the contract factory dependencies.
-    pub factory_dependencies: BTreeMap<String, String>,
 }
 
 impl Build {
@@ -29,7 +25,6 @@ impl Build {
             metadata_hash,
             bytecode,
             bytecode_hash: None,
-            factory_dependencies: BTreeMap::new(),
         }
     }
 }

crates/llvm-context/src/polkavm/context/function/llvm_runtime.rs

@@ -64,24 +64,13 @@ impl<'ctx> LLVMRuntime<'ctx> {
         }
     }
 
-    /// Declares an LLVM runtime function in the `module`,
-    pub fn declare(
-        module: &inkwell::module::Module<'ctx>,
-        name: &str,
-        r#type: inkwell::types::FunctionType<'ctx>,
-        linkage: Option<inkwell::module::Linkage>,
-    ) -> FunctionDeclaration<'ctx> {
-        let value = module.add_function(name, r#type, linkage);
-        FunctionDeclaration::new(r#type, value)
-    }
-
     /// Create the function definition from an existing symbol.
     pub fn define(
         module: &inkwell::module::Module<'ctx>,
         name: &str,
     ) -> Option<FunctionDeclaration<'ctx>> {
         let value = module.get_function(name)?;
-        value.set_linkage(inkwell::module::Linkage::External);
+        value.set_linkage(inkwell::module::Linkage::Private);
         FunctionDeclaration::new(value.get_type(), value).into()
     }
 }

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

@@ -75,15 +75,6 @@ impl<'ctx> Function<'ctx> {
         self.name.as_str()
     }
 
-    /// Checks whether the function is defined outside of the front-end.
-    pub fn is_name_external(name: &str) -> bool {
-        name.starts_with("llvm.")
-            || (name.starts_with("__")
-                && name != self::runtime::FUNCTION_ENTRY
-                && name != self::runtime::FUNCTION_DEPLOY_CODE
-                && name != self::runtime::FUNCTION_RUNTIME_CODE)
-    }
-
     /// Returns the LLVM function declaration.
     pub fn declaration(&self) -> Declaration<'ctx> {
         self.declaration
@@ -223,30 +214,11 @@ impl<'ctx> Function<'ctx> {
         self.stack.get(name).copied()
     }
 
-    /// Removes the pointer to a stack variable.
-    pub fn remove_stack_pointer(&mut self, name: &str) {
-        self.stack.remove(name);
-    }
-
     /// Returns the return entity representation.
     pub fn r#return(&self) -> Return<'ctx> {
         self.r#return
     }
 
-    /// Returns the pointer to the function return value.
-    /// # Panics
-    /// If the pointer has not been set yet.
-    pub fn return_pointer(&self) -> Option<Pointer<'ctx>> {
-        self.r#return.return_pointer()
-    }
-
-    /// Returns the return data size in bytes, based on the default stack alignment.
-    /// # Panics
-    /// If the pointer has not been set yet.
-    pub fn return_data_size(&self) -> usize {
-        self.r#return.return_data_size()
-    }
-
     /// Returns the function entry block.
     pub fn entry_block(&self) -> inkwell::basic_block::BasicBlock<'ctx> {
         self.entry_block

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

@@ -36,7 +36,7 @@ where
             runtime::FUNCTION_DEPLOY_CODE,
             function_type,
             0,
-            Some(inkwell::module::Linkage::External),
+            Some(inkwell::module::Linkage::Private),
             None,
         )?;
 

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

@@ -36,7 +36,7 @@ where
             runtime::FUNCTION_RUNTIME_CODE,
             function_type,
             0,
-            Some(inkwell::module::Linkage::External),
+            Some(inkwell::module::Linkage::Private),
             None,
         )?;
 

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

@@ -30,7 +30,7 @@ pub trait RuntimeFunction {
             Self::NAME,
             Self::r#type(context),
             0,
-            Some(inkwell::module::Linkage::External),
+            Some(inkwell::module::Linkage::External), // TODO: `Private` emits unrelocated AUIPC?
             None,
         )?;
 

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

@@ -83,7 +83,19 @@ pub fn link(
             let bytecode_linked = ElfLinker::setup()?.link(bytecode, symbols.as_slice())?;
             polkavm_linker(&bytecode_linked, strip_binary)
                 .map(|pvm| (pvm, ObjectFormat::PVM))
-                .unwrap_or_else(|_| (bytecode.to_vec(), ObjectFormat::ELF))
+                .unwrap_or_else(|error| {
+                    if !error
+                        .to_string()
+                        .lines()
+                        .map(|line| line.trim())
+                        .filter(|line| !line.is_empty())
+                        .all(|line| line.contains("found undefined symbol"))
+                    {
+                        panic!("ICE: linker: {error}");
+                    }
+
+                    (bytecode.to_vec(), ObjectFormat::ELF)
+                })
         }
         Err(error) => panic!("ICE: linker: {error}"),
     })