From 385d2a143c017c96f6de24bd8a13b34babf9b295 Mon Sep 17 00:00:00 2001
From: Andrea Piseri <andrea.piseri@gmail.com>
Date: Wed, 21 Dec 2022 21:09:22 +0100
Subject: [PATCH 1/3] Fix `core:slice.rotate_left`

This commit includes two fixes:
- a temporary cast to make the function compile
- a fix to a logic error that caused the function to hang or return
  incorrect results
---
 core/slice/ptr.odin   | 18 +++++-------------
 core/slice/slice.odin |  8 +++++---
 2 files changed, 10 insertions(+), 16 deletions(-)

diff --git a/core/slice/ptr.odin b/core/slice/ptr.odin
index 214b745f7..701e55495 100644
--- a/core/slice/ptr.odin
+++ b/core/slice/ptr.odin
@@ -73,25 +73,17 @@ ptr_rotate :: proc(left: int, mid: ^$T, right: int) {
 		left, mid, right := left, mid, right
 
 		// TODO(bill): Optimization with a buffer for smaller ranges
-		if left >= right {
-			for {
-				ptr_swap_non_overlapping(ptr_sub(mid, right), mid, right)
+		for left > 0 && right > 0 {
+			if left >= right {
+				ptr_swap_non_overlapping(ptr_sub(mid, right), mid, right * size_of(T))
 				mid = ptr_sub(mid, right)
 
 				left -= right
-				if left < right {
-					break
-				}
-			}
-		} else {
-			for {
-				ptr_swap_non_overlapping(ptr_sub(mid, left), mid, left)
+			} else {
+				ptr_swap_non_overlapping(ptr_sub(mid, left), mid, left * size_of(T))
 				mid = ptr_add(mid, left)
 
 				right -= left
-				if right < left {
-					break
-				}
 			}
 		}
 	}
diff --git a/core/slice/slice.odin b/core/slice/slice.odin
index 032a8ca6e..f5305f29e 100644
--- a/core/slice/slice.odin
+++ b/core/slice/slice.odin
@@ -218,8 +218,10 @@ rotate_left :: proc(array: $T/[]$E, mid: int) {
 	n := len(array)
 	m := mid %% n
 	k := n - m
-	p := raw_data(array)
-	ptr_rotate(mid, ptr_add(p, mid), k)
+	// FIXME: (ap29600) this cast is a temporary fix for the compiler not matching
+	// [^T] with $P/^$T
+	p := cast(^int)raw_data(array)
+	ptr_rotate(m, ptr_add(p, m), k)
 }
 rotate_right :: proc(array: $T/[]$E, k: int) {
 	rotate_left(array, -k)
@@ -515,4 +517,4 @@ dot_product :: proc(a, b: $S/[]$T) -> (r: T, ok: bool)
 enumerated_array :: proc(ptr: ^$T) -> []intrinsics.type_elem_type(T)
 	where intrinsics.type_is_enumerated_array(T) {
 	return ([^]intrinsics.type_elem_type(T))(ptr)[:len(T)]
-}
\ No newline at end of file
+}

From 191223bb3c6872f952e97d44852823563b47a744 Mon Sep 17 00:00:00 2001
From: Andrea Piseri <andrea.piseri@gmail.com>
Date: Wed, 21 Dec 2022 21:58:01 +0100
Subject: [PATCH 2/3] Fix non-generic cast in core:slice.rotate_left

---
 core/slice/slice.odin | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/core/slice/slice.odin b/core/slice/slice.odin
index f5305f29e..595ec8e37 100644
--- a/core/slice/slice.odin
+++ b/core/slice/slice.odin
@@ -220,7 +220,7 @@ rotate_left :: proc(array: $T/[]$E, mid: int) {
 	k := n - m
 	// FIXME: (ap29600) this cast is a temporary fix for the compiler not matching
 	// [^T] with $P/^$T
-	p := cast(^int)raw_data(array)
+	p := cast(^E)raw_data(array)
 	ptr_rotate(m, ptr_add(p, m), k)
 }
 rotate_right :: proc(array: $T/[]$E, k: int) {

From 3fa971a510172be922eeaaee9fd3533dc9628832 Mon Sep 17 00:00:00 2001
From: Andrea Piseri <andrea.piseri@gmail.com>
Date: Wed, 21 Dec 2022 22:10:02 +0100
Subject: [PATCH 3/3] Add the inner `for` loop back in the logic

This could be easier to predict in cases where one of `left` and `right`
is significantly greater than the other, and as such the same branch is
taken multiple times in a row
---
 core/slice/ptr.odin | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/core/slice/ptr.odin b/core/slice/ptr.odin
index 701e55495..e2f1c3e7b 100644
--- a/core/slice/ptr.odin
+++ b/core/slice/ptr.odin
@@ -75,15 +75,25 @@ ptr_rotate :: proc(left: int, mid: ^$T, right: int) {
 		// TODO(bill): Optimization with a buffer for smaller ranges
 		for left > 0 && right > 0 {
 			if left >= right {
-				ptr_swap_non_overlapping(ptr_sub(mid, right), mid, right * size_of(T))
-				mid = ptr_sub(mid, right)
+				for {
+					ptr_swap_non_overlapping(ptr_sub(mid, right), mid, right * size_of(T))
+					mid = ptr_sub(mid, right)
 
-				left -= right
+					left -= right
+					if left < right {
+						break
+					}
+				}
 			} else {
-				ptr_swap_non_overlapping(ptr_sub(mid, left), mid, left * size_of(T))
-				mid = ptr_add(mid, left)
+				for {
+					ptr_swap_non_overlapping(ptr_sub(mid, left), mid, left * size_of(T))
+					mid = ptr_add(mid, left)
 
-				right -= left
+					right -= left
+					if right < left {
+						break
+					}
+				}
 			}
 		}
 	}