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Auto merge of #126171 - RalfJung:simd_bitmask_multibyte, r=workingjubilee

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simd_bitmask intrinsic: add a non-power-of-2 multi-byte example

r? `@calebzulawski` `@workingjubilee`
This commit is contained in:
bors 2024-07-05 01:58:22 +00:00
commit 51917ba8f2
4 changed files with 144 additions and 26 deletions
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16
compiler/rustc_codegen_llvm/src/intrinsic.rs
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@ -1121,8 +1121,8 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
if name == sym::simd_select_bitmask {
let (len, _) = require_simd!(arg_tys[1], SimdArgument);
let expected_int_bits = (len.max(8) - 1).next_power_of_two();
let expected_bytes = len / 8 + ((len % 8 > 0) as u64);
let expected_int_bits = len.max(8).next_power_of_two();
let expected_bytes = len.div_ceil(8);
let mask_ty = arg_tys[0];
let mask = match mask_ty.kind() {
@ -1379,17 +1379,16 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
}
if name == sym::simd_bitmask {
// The `fn simd_bitmask(vector) -> unsigned integer` intrinsic takes a
// vector mask and returns the most significant bit (MSB) of each lane in the form
// of either:
// The `fn simd_bitmask(vector) -> unsigned integer` intrinsic takes a vector mask and
// returns one bit for each lane (which must all be `0` or `!0`) in the form of either:
// * an unsigned integer
// * an array of `u8`
// If the vector has less than 8 lanes, a u8 is returned with zeroed trailing bits.
//
// The bit order of the result depends on the byte endianness, LSB-first for little
// endian and MSB-first for big endian.
let expected_int_bits = in_len.max(8);
let expected_bytes = expected_int_bits / 8 + ((expected_int_bits % 8 > 0) as u64);
let expected_int_bits = in_len.max(8).next_power_of_two();
let expected_bytes = in_len.div_ceil(8);
// Integer vector <i{in_bitwidth} x in_len>:
let (i_xn, in_elem_bitwidth) = match in_elem.kind() {
@ -1409,7 +1408,8 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
}),
};
// Shift the MSB to the right by "in_elem_bitwidth - 1" into the first bit position.
// LLVM doesn't always know the inputs are `0` or `!0`, so we shift here so it optimizes to
// `pmovmskb` and similar on x86.
let shift_indices =
vec![
bx.cx.const_int(bx.type_ix(in_elem_bitwidth), (in_elem_bitwidth - 1) as _);