tests: update prng.inc

Author: jakubfi

tests/functional/addr/random.asm

@@ -91,7 +91,7 @@ dfill:
 	lw	r5, 0xf000
 floop:
 	rd	r5+r3
-	lj	rand
+	lj	urand
 	awt	r3, 2
 	cw	r3, 0x1000
 	jl	floop
@@ -190,7 +190,7 @@ loop:
 
 ; next address
 	awt	r3, 1
-	lj	rand
+	lj	urand
 	awt	r3, 1
 	cw	r3, 0x1000
 	jls	loop

tests/functional/cchar/flop8-poll-write-positioned.asm

@@ -195,7 +195,7 @@ gen_randoms:
 	lw	r6, write_positions
 .loop:
 
-	lj	rand
+	lj	urand
 	rw	r1, r6+1
 
 	awt	r6, 2

tests/functional/iotester/mem-rw-loop.asm

@@ -30,7 +30,7 @@ mask_ch:.word	IMASK_ALL_CH
 reconfigure_mem:
 	.res	1
 
-	lj	rand ; [r1, r2] = random
+	lj	urand ; [r1, r2] = random
 
 .page14:
 	lw	r3, 14\MEM_PAGE | 0\MEM_SEGMENT ; logical address specification
@@ -57,7 +57,7 @@ reconfigure_mem:
 randomize:
 	.res	1
 
-	lj	rand
+	lj	urand
 
 	nr	r1, 0x0fff ; r1 = random offset
 	rw	r1, offset
@@ -83,7 +83,7 @@ randomize:
 rnd_fill:
 	.res	1
 
-	lj	rand ; r1 = initial random
+	lj	urand ; r1 = initial random
 
 	lw	r5, 0xe000 - 1
 	aw	r5, [offset]

tests/functional/multix/winch-transmit-basic.asm

@@ -180,7 +180,7 @@ fill:	; fill write buffer with random data
 	lw	r4, wrbuf
 	lw	r3, SSIZE/2
 fill_loop:
-	lj	rand
+	lj	urand
 	rd	r4
 	awt	r4, 2
 	drb	r3, fill_loop

tests/include/prng.inc

@@ -28,7 +28,6 @@ im_tm:	.word	IMASK_GROUP_H
 im_0:	.word	0
 otimv:	.res	1
 ostck:	.res	1
-cseed:	.dword	1
 prngseed:
 	.res	1
 	lwt	r1, 0
@@ -53,7 +52,7 @@ rngloop:
 	jes	prngseed_fin
 	ujs	rngloop
 prngseed_fin:
-	rd	cseed
+	rd	urand.seed
 	im	im_0
 	lw	r4, [otimv]
 	rw	r4, INTV_TIMER
@@ -62,57 +61,62 @@ prngseed_fin:
 	uj	[prngseed]
 
 ; ------------------------------------------------------------------------
-; Park-Miller-Carta Pseudo-Random Number Generator implementation for MERA-400
-; out: [r1, r2] - random 32-bit number
-; temp: r3
-	.const	constapmc 16807
-lo:	.res	2
-hi:	.res	2
-tmp_r3:	.res	1
+; Park-Miller-Carta pseudo-random number generator implementation for MERA-400
+;
+; RETURN: [r1, r2] - random 31-bit number
+urand:	.res	1
+	lw	r1, [.seed+1]
+	sxu	r1		; set X if low seed is negative
+
+	; lo = cpmc * (seed & 0xFFFF)
+	lw	r2, .cpmc
+	mw	.seed+1
+	; correct for signed multiply if low seed was negative
+	brc	?X
+	ad	.ufix
+	rd	.lo
+
+	; hi = cpmc * (seed >> 16)
+	lw	r2, .cpmc
+	mw	.seed
+	rd	.hi
 
-rand:	.res	1
-	rw	r3, tmp_r3
-	; lo = self.constapmc * (self.seed & 0xFFFF)
-	lw	r2, constapmc
-	mw	cseed+1
-	rd	lo
-	; hi = self.constapmc * (self.seed >> 16)
-	lw	r2, constapmc
-	mw	cseed
-	rd	hi
 	; lo += (hi & 0x7FFF) << 16
-	lw	r1, [hi+1]
-	er	r1, 1\0
+	lw	r1, [.hi+1]
+	nr	r1, 0x7fff
 	lwt	r2, 0
-	ad	lo
-	rd	lo
+	ad	.lo
+	rd	.lo
+
 	; lo += hi >> 15
-	lwt	r1, 0
-	lw	r2, [hi]
-	lw	r3, [hi+1]
-	slz	r3
+	lw	r2, [.hi]
+	lw	r1, [.hi+1]	; r1 just for temporary use here
+	slz	r1		; just to set Y to .hi+1's MSB
 	sly	r2
-	sly	r1
-	ad	lo
-	; lo = (lo & 0x7FFFFFFF) + (lo >> 31);
-	sxu	r1
-	er	r1, 1\0
-	rd	lo
 	lwt	r1, 0
-	lwt	r2, 0
-	slx	r2
-	ad	lo
-	; self.seed = lo
-	rd	cseed
-	; return lo
-	lw	r3, [tmp_r3]
-	uj	[rand]
+	sly	r1
+	ad	.lo
+
+	; if (lo > 0x7FFFFFFF) lo -= 0x7FFFFFFF
+	blc	?M
+	sd	.fix
+.done:
+	; seed = lo
+	rd	.seed
+	uj	[urand]
+
+	.const	.cpmc 16807
+.seed:	.dword	1
+.fix:	.dword	0x7fffffff
+.ufix:	.dword	0x10000 * .cpmc
+.lo:	.res	2
+.hi:	.res	2
 
 ; ------------------------------------------------------------------------
 ; Seed the PRNG
 ; in: [r1, r2] - seed
 seed:	.res	1
-	rd	cseed
+	rd	urand.seed
 	uj	[seed]
 
 prng_stack: