diff options
5 files changed, 15 insertions, 45 deletions
diff --git a/library/core/src/intrinsics/simd.rs b/library/core/src/intrinsics/simd.rs index 6afe924f99d..86e3f8509ee 100644 --- a/library/core/src/intrinsics/simd.rs +++ b/library/core/src/intrinsics/simd.rs @@ -577,11 +577,9 @@ pub unsafe fn simd_select<M, T>(mask: M, if_true: T, if_false: T) -> T; /// For each element, if the bit in `mask` is `1`, select the element from /// `if_true`. If the corresponding bit in `mask` is `0`, select the element from /// `if_false`. +/// The remaining bits of the mask are ignored. /// /// The bitmask bit order matches `simd_bitmask`. -/// -/// # Safety -/// Padding bits must be all zero. #[rustc_intrinsic] #[rustc_nounwind] pub unsafe fn simd_select_bitmask<M, T>(m: M, yes: T, no: T) -> T; diff --git a/src/tools/miri/src/intrinsics/simd.rs b/src/tools/miri/src/intrinsics/simd.rs index de5da6ec898..c9250ba1b81 100644 --- a/src/tools/miri/src/intrinsics/simd.rs +++ b/src/tools/miri/src/intrinsics/simd.rs @@ -506,7 +506,6 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> { }; let dest_len = u32::try_from(dest_len).unwrap(); - let bitmask_len = u32::try_from(bitmask_len).unwrap(); for i in 0..dest_len { let bit_i = simd_bitmask_index(i, dest_len, this.data_layout().endian); let mask = mask & 1u64.strict_shl(bit_i); @@ -517,17 +516,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> { let val = if mask != 0 { yes } else { no }; this.write_immediate(*val, &dest)?; } - for i in dest_len..bitmask_len { - // If the mask is "padded", ensure that padding is all-zero. - // This deliberately does not use `simd_bitmask_index`; these bits are outside - // the bitmask. It does not matter in which order we check them. - let mask = mask & 1u64.strict_shl(i); - if mask != 0 { - throw_ub_format!( - "a SIMD bitmask less than 8 bits long must be filled with 0s for the remaining bits" - ); - } - } + // The remaining bits of the mask are ignored. } // Converts a "vector of bool" into a bitmask. "bitmask" => { diff --git a/src/tools/miri/tests/fail/intrinsics/simd-select-bitmask-invalid.rs b/src/tools/miri/tests/fail/intrinsics/simd-select-bitmask-invalid.rs deleted file mode 100644 index 409098ac3b5..00000000000 --- a/src/tools/miri/tests/fail/intrinsics/simd-select-bitmask-invalid.rs +++ /dev/null @@ -1,15 +0,0 @@ -#![feature(core_intrinsics, repr_simd)] - -use std::intrinsics::simd::simd_select_bitmask; - -#[repr(simd)] -#[allow(non_camel_case_types)] -#[derive(Copy, Clone)] -struct i32x2([i32; 2]); - -fn main() { - unsafe { - let x = i32x2([0, 1]); - simd_select_bitmask(0b11111111u8, x, x); //~ERROR: bitmask less than 8 bits long must be filled with 0s for the remaining bits - } -} diff --git a/src/tools/miri/tests/fail/intrinsics/simd-select-bitmask-invalid.stderr b/src/tools/miri/tests/fail/intrinsics/simd-select-bitmask-invalid.stderr deleted file mode 100644 index 9acb51d8c5f..00000000000 --- a/src/tools/miri/tests/fail/intrinsics/simd-select-bitmask-invalid.stderr +++ /dev/null @@ -1,15 +0,0 @@ -error: Undefined Behavior: a SIMD bitmask less than 8 bits long must be filled with 0s for the remaining bits - --> tests/fail/intrinsics/simd-select-bitmask-invalid.rs:LL:CC - | -LL | simd_select_bitmask(0b11111111u8, x, x); - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ a SIMD bitmask less than 8 bits long must be filled with 0s for the remaining bits - | - = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior - = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information - = note: BACKTRACE: - = note: inside `main` at tests/fail/intrinsics/simd-select-bitmask-invalid.rs:LL:CC - -note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace - -error: aborting due to 1 previous error - diff --git a/src/tools/miri/tests/pass/intrinsics/portable-simd.rs b/src/tools/miri/tests/pass/intrinsics/portable-simd.rs index cc753dac215..e14ce51f35a 100644 --- a/src/tools/miri/tests/pass/intrinsics/portable-simd.rs +++ b/src/tools/miri/tests/pass/intrinsics/portable-simd.rs @@ -331,6 +331,19 @@ fn simd_mask() { ); assert_eq!(selected1, i32x4::from_array([0, 0, 0, 1])); assert_eq!(selected2, selected1); + // Non-zero "padding" (the extra bits) is also allowed. + let selected1 = simd_select_bitmask::<u8, _>( + if cfg!(target_endian = "little") { 0b11111000 } else { 0b11110001 }, + i32x4::splat(1), // yes + i32x4::splat(0), // no + ); + let selected2 = simd_select_bitmask::<[u8; 1], _>( + if cfg!(target_endian = "little") { [0b11111000] } else { [0b11110001] }, + i32x4::splat(1), // yes + i32x4::splat(0), // no + ); + assert_eq!(selected1, i32x4::from_array([0, 0, 0, 1])); + assert_eq!(selected2, selected1); } // Non-power-of-2 multi-byte mask. |