Add a block garbage-collector that will delete an unused block at end

reid-llvm-lib/src/builder.rs

@@ -143,6 +143,17 @@ impl Builder {
         }
     }
 
+    pub(crate) unsafe fn delete_block(&self, block: &BlockValue) -> Result<(), ()> {
+        unsafe {
+            let mut modules = self.modules.borrow_mut();
+            let module = modules.get_unchecked_mut(block.0.0.0);
+            let function = module.functions.get_unchecked_mut(block.0.1);
+            let block = function.blocks.get_unchecked_mut(block.1);
+            block.data.deleted = true;
+            Ok(())
+        }
+    }
+
     #[allow(dead_code)]
     pub(crate) unsafe fn module_data(&self, value: &ModuleValue) -> ModuleData {
         unsafe { self.modules.borrow().get_unchecked(value.0).data.clone() }
@@ -242,6 +253,39 @@ impl Builder {
             }
         }
     }
+
+    pub fn is_block_used(&self, block_v: BlockValue) -> bool {
+        unsafe {
+            let modules = self.modules.borrow();
+            let module = modules.get_unchecked(block_v.0.0.0);
+            let function = module.functions.get_unchecked(block_v.0.1);
+            let block = function.blocks.get_unchecked(block_v.1);
+
+            if block.instructions.len() > 0 || block.data.terminator.is_some() {
+                return true;
+            }
+
+            for other in &function.blocks {
+                if let Some(term) = &other.data.terminator {
+                    match term {
+                        TerminatorKind::Ret(_) => {}
+                        TerminatorKind::Br(other_val) => {
+                            if other_val == &block_v {
+                                return true;
+                            }
+                        }
+                        TerminatorKind::CondBr(_, then_other_v, else_other_v) => {
+                            if then_other_v == &block_v || else_other_v == &block_v {
+                                return true;
+                            }
+                        }
+                    }
+                }
+            }
+
+            false
+        }
+    }
 }
 
 impl InstructionValue {

reid-llvm-lib/src/compile.rs

@@ -205,6 +205,10 @@ impl FunctionHolder {
             let own_function = *module.functions.get(&self.value).unwrap();
 
             for block in &self.blocks {
+                if block.data.deleted {
+                    continue;
+                }
+
                 let block_ref = LLVMCreateBasicBlockInContext(
                     module.context_ref,
                     into_cstring(&self.data.name).as_ptr(),
@@ -223,6 +227,10 @@ impl FunctionHolder {
 impl BlockHolder {
     unsafe fn compile(&self, module: &mut LLVMModule, function: &LLVMFunction) {
         unsafe {
+            if self.data.deleted {
+                return;
+            }
+
             let block_ref = *module.blocks.get(&self.value).unwrap();
             LLVMPositionBuilderAtEnd(module.builder_ref, block_ref);
 

reid-llvm-lib/src/debug.rs

@@ -32,7 +32,11 @@ impl Debug for FunctionHolder {
 
 impl Debug for BlockHolder {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        f.debug_tuple(&format!("{}[{:?}]", &self.data.name, &self.value))
+        let deleted = if self.data.deleted { " (deleted)" } else { "" };
+        f.debug_tuple(&format!(
+            "{}[{:?}]{} ",
+            &self.data.name, &self.value, deleted
+        ))
         .field(&self.instructions)
         .field(&self.data.terminator)
         .finish()

reid-llvm-lib/src/lib.rs

@@ -95,6 +95,7 @@ impl<'ctx> Function<'ctx> {
                     BlockData {
                         name: name.to_owned(),
                         terminator: None,
+                        deleted: false,
                     },
                 ),
             }
@@ -110,6 +111,7 @@ impl<'ctx> Function<'ctx> {
 pub struct BlockData {
     name: String,
     terminator: Option<TerminatorKind>,
+    deleted: bool,
 }
 
 pub struct Block<'builder> {
@@ -130,6 +132,16 @@ impl<'builder> Block<'builder> {
         unsafe { self.builder.terminate(&self.value, instruction) }
     }
 
+    pub fn delete_if_unused(&mut self) -> Result<(), ()> {
+        unsafe {
+            if !self.builder.is_block_used(self.value()) {
+                self.builder.delete_block(&self.value)
+            } else {
+                Ok(())
+            }
+        }
+    }
+
     pub fn value(&self) -> BlockValue {
         self.value
     }

reid/examples/reid/fibonacci.reid

@@ -1,14 +1,13 @@
 // Main
 fn main() -> bool {
-    return (5 == fibonacci(5)) && false;
+    return 5 == fibonacci(5);
 }
 
 // Fibonacci
 fn fibonacci(value: u16) -> u16 {
-    let ret = if value <= 2 {
-        1
+    if value <= 2 {
+        return 1;
     } else {
-        fibonacci(value - 1) + fibonacci(value - 2)
-    };
-    ret
+        return fibonacci(value - 1) + fibonacci(value - 2);
+    }
 }

reid/src/codegen.rs

@@ -89,6 +89,8 @@ impl mir::Module {
                 mir::FunctionDefinitionKind::Local(block, _) => {
                     if let Some(ret) = block.codegen(&mut scope) {
                         scope.block.terminate(Term::Ret(ret)).unwrap();
+                    } else {
+                        scope.block.delete_if_unused().unwrap();
                     }
                 }
                 mir::FunctionDefinitionKind::Extern => {}
@@ -298,7 +300,7 @@ impl mir::Block {
         }
 
         if let Some((kind, expr)) = &self.return_expression {
-            let ret = expr.codegen(&mut scope).unwrap();
+            if let Some(ret) = expr.codegen(&mut scope) {
                 match kind {
                     mir::ReturnKind::Hard => {
                         scope.block.terminate(Term::Ret(ret)).unwrap();
@@ -309,6 +311,9 @@ impl mir::Block {
             } else {
                 None
             }
+        } else {
+            None
+        }
     }
 }