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start.S
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// This is free and unencumbered software released into the public domain.
//
// Anyone is free to copy, modify, publish, use, compile, sell, or
// distribute this software, either in source code form or as a compiled
// binary, for any purpose, commercial or non-commercial, and by any
// means.
#define ENABLE_QREGS
#include "custom_ops.S"
.section .text;
.global setup;
.global loop;
.global yield;
.global _start;
.global irq;
.global cli;
.global sei;
.global seai;
reset_vec:
#ifdef ENABLE_INTERRUPTS
// no more than 16 bytes here !
picorv32_waitirq_insn(zero)
picorv32_maskirq_insn(zero, zero)
j start
/* Interrupt handler
**********************************/
.balign 16
irq_vec:
/* save registers */
#ifdef ENABLE_QREGS
picorv32_setq_insn(q2, x1)
picorv32_setq_insn(q3, x2)
lui x1, %hi(irq_regs)
addi x1, x1, %lo(irq_regs)
picorv32_getq_insn(x2, q0)
sw x2, 0*4(x1)
picorv32_getq_insn(x2, q2)
sw x2, 1*4(x1)
picorv32_getq_insn(x2, q3)
sw x2, 2*4(x1)
#ifdef ENABLE_FASTIRQ
sw x5, 5*4(x1)
sw x6, 6*4(x1)
sw x7, 7*4(x1)
sw x10, 10*4(x1)
sw x11, 11*4(x1)
sw x12, 12*4(x1)
sw x13, 13*4(x1)
sw x14, 14*4(x1)
sw x15, 15*4(x1)
sw x16, 16*4(x1)
sw x17, 17*4(x1)
sw x28, 28*4(x1)
sw x29, 29*4(x1)
sw x30, 30*4(x1)
sw x31, 31*4(x1)
#else
sw x3, 3*4(x1)
sw x4, 4*4(x1)
sw x5, 5*4(x1)
sw x6, 6*4(x1)
sw x7, 7*4(x1)
sw x8, 8*4(x1)
sw x9, 9*4(x1)
sw x10, 10*4(x1)
sw x11, 11*4(x1)
sw x12, 12*4(x1)
sw x13, 13*4(x1)
sw x14, 14*4(x1)
sw x15, 15*4(x1)
sw x16, 16*4(x1)
sw x17, 17*4(x1)
sw x18, 18*4(x1)
sw x19, 19*4(x1)
sw x20, 20*4(x1)
sw x21, 21*4(x1)
sw x22, 22*4(x1)
sw x23, 23*4(x1)
sw x24, 24*4(x1)
sw x25, 25*4(x1)
sw x26, 26*4(x1)
sw x27, 27*4(x1)
sw x28, 28*4(x1)
sw x29, 29*4(x1)
sw x30, 30*4(x1)
sw x31, 31*4(x1)
#endif
#else // ENABLE_QREGS
#ifdef ENABLE_FASTIRQ
sw gp, 0*4+0x200(zero)
sw x1, 1*4+0x200(zero)
sw x2, 2*4+0x200(zero)
sw x5, 5*4+0x200(zero)
sw x6, 6*4+0x200(zero)
sw x7, 7*4+0x200(zero)
sw x10, 10*4+0x200(zero)
sw x11, 11*4+0x200(zero)
sw x12, 12*4+0x200(zero)
sw x13, 13*4+0x200(zero)
sw x14, 14*4+0x200(zero)
sw x15, 15*4+0x200(zero)
sw x16, 16*4+0x200(zero)
sw x17, 17*4+0x200(zero)
sw x28, 28*4+0x200(zero)
sw x29, 29*4+0x200(zero)
sw x30, 30*4+0x200(zero)
sw x31, 31*4+0x200(zero)
#else
sw gp, 0*4+0x200(zero)
sw x1, 1*4+0x200(zero)
sw x2, 2*4+0x200(zero)
sw x3, 3*4+0x200(zero)
sw x4, 4*4+0x200(zero)
sw x5, 5*4+0x200(zero)
sw x6, 6*4+0x200(zero)
sw x7, 7*4+0x200(zero)
sw x8, 8*4+0x200(zero)
sw x9, 9*4+0x200(zero)
sw x10, 10*4+0x200(zero)
sw x11, 11*4+0x200(zero)
sw x12, 12*4+0x200(zero)
sw x13, 13*4+0x200(zero)
sw x14, 14*4+0x200(zero)
sw x15, 15*4+0x200(zero)
sw x16, 16*4+0x200(zero)
sw x17, 17*4+0x200(zero)
sw x18, 18*4+0x200(zero)
sw x19, 19*4+0x200(zero)
sw x20, 20*4+0x200(zero)
sw x21, 21*4+0x200(zero)
sw x22, 22*4+0x200(zero)
sw x23, 23*4+0x200(zero)
sw x24, 24*4+0x200(zero)
sw x25, 25*4+0x200(zero)
sw x26, 26*4+0x200(zero)
sw x27, 27*4+0x200(zero)
sw x28, 28*4+0x200(zero)
sw x29, 29*4+0x200(zero)
sw x30, 30*4+0x200(zero)
sw x31, 31*4+0x200(zero)
#endif
#endif // ENABLE_QREGS
/* call interrupt handler C function */
lui sp, %hi(irq_stack)
addi sp, sp, %lo(irq_stack)
// arg0 = address of regs
lui a0, %hi(irq_regs)
addi a0, a0, %lo(irq_regs)
// arg1 = interrupt type
#ifdef ENABLE_QREGS
picorv32_getq_insn(a1, q1)
#else
addi a1, tp, 0
#endif
// call to C function
jal ra, irq
/* restore registers */
#ifdef ENABLE_QREGS
// new irq_regs address returned from C code in a0
addi x1, a0, 0
lw x2, 0*4(x1)
picorv32_setq_insn(q0, x2)
lw x2, 1*4(x1)
picorv32_setq_insn(q1, x2)
lw x2, 2*4(x1)
picorv32_setq_insn(q2, x2)
#ifdef ENABLE_FASTIRQ
lw x5, 5*4(x1)
lw x6, 6*4(x1)
lw x7, 7*4(x1)
lw x10, 10*4(x1)
lw x11, 11*4(x1)
lw x12, 12*4(x1)
lw x13, 13*4(x1)
lw x14, 14*4(x1)
lw x15, 15*4(x1)
lw x16, 16*4(x1)
lw x17, 17*4(x1)
lw x28, 28*4(x1)
lw x29, 29*4(x1)
lw x30, 30*4(x1)
lw x31, 31*4(x1)
#else
lw x3, 3*4(x1)
lw x4, 4*4(x1)
lw x5, 5*4(x1)
lw x6, 6*4(x1)
lw x7, 7*4(x1)
lw x8, 8*4(x1)
lw x9, 9*4(x1)
lw x10, 10*4(x1)
lw x11, 11*4(x1)
lw x12, 12*4(x1)
lw x13, 13*4(x1)
lw x14, 14*4(x1)
lw x15, 15*4(x1)
lw x16, 16*4(x1)
lw x17, 17*4(x1)
lw x18, 18*4(x1)
lw x19, 19*4(x1)
lw x20, 20*4(x1)
lw x21, 21*4(x1)
lw x22, 22*4(x1)
lw x23, 23*4(x1)
lw x24, 24*4(x1)
lw x25, 25*4(x1)
lw x26, 26*4(x1)
lw x27, 27*4(x1)
lw x28, 28*4(x1)
lw x29, 29*4(x1)
lw x30, 30*4(x1)
lw x31, 31*4(x1)
#endif
picorv32_getq_insn(x1, q1)
picorv32_getq_insn(x2, q2)
#else // ENABLE_QREGS
// new irq_regs address returned from C code in a0
addi a1, zero, 0x200
beq a0, a1, 1f
ebreak
1:
#ifdef ENABLE_FASTIRQ
lw gp, 0*4+0x200(zero)
lw x1, 1*4+0x200(zero)
lw x2, 2*4+0x200(zero)
lw x5, 5*4+0x200(zero)
lw x6, 6*4+0x200(zero)
lw x7, 7*4+0x200(zero)
lw x10, 10*4+0x200(zero)
lw x11, 11*4+0x200(zero)
lw x12, 12*4+0x200(zero)
lw x13, 13*4+0x200(zero)
lw x14, 14*4+0x200(zero)
lw x15, 15*4+0x200(zero)
lw x16, 16*4+0x200(zero)
lw x17, 17*4+0x200(zero)
lw x28, 28*4+0x200(zero)
lw x29, 29*4+0x200(zero)
lw x30, 30*4+0x200(zero)
lw x31, 31*4+0x200(zero)
#else
lw gp, 0*4+0x200(zero)
lw x1, 1*4+0x200(zero)
lw x2, 2*4+0x200(zero)
// do not restore x3 (gp)
lw x4, 4*4+0x200(zero)
lw x5, 5*4+0x200(zero)
lw x6, 6*4+0x200(zero)
lw x7, 7*4+0x200(zero)
lw x8, 8*4+0x200(zero)
lw x9, 9*4+0x200(zero)
lw x10, 10*4+0x200(zero)
lw x11, 11*4+0x200(zero)
lw x12, 12*4+0x200(zero)
lw x13, 13*4+0x200(zero)
lw x14, 14*4+0x200(zero)
lw x15, 15*4+0x200(zero)
lw x16, 16*4+0x200(zero)
lw x17, 17*4+0x200(zero)
lw x18, 18*4+0x200(zero)
lw x19, 19*4+0x200(zero)
lw x20, 20*4+0x200(zero)
lw x21, 21*4+0x200(zero)
lw x22, 22*4+0x200(zero)
lw x23, 23*4+0x200(zero)
lw x24, 24*4+0x200(zero)
lw x25, 25*4+0x200(zero)
lw x26, 26*4+0x200(zero)
lw x27, 27*4+0x200(zero)
lw x28, 28*4+0x200(zero)
lw x29, 29*4+0x200(zero)
lw x30, 30*4+0x200(zero)
lw x31, 31*4+0x200(zero)
#endif
#endif // ENABLE_QREGS
picorv32_retirq_insn()
#ifndef ENABLE_QREGS
.balign 0x200
#endif
irq_regs:
// registers are saved to this memory region during interrupt handling
// the program counter is saved as register 0
.fill 32,4
// stack for the interrupt handler
.fill 128,4
irq_stack:
#endif // ENABLE_INTERRUPTS
_start:
addi x1, zero, 0
addi x2, zero, 0
addi x3, zero, 0
addi x4, zero, 0
addi x5, zero, 0
addi x6, zero, 0
addi x7, zero, 0
addi x8, zero, 0
addi x9, zero, 0
addi x10, zero, 0
addi x11, zero, 0
addi x12, zero, 0
addi x13, zero, 0
addi x14, zero, 0
addi x15, zero, 0
addi x16, zero, 0
addi x17, zero, 0
addi x18, zero, 0
addi x19, zero, 0
addi x20, zero, 0
addi x21, zero, 0
addi x22, zero, 0
addi x23, zero, 0
addi x24, zero, 0
addi x25, zero, 0
addi x26, zero, 0
addi x27, zero, 0
addi x28, zero, 0
addi x29, zero, 0
addi x30, zero, 0
addi x31, zero, 0
/* set stack pointer */
li sp,4*1024
/* set gp and tp */
lui gp, %hi(0xdeadbeef)
addi gp, gp, %lo(0xdeadbeef)
addi tp, gp, 0
jal ra,main;
j reset_vec;
#ifdef ENABLE_INTERRUPTS
seai:
// Activate interrupts
maskirq a0, a0
ret
sei:
// Activate interrupts
maskirq a0, zero
ret
cli:
// Deactivate interrupts
li t0, 0xFFFFFFFF
maskirq a0, t0
ret
#endif // ENABLE_INTERRUPTS