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py/asmrv32: Use REG_TEMP2 whenever possible.
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The RV32 emitter used an additional temporary register, as certain code
sequences required extra storage.  This commit removes its usage in all
but one case, using REG_TEMP2 instead.

Signed-off-by: Alessandro Gatti <a.gatti@frob.it>
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@agatti @dpgeorge
agatti authored and dpgeorge committed Aug 19, 2024
1 parent da0e027 commit 7d8b2d8
Showing 1 changed file with 18 additions and 28 deletions.
46 changes: 18 additions & 28 deletions py/asmrv32.c
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Original file line number Diff line number Diff line change
Expand Up @@ -312,25 +312,23 @@ void asm_rv32_emit_call_ind(asm_rv32_t *state, mp_uint_t index) {
if (FIT_UNSIGNED(offset, 11)) {
// lw temporary, offset(fun_table)
// c.jalr temporary
asm_rv32_opcode_lw(state, INTERNAL_TEMPORARY, REG_FUN_TABLE, offset);
asm_rv32_opcode_cjalr(state, INTERNAL_TEMPORARY);
asm_rv32_opcode_lw(state, REG_TEMP2, REG_FUN_TABLE, offset);
asm_rv32_opcode_cjalr(state, REG_TEMP2);
return;
}

mp_uint_t upper = 0;
mp_uint_t lower = 0;
split_immediate(offset, &upper, &lower);

// TODO: Can this clobber REG_TEMP[0:2]?

// lui temporary, HI(index) ; Or c.lui if possible
// c.add temporary, fun_table
// lw temporary, LO(index)(temporary)
// c.jalr temporary
load_upper_immediate(state, INTERNAL_TEMPORARY, upper);
asm_rv32_opcode_cadd(state, INTERNAL_TEMPORARY, REG_FUN_TABLE);
asm_rv32_opcode_lw(state, INTERNAL_TEMPORARY, INTERNAL_TEMPORARY, lower);
asm_rv32_opcode_cjalr(state, INTERNAL_TEMPORARY);
load_upper_immediate(state, REG_TEMP2, upper);
asm_rv32_opcode_cadd(state, REG_TEMP2, REG_FUN_TABLE);
asm_rv32_opcode_lw(state, REG_TEMP2, REG_TEMP2, lower);
asm_rv32_opcode_cjalr(state, REG_TEMP2);
}

void asm_rv32_emit_jump_if_reg_eq(asm_rv32_t *state, mp_uint_t rs1, mp_uint_t rs2, mp_uint_t label) {
Expand All @@ -350,15 +348,13 @@ void asm_rv32_emit_jump_if_reg_eq(asm_rv32_t *state, mp_uint_t rs1, mp_uint_t rs
mp_uint_t lower = 0;
split_immediate(displacement, &upper, &lower);

// TODO: Can this clobber REG_TEMP[0:2]?

// bne rs1, rs2, 12 ; PC + 0
// auipc temporary, HI(displacement) ; PC + 4
// jalr zero, temporary, LO(displacement) ; PC + 8
// ... ; PC + 12
asm_rv32_opcode_bne(state, rs1, rs2, 12);
asm_rv32_opcode_auipc(state, INTERNAL_TEMPORARY, upper);
asm_rv32_opcode_jalr(state, ASM_RV32_REG_ZERO, INTERNAL_TEMPORARY, lower);
asm_rv32_opcode_auipc(state, REG_TEMP2, upper);
asm_rv32_opcode_jalr(state, ASM_RV32_REG_ZERO, REG_TEMP2, lower);
}

void asm_rv32_emit_jump_if_reg_nonzero(asm_rv32_t *state, mp_uint_t rs, mp_uint_t label) {
Expand All @@ -377,8 +373,6 @@ void asm_rv32_emit_jump_if_reg_nonzero(asm_rv32_t *state, mp_uint_t rs, mp_uint_
return;
}

// TODO: Can this clobber REG_TEMP[0:2]?

// if rs1 in C window and displacement is negative:
// c.beqz rs', 10 ; PC + 0
// auipc temporary, HI(displacement) ; PC + 2
Expand All @@ -403,8 +397,8 @@ void asm_rv32_emit_jump_if_reg_nonzero(asm_rv32_t *state, mp_uint_t rs, mp_uint_
mp_uint_t upper = 0;
mp_uint_t lower = 0;
split_immediate(displacement, &upper, &lower);
asm_rv32_opcode_auipc(state, INTERNAL_TEMPORARY, upper);
asm_rv32_opcode_jalr(state, ASM_RV32_REG_ZERO, INTERNAL_TEMPORARY, lower);
asm_rv32_opcode_auipc(state, REG_TEMP2, upper);
asm_rv32_opcode_jalr(state, ASM_RV32_REG_ZERO, REG_TEMP2, lower);
}

void asm_rv32_emit_mov_local_reg(asm_rv32_t *state, mp_uint_t local, mp_uint_t rs) {
Expand All @@ -426,14 +420,12 @@ void asm_rv32_emit_mov_local_reg(asm_rv32_t *state, mp_uint_t local, mp_uint_t r
mp_uint_t lower = 0;
split_immediate(offset, &upper, &lower);

// TODO: Can this clobber REG_TEMP[0:2]?

// lui temporary, HI(offset) ; Or c.lui if possible
// c.add temporary, sp
// sw rs, LO(offset)(temporary)
load_upper_immediate(state, INTERNAL_TEMPORARY, upper);
asm_rv32_opcode_cadd(state, INTERNAL_TEMPORARY, ASM_RV32_REG_SP);
asm_rv32_opcode_sw(state, rs, INTERNAL_TEMPORARY, lower);
load_upper_immediate(state, REG_TEMP2, upper);
asm_rv32_opcode_cadd(state, REG_TEMP2, ASM_RV32_REG_SP);
asm_rv32_opcode_sw(state, rs, REG_TEMP2, lower);
}

void asm_rv32_emit_mov_reg_local(asm_rv32_t *state, mp_uint_t rd, mp_uint_t local) {
Expand Down Expand Up @@ -525,12 +517,10 @@ void asm_rv32_emit_jump(asm_rv32_t *state, mp_uint_t label) {
mp_uint_t lower = 0;
split_immediate(displacement, &upper, &lower);

// TODO: Can this clobber REG_TEMP[0:2]?

// auipc temporary, HI(displacement)
// jalr zero, temporary, LO(displacement)
asm_rv32_opcode_auipc(state, INTERNAL_TEMPORARY, upper);
asm_rv32_opcode_jalr(state, ASM_RV32_REG_ZERO, INTERNAL_TEMPORARY, lower);
asm_rv32_opcode_auipc(state, REG_TEMP2, upper);
asm_rv32_opcode_jalr(state, ASM_RV32_REG_ZERO, REG_TEMP2, lower);
}

void asm_rv32_emit_store_reg_reg_offset(asm_rv32_t *state, mp_uint_t rd, mp_uint_t rs, mp_int_t offset) {
Expand All @@ -549,9 +539,9 @@ void asm_rv32_emit_store_reg_reg_offset(asm_rv32_t *state, mp_uint_t rd, mp_uint
// lui temporary, HI(offset) ; Or c.lui if possible
// c.add temporary, rs
// sw rd, LO(offset)(temporary)
load_upper_immediate(state, INTERNAL_TEMPORARY, upper);
asm_rv32_opcode_cadd(state, INTERNAL_TEMPORARY, rs);
asm_rv32_opcode_sw(state, rd, INTERNAL_TEMPORARY, lower);
load_upper_immediate(state, REG_TEMP2, upper);
asm_rv32_opcode_cadd(state, REG_TEMP2, rs);
asm_rv32_opcode_sw(state, rd, REG_TEMP2, lower);
}

void asm_rv32_emit_mov_reg_pcrel(asm_rv32_t *state, mp_uint_t rd, mp_uint_t label) {
Expand Down

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