Discussion:
aarch64: Use ldurb/sturb for loads/stores with negative offsets
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Martin Storsjö
2017-12-25 19:40:07 UTC
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x264 | branch: master | Martin Storsjö <***@martin.st> | Wed Oct 18 10:40:02 2017 +0300| [99ca611d2e667553e026f487dc787b595dde84c5] | committer: Anton Mitrofanov

aarch64: Use ldurb/sturb for loads/stores with negative offsets

The assembler (both gas and clang/llvm) automatically fixes this,
armasm64 doesn't. We can fix it in gas-preprocessor, but we should
also be using the right instruction form.
http://git.videolan.org/gitweb.cgi/x264.git/?a=commit;h=99ca611d2e667553e026f487dc787b595dde84c5
---

common/aarch64/cabac-a.S | 4 ++--
common/aarch64/predict-a.S | 18 +++++++++++-------
2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/common/aarch64/cabac-a.S b/common/aarch64/cabac-a.S
index c05f963d..70e112f4 100644
--- a/common/aarch64/cabac-a.S
+++ b/common/aarch64/cabac-a.S
@@ -82,10 +82,10 @@ cabac_putbyte:
1:
ldr x7, [x0, #CABAC_P]
asr w5, w4, #8 // carry
- ldrb w8, [x7, #-1]
+ ldurb w8, [x7, #-1]
add w8, w8, w5
sub w5, w5, #1
- strb w8, [x7, #-1]
+ sturb w8, [x7, #-1]
cbz w6, 3f
2:
subs w6, w6, #1
diff --git a/common/aarch64/predict-a.S b/common/aarch64/predict-a.S
index d287b121..c64d6d16 100644
--- a/common/aarch64/predict-a.S
+++ b/common/aarch64/predict-a.S
@@ -63,7 +63,7 @@ endconst


function predict_4x4_h_aarch64, export=1
- ldrb w1, [x0, #0*FDEC_STRIDE-1]
+ ldurb w1, [x0, #0*FDEC_STRIDE-1]
mov w5, #0x01010101
ldrb w2, [x0, #1*FDEC_STRIDE-1]
ldrb w3, [x0, #2*FDEC_STRIDE-1]
@@ -80,7 +80,7 @@ function predict_4x4_h_aarch64, export=1
endfunc

function predict_4x4_v_aarch64, export=1
- ldr w1, [x0, #0 - 1 * FDEC_STRIDE]
+ ldur w1, [x0, #0 - 1 * FDEC_STRIDE]
str w1, [x0, #0 + 0 * FDEC_STRIDE]
str w1, [x0, #0 + 1 * FDEC_STRIDE]
str w1, [x0, #0 + 2 * FDEC_STRIDE]
@@ -90,7 +90,7 @@ endfunc

function predict_4x4_dc_neon, export=1
sub x1, x0, #FDEC_STRIDE
- ldrb w4, [x0, #-1 + 0 * FDEC_STRIDE]
+ ldurb w4, [x0, #-1 + 0 * FDEC_STRIDE]
ldrb w5, [x0, #-1 + 1 * FDEC_STRIDE]
ldrb w6, [x0, #-1 + 2 * FDEC_STRIDE]
ldrb w7, [x0, #-1 + 3 * FDEC_STRIDE]
@@ -430,7 +430,7 @@ function predict_8x8c_dc_top_neon, export=1
endfunc

function predict_8x8c_dc_left_neon, export=1
- ldrb w2, [x0, #0 * FDEC_STRIDE - 1]
+ ldurb w2, [x0, #0 * FDEC_STRIDE - 1]
ldrb w3, [x0, #1 * FDEC_STRIDE - 1]
ldrb w4, [x0, #2 * FDEC_STRIDE - 1]
ldrb w5, [x0, #3 * FDEC_STRIDE - 1]
@@ -455,7 +455,7 @@ endfunc
function predict_8x8c_dc_neon, export=1
mov x1, #FDEC_STRIDE
sub x2, x0, #FDEC_STRIDE
- ldrb w10, [x0, #0 * FDEC_STRIDE - 1]
+ ldurb w10, [x0, #0 * FDEC_STRIDE - 1]
ldrb w11, [x0, #1 * FDEC_STRIDE - 1]
ldrb w12, [x0, #2 * FDEC_STRIDE - 1]
ldrb w13, [x0, #3 * FDEC_STRIDE - 1]
@@ -511,7 +511,7 @@ function predict_8x8c_h_neon, export=1
endfunc

function predict_8x8c_v_aarch64, export=1
- ldr x1, [x0, #-FDEC_STRIDE]
+ ldur x1, [x0, #-FDEC_STRIDE]
.irp c, 0,1,2,3,4,5,6,7
str x1, [x0, #\c * FDEC_STRIDE]
.endr
@@ -568,7 +568,11 @@ endfunc


.macro loadsum4 wd, t1, t2, t3, x, idx
+ .if \idx == 0
+ ldurb \wd, [\x, #(\idx + 0) * FDEC_STRIDE - 1]
+ .else
ldrb \wd, [\x, #(\idx + 0) * FDEC_STRIDE - 1]
+ .endif
ldrb \t1, [\x, #(\idx + 1) * FDEC_STRIDE - 1]
ldrb \t2, [\x, #(\idx + 2) * FDEC_STRIDE - 1]
ldrb \t3, [\x, #(\idx + 3) * FDEC_STRIDE - 1]
@@ -720,7 +724,7 @@ endfunc

function predict_8x16c_dc_left_neon, export=1
mov x1, #FDEC_STRIDE
- ldrb w2, [x0, # 0 * FDEC_STRIDE - 1]
+ ldurb w2, [x0, # 0 * FDEC_STRIDE - 1]
ldrb w3, [x0, # 1 * FDEC_STRIDE - 1]
ldrb w4, [x0, # 2 * FDEC_STRIDE - 1]
ldrb w5, [x0, # 3 * FDEC_STRIDE - 1]

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