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commit 91130730f418b6057e7e976e13611e910dc6b789
Author: Cedric BAIL <[email protected]>
AuthorDate: Mon Aug 3 13:50:34 2026 -0600
termpty: vectorise the autowrapped marking of saved rows
Every row that scrolls into the backlog is walked to flag its cells as
continuing onto the next line. GCC already compiles that to five instructions
per cell -- load the bitfield word, or, store back, advance twelve bytes,
test -- so there was nothing left to gain from rewriting it scalar.
A twelve-byte stride lines up with a sixteen-byte vector every four cells, so
the mask repeats every forty-eight bytes and can be applied as three fixed
vectors, a little over two instructions per cell.
Which byte carries att.autowrapped depends on how the compiler lays out
Termatt's bitfields, so it is worked out once from a cell that has the bit
set. Hardcoding the offset would have been quietly invalidated by any change
to Termatt.
The marking cannot be folded into the copy that follows it:
termpty_text_scroll() only clears the row it just saved when asked to, so the
source has to keep its marks, and glibc's memcpy is already cheap enough that
fusing the two passes would not pay for itself.
Co-Authored-By: Claude Opus 5 <[email protected]>
---
src/bin/termpty.c | 39 ++++++++++++++++++++++++++++++++++-----
1 file changed, 34 insertions(+), 5 deletions(-)
diff --git a/src/bin/termpty.c b/src/bin/termpty.c
index 829eb9bd..9ba8382c 100644
--- a/src/bin/termpty.c
+++ b/src/bin/termpty.c
@@ -990,11 +990,42 @@ termpty_line_length(const Termcell *cells, ssize_t nb_cells)
}
+/* Flag a run of cells as continuing onto the next line. The byte carrying
+ * att.autowrapped depends on the compiler's bitfield layout, so it is worked
+ * out once from a cell that has the bit set. */
+static void
+_mark_autowrapped(Termcell *cells, ssize_t n)
+{
+ static size_t off;
+ static unsigned char bit;
+
+ if (EINA_UNLIKELY(bit == 0))
+ {
+ Termcell probe;
+ size_t i;
+
+ memset(&probe, 0, sizeof(probe));
+ probe.att.autowrapped = 1;
+ for (i = 0; i < sizeof(probe); i++)
+ {
+ if (((const unsigned char *)&probe)[i])
+ {
+ off = i;
+ bit = ((const unsigned char *)&probe)[i];
+ break;
+ }
+ }
+ assert(bit != 0);
+ }
+
+ simd_records_or_byte(cells, (size_t)n, sizeof(Termcell), off, bit);
+}
+
void
termpty_text_save_top(Termpty *ty, Termcell *cells, ssize_t w_max)
{
Termsave *ts;
- ssize_t w, i;
+ ssize_t w;
if (ty->backsize == 0)
return;
@@ -1003,10 +1034,8 @@ termpty_text_save_top(Termpty *ty, Termcell *cells, ssize_t w_max)
termpty_backlog_lock();
w = termpty_line_length(cells, w_max);
- for (i = 0; i < w - 1; i++)
- {
- cells[i].att.autowrapped = 1;
- }
+ if (w > 1)
+ _mark_autowrapped(cells, w - 1);
if (ty->backsize > 0)
{
ts = BACKLOG_ROW_GET(ty, 1);
--
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