64 lines
1.9 KiB
ArmAsm
64 lines
1.9 KiB
ArmAsm
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// ----------------------------------------------------------------------------
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// Copyright (c) 1992 Olivetti
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//
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// File: subrout.s
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//
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// Description: Assembly subroutines used throughout the ROM.
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// ----------------------------------------------------------------------------
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//
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// include header files
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//
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#include <ksmips.h>
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.text
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.set noreorder
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// ----------------------------------------------------------------------------
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// PROCEDURE: StatusReg:
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//
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// DESCRIPTION: This function updates the CPU status register
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// ( CPU0 reg. 12 ).
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// The register is "&" with a0 and "|" with a1.
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// The old register value is returned to the calling
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// routine in v0.
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//
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//
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// ARGUMENTS: a0 & with Status register
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// a1 | with Status register
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//
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// RETURN: v0 Old Status register value
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//
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// ASSUMPTIONS: none
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//
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// CALLS: none
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//
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// GLOBALS: none
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//
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// NOTES: none
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// ----------------------------------------------------------------------------
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//
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LEAF_ENTRY(StatusReg)
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.set noat
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//
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// The first argument is "&" and the second is "|" with the status register.
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//
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mfc0 v0, psr // read status register
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nop // required by mfc before using v0
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nop // to avoid hazards
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move t0, v0 // make a copy of it
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and t0, t0, a0 // "&" with 1st parameter
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or t0, t0, a1 // "|" with 2nd parameter
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mtc0 t0, psr // write status register
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nop
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nop
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j ra // return
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nop // required by "j ra"
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.end StatusReg
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