diff options
| -rw-r--r-- | src/librustc_mir/interpret/intrinsics.rs | 2 | ||||
| -rw-r--r-- | src/test/run-pass/const-int-rotate.rs | 36 |
2 files changed, 36 insertions, 2 deletions
diff --git a/src/librustc_mir/interpret/intrinsics.rs b/src/librustc_mir/interpret/intrinsics.rs index 34e9b4972a1..3f3651fd817 100644 --- a/src/librustc_mir/interpret/intrinsics.rs +++ b/src/librustc_mir/interpret/intrinsics.rs @@ -194,7 +194,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> InterpretCx<'a, 'mir, 'tcx, M> let raw_shift_bits = self.read_scalar(args[1])?.to_bits(layout.size)?; let width_bits = layout.size.bits() as u128; let shift_bits = raw_shift_bits % width_bits; - let inv_shift_bits = (width_bits - raw_shift_bits) % width_bits; + let inv_shift_bits = (width_bits - shift_bits) % width_bits; let result_bits = if intrinsic_name == "rotate_left" { (val_bits << shift_bits) | (val_bits >> inv_shift_bits) } else { diff --git a/src/test/run-pass/const-int-rotate.rs b/src/test/run-pass/const-int-rotate.rs index c014e97ef19..965f317c424 100644 --- a/src/test/run-pass/const-int-rotate.rs +++ b/src/test/run-pass/const-int-rotate.rs @@ -1,11 +1,45 @@ const LEFT: u32 = 0x10000b3u32.rotate_left(8); const RIGHT: u32 = 0xb301u32.rotate_right(8); +// Rotating these should make no difference +// +// We test using 124 bits because to ensure that overlong bit shifts do +// not cause undefined behaviour. See #10183. +const LEFT_OVERFLOW: i16 = 0i16.rotate_left(124); +const RIGHT_OVERFLOW: i16 = 0i16.rotate_right(124); +const ONE_LEFT_OVERFLOW: u16 = 1u16.rotate_left(124); +const ONE_RIGHT_OVERFLOW: u16 = 1u16.rotate_right(124); + +const NON_ZERO_LEFT_OVERFLOW: u16 = 0b10u16.rotate_left(124); +const NON_ZERO_RIGHT_OVERFLOW: u16 = 0b10u16.rotate_right(124); + +// Rotating by 0 should have no effect +const ZERO_ROTATE_LEFT: i8 = 0b0010_0001i8.rotate_left(0); +const ZERO_ROTATE_RIGHT: i8 = 0b0111_1001i8.rotate_right(0); + +// Rotating by a multiple of word size should also have no effect +const MULTIPLE_ROTATE_LEFT: i32 = 0b0010_0001i32.rotate_left(128); +const MULTIPLE_ROTATE_RIGHT: i32 = 0b0010_0001i32.rotate_right(128); + fn ident<T>(ident: T) -> T { ident } fn main() { assert_eq!(LEFT, ident(0xb301)); - assert_eq!(RIGHT, ident(0x10000b3)); + assert_eq!(RIGHT, ident(0x0100_00b3)); + + assert_eq!(LEFT_OVERFLOW, ident(0)); + assert_eq!(RIGHT_OVERFLOW, ident(0)); + assert_eq!(ONE_LEFT_OVERFLOW, ident(0b0001_0000_0000_0000)); + assert_eq!(ONE_RIGHT_OVERFLOW, ident(0b0001_0000)); + + assert_eq!(NON_ZERO_LEFT_OVERFLOW, ident(0b0010_0000_0000_0000)); + assert_eq!(NON_ZERO_RIGHT_OVERFLOW, ident(0b0000_0000_0010_0000)); + + assert_eq!(ZERO_ROTATE_LEFT, ident(0b0010_0001)); + assert_eq!(ZERO_ROTATE_RIGHT, ident(0b0111_1001)); + + assert_eq!(MULTIPLE_ROTATE_LEFT, ident(0b0010_0001)); + assert_eq!(MULTIPLE_ROTATE_RIGHT, ident(0b0010_0001)); } |