sim: pru: Fix emulation of carry bit

The PRU architecture documentation [1] was used for the initial GNU
simulator implementation.  But recently [2] TI confirmed the carry
behaviour was wrongly documented.  In reality, the PRU carry behaves
like the carry in ARM processors.

This patch fixes simulator to align with latest recommendations from TI.

The new carry.s test was also validated to pass on real hardware -
a BeaglePlay board [3].  That test is a bit long because TI still
has not released official updates for the PRU documents.  And I wanted
to ensure simulator handles all edge cases exactly as the real hardware
does.

[1] https://www.ti.com/lit/pdf/spruij2
[2] https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1244359/sk-am64b-am64x-pru-assembler-how-works-this-bloody-carry
[3] https://www.beagleboard.org/boards/beagleplay

Signed-off-by: Dimitar Dimitrov <dimitar@dinux.eu>

2 files changed, 424 insertions, 4 deletions

diff --git a/sim/pru/pru.isa b/sim/pru/pru.isa
index fb2d049..e88522b 100644
--- a/sim/pru/pru.isa
+++ b/sim/pru/pru.isa
@@ -40,26 +40,30 @@ INSTRUCTION (sub,
 	     OP2 = (IO ? IMM8 : RS2);
 	     RD = RS1 - OP2;
 	     CARRY = (((uint64_t) RS1 - (uint64_t) OP2) >> RD_WIDTH) & 1;
+	     CARRY = !CARRY;
 	     PC++)
 
 INSTRUCTION (suc,
 	     OP2 = (IO ? IMM8 : RS2);
-	     RD = RS1 - OP2 - CARRY;
-	     CARRY = (((uint64_t) RS1 - (uint64_t) OP2 - (uint64_t) CARRY)
+	     RD = RS1 - OP2 - !CARRY;
+	     CARRY = (((uint64_t) RS1 - (uint64_t) OP2 - (uint64_t) !CARRY)
 		      >> RD_WIDTH) & 1;
+	     CARRY = !CARRY;
 	     PC++)
 
 INSTRUCTION (rsb,
 	     OP2 = (IO ? IMM8 : RS2);
 	     RD = OP2 - RS1;
 	     CARRY = (((uint64_t) OP2 - (uint64_t) RS1) >> RD_WIDTH) & 1;
+	     CARRY = !CARRY;
 	     PC++)
 
 INSTRUCTION (rsc,
 	     OP2 = (IO ? IMM8 : RS2);
-	     RD = OP2 - RS1 - CARRY;
-	     CARRY = (((uint64_t) OP2 - (uint64_t) RS1 - (uint64_t) CARRY)
+	     RD = OP2 - RS1 - !CARRY;
+	     CARRY = (((uint64_t) OP2 - (uint64_t) RS1 - (uint64_t) !CARRY)
 		      >> RD_WIDTH) & 1;
+	     CARRY = !CARRY;
 	     PC++)
 
 INSTRUCTION (lsl,
diff --git a/sim/testsuite/pru/carry.s b/sim/testsuite/pru/carry.s
new file mode 100644
index 0000000..cff75d2
--- /dev/null
+++ b/sim/testsuite/pru/carry.s
@@ -0,0 +1,416 @@
+# Check that carry for addition and subtraction works.
+# mach: pru
+
+# Copyright (C) 2023 Free Software Foundation, Inc.
+# Contributed by Dimitar Dimitrov <dimitar@dinux.eu>
+#
+# This file is part of the GNU simulators.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+.include "testutils.inc"
+
+	# Helper macro to exercise three consecutive
+	# instructions using the carry bit.
+	.macro test_seq srcmode, dstmode, init0, init1, init2, init3, alu0, alu1, alu2, expected
+	# In case srcmode>dstmode, "garbage" in the r20 MSB
+	# bits could falsely be interpreted as carry.
+	# So start with initialized destination to make tests consistent.
+	ldi	r20, 0
+	ldi32	r15, \init0
+	ldi32	r16, \init1
+	ldi32	r17, \init2
+	ldi32	r18, \init3
+	ldi32	r0, \expected
+	\alu0	r20\dstmode, r15\srcmode, r16\srcmode
+	\alu1	r20\dstmode, r20\srcmode, r17\srcmode
+	\alu2	r20\dstmode, r20\srcmode, r18\srcmode
+	qbeq	1f, r0, r20\dstmode
+	jmp	EXIT_FAIL
+1:
+	.endm
+
+	# Helper macro to verify one ALU instruction
+	# using the carry bit.
+	.macro test1 alu, dstmode, src0mode, src0init, src1mode, src1init, expected
+	ldi32	r15, \src0init
+	ldi32	r16, \src1init
+	ldi32	r0, \expected
+	\alu	r20\dstmode, r15\src0mode, r16\src1mode
+	qbeq	1f, r0, r20\dstmode
+	jmp	EXIT_FAIL
+1:
+	.endm
+
+	start
+
+	# ***** ADD 32-bit dst, 32-bit src *****
+	# {add, clear carry}
+	test1	add, "   ", "   ", 0x00000000, "   ", 0x00000000, 0x00000000
+	# {add with carry=0, clear carry}
+	test1	adc, "   ", "   ", 0x00000000, "   ", 0x00000000, 0x00000000
+	# {add with carry=0, set carry}
+	test1	adc, "   ", "   ", 0x00000001, "   ", 0xffffffff, 0x00000000
+	# {add with carry=1, set carry}
+	test1	adc, "   ", "   ", 0x00000010, "   ", 0xfffffffe, 0x0000000f
+	# {add with carry=1, clear carry}
+	test1	adc, "   ", "   ", 0x00000010, "   ", 0x0ffffffe, 0x1000000f
+	# {add with carry=0, set carry}
+	test1	adc, "   ", "   ", 0x00000001, "   ", 0xffffffff, 0x00000000
+	# {add, set carry}
+	test1	add, "   ", "   ", 0x00000001, "   ", 0xffffffff, 0x00000000
+	# {add with carry=1, set carry}
+	test1	adc, "   ", "   ", 0x00000010, "   ", 0xfffffffe, 0x0000000f
+
+	# ***** ADD 32-bit dst, 16-bit src *****
+	test1	add, "   ", ".w0", 0x00000000, ".w0", 0x00000000, 0x00000000
+	test1	adc, "   ", ".w0", 0x00000000, ".w0", 0x00000000, 0x00000000
+	test1	adc, "   ", ".w0", 0x00000003, ".w0", 0xffffffff, 0x00010002
+	test1	adc, "   ", ".w0", 0x00000010, ".w0", 0x0000fffe, 0x0001000e
+
+	# ***** ADD 32-bit dst, 8-bit src *****
+	test1	add, "   ", ".b0", 0x00000000, ".b0", 0x00000000, 0x00000000
+	test1	adc, "   ", ".b0", 0x00000000, ".b0", 0x00000000, 0x00000000
+	test1	adc, "   ", ".b0", 0x00000003, ".b0", 0xffffffff, 0x00000102
+	test1	adc, "   ", ".b0", 0x00000010, ".b0", 0x0000f0fe, 0x0000010e
+
+	# ***** ADD 16-bit dst, 32-bit src *****
+	test1	add, ".w0", "   ", 0x00000000, "   ", 0x00000000, 0x00000000
+	test1	adc, ".w0", "   ", 0x00000000, "   ", 0x00000000, 0x00000000
+	test1	adc, ".w0", "   ", 0x00000001, "   ", 0xfff0ffff, 0x00000000
+	test1	adc, ".w0", "   ", 0x00000010, "   ", 0x0000fffe, 0x0000000f
+	test1	adc, ".w0", "   ", 0x00000010, "   ", 0x00000ffe, 0x0000100f
+	test1	adc, ".w0", "   ", 0x00000001, "   ", 0x0000ffff, 0x00000000
+	test1	add, ".w0", "   ", 0x00000001, "   ", 0x0000ffff, 0x00000000
+	test1	adc, ".w0", "   ", 0x00000010, "   ", 0x0000fffe, 0x0000000f
+	# Test when intermediate sum sets the carry.
+	test1	add, ".w0", "   ", 0x00010000, "   ", 0x00000000, 0x00000000
+	test1	adc, ".w0", "   ", 0x00000000, "   ", 0x00000000, 0x00000001
+	test1	add, ".w0", "   ", 0x00020000, "   ", 0x00000000, 0x00000000
+	test1	adc, ".w0", "   ", 0x00000000, "   ", 0x00000000, 0x00000000
+
+	# ***** ADD 16-bit dst, 16-bit src *****
+	test1	add, ".w0", ".w0", 0x00000210, ".w0", 0x00000130, 0x00000340
+	test1	adc, ".w0", ".w0", 0x00000000, ".w0", 0x00000000, 0x00000000
+	test1	adc, ".w0", ".w0", 0x00000001, ".w0", 0xffffffff, 0x00000000
+	test1	adc, ".w0", ".w0", 0x00000010, ".w0", 0xfffffffe, 0x0000000f
+	test1	adc, ".w0", ".w0", 0x00000010, ".w0", 0x00000ffe, 0x0000100f
+	test1	adc, ".w0", ".w0", 0x00000001, ".w0", 0xfff0ffff, 0x00000000
+	test1	add, ".w0", ".w0", 0x00000001, ".w0", 0xfff0ffff, 0x00000000
+	test1	adc, ".w0", ".w0", 0x00000010, ".w0", 0xfff1fffe, 0x0000000f
+
+	# ***** ADD 16-bit dst, 8-bit src *****
+	test1	add, ".w0", ".b0", 0x00000000, ".b0", 0x00000000, 0x00000000
+	test1	adc, ".w0", ".b0", 0x00000000, ".b0", 0x00000000, 0x00000000
+	test1	adc, ".w0", ".b0", 0x00000003, ".b0", 0xffffffff, 0x00000102
+	test1	adc, ".w0", ".b0", 0x00000010, ".b0", 0x0000f0fe, 0x0000010e
+
+	# ***** ADD 8-bit dst, 32-bit src *****
+	test1	add, ".b0", "   ", 0x00000000, "   ", 0x00000000, 0x00000000
+	test1	adc, ".b0", "   ", 0x00000000, "   ", 0x00000000, 0x00000000
+	test1	adc, ".b0", "   ", 0x00000001, "   ", 0x000000ff, 0x00000000
+	test1	adc, ".b0", "   ", 0x00000010, "   ", 0x000000fe, 0x0000000f
+	test1	adc, ".b0", "   ", 0x00000021, "   ", 0x0000001e, 0x00000040
+	test1	adc, ".b0", "   ", 0x00000001, "   ", 0x000000ff, 0x00000000
+	test1	add, ".b0", "   ", 0x00000001, "   ", 0x000000ff, 0x00000000
+	test1	adc, ".b0", "   ", 0x00000010, "   ", 0x000000fe, 0x0000000f
+	# Test when intermediate sum sets the carry.
+	test1	add, ".b0", "   ", 0x10000100, "   ", 0x00000000, 0x00000000
+	test1	adc, ".b0", "   ", 0x00000000, "   ", 0x00000000, 0x00000001
+
+	# ***** ADD 8-bit dst, 16-bit src *****
+	test1	add, ".b0", ".w0", 0x10000000, ".w0", 0x00000000, 0x00000000
+	test1	adc, ".b0", ".w0", 0x02000000, ".w0", 0x00000000, 0x00000000
+	test1	adc, ".b0", ".w0", 0x00030001, ".w0", 0x000000ff, 0x00000000
+	test1	adc, ".b0", ".w0", 0x00004010, ".w0", 0x000000fe, 0x0000000f
+	test1	adc, ".b0", ".w0", 0x00000021, ".w0", 0x0000001e, 0x00000040
+	test1	adc, ".b0", ".w0", 0x00000001, ".w0", 0x000000ff, 0x00000000
+	test1	add, ".b0", ".w0", 0x00000001, ".w0", 0x000000ff, 0x00000000
+	test1	adc, ".b0", ".w0", 0x00000010, ".w0", 0x000000fe, 0x0000000f
+	# Test when intermediate sum sets the carry.
+	test1	add, ".b0", ".w0", 0x10003100, ".w0", 0x00000000, 0x00000000
+	test1	adc, ".b0", ".w0", 0x00000000, ".w0", 0x00000000, 0x00000001
+
+	# ***** ADD 8-bit dst, 8-bit src  *****
+	test1	add, ".b0", ".b0", 0x00000210, ".b0", 0x00000130, 0x00000040
+	test1	adc, ".b0", ".b0", 0x00000000, ".b0", 0x00000000, 0x00000000
+	test1	adc, ".b0", ".b0", 0x00000001, ".b0", 0xffffffff, 0x00000000
+	test1	adc, ".b0", ".b0", 0x00000010, ".b0", 0xfffffffe, 0x0000000f
+	test1	adc, ".b0", ".b0", 0x00000010, ".b0", 0x0000000e, 0x0000001f
+	test1	adc, ".b0", ".b0", 0x00000001, ".b0", 0xfff0ffff, 0x00000000
+	test1	add, ".b0", ".b0", 0x00000001, ".b0", 0xfff0ffff, 0x00000000
+	test1	adc, ".b0", ".b0", 0x00000010, ".b0", 0xfff1fffe, 0x0000000f
+
+	# ***** SUB 32-bit dst, 32-bit src *****
+	# {sub, clear borrow}
+	test1	sub, "   ", "   ", 0x00000000, "   ", 0x00000000, 0x00000000
+	# {sub with borrow=0, clear borrow}
+	test1	suc, "   ", "   ", 0x00000010, "   ", 0x00000001, 0x0000000f
+	# {sub with borrow=0, set borrow}
+	test1	suc, "   ", "   ", 0x00000008, "   ", 0x00000009, 0xffffffff
+	# {sub with borrow=1, set borrow}
+	test1	suc, "   ", "   ", 0x00000008, "   ", 0x00000009, 0xfffffffe
+	# {sub with borrow=1, clear borrow}
+	test1	suc, "   ", "   ", 0x00000008, "   ", 0x00000001, 0x00000006
+	# {sub with borrow=0, set borrow}
+	test1	suc, "   ", "   ", 0x80000000, "   ", 0x90000000, 0xf0000000
+	# {sub, set borrow}
+	test1	sub, "   ", "   ", 0x00000000, "   ", 0x00000001, 0xffffffff
+	# {sub with borrow=1, set borrow}
+	test1	suc, "   ", "   ", 0x80000000, "   ", 0x90000000, 0xefffffff
+
+	# ***** SUB 32-bit dst, 16-bit src *****
+	test1	sub, "   ", ".w0", 0x00000000, ".w0", 0x00000000, 0x00000000
+	test1	suc, "   ", ".w0", 0x00000010, ".w0", 0x00000001, 0x0000000f
+	test1	suc, "   ", ".w0", 0x00000008, ".w0", 0x00000009, 0xffffffff
+	test1	suc, "   ", ".w0", 0x00000008, ".w0", 0x00000009, 0xfffffffe
+	test1	suc, "   ", ".w0", 0x00000008, ".w0", 0x00000001, 0x00000006
+	test1	suc, "   ", ".w0", 0x00108000, ".w0", 0x00009000, 0xfffff000
+	test1	sub, "   ", ".w0", 0x00000000, ".w0", 0x00000001, 0xffffffff
+	test1	suc, "   ", ".w0", 0x00008000, ".w0", 0x00009000, 0xffffefff
+
+	# ***** SUB 32-bit dst, 8-bit src *****
+	test1	sub, "   ", ".b0", 0x00000000, ".b0", 0x00000000, 0x00000000
+	test1	suc, "   ", ".b0", 0x00000010, ".b0", 0x00000001, 0x0000000f
+	test1	suc, "   ", ".b0", 0x00000008, ".b0", 0x00000009, 0xffffffff
+	test1	suc, "   ", ".b0", 0x00000008, ".b0", 0x00000009, 0xfffffffe
+	test1	suc, "   ", ".b0", 0x00000008, ".b0", 0x00000001, 0x00000006
+	test1	suc, "   ", ".b0", 0x00108080, ".b0", 0x00009090, 0xfffffff0
+	test1	sub, "   ", ".b0", 0x00000000, ".b0", 0x00000001, 0xffffffff
+	test1	suc, "   ", ".b0", 0x00008080, ".b0", 0x00009090, 0xffffffef
+
+	# ***** SUB 16-bit dst, 32-bit src *****
+	test1	sub, ".w0", "   ", 0x00000000, "   ", 0x00000000, 0x00000000
+	test1	suc, ".w0", "   ", 0x00000010, "   ", 0x00000001, 0x0000000f
+	test1	suc, ".w0", "   ", 0x00000008, "   ", 0x00000009, 0x0000ffff
+	test1	suc, ".w0", "   ", 0x00000008, "   ", 0x00000009, 0x0000fffe
+	test1	suc, ".w0", "   ", 0x00000008, "   ", 0x00000001, 0x00000006
+	test1	suc, ".w0", "   ", 0x00108000, "   ", 0x00009000, 0x0000f000
+	test1	sub, ".w0", "   ", 0x00000000, "   ", 0x00000001, 0x0000ffff
+	test1	suc, ".w0", "   ", 0x00008000, "   ", 0x00009000, 0x0000efff
+	# Test when intermediate value sets the borrow.
+	test1	sub, ".w0", "   ", 0x00010000, "   ", 0x00000000, 0x00000000
+	test1	suc, ".w0", "   ", 0x00000002, "   ", 0x00000000, 0x00000001
+
+	# ***** SUB 16-bit dst, 16-bit src *****
+	test1	sub, ".w0", ".w0", 0x00000000, ".w0", 0x00000000, 0x00000000
+	test1	suc, ".w0", ".w0", 0x00000010, ".w0", 0x00000001, 0x0000000f
+	test1	suc, ".w0", ".w0", 0x00000008, ".w0", 0x00000009, 0x0000ffff
+	test1	suc, ".w0", ".w0", 0x00000008, ".w0", 0x00000009, 0x0000fffe
+	test1	suc, ".w0", ".w0", 0x00000008, ".w0", 0x00000001, 0x00000006
+	test1	suc, ".w0", ".w0", 0x00108000, ".w0", 0x00009000, 0x0000f000
+	test1	sub, ".w0", ".w0", 0x00000000, ".w0", 0x00000001, 0x0000ffff
+	test1	suc, ".w0", ".w0", 0x00008000, ".w0", 0x00009000, 0x0000efff
+
+	# ***** SUB 16-bit dst, 8-bit src *****
+	test1	sub, ".w0", ".b0", 0x00000000, ".b0", 0x00000000, 0x00000000
+	test1	suc, ".w0", ".b0", 0x00000010, ".b0", 0x00000001, 0x0000000f
+	test1	suc, ".w0", ".b0", 0x00000008, ".b0", 0x00000009, 0x0000ffff
+	test1	suc, ".w0", ".b0", 0x00000008, ".b0", 0x00000009, 0x0000fffe
+	test1	suc, ".w0", ".b0", 0x00000008, ".b0", 0x00000001, 0x00000006
+	test1	suc, ".w0", ".b0", 0x00108080, ".b0", 0x00009090, 0x0000fff0
+	test1	sub, ".w0", ".b0", 0x00000000, ".b0", 0x00000001, 0x0000ffff
+	test1	suc, ".w0", ".b0", 0x0000a080, ".b0", 0x0000c090, 0x0000ffef
+
+	# ***** SUB 8-bit dst, 32-bit src *****
+	test1	sub, ".b0", "   ", 0x00000000, "   ", 0x00000000, 0x00000000
+	test1	suc, ".b0", "   ", 0x00000010, "   ", 0x00000001, 0x0000000f
+	test1	suc, ".b0", "   ", 0x00000008, "   ", 0x00000009, 0x000000ff
+	test1	suc, ".b0", "   ", 0x00000008, "   ", 0x00000009, 0x000000fe
+	test1	suc, ".b0", "   ", 0x00000008, "   ", 0x00000001, 0x00000006
+	test1	suc, ".b0", "   ", 0x00000080, "   ", 0x00000090, 0x000000f0
+	test1	sub, ".b0", "   ", 0x00000000, "   ", 0x00000001, 0x000000ff
+	test1	suc, ".b0", "   ", 0x00000080, "   ", 0x00000090, 0x000000ef
+	# Test when intermediate value sets the borrow.
+	test1	sub, ".b0", "   ", 0x00000100, "   ", 0x00000000, 0x00000000
+	test1	suc, ".b0", "   ", 0x00000002, "   ", 0x00000000, 0x00000001
+	test1	sub, ".b0", "   ", 0x00000100, "   ", 0x00000000, 0x00000000
+	test1	rsc, ".b0", "   ", 0x00000000, "   ", 0x00000002, 0x00000001
+
+	# ***** SUB 8-bit dst, 16-bit src *****
+	test1	sub, ".b0", ".w0", 0x00000000, ".w0", 0x00000000, 0x00000000
+	test1	suc, ".b0", ".w0", 0x00000010, ".w0", 0x00000001, 0x0000000f
+	test1	suc, ".b0", ".w0", 0x00000008, ".w0", 0x00000009, 0x000000ff
+	test1	suc, ".b0", ".w0", 0x00000008, ".w0", 0x00000009, 0x000000fe
+	test1	suc, ".b0", ".w0", 0x00000008, ".w0", 0x00000001, 0x00000006
+	test1	suc, ".b0", ".w0", 0x00000080, ".w0", 0x00000090, 0x000000f0
+	test1	sub, ".b0", ".w0", 0x00000000, ".w0", 0x00000001, 0x000000ff
+	test1	suc, ".b0", ".w0", 0x00000080, ".w0", 0x00000090, 0x000000ef
+	# Test when intermediate value sets the borrow.
+	test1	sub, ".b0", ".w0", 0x00000100, ".w0", 0x00000000, 0x00000000
+	test1	suc, ".b0", ".w0", 0x00000002, ".w0", 0x00000000, 0x00000001
+	test1	sub, ".b0", ".w0", 0x00000100, ".w0", 0x00000000, 0x00000000
+	test1	rsc, ".b0", ".w0", 0x00000000, ".w0", 0x00000002, 0x00000001
+
+	# ***** SUB 8-bit dst, 8-bit src *****
+	test1	sub, ".b0", ".w0", 0x00000000, ".w0", 0x00000000, 0x00000000
+	test1	suc, ".b0", ".w0", 0x00000010, ".w0", 0x00000001, 0x0000000f
+	test1	suc, ".b0", ".w0", 0x00000008, ".w0", 0x00000009, 0x000000ff
+	test1	suc, ".b0", ".w0", 0x00000008, ".w0", 0x00000009, 0x000000fe
+	test1	suc, ".b0", ".w0", 0x00000008, ".w0", 0x00000001, 0x00000006
+	test1	suc, ".b0", ".w0", 0x00000080, ".w0", 0x00000090, 0x000000f0
+	test1	sub, ".b0", ".w0", 0x00000000, ".w0", 0x00000001, 0x000000ff
+	test1	suc, ".b0", ".w0", 0x00000080, ".w0", 0x00000090, 0x000000ef
+
+	# ***** Reverse SUB 32-bit dst, 32-bit src *****
+	# {rsb, clear borrow}
+	test1	rsb, "   ", "   ", 0x00000000, "   ", 0x00000000, 0x00000000
+	# {rsb with borrow=0, clear borrow}
+	test1	rsc, "   ", "   ", 0x00000001, "   ", 0x00000010, 0x0000000f
+	# {rsb with borrow=0, set borrow}
+	test1	rsc, "   ", "   ", 0x00000009, "   ", 0x00000008, 0xffffffff
+	# {rsb with borrow=1, set borrow}
+	test1	rsc, "   ", "   ", 0x00000009, "   ", 0x00000008, 0xfffffffe
+	# {rsb with borrow=1, clear borrow}
+	test1	rsc, "   ", "   ", 0x00000001, "   ", 0x00000008, 0x00000006
+	# {rsb with borrow=0, set borrow}
+	test1	rsc, "   ", "   ", 0x90000000, "   ", 0x80000000, 0xf0000000
+	# {rsb, set borrow}
+	test1	rsb, "   ", "   ", 0x00000001, "   ", 0x00000000, 0xffffffff
+	# {rsb with borrow=1, set borrow}
+	test1	rsc, "   ", "   ", 0x90000000, "   ", 0x80000000, 0xefffffff
+
+	# ***** Reverse SUB 32-bit dst, 16-bit src *****
+	test1	rsb, "   ", ".w0", 0x00000000, ".w0", 0x00000000, 0x00000000
+	test1	rsc, "   ", ".w0", 0x00000001, ".w0", 0x00000010, 0x0000000f
+	test1	rsc, "   ", ".w0", 0x00000009, ".w0", 0x00000008, 0xffffffff
+	test1	rsc, "   ", ".w0", 0x00000009, ".w0", 0x00000008, 0xfffffffe
+	test1	rsc, "   ", ".w0", 0x00000001, ".w0", 0x00000008, 0x00000006
+	test1	rsc, "   ", ".w0", 0x00109000, ".w0", 0x00008000, 0xfffff000
+	test1	rsb, "   ", ".w0", 0x00000001, ".w0", 0x00000000, 0xffffffff
+	test1	rsc, "   ", ".w0", 0x00009000, ".w0", 0x00008000, 0xffffefff
+
+	# ***** Reverse SUB 32-bit dst, 8-bit src *****
+	test1	rsb, "   ", ".b0", 0x00000000, ".b0", 0x00000000, 0x00000000
+	test1	rsc, "   ", ".b0", 0x00000001, ".b0", 0x00000010, 0x0000000f
+	test1	rsc, "   ", ".b0", 0x00000009, ".b0", 0x00000008, 0xffffffff
+	test1	rsc, "   ", ".b0", 0x00000009, ".b0", 0x00000008, 0xfffffffe
+	test1	rsc, "   ", ".b0", 0x00000001, ".b0", 0x00000008, 0x00000006
+	test1	rsc, "   ", ".b0", 0x00108090, ".b0", 0x00009080, 0xfffffff0
+	test1	rsb, "   ", ".b0", 0x00000001, ".b0", 0x00000000, 0xffffffff
+	test1	rsc, "   ", ".b0", 0x00008090, ".b0", 0x00009080, 0xffffffef
+
+	# ***** Reverse SUB 16-bit dst, 32-bit src *****
+	test1	rsb, ".w0", "   ", 0x00000000, "   ", 0x00000000, 0x00000000
+	test1	rsc, ".w0", "   ", 0x00000001, "   ", 0x00000010, 0x0000000f
+	test1	rsc, ".w0", "   ", 0x00000009, "   ", 0x00000008, 0x0000ffff
+	test1	rsc, ".w0", "   ", 0x00000009, "   ", 0x00000008, 0x0000fffe
+	test1	rsc, ".w0", "   ", 0x00000001, "   ", 0x00000008, 0x00000006
+	test1	rsc, ".w0", "   ", 0x00109000, "   ", 0x00008000, 0x0000f000
+	test1	rsb, ".w0", "   ", 0x00000001, "   ", 0x00000000, 0x0000ffff
+	test1	rsc, ".w0", "   ", 0x00009000, "   ", 0x00008000, 0x0000efff
+	# Test when intermediate value sets the borrow.
+	test1	rsb, ".w0", "   ", 0x00000000, "   ", 0x00010000, 0x00000000
+	test1	rsc, ".w0", "   ", 0x00000000, "   ", 0x00000002, 0x00000001
+
+	# ***** Reverse SUB 16-bit dst, 16-bit src *****
+	test1	rsb, ".w0", ".w0", 0x00000000, ".w0", 0x00000000, 0x00000000
+	test1	rsc, ".w0", ".w0", 0x00000001, ".w0", 0x00000010, 0x0000000f
+	test1	rsc, ".w0", ".w0", 0x00000009, ".w0", 0x00000008, 0x0000ffff
+	test1	rsc, ".w0", ".w0", 0x00000009, ".w0", 0x00000008, 0x0000fffe
+	test1	rsc, ".w0", ".w0", 0x00000001, ".w0", 0x00000008, 0x00000006
+	test1	rsc, ".w0", ".w0", 0x00109000, ".w0", 0x00008000, 0x0000f000
+	test1	rsb, ".w0", ".w0", 0x00000001, ".w0", 0x00000000, 0x0000ffff
+	test1	rsc, ".w0", ".w0", 0x00009000, ".w0", 0x00008000, 0x0000efff
+
+	# ***** Reverse SUB 16-bit dst, 8-bit src *****
+	test1	rsb, ".w0", ".b0", 0x00000000, ".b0", 0x00000000, 0x00000000
+	test1	rsc, ".w0", ".b0", 0x00000001, ".b0", 0x00000010, 0x0000000f
+	test1	rsc, ".w0", ".b0", 0x00000009, ".b0", 0x00000008, 0x0000ffff
+	test1	rsc, ".w0", ".b0", 0x00000009, ".b0", 0x00000008, 0x0000fffe
+	test1	rsc, ".w0", ".b0", 0x00000001, ".b0", 0x00000008, 0x00000006
+	test1	rsc, ".w0", ".b0", 0x00108090, ".b0", 0x00009080, 0x0000fff0
+	test1	rsb, ".w0", ".b0", 0x00000001, ".b0", 0x00000000, 0x0000ffff
+	test1	rsc, ".w0", ".b0", 0x0000a090, ".b0", 0x0000c080, 0x0000ffef
+
+	# ***** Reverse SUB 8-bit dst, 32-bit src *****
+	test1	rsb, ".b0", "   ", 0x00000000, "   ", 0x00000000, 0x00000000
+	test1	rsc, ".b0", "   ", 0x00000001, "   ", 0x00000010, 0x0000000f
+	test1	rsc, ".b0", "   ", 0x00000009, "   ", 0x00000008, 0x000000ff
+	test1	rsc, ".b0", "   ", 0x00000009, "   ", 0x00000008, 0x000000fe
+	test1	rsc, ".b0", "   ", 0x00000001, "   ", 0x00000008, 0x00000006
+	test1	rsc, ".b0", "   ", 0x00000090, "   ", 0x00000080, 0x000000f0
+	test1	rsb, ".b0", "   ", 0x00000001, "   ", 0x00000000, 0x000000ff
+	test1	rsc, ".b0", "   ", 0x00000090, "   ", 0x00000080, 0x000000ef
+	# Test when intermediate value sets the borrow.
+	test1	rsb, ".b0", "   ", 0x00000000, "   ", 0x00000100, 0x00000000
+	test1	rsc, ".b0", "   ", 0x00000000, "   ", 0x00000002, 0x00000001
+	test1	rsb, ".b0", "   ", 0x00000000, "   ", 0x00000100, 0x00000000
+	test1	suc, ".b0", "   ", 0x00000002, "   ", 0x00000000, 0x00000001
+
+	# ***** Reverse SUB 8-bit dst, 16-bit src *****
+	test1	rsb, ".b0", ".w0", 0x00000000, ".w0", 0x00000000, 0x00000000
+	test1	rsc, ".b0", ".w0", 0x00000001, ".w0", 0x00000010, 0x0000000f
+	test1	rsc, ".b0", ".w0", 0x00000009, ".w0", 0x00000008, 0x000000ff
+	test1	rsc, ".b0", ".w0", 0x00000009, ".w0", 0x00000008, 0x000000fe
+	test1	rsc, ".b0", ".w0", 0x00000001, ".w0", 0x00000008, 0x00000006
+	test1	rsc, ".b0", ".w0", 0x00000090, ".w0", 0x00000080, 0x000000f0
+	test1	rsb, ".b0", ".w0", 0x00000001, ".w0", 0x00000000, 0x000000ff
+	test1	rsc, ".b0", ".w0", 0x00000090, ".w0", 0x00000080, 0x000000ef
+	# Test when intermediate value sets the borrow.
+	test1	rsb, ".b0", ".w0", 0x00000000, ".w0", 0x00000100, 0x00000000
+	test1	rsc, ".b0", ".w0", 0x00000000, ".w0", 0x00000002, 0x00000001
+	test1	rsb, ".b0", ".w0", 0x00000000, ".w0", 0x00000100, 0x00000000
+	test1	suc, ".b0", ".w0", 0x00000002, ".w0", 0x00000000, 0x00000001
+
+	# ***** Reverse SUB 8-bit dst, 8-bit src *****
+	test1	rsb, ".b0", ".w0", 0x00000000, ".w0", 0x00000000, 0x00000000
+	test1	rsc, ".b0", ".w0", 0x00000001, ".w0", 0x00000010, 0x0000000f
+	test1	rsc, ".b0", ".w0", 0x00000009, ".w0", 0x00000008, 0x000000ff
+	test1	rsc, ".b0", ".w0", 0x00000009, ".w0", 0x00000008, 0x000000fe
+	test1	rsc, ".b0", ".w0", 0x00000001, ".w0", 0x00000008, 0x00000006
+	test1	rsc, ".b0", ".w0", 0x00000090, ".w0", 0x00000080, 0x000000f0
+	test1	rsb, ".b0", ".w0", 0x00000001, ".w0", 0x00000000, 0x000000ff
+	test1	rsc, ".b0", ".w0", 0x00000090, ".w0", 0x00000080, 0x000000ef
+
+	# ***** Mixed 32-bit *****
+	test1	sub, "   ", " ", 0x00000000, " ", 0x00000000, 0x00000000
+	test1	adc, "   ", " ", 0x00000000, " ", 0x00000000, 0x00000001
+	test1	suc, "   ", " ", 0x00000001, " ", 0x00000001, 0xffffffff
+	test1	adc, "   ", " ", 0x00000001, " ", 0x00000000, 0x00000001
+
+	test_seq "", "", 0xffffffff, 0x00000001, 0x00000000, 0x00000000 add, suc, add, 0x00000000
+	test_seq "", "", 0xffffffff, 0x00000001, 0x00000000, 0x00000000 add, rsc, add, 0x00000000
+	test_seq "", "", 0xfffffffe, 0x00000001, 0x00000000, 0x00000000 add, suc, add, 0xfffffffe
+	test_seq "", "", 0xffffffff, 0x00000001, 0x00000000, 0x00000000 add, suc, adc, 0x00000001
+	test_seq "", "", 0xfffffffe, 0x00000001, 0x00000000, 0x00000000 add, suc, adc, 0xffffffff
+
+	test_seq "", "", 0xffffffff, 0x00000010, 0x00000000, 0x00000000 sub, adc, add, 0xfffffff0
+	test_seq "", "", 0x0fffffff, 0x00000010, 0x00000000, 0x00000000 sub, adc, add, 0x0ffffff0
+	test_seq "", "", 0x00000000, 0x00000010, 0x00000000, 0x00000000 sub, adc, add, 0xfffffff0
+	test_seq "", "", 0x00000000, 0x00000010, 0x00000000, 0x00000000 sub, adc, adc, 0xfffffff0
+	test_seq "", "", 0x00000000, 0x00000010, 0x00000000, 0x00000000 sub, adc, suc, 0xffffffef
+
+
+	# For coverage, also test sequences of ALU instructions
+	# (i.e. no other instructions in between).
+	test_seq "", "", 0x00000000, 0x00000000, 0x00000000, 0x00000000 add, adc, adc, 0x00000000
+	test_seq "", "", 0x80000000, 0xfffffff0, 0xc0000000, 0x0000001a add, adc, adc, 0x4000000c
+	test_seq "", ".b0", 0x00000000, 0x00000001, 0x000000ff, 0x00000000 add, adc, adc, 0x00000001
+	test_seq "", ".b0", 0x00000000, 0x00000001, 0x000000ff, 0x00000000 add, adc, adc, 0x00000001
+	test_seq ".b0", ".b0", 0x00000000, 0x00000001, 0x00000000, 0x0000ffff add, adc, adc, 0x00000000
+	test_seq ".b0", ".w0", 0x00000001, 0x00000020, 0x00000400, 0x00008000 add, adc, adc, 0x00000021
+	test_seq "", "", 0x00000010, 0x0000000f, 0x00000002, 0x00000020 sub, suc, suc, 0xffffffde
+	test_seq "", ".b0", 0x00000202, 0x00000000, 0x00000000, 0x00000000 sub, suc, suc, 0x00000002
+	test_seq ".w0", ".b0", 0x00000008, 0x00000000, 0x00000000, 0x00000000, sub, suc, suc, 0x00000008
+	test_seq ".w0", ".b0", 0x00000008, 0x000000ff, 0x000000ff, 0x000000ff, sub, suc, suc, 0x00000009
+	test_seq ".w0", ".b0", 0x00000008, 0x00000fff, 0x00000fff, 0x00000fff, sub, suc, suc, 0x0000000b
+	test_seq "", "", 0x0000000f, 0x00000010, 0x00000002, 0x00000020 rsb, suc, suc, 0xffffffde
+	test_seq "", "", 0xffffffff, 0x00000001, 0x00000000, 0x00000000 add, suc, adc, 0x00000001
+	test_seq "", "", 0x00000000, 0x00000010, 0x00000000, 0x00000000 sub, adc, adc, 0xfffffff0
+	test_seq "", "", 0x00000000, 0x00000010, 0x00000000, 0x00000000 sub, adc, suc, 0xffffffef
+
+	pass
+EXIT_FAIL:
+	fail