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Recognize that LSR always clears the 'N' flag

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The instruction shifts 0 into the high bit, so the result is never
negative.  Added a test case to 1003-flags-and-branches.
This commit is contained in:
Andy McFadden 2020-04-23 17:23:12 -07:00
parent ea379fce18
commit 59b7ec0dea
8 changed files with 103 additions and 62 deletions
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8
Asm65/OpDef.cs
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@ -709,6 +709,12 @@ namespace Asm65 {
} }
return flags; return flags;
} }
private static StatusFlags FlagUpdater_LSR(StatusFlags flags, int immVal,
ref StatusFlags condBranchTakenFlags) {
flags.C = flags.Z = TriState16.INDETERMINATE;
flags.N = 0; // always shifts 0 into high bit
return flags;
}
private static StatusFlags FlagUpdater_ROL(StatusFlags flags, int immVal, private static StatusFlags FlagUpdater_ROL(StatusFlags flags, int immVal,
ref StatusFlags condBranchTakenFlags) { ref StatusFlags condBranchTakenFlags) {
// this rotates the N flag into C, so set C=N // this rotates the N flag into C, so set C=N
@ -1152,7 +1158,7 @@ namespace Asm65 {
Effect = FlowEffect.Cont, Effect = FlowEffect.Cont,
BaseMemEffect = MemoryEffect.ReadModifyWrite, BaseMemEffect = MemoryEffect.ReadModifyWrite,
FlagsAffected = FlagsAffected_NZC, FlagsAffected = FlagsAffected_NZC,
StatusFlagUpdater = FlagUpdater_NZC StatusFlagUpdater = FlagUpdater_LSR
}; };
private static OpDef OpMVN = new OpDef() { private static OpDef OpMVN = new OpDef() {
Mnemonic = OpName.MVN, Mnemonic = OpName.MVN,

BIN
SourceGen/SGTestData/1003-flags-and-branches
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37
SourceGen/SGTestData/Expected/1003-flags-and-branches_64tass.S
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@ -219,50 +219,57 @@ _L10F2 lda #$00
.byte $00 .byte $00
.byte $dc .byte $dc
_L10FA clc _L10FA lda #$ff
lsr a
bpl _L1101
.byte $00
.byte $dd
_L1101 clc
php php
sec sec
plp plp
bcc _L1102 bcc _L1109
.byte $00 .byte $00
.byte $00 .byte $00
_L1102 sec _L1109 sec
bcs _L1106 bcs _L110D
_L1105 clc _L110C clc
_L1106 lda $33 _L110D lda $33
beq _L1105 beq _L110C
bcs _L110E bcs _L1115
lda $44 lda $44
_L110E nop _L1115 nop
rep #$20 rep #$20
.al .al
sep #$10 sep #$10
jsr _L112A jsr _L1131
rep #$30 rep #$30
.xl .xl
jsr _L1130 jsr _L1137
sep #$30 sep #$30
.as .as
.xs .xs
jsr _L1130 jsr _L1137
rep #$20 rep #$20
.al .al
sep #$10 sep #$10
jsr _L112A jsr _L1131
sep #$30 sep #$30
.as .as
rts rts
.al .al
_L112A lda #$1234 _L1131 lda #$1234
ldx #$ff ldx #$ff
rts rts
.as .as
_L1130 lda #$ff _L1137 lda #$ff
ldx #$ee ldx #$ee
ldy #$dd ldy #$dd
rts rts

37
SourceGen/SGTestData/Expected/1003-flags-and-branches_Merlin32.S
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@ -214,49 +214,56 @@ L105F sep #$80
dfb $00 dfb $00
dfb $dc dfb $dc
:L10FA clc :L10FA lda #$ff
lsr A
bpl :L1101
dfb $00
dfb $dd
:L1101 clc
php php
sec sec
plp plp
bcc :L1102 bcc :L1109
dfb $00 dfb $00
dfb $00 dfb $00
:L1102 sec :L1109 sec
bcs :L1106 bcs :L110D
:L1105 clc :L110C clc
:L1106 lda $33 :L110D lda $33
beq :L1105 beq :L110C
bcs :L110E bcs :L1115
lda $44 lda $44
:L110E nop :L1115 nop
rep #$20 rep #$20
mx %01 mx %01
sep #$10 sep #$10
jsr :L112A jsr :L1131
rep #$30 rep #$30
mx %00 mx %00
jsr :L1130 jsr :L1137
sep #$30 sep #$30
mx %11 mx %11
jsr :L1130 jsr :L1137
rep #$20 rep #$20
mx %01 mx %01
sep #$10 sep #$10
jsr :L112A jsr :L1131
sep #$30 sep #$30
mx %11 mx %11
rts rts
mx %01 mx %01
:L112A lda #$1234 :L1131 lda #$1234
ldx #$ff ldx #$ff
rts rts
mx %11 mx %11
:L1130 lda #$ff :L1137 lda #$ff
ldx #$ee ldx #$ee
ldy #$dd ldy #$dd
rts rts

37
SourceGen/SGTestData/Expected/1003-flags-and-branches_acme.S
View File

@ -219,50 +219,57 @@ L105F sep #$80
!byte $00 !byte $00
!byte $dc !byte $dc
@L10FA clc @L10FA lda #$ff
lsr
bpl @L1101
!byte $00
!byte $dd
@L1101 clc
php php
sec sec
plp plp
bcc @L1102 bcc @L1109
!byte $00 !byte $00
!byte $00 !byte $00
@L1102 sec @L1109 sec
bcs @L1106 bcs @L110D
@L1105 clc @L110C clc
@L1106 lda $33 @L110D lda $33
beq @L1105 beq @L110C
bcs @L110E bcs @L1115
lda $44 lda $44
@L110E nop @L1115 nop
rep #$20 rep #$20
!al !al
sep #$10 sep #$10
jsr @L112A jsr @L1131
rep #$30 rep #$30
!rl !rl
jsr @L1130 jsr @L1137
sep #$30 sep #$30
!as !as
!rs !rs
jsr @L1130 jsr @L1137
rep #$20 rep #$20
!al !al
sep #$10 sep #$10
jsr @L112A jsr @L1131
sep #$30 sep #$30
!as !as
rts rts
!al !al
@L112A lda #$1234 @L1131 lda #$1234
ldx #$ff ldx #$ff
rts rts
!as !as
@L1130 lda #$ff @L1137 lda #$ff
ldx #$ee ldx #$ee
ldy #$dd ldy #$dd
rts rts

37
SourceGen/SGTestData/Expected/1003-flags-and-branches_cc65.S
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@ -220,50 +220,57 @@ L105F: sep #$80
.byte $00 .byte $00
.byte $dc .byte $dc
@L10FA: clc @L10FA: lda #$ff
lsr A
bpl @L1101
.byte $00
.byte $dd
@L1101: clc
php php
sec sec
plp plp
bcc @L1102 bcc @L1109
.byte $00 .byte $00
.byte $00 .byte $00
@L1102: sec @L1109: sec
bcs @L1106 bcs @L110D
@L1105: clc @L110C: clc
@L1106: lda $33 @L110D: lda $33
beq @L1105 beq @L110C
bcs @L110E bcs @L1115
lda $44 lda $44
@L110E: nop @L1115: nop
rep #$20 rep #$20
.a16 .a16
sep #$10 sep #$10
jsr @L112A jsr @L1131
rep #$30 rep #$30
.i16 .i16
jsr @L1130 jsr @L1137
sep #$30 sep #$30
.a8 .a8
.i8 .i8
jsr @L1130 jsr @L1137
rep #$20 rep #$20
.a16 .a16
sep #$10 sep #$10
jsr @L112A jsr @L1131
sep #$30 sep #$30
.a8 .a8
rts rts
.a16 .a16
@L112A: lda #$1234 @L1131: lda #$1234
ldx #$ff ldx #$ff
rts rts
.a8 .a8
@L1130: lda #$ff @L1137: lda #$ff
ldx #$ee ldx #$ee
ldy #$dd ldy #$dd
rts rts

2
SourceGen/SGTestData/Expected/1003-flags-and-branches_cc65.cfg
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@ -1,7 +1,7 @@
# 6502bench SourceGen generated linker script for 1003-flags-and-branches # 6502bench SourceGen generated linker script for 1003-flags-and-branches
MEMORY { MEMORY {
MAIN: file=%O, start=%S, size=65536; MAIN: file=%O, start=%S, size=65536;
# MEM000: file=%O, start=$1000, size=311; # MEM000: file=%O, start=$1000, size=318;
} }
SEGMENTS { SEGMENTS {
CODE: load=MAIN, type=rw; CODE: load=MAIN, type=rw;

7
SourceGen/SGTestData/Source/1003-flags-and-branches.S
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@ -195,6 +195,13 @@ ok_ror2
brk $dc brk $dc
ok_rol1 ok_rol1
; check lsr
lda #$ff
lsr A ;lsr always clears the high bit
bpl ok_lsr
brk $dd
ok_lsr
; simple php/plp pair test ; simple php/plp pair test
clc clc
php php