diff --git a/libc/src/string/memory_utils/op_aarch64.h b/libc/src/string/memory_utils/op_aarch64.h index e552601fbb708..b5c3bb74e7418 100644 --- a/libc/src/string/memory_utils/op_aarch64.h +++ b/libc/src/string/memory_utils/op_aarch64.h @@ -84,8 +84,7 @@ template struct Bcmp { uint8x16_t a = vld1q_u8(_p1); uint8x16_t n = vld1q_u8(_p2); uint8x16_t an = veorq_u8(a, n); - uint32x2_t an_reduced = vqmovn_u64(vreinterpretq_u64_u8(an)); - return vmaxv_u32(an_reduced); + return vmaxvq_u32(vreinterpretq_u32_u8(an)); } else if constexpr (Size == 32) { auto _p1 = as_u8(p1); auto _p2 = as_u8(p2); @@ -97,12 +96,9 @@ template struct Bcmp { uint8x16_t bo = veorq_u8(b, o); // anbo = (a ^ n) | (b ^ o). At least one byte is nonzero if there is // a difference between the two buffers. We reduce this value down to 4 - // bytes in two steps. First, calculate the saturated move value when - // going from 2x64b to 2x32b. Second, compute the max of the 2x32b to get - // a single 32 bit nonzero value if a mismatch occurred. + // bytes using the UMAXV instruction to compute the max across the vector. uint8x16_t anbo = vorrq_u8(an, bo); - uint32x2_t anbo_reduced = vqmovn_u64(vreinterpretq_u64_u8(anbo)); - return vmaxv_u32(anbo_reduced); + return vmaxvq_u32(vreinterpretq_u32_u8(anbo)); } else if constexpr ((Size % BlockSize) == 0) { for (size_t offset = 0; offset < Size; offset += BlockSize) if (auto value = Bcmp::block(p1 + offset, p2 + offset)) @@ -129,8 +125,7 @@ template struct Bcmp { uint8x16_t bo = veorq_u8(b, o); // anbo = (a ^ n) | (b ^ o) uint8x16_t anbo = vorrq_u8(an, bo); - uint32x2_t anbo_reduced = vqmovn_u64(vreinterpretq_u64_u8(anbo)); - return vmaxv_u32(anbo_reduced); + return vmaxvq_u32(vreinterpretq_u32_u8(anbo)); } else if constexpr (Size == 32) { auto _p1 = as_u8(p1); auto _p2 = as_u8(p2); @@ -150,9 +145,8 @@ template struct Bcmp { uint8x16_t cpdq = vorrq_u8(cp, dq); // abnocpdq = ((a ^ n) | (b ^ o)) | ((c ^ p) | (d ^ q)). Reduce this to // a nonzero 32 bit value if a mismatch occurred. - uint64x2_t abnocpdq = vreinterpretq_u64_u8(anbo | cpdq); - uint32x2_t abnocpdq_reduced = vqmovn_u64(abnocpdq); - return vmaxv_u32(abnocpdq_reduced); + uint8x16_t abnocpdq = anbo | cpdq; + return vmaxvq_u32(vreinterpretq_u32_u8(abnocpdq)); } else { static_assert(cpp::always_false, "SIZE not implemented"); }