picorv32/firmware/start.S

	.section .text
	.global irq
	.global sieve
	.global stats

#define TEST(n) \
	.global n; .global n ## _ret; \
	addi x1, zero, 1000; \
	custom0 0,1,0,5; /* timer x1 */ \
	jal zero,n; n ## _ret:

reset_vec:
	custom0 0,0,0,3 // maskirq zero, zero
	j start
	nop
	nop

irq_vec:
	/* save registers */

	custom0 2,1,0,1 // setq q2, x1
	custom0 3,2,0,1 // setq q3, x2

	lui x1, %hi(irq_regs)
	addi x1, x1, %lo(irq_regs)

	custom0 2,0,0,0 // getq x2, q0
	sw x2,   0*4(x1)

	custom0 2,2,0,0 // getq x2, q2
	sw x2,   1*4(x1)

	custom0 2,3,0,0 // getq x2, q3
	sw x2,   2*4(x1)

	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)

	/* call interrupt handler */

	lui sp, %hi(irq_stack_top)
	addi sp, sp, %lo(irq_stack_top)

	// arg0 = address of regs
	lui a0, %hi(irq_regs)
	addi a0, a0, %lo(irq_regs)

	// arg1 = interrupt type
	custom0 11,1,0,0 // getq x11, q1

	// call to c function
	jal ra, irq

	/* restore registers */

	lui x1, %hi(irq_regs)
	addi x1, x1, %lo(irq_regs)

	lw x2,   0*4(x1)
	custom0 0,2,0,1 // setq q0, x2

	lw x2,   1*4(x1)
	custom0 1,2,0,1 // setq q1, x2

	lw x2,   2*4(x1)
	custom0 2,2,0,1 // setq q2, x2

	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)

	custom0 1,1,0,0 // getq x1, q1
	custom0 2,2,0,0 // getq x2, q2

	custom0 0,0,0,2 // retirq

irq_regs:
	// registers are saved to this memory region
	// the program counter is saved as register 0
	.fill 32,4

irq_stack:
	.fill 128,4
irq_stack_top:

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

	TEST(lui)
	TEST(auipc)
	TEST(j)
	TEST(jal)
	TEST(jalr)

	TEST(beq)
	TEST(bne)
	TEST(blt)
	TEST(bge)
	TEST(bltu)
	TEST(bgeu)

	TEST(lb)
	TEST(lh)
	TEST(lw)
	TEST(lbu)
	TEST(lhu)

	TEST(sb)
	TEST(sh)
	TEST(sw)

	TEST(addi)
	TEST(slti) // also tests sltiu
	TEST(xori)
	TEST(ori)
	TEST(andi)
	TEST(slli)
	TEST(srli)
	TEST(srai)

	TEST(add)
	TEST(sub)
	TEST(sll)
	TEST(slt) // what is with sltu ?
	TEST(xor)
	TEST(srl)
	TEST(sra)
	TEST(or)
	TEST(and)

	TEST(simple)

	/* set stack pointer */
	lui sp,(64*1024)>>12

	/* jump to sieve C code */
	jal ra,sieve

	/* jump to stats C code */
	jal ra,stats

	/* print "DONE\n" */
	lui a0,0x10000000>>12
	addi a1,zero,'D'
	addi a2,zero,'O'
	addi a3,zero,'N'
	addi a4,zero,'E'
	addi a5,zero,'\n'
	sw a1,0(a0)
	sw a2,0(a0)
	sw a3,0(a0)
	sw a4,0(a0)
	sw a5,0(a0)

	/* break */
	sbreak