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barrel shifter handle rotation of 0 bits

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Matthew Berry 2020-10-14 00:00:01 -07:00
parent 0f0d2a4c20
commit e1f348ac1c
1 changed files with 4 additions and 0 deletions
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4
src/crab/cpu.cr
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@ -87,6 +87,7 @@ class CPU
# Logical shift left
def lsl(word : Word, bits : Int, set_conditions : Bool) : Word
log "lsl - word:#{hex_str word}, bits:#{bits}"
return word if bits == 0
@cpsr.carry = bit?(word, 32 - bits) if set_conditions
word << bits
end
@ -94,6 +95,7 @@ class CPU
# Logical shift right
def lsr(word : Word, bits : Int, set_conditions : Bool) : Word
log "lsr - word:#{hex_str word}, bits:#{bits}"
bits = 32 if bits == 0
@cpsr.carry = bit?(word, bits - 1) if set_conditions
word >> bits
end
@ -101,6 +103,7 @@ class CPU
# Arithmetic shift right
def asr(word : Word, bits : Int, set_conditions : Bool) : Word
log "asr - word:#{hex_str word}, bits:#{bits}"
bits = 32 if bits == 0
@cpsr.carry = bit?(word, bits - 1) if set_conditions
word >> bits | (0xFFFFFFFF_u32 &* (word >> 31)) << (32 - bits)
end
@ -108,6 +111,7 @@ class CPU
# Rotate right
def ror(word : Word, bits : Int, set_conditions : Bool) : Word
log "ror - word:#{hex_str word}, bits:#{bits}"
return word if bits == 0
@cpsr.carry = bit?(word, bits - 1) if set_conditions
word >> bits | word << (32 - bits)
end