arm: vp9itxfm: Make the larger core transforms standalone functions

This work is sponsored by, and copyright, Google.

This reduces the code size of libavcodec/arm/vp9itxfm_neon.o from
15324 to 12388 bytes.

This gives a small slowdown of a couple tens of cycles, up to around
150 cycles for the full case of the largest transform, but makes
it more feasible to add more optimized versions of these transforms.

Before:                              Cortex A7       A8       A9      A53
vp9_inv_dct_dct_16x16_sub4_add_neon:    2063.4   1516.0   1719.5   1245.1
vp9_inv_dct_dct_16x16_sub16_add_neon:   3279.3   2454.5   2525.2   1982.3
vp9_inv_dct_dct_32x32_sub4_add_neon:   10750.0   7955.4   8525.6   6754.2
vp9_inv_dct_dct_32x32_sub32_add_neon:  18574.0  17108.4  14216.7  12010.2

After:
vp9_inv_dct_dct_16x16_sub4_add_neon:    2060.8   1608.5   1735.7   1262.0
vp9_inv_dct_dct_16x16_sub16_add_neon:   3211.2   2443.5   2546.1   1999.5
vp9_inv_dct_dct_32x32_sub4_add_neon:   10682.0   8043.8   8581.3   6810.1
vp9_inv_dct_dct_32x32_sub32_add_neon:  18522.4  17277.4  14286.7  12087.9

Signed-off-by: Martin Storsjö <martin@martin.st>

libavcodec/arm/vp9itxfm_neon.S

@@ -534,7 +534,7 @@ function idct16x16_dc_add_neon
 endfunc
 .ltorg
 
-.macro idct16
+function idct16
         mbutterfly0     d16, d24, d16, d24, d4, d6,  q2,  q3 @ d16 = t0a,  d24 = t1a
         mbutterfly      d20, d28, d0[1], d0[2], q2,  q3  @ d20 = t2a,  d28 = t3a
         mbutterfly      d18, d30, d0[3], d1[0], q2,  q3  @ d18 = t4a,  d30 = t7a
@@ -580,9 +580,10 @@ endfunc
         vmov            d4,  d21                         @ d4  = t10a
         butterfly       d20, d27, d6,  d27               @ d20 = out[4], d27 = out[11]
         butterfly       d21, d26, d26, d4                @ d21 = out[5], d26 = out[10]
-.endm
+        bx              lr
+endfunc
 
-.macro iadst16
+function iadst16
         movrel          r12, iadst16_coeffs
         vld1.16         {q0-q1}, [r12,:128]
 
@@ -653,7 +654,8 @@ endfunc
 
         vmov            d16, d2
         vmov            d30, d4
-.endm
+        bx              lr
+endfunc
 
 .macro itxfm16_1d_funcs txfm
 @ Read a vertical 4x16 slice out of a 16x16 matrix, do a transform on it,
@@ -662,6 +664,8 @@ endfunc
 @ r1 = slice offset
 @ r2 = src
 function \txfm\()16_1d_4x16_pass1_neon
+        push            {lr}
+
         mov             r12, #32
         vmov.s16        q2, #0
 .irp i, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31
@@ -669,7 +673,7 @@ function \txfm\()16_1d_4x16_pass1_neon
         vst1.16         {d4},  [r2,:64], r12
 .endr
 
-        \txfm\()16
+        bl              \txfm\()16
 
         @ Do four 4x4 transposes. Originally, d16-d31 contain the
         @ 16 rows. Afterwards, d16-d19, d20-d23, d24-d27, d28-d31
@@ -682,7 +686,7 @@ function \txfm\()16_1d_4x16_pass1_neon
 .irp i, 16, 20, 24, 28, 17, 21, 25, 29, 18, 22, 26, 30, 19, 23, 27, 31
         vst1.16         {d\i}, [r0,:64]!
 .endr
-        bx              lr
+        pop             {pc}
 1:
         @ Special case: For the last input column (r1 == 12),
         @ which would be stored as the last row in the temp buffer,
@@ -709,7 +713,7 @@ function \txfm\()16_1d_4x16_pass1_neon
         vmov            d29, d17
         vmov            d30, d18
         vmov            d31, d19
-        bx              lr
+        pop             {pc}
 endfunc
 
 @ Read a vertical 4x16 slice out of a 16x16 matrix, do a transform on it,
@@ -719,6 +723,7 @@ endfunc
 @ r2 = src (temp buffer)
 @ r3 = slice offset
 function \txfm\()16_1d_4x16_pass2_neon
+        push            {lr}
         mov             r12, #32
 .irp i, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27
         vld1.16         {d\i}, [r2,:64], r12
@@ -732,7 +737,7 @@ function \txfm\()16_1d_4x16_pass2_neon
 
         add             r3,  r0,  r1
         lsl             r1,  r1,  #1
-        \txfm\()16
+        bl              \txfm\()16
 
 .macro load_add_store coef0, coef1, coef2, coef3
         vrshr.s16       \coef0, \coef0, #6
@@ -773,7 +778,7 @@ function \txfm\()16_1d_4x16_pass2_neon
         load_add_store  q12, q13, q14, q15
 .purgem load_add_store
 
-        bx              lr
+        pop             {pc}
 endfunc
 .endm
 
@@ -908,7 +913,7 @@ function idct32x32_dc_add_neon
         bx              lr
 endfunc
 
-.macro idct32_odd
+function idct32_odd
         movrel          r12, idct_coeffs
         add             r12, r12, #32
         vld1.16         {q0-q1}, [r12,:128]
@@ -967,7 +972,8 @@ endfunc
         mbutterfly0     d26, d21, d26, d21, d4, d6, q2, q3 @ d26 = t26a, d21 = t21a
         mbutterfly0     d25, d22, d25, d22, d4, d6, q2, q3 @ d25 = t25,  d22 = t22
         mbutterfly0     d24, d23, d24, d23, d4, d6, q2, q3 @ d24 = t24a, d23 = t23a
-.endm
+        bx              lr
+endfunc
 
 @ Do an 32-point IDCT of a 4x32 slice out of a 32x32 matrix.
 @ We don't have register space to do a single pass IDCT of 4x32 though,
@@ -979,6 +985,8 @@ endfunc
 @ r1 = unused
 @ r2 = src
 function idct32_1d_4x32_pass1_neon
+        push            {lr}
+
         movrel          r12, idct_coeffs
         vld1.16         {q0-q1}, [r12,:128]
 
@@ -992,7 +1000,7 @@ function idct32_1d_4x32_pass1_neon
         vst1.16         {d4},  [r2,:64], r12
 .endr
 
-        idct16
+        bl              idct16
 
         @ Do four 4x4 transposes. Originally, d16-d31 contain the
         @ 16 rows. Afterwards, d16-d19, d20-d23, d24-d27, d28-d31
@@ -1028,7 +1036,7 @@ function idct32_1d_4x32_pass1_neon
         vst1.16         {d4},  [r2,:64], r12
 .endr
 
-        idct32_odd
+        bl              idct32_odd
 
         transpose16_q_4x_4x4 q15, q14, q13, q12, q11, q10, q9,  q8,  d31, d30, d29, d28, d27, d26, d25, d24, d23, d22, d21, d20, d19, d18, d17, d16
 
@@ -1054,7 +1062,7 @@ function idct32_1d_4x32_pass1_neon
         store_rev       29, 25, 21, 17
         store_rev       28, 24, 20, 16
 .purgem store_rev
-        bx              lr
+        pop             {pc}
 endfunc
 .ltorg
 
@@ -1065,6 +1073,7 @@ endfunc
 @ r1 = dst stride
 @ r2 = src (temp buffer)
 function idct32_1d_4x32_pass2_neon
+        push            {lr}
         movrel          r12, idct_coeffs
         vld1.16         {q0-q1}, [r12,:128]
 
@@ -1075,7 +1084,7 @@ function idct32_1d_4x32_pass2_neon
 .endr
         sub             r2,  r2,  r12, lsl #4
 
-        idct16
+        bl              idct16
 
 .irp i, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31
         vst1.16         {d\i}, [r2,:64], r12
@@ -1091,7 +1100,7 @@ function idct32_1d_4x32_pass2_neon
         sub             r2,  r2,  r12, lsl #4
         sub             r2,  r2,  #64
 
-        idct32_odd
+        bl              idct32_odd
 
         mov             r12, #128
 .macro load_acc_store a, b, c, d, neg=0
@@ -1139,7 +1148,7 @@ function idct32_1d_4x32_pass2_neon
         load_acc_store  24, 25, 26, 27, 1
         load_acc_store  28, 29, 30, 31, 1
 .purgem load_acc_store
-        bx              lr
+        pop             {pc}
 endfunc
 
 const min_eob_idct_idct_32, align=4