[RFC PATCH 1/4] ntdll: Consolidate 2 STRs into 1 STRD in ARM syscall dispatcher.

[Jinoh Kang]

STRD is an ARMv7 instruction that stores two consecutive 32-bit words in
one operation.  A single STRD saves one clock cycle compared to two
LDRs.  Shortened code also leads to less time spent on instruction fetch
and more efficient I-cache utilization.

Running llvm-mca --timeline on the old code reports:
                    0123
Index     0123456789

[0,0]     DeeeeER   .  .   ldr.w r1, [r1, #472]
[0,1]     D====eER  .  .   add.w r0, r1, #16
[0,2]     D=====eeeeeER.   stm.w r0, {r4, r5, r6, r7, r8, r9, r10, r11, r12, lr}
[0,3]     .DeE--------R.   add   r2, sp, #16
[0,4]     .D=====eE---R.   str   r2, [r1, #56]
[0,5]     .D======eE--R.   str   r3, [r1, #60]
[0,6]     . D---------R.   mrs   r0, apsr
[0,7]     . DeeE------R.   bfi   r0, lr, #5, #1
[0,8]     . D======eE-R.   str   r0, [r1, #64]
[0,9]     . DeE-------R.   mov.w r0, #0
[0,10]    .  D======eER.   str   r0, [r1, #68]
[0,11]    .  D======E-R.   vmrs  r0, fpscr
[0,12]    .  D=======eER   str   r0, [r1, #72]
[0,13]    .  D=eE------R   add.w r0, r1, #96

Running llvm-mca --timeline on the new code reports:
                    012
Index     0123456789

[0,0]     DeeeeER   . .   ldr.w r1, [r1, #472]
[0,1]     D====eER  . .   add.w r0, r1, #16
[0,2]     D=====eeeeeER   stm.w r0, {r4, r5, r6, r7, r8, r9, r10, r11, r12, lr}
[0,3]     .DeE--------R   add   r2, sp, #16
[0,4]     .D=====eE---R   strd  r2, r3, [r1, #56]
[0,5]     .D----------R   mrs   r0, apsr
[0,6]     .DeeE-------R   bfi   r0, lr, #5, #1
[0,7]     . D=====eE--R   str   r0, [r1, #64]
[0,8]     . DeE-------R   mov.w r0, #0
[0,9]     . D======eE-R   str   r0, [r1, #68]
[0,10]    .  D=====E--R   vmrs  r0, fpscr
[0,11]    .  D======eER   str   r0, [r1, #72]
[0,12]    .  D=eE-----R   add.w r0, r1, #96

Signed-off-by: Jinoh Kang <jinoh.kang.kr at gmail.com>
---
 dlls/ntdll/unix/signal_arm.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/dlls/ntdll/unix/signal_arm.c b/dlls/ntdll/unix/signal_arm.c
index a1bcb0ddd32..8c8750153df 100644
--- a/dlls/ntdll/unix/signal_arm.c
+++ b/dlls/ntdll/unix/signal_arm.c
@@ -1157,8 +1157,7 @@ __ASM_GLOBAL_FUNC( __wine_syscall_dispatcher,
                    "add r0, r1, #0x10\n\t"
                    "stm r0, {r4-r12,lr}\n\t"
                    "add r2, sp, #0x10\n\t"
-                   "str r2, [r1, #0x38]\n\t"
-                   "str r3, [r1, #0x3c]\n\t"
+                   "strd r2, r3, [r1, #0x38]\n\t"
                    "mrs r0, CPSR\n\t"
                    "bfi r0, lr, #5, #1\n\t"         /* set thumb bit */
                    "str r0, [r1, #0x40]\n\t"
-- 
2.35.1