vnf: also set the carry on a zero compare

Add also a test to further check corner cases on compare instructions.

Signed-off-by: Miquel Sabaté Solà <mssola@mssola.com>

4 files changed, 62 insertions, 1 deletions

diff --git a/lib/vnf/src/lib.rs b/lib/vnf/src/lib.rs
index a46d291..6c0a6f2 100644
--- a/lib/vnf/src/lib.rs
+++ b/lib/vnf/src/lib.rs
@@ -834,7 +834,7 @@ impl Machine {
         // And set flags accordingly.
         self.status_register.zero = res == 0;
         self.status_register.negative = (res as u8 & 0x80) == 0x80;
-        self.status_register.carry = (res as u16 & 0xFF00) != 0;
+        self.status_register.carry = res >= 0;
 
         Ok(())
     }
diff --git a/scripts/test-e2e.sh b/scripts/test-e2e.sh
index 7628ab4..be43685 100755
--- a/scripts/test-e2e.sh
+++ b/scripts/test-e2e.sh
@@ -288,6 +288,12 @@ echo "test: runrom => stack.nes"
 diff tests/out/stack.txt tests/expected/runrom/stack.txt
 exit_code=$((exit_code + $?))
 
+echo "test: runrom => cmp.nes"
+./target/debug/nasm -Werror --asan -o tests/out/cmp.nes tests/runrom/cmp.s
+./target/debug/runrom --function --dump-memory tests/out/cmp.nes > tests/out/cmp.txt
+diff tests/out/cmp.txt tests/expected/runrom/cmp.txt
+exit_code=$((exit_code + $?))
+
 echo "test: runrom => misc.nes"
 ./target/debug/nasm -Werror --asan --write-info --allow-unused --out tests/out/misc.nes tests/runrom/misc.s
 ./target/debug/runrom --nasm .nasm --dump-memory --function tests/out/misc.nes > tests/out/misc-all.txt
diff --git a/tests/expected/runrom/cmp.txt b/tests/expected/runrom/cmp.txt
new file mode 100644
index 0000000..e76570b
--- /dev/null
+++ b/tests/expected/runrom/cmp.txt
@@ -0,0 +1,18 @@
+<start>		PC: $8000, cycles: 7, registers: [a: $00, x: $00, y: $00, sp: $FD], status: ----I--
+lda #$00	PC: $8002, cycles: 9, registers: [a: $00, x: $00, y: $00, sp: $FD], status: ----IZ-
+sta $00		PC: $8004, cycles: 12, registers: [a: $00, x: $00, y: $00, sp: $FD], status: ----IZ-
+cmp $00		PC: $8006, cycles: 15, registers: [a: $00, x: $00, y: $00, sp: $FD], status: ----IZC
+inc $00		PC: $8008, cycles: 20, registers: [a: $00, x: $00, y: $00, sp: $FD], status: ----I-C
+cmp $00		PC: $800A, cycles: 23, registers: [a: $00, x: $00, y: $00, sp: $FD], status: N---I--
+lda #$02	PC: $800C, cycles: 25, registers: [a: $02, x: $00, y: $00, sp: $FD], status: ----I--
+cmp $00		PC: $800E, cycles: 28, registers: [a: $02, x: $00, y: $00, sp: $FD], status: ----I-C
+lda #$01	PC: $8010, cycles: 30, registers: [a: $01, x: $00, y: $00, sp: $FD], status: ----I-C
+cmp $00		PC: $8012, cycles: 33, registers: [a: $01, x: $00, y: $00, sp: $FD], status: ----IZC
+lda #$FF	PC: $8014, cycles: 35, registers: [a: $FF, x: $00, y: $00, sp: $FD], status: N---I-C
+cmp $00		PC: $8016, cycles: 38, registers: [a: $FF, x: $00, y: $00, sp: $FD], status: N---I-C
+rts		PC: $8017, cycles: 44, registers: [a: $FF, x: $00, y: $00, sp: $FD], status: N---I-C
+<end>
+
+== Memory dump ==
+
+[$0] = $01 [reads=6, writes=2]
diff --git a/tests/runrom/cmp.s b/tests/runrom/cmp.s
new file mode 100644
index 0000000..29deda3
--- /dev/null
+++ b/tests/runrom/cmp.s
@@ -0,0 +1,37 @@
+.segment "HEADER"
+    .byte 'N', 'E', 'S', $1A
+    .byte $02, $01
+    .byte $00
+    .byte $00
+
+.segment "CHARS"
+.byte 0
+
+.segment "VECTORS"
+    .addr reset, reset, reset
+
+.segment "CODE"
+;; asan:stack full
+
+zp_mem = $00
+
+.proc reset
+    lda #0
+    sta zp_mem
+
+    cmp zp_mem
+
+    inc zp_mem
+    cmp zp_mem
+
+    lda #2
+    cmp zp_mem
+
+    lda #1
+    cmp zp_mem
+
+    lda #$FF
+    cmp zp_mem
+
+    rts
+.endproc