Auto merge of #33460 - shepmaster:16-bit-pointers, r=Aatch

Support 16-bit pointers as well as i/usize

I'm opening this pull request to get some feedback from the community.

Although Rust doesn't support any platforms with a native 16-bit pointer at the moment, the [AVR-Rust][ar] fork is working towards that goal. Keeping this forked logic up-to-date with the changes in master has been onerous so I'd like to merge these changes so that they get carried along when refactoring happens. I do not believe this should increase the maintenance burden.

This is based on the original work of Dylan McKay (@dylanmckay).

[ar]: https://github.com/avr-rust/rust

4 files changed, 31 insertions, 0 deletions

diff --git a/src/libcore/num/isize.rs b/src/libcore/num/isize.rs
index de5b1777f93..86bcef4011d 100644
--- a/src/libcore/num/isize.rs
+++ b/src/libcore/num/isize.rs
@@ -14,6 +14,8 @@
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
+#[cfg(target_pointer_width = "16")]
+int_module! { isize, 16 }
 #[cfg(target_pointer_width = "32")]
 int_module! { isize, 32 }
 #[cfg(target_pointer_width = "64")]
diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs
index 9b6f6698def..5988a6375d4 100644
--- a/src/libcore/num/mod.rs
+++ b/src/libcore/num/mod.rs
@@ -1176,6 +1176,15 @@ impl i64 {
         intrinsics::mul_with_overflow }
 }
 
+#[cfg(target_pointer_width = "16")]
+#[lang = "isize"]
+impl isize {
+    int_impl! { i16, u16, 16,
+        intrinsics::add_with_overflow,
+        intrinsics::sub_with_overflow,
+        intrinsics::mul_with_overflow }
+}
+
 #[cfg(target_pointer_width = "32")]
 #[lang = "isize"]
 impl isize {
@@ -2188,6 +2197,18 @@ impl u64 {
         intrinsics::mul_with_overflow }
 }
 
+#[cfg(target_pointer_width = "16")]
+#[lang = "usize"]
+impl usize {
+    uint_impl! { u16, 16,
+        intrinsics::ctpop,
+        intrinsics::ctlz,
+        intrinsics::cttz,
+        intrinsics::bswap,
+        intrinsics::add_with_overflow,
+        intrinsics::sub_with_overflow,
+        intrinsics::mul_with_overflow }
+}
 #[cfg(target_pointer_width = "32")]
 #[lang = "usize"]
 impl usize {
diff --git a/src/libcore/num/usize.rs b/src/libcore/num/usize.rs
index 0c7d16a41bc..685c52e271e 100644
--- a/src/libcore/num/usize.rs
+++ b/src/libcore/num/usize.rs
@@ -14,6 +14,8 @@
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
+#[cfg(target_pointer_width = "16")]
+uint_module! { usize, 16 }
 #[cfg(target_pointer_width = "32")]
 uint_module! { usize, 32 }
 #[cfg(target_pointer_width = "64")]
diff --git a/src/libcore/num/wrapping.rs b/src/libcore/num/wrapping.rs
index 04e8bc4913b..4857817e84e 100644
--- a/src/libcore/num/wrapping.rs
+++ b/src/libcore/num/wrapping.rs
@@ -292,6 +292,12 @@ wrapping_impl! { usize u8 u16 u32 u64 isize i8 i16 i32 i64 }
 mod shift_max {
     #![allow(non_upper_case_globals)]
 
+    #[cfg(target_pointer_width = "16")]
+    mod platform {
+        pub const usize: u32 = super::u16;
+        pub const isize: u32 = super::i16;
+    }
+
     #[cfg(target_pointer_width = "32")]
     mod platform {
         pub const usize: u32 = super::u32;