From befd01b240963057e2d41becf17edc9b4be8523e Mon Sep 17 00:00:00 2001
From: Sebastien Bourdeauducq <sb@m-labs.hk>
Date: Sun, 29 Mar 2020 12:12:08 +0800
Subject: [PATCH] implement simple expressions and return statement

---
 src/main.rs | 80 +++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 74 insertions(+), 6 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 8caf38158..daa32336c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -10,16 +10,19 @@ use inkwell::module::Module;
 use inkwell::targets::*;
 use inkwell::types;
 use inkwell::types::BasicType;
+use inkwell::values;
 
 use std::error::Error;
 use std::fmt;
 use std::path::Path;
+use std::collections::HashMap;
 
 #[derive(Debug)]
 enum CompileErrorKind {
     Unsupported(&'static str),
     MissingTypeAnnotation,
     UnknownTypeAnnotation,
+    IncompatibleTypes,
     Internal(&'static str)
 }
 
@@ -32,6 +35,8 @@ impl fmt::Display for CompileErrorKind {
                 => write!(f, "Missing type annotation"),
             CompileErrorKind::UnknownTypeAnnotation
                 => write!(f, "Unknown type annotation"),
+            CompileErrorKind::IncompatibleTypes
+                => write!(f, "Incompatible types"),
             CompileErrorKind::Internal(details)
                 => write!(f, "Internal compiler error: {}", details),
         }
@@ -59,6 +64,7 @@ struct CodeGen<'ctx> {
     module: Module<'ctx>,
     builder: Builder<'ctx>,
     current_source_location: ast::Location,
+    namespace: HashMap<String, values::BasicValueEnum<'ctx>>,
 }
 
 impl<'ctx> CodeGen<'ctx> {
@@ -68,6 +74,7 @@ impl<'ctx> CodeGen<'ctx> {
             module: context.create_module("kernel"),
             builder: context.create_builder(),
             current_source_location: ast::Location::default(),
+            namespace: HashMap::new(),
         }
     }
 
@@ -147,21 +154,82 @@ impl<'ctx> CodeGen<'ctx> {
         let function = self.module.add_function(name, fn_type, None);
         let basic_block = self.context.append_basic_block(function, "entry");
         self.builder.position_at_end(basic_block);
-        let x = function.get_nth_param(0).unwrap().into_int_value();
-        let y = function.get_nth_param(1).unwrap().into_int_value();
-        let sum = self.builder.build_int_add(x, y, "sum");
-        self.builder.build_return(Some(&sum));
+
+        for (n, arg) in args.args.iter().enumerate() {
+            self.namespace.insert(arg.arg.clone(), function.get_nth_param(n as u32).unwrap());
+        }
+
         for statement in body.iter() {
-            self.compile_statement(statement)?;
+            self.compile_statement(statement, return_type)?;
         }
         Ok(())
     }
 
-    fn compile_statement(&mut self, statement: &ast::Statement) -> CompileResult<()> {
+    fn compile_expression(
+        &mut self,
+        expression: &ast::Expression
+    ) -> CompileResult<values::BasicValueEnum<'ctx>> {
+        self.set_source_location(expression.location);
+
+        use ast::ExpressionType::*;
+        match &expression.node {
+            Identifier { name } => {
+                Ok(*self.namespace.get(name).unwrap())
+            },
+            Binop { a, op, b } => {
+                let a = self.compile_expression(&a)?;
+                let b = self.compile_expression(&b)?;
+                if a.get_type() != b.get_type() {
+                    return Err(self.compile_error(CompileErrorKind::IncompatibleTypes));
+                }
+                use ast::Operator::*;
+                match (op, a, b) {
+                    (Add, values::BasicValueEnum::IntValue(a), values::BasicValueEnum::IntValue(b))
+                        => Ok(self.builder.build_int_add(a, b, "tmpadd").into()),
+                    (Sub, values::BasicValueEnum::IntValue(a), values::BasicValueEnum::IntValue(b))
+                        => Ok(self.builder.build_int_sub(a, b, "tmpsub").into()),
+                    (Mult, values::BasicValueEnum::IntValue(a), values::BasicValueEnum::IntValue(b))
+                        => Ok(self.builder.build_int_mul(a, b, "tmpmul").into()),
+
+                    (Add, values::BasicValueEnum::FloatValue(a), values::BasicValueEnum::FloatValue(b))
+                        => Ok(self.builder.build_float_add(a, b, "tmpadd").into()),
+                    (Sub, values::BasicValueEnum::FloatValue(a), values::BasicValueEnum::FloatValue(b))
+                        => Ok(self.builder.build_float_sub(a, b, "tmpsub").into()),
+                    (Mult, values::BasicValueEnum::FloatValue(a), values::BasicValueEnum::FloatValue(b))
+                        => Ok(self.builder.build_float_mul(a, b, "tmpmul").into()),
+                    _ => return Err(self.compile_error(CompileErrorKind::Unsupported("unimplemented operation"))),
+                }
+            }
+            _ => return Err(self.compile_error(CompileErrorKind::Unsupported("unimplemented expression"))),
+        }
+    }
+
+    fn compile_statement(
+        &mut self,
+        statement: &ast::Statement,
+        return_type: Option<types::BasicTypeEnum>
+    ) -> CompileResult<()> {
         self.set_source_location(statement.location);
 
         use ast::StatementType::*;
         match &statement.node {
+            Return { value: Some(value) } => {
+                if let Some(return_type) = return_type {
+                    let value = self.compile_expression(value)?;
+                    if value.get_type() != return_type {
+                        return Err(self.compile_error(CompileErrorKind::IncompatibleTypes));
+                    }
+                    self.builder.build_return(Some(&value));
+                } else {
+                    return Err(self.compile_error(CompileErrorKind::IncompatibleTypes));
+                }
+            },
+            Return { value: None } => {
+                if !return_type.is_none() {
+                    return Err(self.compile_error(CompileErrorKind::IncompatibleTypes));
+                }
+                self.builder.build_return(None);
+            },
             Pass => (),
             _ => return Err(self.compile_error(CompileErrorKind::Unsupported("special statement"))),
         }