decr-stack-reg ( n -- )
CPU x86 compiler backend

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Vocabulary
cpu.x86

Inputs

n

a number

Outputs
None

Word description
Emits an instruction for decrementing the stack register the given number of bytes. If n is equal to the cell size, then a PUSH instruction is emitted instead because it has a shorter encoding.

Definition

USING: cpu.x86.assembler kernel layouts math ;

IN: cpu.x86

: decr-stack-reg ( n -- )
    [
        dup cell =
        [ drop pic-tail-reg PUSH ] [ stack-reg swap SUB ] if
    ] unless-zero ;