[FFmpeg-devel] [PATCH] arm32/neon: Avoid using bge/beq for function calls

[Rui Ueyama]

It looks like compiler-generated code always uses `b`, `bl` or `blx`
instructions for function calls. These instructions have a 24-bit
immediate and therefore can jump anywhere between PC +- 16 MiB.

This hand-written assembly code instead uses `bge` and `beq` for
interprocedural jumps. Since these instructions have only a 19-bit
immediate (we have less bits for condition code), they can jump only
within PC +- 512 KiB. This sometimes causes a "relocation R_ARM_THM_JUMP19
out of range" error when linked with the mold linker. This error can
easily be avoided by using `b` instead of `bge` or `beq`.

Signed-off-by: Rui Ueyama <rui314 at gmail.com>
---
 libswresample/arm/audio_convert_neon.S | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/libswresample/arm/audio_convert_neon.S
b/libswresample/arm/audio_convert_neon.S
index 085d50aafa..3fe114772c 100644
--- a/libswresample/arm/audio_convert_neon.S
+++ b/libswresample/arm/audio_convert_neon.S
@@ -133,12 +133,13 @@ endfunc

 function swri_oldapi_conv_fltp_to_s16_nch_neon, export=1
         cmp             r3,  #2
-        itt             lt
-        ldrlt           r1,  [r1]
-        blt             .L_swri_oldapi_conv_flt_to_s16_neon
-        beq             .L_swri_oldapi_conv_fltp_to_s16_2ch_neon
+        bgt             2f
+        beq             1f
+        ldr             r1,  [r1]
+        b               .L_swri_oldapi_conv_flt_to_s16_neon
+1:      b               .L_swri_oldapi_conv_fltp_to_s16_2ch_neon

-        push            {r4-r8, lr}
+2:      push            {r4-r8, lr}
         cmp             r3,  #4
         lsl             r12, r3,  #1
         blt             4f
--
2.34.1