[Pixman] [PATCH 2/4] ARMv6: remove 1 instr per row in generate_composite_function

[Pekka Paalanen]

From: Ben Avison <bavison at riscosopen.org>

This knocks off one instruction per row. The effect is probably too small to
be measurable, but might as well be included. The second occurrence of this
sequence doesn't actually benefit at all, but is changed for consistency.

The saved instruction comes from combining the "and" inside the .if
statement with an earlier "tst". The "and" was normally needed, except
for in one special case, where bits 4-31 were all shifted off the top of
the register later on in preload_leading_step2, so we didn't care about
their values.

v4, Pekka Paalanen <pekka.paalanen at collabora.co.uk> :
	Remove "bits 0-3" from the comments, update patch summary, and
	augment message with Ben's suggestion.
---
 pixman/pixman-arm-simd-asm.h | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/pixman/pixman-arm-simd-asm.h b/pixman/pixman-arm-simd-asm.h
index 74400c1..24b1ad2 100644
--- a/pixman/pixman-arm-simd-asm.h
+++ b/pixman/pixman-arm-simd-asm.h
@@ -741,12 +741,9 @@ fname:
         preload_leading_step1  mask_bpp, WK2, MASK
         preload_leading_step1  dst_r_bpp, WK3, DST
         
-        tst     DST, #15
+        ands    WK0, DST, #15
         beq     154f
-        rsb     WK0, DST, #0 /* bits 0-3 = number of leading bytes until destination aligned */
-  .if (src_bpp != 0 && src_bpp != 2*dst_w_bpp) || (mask_bpp != 0 && mask_bpp != 2*dst_w_bpp)
-        PF  and,    WK0, WK0, #15
-  .endif
+        rsb     WK0, WK0, #16 /* number of leading bytes until destination aligned */
 
         preload_leading_step2  src_bpp, src_bpp_shift, WK1, SRC
         preload_leading_step2  mask_bpp, mask_bpp_shift, WK2, MASK
@@ -787,9 +784,9 @@ fname:
         preload_line 0, dst_r_bpp, dst_bpp_shift, DST
         
         sub     X, X, #128/dst_w_bpp     /* simplifies inner loop termination */
-        tst     DST, #15
+        ands    WK0, DST, #15
         beq     164f
-        rsb     WK0, DST, #0 /* bits 0-3 = number of leading bytes until destination aligned */
+        rsb     WK0, WK0, #16 /* number of leading bytes until destination aligned */
         
         leading_15bytes  process_head, process_tail
         
-- 
1.8.3.2