Rollup merge of #146290 - heiher:r-src-analysis-lsx, r=lqd

Revert "Add LSX accelerated implementation for source file analysis"

This reverts commit 5b43244 to fix native build failures on LoongArch.

Link: #145963 (comment)
Link: #145963 (comment)

Author: matthiaskrgr

compiler/rustc_span/src/analyze_source_file.rs

@@ -81,8 +81,8 @@ cfg_select! {
                 // use `loadu`, which supports unaligned loading.
                 let chunk = unsafe { _mm_loadu_si128(chunk.as_ptr() as *const __m128i) };
 
-                // For each character in the chunk, see if its byte value is < 0,
-                // which indicates that it's part of a UTF-8 char.
+                // For character in the chunk, see if its byte value is < 0, which
+                // indicates that it's part of a UTF-8 char.
                 let multibyte_test = _mm_cmplt_epi8(chunk, _mm_set1_epi8(0));
                 // Create a bit mask from the comparison results.
                 let multibyte_mask = _mm_movemask_epi8(multibyte_test);
@@ -132,111 +132,8 @@ cfg_select! {
             }
         }
     }
-    target_arch = "loongarch64" => {
-        fn analyze_source_file_dispatch(
-            src: &str,
-            lines: &mut Vec<RelativeBytePos>,
-            multi_byte_chars: &mut Vec<MultiByteChar>,
-        ) {
-            use std::arch::is_loongarch_feature_detected;
-
-            if is_loongarch_feature_detected!("lsx") {
-                unsafe {
-                    analyze_source_file_lsx(src, lines, multi_byte_chars);
-                }
-            } else {
-                analyze_source_file_generic(
-                    src,
-                    src.len(),
-                    RelativeBytePos::from_u32(0),
-                    lines,
-                    multi_byte_chars,
-                );
-            }
-        }
-
-        /// Checks 16 byte chunks of text at a time. If the chunk contains
-        /// something other than printable ASCII characters and newlines, the
-        /// function falls back to the generic implementation. Otherwise it uses
-        /// LSX intrinsics to quickly find all newlines.
-        #[target_feature(enable = "lsx")]
-        unsafe fn analyze_source_file_lsx(
-            src: &str,
-            lines: &mut Vec<RelativeBytePos>,
-            multi_byte_chars: &mut Vec<MultiByteChar>,
-        ) {
-            use std::arch::loongarch64::*;
-
-            const CHUNK_SIZE: usize = 16;
-
-            let (chunks, tail) = src.as_bytes().as_chunks::<CHUNK_SIZE>();
-
-            // This variable keeps track of where we should start decoding a
-            // chunk. If a multi-byte character spans across chunk boundaries,
-            // we need to skip that part in the next chunk because we already
-            // handled it.
-            let mut intra_chunk_offset = 0;
-
-            for (chunk_index, chunk) in chunks.iter().enumerate() {
-                // All LSX memory instructions support unaligned access, so using
-                // vld is fine.
-                let chunk = unsafe { lsx_vld::<0>(chunk.as_ptr() as *const i8) };
-
-                // For each character in the chunk, see if its byte value is < 0,
-                // which indicates that it's part of a UTF-8 char.
-                let multibyte_mask = lsx_vmskltz_b(chunk);
-                // Create a bit mask from the comparison results.
-                let multibyte_mask = lsx_vpickve2gr_w::<0>(multibyte_mask);
-
-                // If the bit mask is all zero, we only have ASCII chars here:
-                if multibyte_mask == 0 {
-                    assert!(intra_chunk_offset == 0);
-
-                    // Check for newlines in the chunk
-                    let newlines_test = lsx_vseqi_b::<{b'\n' as i32}>(chunk);
-                    let newlines_mask = lsx_vmskltz_b(newlines_test);
-                    let mut newlines_mask = lsx_vpickve2gr_w::<0>(newlines_mask);
-
-                    let output_offset = RelativeBytePos::from_usize(chunk_index * CHUNK_SIZE + 1);
-
-                    while newlines_mask != 0 {
-                        let index = newlines_mask.trailing_zeros();
-
-                        lines.push(RelativeBytePos(index) + output_offset);
-
-                        // Clear the bit, so we can find the next one.
-                        newlines_mask &= newlines_mask - 1;
-                    }
-                } else {
-                    // The slow path.
-                    // There are multibyte chars in here, fallback to generic decoding.
-                    let scan_start = chunk_index * CHUNK_SIZE + intra_chunk_offset;
-                    intra_chunk_offset = analyze_source_file_generic(
-                        &src[scan_start..],
-                        CHUNK_SIZE - intra_chunk_offset,
-                        RelativeBytePos::from_usize(scan_start),
-                        lines,
-                        multi_byte_chars,
-                    );
-                }
-            }
-
-            // There might still be a tail left to analyze
-            let tail_start = src.len() - tail.len() + intra_chunk_offset;
-            if tail_start < src.len() {
-                analyze_source_file_generic(
-                    &src[tail_start..],
-                    src.len() - tail_start,
-                    RelativeBytePos::from_usize(tail_start),
-                    lines,
-                    multi_byte_chars,
-                );
-            }
-        }
-    }
     _ => {
-        // The target (or compiler version) does not support vector instructions
-        // our specialized implementations need (x86 SSE2, loongarch64 LSX)...
+        // The target (or compiler version) does not support SSE2 ...
         fn analyze_source_file_dispatch(
             src: &str,
             lines: &mut Vec<RelativeBytePos>,

compiler/rustc_span/src/lib.rs

@@ -18,7 +18,6 @@
 // tidy-alphabetical-start
 #![allow(internal_features)]
 #![cfg_attr(bootstrap, feature(round_char_boundary))]
-#![cfg_attr(target_arch = "loongarch64", feature(stdarch_loongarch))]
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![doc(rust_logo)]
 #![feature(array_windows)]