Boolean vs Int in Javascript
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; JavaScript Code : "!a" | |
movabsq $0xfff9800000000000, %r11 ; type tag of boolean (SpiderMonkey uses a trait of NaN-boxing) | |
cmpq %r11, %r9 ; compare with type tag of a | |
jne ((165)) ; if not equal jump to stub | |
xorl 1, %r15d ; xor value of a with 1, true is value 1 so 1^1 = 0, false is 0 so 1^0 = 1 | |
; JavaScript Code: "a - 1" | |
movabsq $0xfff8800000000000, %r11 ; type tag of int | |
cmpq %r11, %r15 | |
jne ((73)) ; jump if not int | |
subl $0x1, %r9d ; subtract 1 | |
jo ((83)) ; jump if overflow | |
; JavaScript Code: "if (a)" | |
movabsq $0xfff9800000000000, %r11 | |
cmpq %r11, %r15 | |
jne ((86)) ; jump if not boolean | |
testl %r9d, %r9d ; test | |
jne ((95)) ; jump false | |
jmp ((100)) ; jump true | |
; JavaScript Code: "if (a == 1) | |
movabsq $0xfff8800000000000, %r11 | |
cmpq %r11, %r12 | |
jne ((70)) | |
cmpl $0x1, %r15d | |
jne ((80)) |
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