From a3719e08e532763d044848b6871ef3c960b7d3e3 Mon Sep 17 00:00:00 2001
From: Sergey Pepyakin <sergei@parity.io>
Date: Tue, 11 Dec 2018 19:45:33 +0100
Subject: [PATCH] Pass arguments.

---
 src/backend.rs       | 28 +++++++++++++++++++++++-----
 src/function_body.rs |  5 +----
 src/tests.rs         | 12 +++++++++---
 3 files changed, 33 insertions(+), 12 deletions(-)

diff --git a/src/backend.rs b/src/backend.rs
index b3cf12a91b..dfcd301c32 100644
--- a/src/backend.rs
+++ b/src/backend.rs
@@ -81,6 +81,7 @@ impl Registers {
 }
 
 /// Describes location of a argument.
+#[derive(Debug)]
 enum ArgLocation {
     /// Argument is passed via some register.
     Reg(GPR),
@@ -336,6 +337,22 @@ pub fn copy_incoming_arg(ctx: &mut Context, arg_pos: u32) {
     );
 }
 
+pub fn pass_outgoing_args(ctx: &mut Context, arity: u32) {
+    for arg_pos in (0..arity).rev() {
+        ctx.sp_depth.free(1);
+
+        let loc = abi_loc_for_arg(arg_pos);
+        match loc {
+            ArgLocation::Reg(gpr) => {
+                dynasm!(ctx.asm
+                    ; pop Rq(gpr)
+                );
+            }
+            _ => unimplemented!("don't know how to pass argument {} via {:?}", arg_pos, loc),
+        }
+    }
+}
+
 pub fn call_direct(ctx: &mut Context, index: u32) {
     let label = &ctx.func_starts[index as usize].1;
     dynasm!(ctx.asm
@@ -358,11 +375,12 @@ pub fn prologue(ctx: &mut Context, stack_slots: u32) {
 }
 
 pub fn epilogue(ctx: &mut Context) {
-    assert_eq!(
-        ctx.sp_depth,
-        StackDepth(0),
-        "imbalanced pushes and pops detected"
-    );
+    // TODO: This doesn't work with stack alignment.
+    // assert_eq!(
+    //     ctx.sp_depth,
+    //     StackDepth(0),
+    //     "imbalanced pushes and pops detected"
+    // );
     dynasm!(ctx.asm
         ; mov rsp, rbp
         ; pop rbp
diff --git a/src/function_body.rs b/src/function_body.rs
index 18733c644a..bffca70b98 100644
--- a/src/function_body.rs
+++ b/src/function_body.rs
@@ -219,15 +219,12 @@ pub fn translate(
             }
             Operator::Call { function_index } => {
                 let callee_ty = translation_ctx.func_type(function_index);
-                assert!(callee_ty.params.len() == 0, "is not supported");
                 assert!(callee_ty.returns.len() == 0, "is not supported");
 
                 // TODO: ensure that this function is locally defined
                 // We would like to support imported functions at some point
 
-                // TODO: pop arguments and move them in appropriate positions.
-                // only 6 for now.
-
+                pass_outgoing_args(&mut ctx, callee_ty.params.len() as u32);
                 call_direct(&mut ctx, function_index);
             }
             _ => {
diff --git a/src/tests.rs b/src/tests.rs
index 980d100bc4..d2e2effb78 100644
--- a/src/tests.rs
+++ b/src/tests.rs
@@ -111,16 +111,22 @@ fn function_call() {
     let code = r#"
 (module
   (func (param i32) (param i32) (result i32)
-    (call 1)
+    (call $assert_zero
+      (get_local 1)
+    )
     (get_local 0)
   )
 
-  (func
+  (func $assert_zero (param $v i32)
+    (local i32)
+    (if (get_local $v)
+      (unreachable)
+    )
   )
 )
     "#;
 
-    assert_eq!(execute_wat(code, 2, 3), 2);
+    assert_eq!(execute_wat(code, 2, 0), 2);
 }
 
 // TODO: Add a test that checks argument passing via the stack.