Add bitreverse intrinsic

Author: Amanieu

src/libcore/intrinsics.rs

@@ -1292,6 +1292,10 @@ extern "rust-intrinsic" {
     /// Reverses the bytes in an integer type `T`.
     pub fn bswap<T>(x: T) -> T;
 
+    /// Reverses the bits in an integer type `T`.
+    #[cfg(not(stage0))]
+    pub fn bitreverse<T>(x: T) -> T;
+
     /// Performs checked integer addition.
     /// The stabilized versions of this intrinsic are available on the integer
     /// primitives via the `overflowing_add` method. For example,

src/librustc_trans/context.rs

@@ -597,6 +597,12 @@ fn declare_intrinsic(cx: &CodegenCx, key: &str) -> Option<ValueRef> {
     ifn!("llvm.bswap.i64", fn(t_i64) -> t_i64);
     ifn!("llvm.bswap.i128", fn(t_i128) -> t_i128);
 
+    ifn!("llvm.bitreverse.i8", fn(t_i8) -> t_i8);
+    ifn!("llvm.bitreverse.i16", fn(t_i16) -> t_i16);
+    ifn!("llvm.bitreverse.i32", fn(t_i32) -> t_i32);
+    ifn!("llvm.bitreverse.i64", fn(t_i64) -> t_i64);
+    ifn!("llvm.bitreverse.i128", fn(t_i128) -> t_i128);
+
     ifn!("llvm.sadd.with.overflow.i8", fn(t_i8, t_i8) -> mk_struct!{t_i8, i1});
     ifn!("llvm.sadd.with.overflow.i16", fn(t_i16, t_i16) -> mk_struct!{t_i16, i1});
     ifn!("llvm.sadd.with.overflow.i32", fn(t_i32, t_i32) -> mk_struct!{t_i32, i1});

src/librustc_trans/intrinsic.rs

@@ -287,8 +287,8 @@ pub fn trans_intrinsic_call<'a, 'tcx>(bx: &Builder<'a, 'tcx>,
             ], None)
         },
         "ctlz" | "ctlz_nonzero" | "cttz" | "cttz_nonzero" | "ctpop" | "bswap" |
-        "add_with_overflow" | "sub_with_overflow" | "mul_with_overflow" |
-        "overflowing_add" | "overflowing_sub" | "overflowing_mul" |
+        "bitreverse" | "add_with_overflow" | "sub_with_overflow" |
+        "mul_with_overflow" | "overflowing_add" | "overflowing_sub" | "overflowing_mul" |
         "unchecked_div" | "unchecked_rem" | "unchecked_shl" | "unchecked_shr" => {
             let ty = arg_tys[0];
             match int_type_width_signed(ty, cx) {
@@ -315,6 +315,10 @@ pub fn trans_intrinsic_call<'a, 'tcx>(bx: &Builder<'a, 'tcx>,
                                         &[args[0].immediate()], None)
                             }
                         }
+                        "bitreverse" => {
+                            bx.call(cx.get_intrinsic(&format!("llvm.bitreverse.i{}", width)),
+                                &[args[0].immediate()], None)
+                        }
                         "add_with_overflow" | "sub_with_overflow" | "mul_with_overflow" => {
                             let intrinsic = format!("llvm.{}{}.with.overflow.i{}",
                                                     if signed { 's' } else { 'u' },

src/librustc_typeck/check/intrinsic.rs

@@ -275,7 +275,8 @@ pub fn check_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             "volatile_store" =>
                 (1, vec![ tcx.mk_mut_ptr(param(0)), param(0) ], tcx.mk_nil()),
 
-            "ctpop" | "ctlz" | "ctlz_nonzero" | "cttz" | "cttz_nonzero" | "bswap" =>
+            "ctpop" | "ctlz" | "ctlz_nonzero" | "cttz" | "cttz_nonzero" |
+            "bswap" | "bitreverse" =>
                 (1, vec![param(0)], param(0)),
 
             "add_with_overflow" | "sub_with_overflow"  | "mul_with_overflow" =>

src/test/run-pass/intrinsics-integer.rs

@@ -18,6 +18,7 @@ mod rusti {
         pub fn cttz<T>(x: T) -> T;
         pub fn cttz_nonzero<T>(x: T) -> T;
         pub fn bswap<T>(x: T) -> T;
+        pub fn bitreverse<T>(x: T) -> T;
     }
 }
 
@@ -138,5 +139,14 @@ pub fn main() {
         assert_eq!(bswap(0x0ABBCC0Di32), 0x0DCCBB0A);
         assert_eq!(bswap(0x0122334455667708u64), 0x0877665544332201);
         assert_eq!(bswap(0x0122334455667708i64), 0x0877665544332201);
+
+        assert_eq!(bitreverse(0x0Au8), 0x50);
+        assert_eq!(bitreverse(0x0Ai8), 0x50);
+        assert_eq!(bitreverse(0x0A0Cu16), 0x3050);
+        assert_eq!(bitreverse(0x0A0Ci16), 0x3050);
+        assert_eq!(bitreverse(0x0ABBCC0Eu32), 0x7033DD50);
+        assert_eq!(bitreverse(0x0ABBCC0Ei32), 0x7033DD50);
+        assert_eq!(bitreverse(0x0122334455667708u64), 0x10EE66AA22CC4480);
+        assert_eq!(bitreverse(0x0122334455667708i64), 0x10EE66AA22CC4480);
     }
 }