From 6e5acadfead7913c438c7dd363a45074bf96e2e0 Mon Sep 17 00:00:00 2001
From: Brian Carroll <brian.carroll.ireland@gmail.com>
Date: Wed, 24 Nov 2021 16:07:31 +0000
Subject: [PATCH] Create new lowlevels for refcounting

---
 compiler/builtins/bitcode/src/main.zig  |  1 +
 compiler/builtins/bitcode/src/utils.zig | 20 ++++++++++++++++++++
 compiler/builtins/src/bitcode.rs        |  1 +
 compiler/gen_llvm/src/llvm/build.rs     |  4 ++++
 compiler/gen_wasm/src/low_level.rs      |  1 +
 compiler/module/src/low_level.rs        |  3 +++
 compiler/mono/src/borrow.rs             |  4 ++++
 7 files changed, 34 insertions(+)

diff --git a/compiler/builtins/bitcode/src/main.zig b/compiler/builtins/bitcode/src/main.zig
index 8b081cd1cf..37c0a3011a 100644
--- a/compiler/builtins/bitcode/src/main.zig
+++ b/compiler/builtins/bitcode/src/main.zig
@@ -138,6 +138,7 @@ comptime {
 
 comptime {
     exportUtilsFn(utils.test_panic, "test_panic");
+    exportUtilsFn(utils.increfC, "incref");
     exportUtilsFn(utils.decrefC, "decref");
     exportUtilsFn(utils.decrefCheckNullC, "decref_check_null");
 
diff --git a/compiler/builtins/bitcode/src/utils.zig b/compiler/builtins/bitcode/src/utils.zig
index ab2ea26171..940e8d945b 100644
--- a/compiler/builtins/bitcode/src/utils.zig
+++ b/compiler/builtins/bitcode/src/utils.zig
@@ -104,6 +104,12 @@ pub const IntWidth = enum(u8) {
     I128 = 9,
 };
 
+pub fn increfC(ptr_to_refcount: *isize, amount: isize) callconv(.C) void {
+    var refcount = ptr_to_refcount.*;
+    var masked_amount = if (refcount == REFCOUNT_MAX_ISIZE) 0 else amount;
+    ptr_to_refcount.* = refcount + masked_amount;
+}
+
 pub fn decrefC(
     bytes_or_null: ?[*]isize,
     alignment: u32,
@@ -261,3 +267,17 @@ pub const UpdateMode = enum(u8) {
     Immutable = 0,
     InPlace = 1,
 };
+
+test "increfC, refcounted data" {
+    var mock_rc: isize = REFCOUNT_ONE_ISIZE + 17;
+    var ptr_to_refcount: *isize = &mock_rc;
+    increfC(ptr_to_refcount, 2);
+    try std.testing.expectEqual(mock_rc, REFCOUNT_ONE_ISIZE + 19);
+}
+
+test "increfC, static data" {
+    var mock_rc: isize = REFCOUNT_MAX_ISIZE;
+    var ptr_to_refcount: *isize = &mock_rc;
+    increfC(ptr_to_refcount, 2);
+    try std.testing.expectEqual(mock_rc, REFCOUNT_MAX_ISIZE);
+}
diff --git a/compiler/builtins/src/bitcode.rs b/compiler/builtins/src/bitcode.rs
index afffd31dd9..da9de5a6e6 100644
--- a/compiler/builtins/src/bitcode.rs
+++ b/compiler/builtins/src/bitcode.rs
@@ -309,5 +309,6 @@ pub const DEC_MUL_WITH_OVERFLOW: &str = "roc_builtins.dec.mul_with_overflow";
 pub const DEC_DIV: &str = "roc_builtins.dec.div";
 
 pub const UTILS_TEST_PANIC: &str = "roc_builtins.utils.test_panic";
+pub const UTILS_INCREF: &str = "roc_builtins.utils.incref";
 pub const UTILS_DECREF: &str = "roc_builtins.utils.decref";
 pub const UTILS_DECREF_CHECK_NULL: &str = "roc_builtins.utils.decref_check_null";
diff --git a/compiler/gen_llvm/src/llvm/build.rs b/compiler/gen_llvm/src/llvm/build.rs
index 69168415c0..e95cc2cb37 100644
--- a/compiler/gen_llvm/src/llvm/build.rs
+++ b/compiler/gen_llvm/src/llvm/build.rs
@@ -6020,6 +6020,10 @@ fn run_low_level<'a, 'ctx, 'env>(
         | ListAny | ListAll | ListFindUnsafe | DictWalk => {
             unreachable!("these are higher order, and are handled elsewhere")
         }
+
+        RefCountGetPtr | RefCountInc | RefCountDec => {
+            unreachable!("LLVM backend does not use lowlevels for refcounting");
+        }
     }
 }
 
diff --git a/compiler/gen_wasm/src/low_level.rs b/compiler/gen_wasm/src/low_level.rs
index 7cf781490a..c3698a24bb 100644
--- a/compiler/gen_wasm/src/low_level.rs
+++ b/compiler/gen_wasm/src/low_level.rs
@@ -370,6 +370,7 @@ pub fn decode_low_level<'a>(
         Not => code_builder.i32_eqz(),
         Hash => return NotImplemented,
         ExpectTrue => return NotImplemented,
+        RefCountGetPtr | RefCountInc | RefCountDec => return NotImplemented,
     }
     Done
 }
diff --git a/compiler/module/src/low_level.rs b/compiler/module/src/low_level.rs
index 9405956fc0..25acb8cc2d 100644
--- a/compiler/module/src/low_level.rs
+++ b/compiler/module/src/low_level.rs
@@ -115,6 +115,9 @@ pub enum LowLevel {
     Not,
     Hash,
     ExpectTrue,
+    RefCountGetPtr,
+    RefCountInc,
+    RefCountDec,
 }
 
 macro_rules! higher_order {
diff --git a/compiler/mono/src/borrow.rs b/compiler/mono/src/borrow.rs
index e29eca34ed..ca59b30b39 100644
--- a/compiler/mono/src/borrow.rs
+++ b/compiler/mono/src/borrow.rs
@@ -1008,6 +1008,10 @@ pub fn lowlevel_borrow_signature(arena: &Bump, op: LowLevel) -> &[bool] {
         SetFromList => arena.alloc_slice_copy(&[owned]),
 
         ExpectTrue => arena.alloc_slice_copy(&[irrelevant]),
+
+        RefCountGetPtr | RefCountInc | RefCountDec => {
+            unreachable!("Refcounting lowlevel calls are inserted *after* borrow checking");
+        }
     }
 }