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5139 

Replace the 'negative?' variable with a second read from the stack.

It's not clear if this is more or less efficient (https://github.com/akkartik/mu/pull/20#issuecomment-489285130)
but taking out the local variable does seem easier to read.
This commit is contained in:
Kartik Agaram 2019-05-04 14:17:13 -07:00
parent e450523829
commit d2410e14c6
1 changed files with 6 additions and 10 deletions
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16
subx/074print-int-decimal.subx
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@ -16,14 +16,14 @@
print-int32-decimal: # out : (address stream), n : int32
# pseudocode:
# push sentinel
# EAX, negative? = abs(n), sign(n)
# EAX = abs(n)
# while true
# sign-extend EAX into EDX
# EAX, EDX = EAX/10, EAX%10
# EDX += '0'
# push EDX
# if (EAX == 0) break
# if negative?
# if n < 0
# push '-'
# while true
# pop into EAX
@ -42,18 +42,15 @@ print-int32-decimal: # out : (address stream), n : int32
51/push-ECX
52/push-EDX
53/push-EBX
57/push-EDI
# ten/ECX = 10
b9/copy-to-ECX 0xa/imm32
# push sentinel
68/push 0/imm32/sentinel
# EAX, negative?/EDI = abs(n), sign(n)
bf/copy-to-EDI 0/imm32/false
# EAX = abs(n)
8b/copy 1/mod/*+disp8 5/rm32/EBP . . . 0/r32/EAX 0xc/disp8 . # EAX = *(EBP+12)
3d/compare-EAX-with 0/imm32
7d/jump-if-greater-or-equal $print-int32-decimal:read-loop/disp8
f7 3/subop/negate 3/mod/direct 0/rm32/EAX . . . . . . # negate EAX
bf/copy-to-EDI 1/imm32/true
$print-int32-decimal:read-loop:
# EAX, EDX = EAX / 10, EAX % 10
99/sign-extend-EAX-into-EDX
@ -66,9 +63,9 @@ $print-int32-decimal:read-loop:
3d/compare-EAX-and 0/imm32
7f/jump-if-greater $print-int32-decimal:read-loop/disp8
$print-int32-decimal:read-break:
# if (negative?) push('-')
81 7/subop/compare 3/mod/direct 7/rm32/EDI . . . . . 0/imm32/false # compare EDI
74/jump-if-equal $print-int32-decimal:write/disp8
# if (n < 0) push('-')
81 7/subop/compare 1/mod/*+disp8 5/rm32/EBP . . . . 0xc/disp8 0/imm32 # compare *(EBP+12)
7d/jump-if-greater-or-equal $print-int32-decimal:write/disp8
68/push 0x2d/imm32/-
$print-int32-decimal:write:
# EBX = out
@ -91,7 +88,6 @@ $print-int32-decimal:write-loop:
eb/jump $print-int32-decimal:write-loop/disp8
$print-int32-decimal:end:
# . restore registers
57/pop-to-EDI
5b/pop-to-EBX
5a/pop-to-EDX
59/pop-to-ECX