quake: clean up asm mixer

Fixes my ugly formatting.

1 files changed, 46 insertions, 63 deletions

diff --git a/apps/plugins/sdl/progs/quake/snd_mix_arm.S b/apps/plugins/sdl/progs/quake/snd_mix_arm.S
index 15733d8912..0573e85923 100644
--- a/apps/plugins/sdl/progs/quake/snd_mix_arm.S
+++ b/apps/plugins/sdl/progs/quake/snd_mix_arm.S
@@ -19,12 +19,14 @@
  *
  ***************************************************************************/
 
-        /** Sound mixing code for ARM. **/
-        /* Takes 8-bit mono audio and outputs stereo 16-bit samples.
-         * stereo volumes are passed as arguments.
-         *
-         * Bear with me. This is my first ARM assembly, ever.
-        */
+	/*
+	 * Sound mixing code for ARM.
+	 *
+	 * Takes an array of 8-bit mono audio and outputs stereo 16-bit
+	 * samples. Stereo volumes are passed as arguments r0 and r1.
+	 *
+	 * Bear with me. This is my first ARM assembly, ever.
+	 */
 
         .text
         .align  2
@@ -33,93 +35,74 @@
 
 #if defined(__ARM_ARCH_5TEJ__)
 SND_PaintChannelFrom8:
-        // r0: int true_lvol
-        // r1: int true_rvol
-        // r2: char *sfx
-        // r3: int count
+        ;; r0: int true_lvol
+        ;; r1: int true_rvol
+        ;; r2: char *sfx
+        ;; r3: int count
 
         stmfd sp!, {r4, r5, r6, r7, r8, sl}
 
         ldr ip, =paintbuffer
         ldr ip, [ip]
 
-        mov r0, r0, asl #16 // pre-scale both volumes by 2^16
+        mov r0, r0, asl #16					; prescale by 2^16
         mov r1, r1, asl #16
 
-        sub r3, r3, #1 // we'll count backwards
-        // sl = 0xffff0000
-        ldrh sl, =0xffff
+        sub r3, r3, #1						; count backwards
 
-.loop:
-        ldrsb r4, [r2, r3] // load *sfx[i] -> r4
+        ldrh sl, =0xffff 					; halfword mask
 
-        // keep endianness in mind here
-        // buffer looks like [left_0, left_1, right_0, right_1] in memory
-        // but it is loaded as [right1, right0, left1, left0] to registers
-        ldr r8, [ip, r3, lsl #2] // load paintbuffer[0:1] = RIGHTCHANNEL:LEFTCHANNEL
+1:
+        ldrsb r4, [r2, r3]					; load input sample
+        ldr r8, [ip, r3, lsl #2]				; load output sample pair from paintbuffer
+								; (left:right in memory -> right:left in register)
+        ;; right channel (high half)
+        mul r5, r4, r1						; scaledright = sfx[i] * (true_rvol << 16) -- bottom half is zero
+        qadd r7, r5, r8						; right = scaledright + right (in high half of word)
+        bic r7, r7, sl						; zero bottom half of r7
 
-        // handle high half (right channel) first
-        mul r5, r4, r1 // SCALEDRIGHT = SFXI * (true_rvol << 16) -- bottom half is zero
+        ;; left channel (low half)
+        mul r5, r4, r0						; scaledleft = sfx[i] * (true_rvol << 16)
+        mov r8, r8, lsl #16					; extract original left channel from paintbuffer
+        qadd r8, r5, r8						; left = scaledleft + left
 
-        // r7 holds right channel in high half (dirty bottom half)
-        qadd r7, r5, r8 // RIGHTCHANORIG = SCALEDRIGHT + RIGHTCHANORIG (high half)
-
-        bic r7, r7, sl // zero bottom bits of r7
-
-        // trash r5, r6 and handle left channel
-        mul r5, r4, r0 // SCALEDLEFT = SFXI * (true_rvol << 16)
-
-        mov r8, r8, lsl #16 // extract original left channel from paintbuffer
-
-        // r8 holds left channel in high half with zero bottom half
-        qadd r8, r5, r8
-
-        // combine the two 16-bit samples in r7 as 32-bit [left:right]
-        // (use lsr to not sign-extend the lower half)
-        orr r7, r7, r8, lsr #16
-
-        str r7, [ip, r3, lsl #2] // write 32-bit to paintbuffer
+        orr r7, r7, r8, lsr #16					; combine right:left in r7
+        str r7, [ip, r3, lsl #2]				; write right:left to output buffer
         subs r3, r3, #1
-        bgt .loop // must use instead of bne because of the corner case count=1
-
 
+        bgt 1b							; must use bgt instead of bne in case count=1
 
         ldmfd sp!, {r4, r5, r6, r7, r8, sl}
 
         bx lr
 
-#elif defined(__ARM_ARCH_6__) // ARMv6 with QADD16 (disabled)
+#elif defined(__ARM_ARCH_6__) ; ARMv6 with QADD16 (disabled)
 SND_PaintChannelFrom8:
-        // r0: int true_lvol
-        // r1: int true_rvol
-        // r2: char *sfx
-        // r3: int count
+        ;; r0: int true_lvol
+        ;; r1: int true_rvol
+        ;; r2: char *sfx
+        ;; r3: int count
 
         stmfd sp!, {r4, r5, r6, r7}
 
         ldr ip, =paintbuffer
-        ldr ip, [ip]
-        sub r3, r3, #1 // we'll count backwards
-.loop:
-        ldrsb r4, [r2, r3] // load *sfx[i] -> r4
-
-        // keep endianness in mind here
-        // buffer looks like [left_0, left_1, right_0, right_1] in memory
-        // but it is loaded as [right1, right0, left1, left0] to registers
-        ldr r7, [ip, r3, lsl #2] // load paintbuffer[0:1] = RIGHTCHANNEL:LEFTCHANNEL
+        ldr ip, [ip]						; load paintbuffer address
+        sub r3, r3, #1						; we'll count backwards
+1:
+        ldrsb r4, [r2, r3]					; load sfx[i] -> r4
+	ldr r7, [ip, r3, lsl #2]				; load old sample pair
 
-        // handle high half (right channel) first
-        mul r5, r4, r1 // SCALEDRIGHT = SFXI * true_rvol
-        mul r6, r4, r0 // SCALEDLEFT = SFXI * true_rvol
+        mul r5, r4, r1 						; SCALEDRIGHT = SFXI * true_rvol
+        mul r6, r4, r0						; SCALEDLEFT = SFXI * true_rvol
 
-        orr r6, r6, r5, lsl #16
+        orr r6, r6, r5, lsl #16					; combine samples as 32-bit
 
-        qadd16 r6, r6, r7
+        qadd16 r6, r6, r7					; parallel 16-bit add
 
-        str r6, [ip, r3, lsl #2] // write 32-bit to paintbuffer
+        str r6, [ip, r3, lsl #2]				; write 32-bit to paintbuffer
 
         subs r3, r3, #1
-        bne .loop
+        bgt 1b
 
         ldmfd sp!, {r4, r5, r6, r7}