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py/asmthumb: Optimise native code calling runtime glue functions. 

This patch makes the Thumb-2 native emitter use wide ldr instructions to
call into the runtime, when the index into the native glue function table
is 32 or greater.  This reduces the generated assembler code from 10 bytes
to 6 bytes, saving RAM and making native code run about 0.8% faster.
This commit is contained in:
Damien George 2018-07-31 15:06:28 +10:00
parent f6f6452b6f
commit 1e3a7f561f
1 changed files with 4 additions and 2 deletions
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6
py/asmthumb.c
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@ -353,6 +353,8 @@ void asm_thumb_bcc_label(asm_thumb_t *as, int cond, uint label) {
}
#define OP_BLX(reg) (0x4780 | ((reg) << 3))
#define OP_LDR_W_HI(reg_base) (0xf8d0 | (reg_base))
#define OP_LDR_W_LO(reg_dest, imm12) ((reg_dest) << 12 | (imm12))
#define OP_SVC(arg) (0xdf00 | (arg))
void asm_thumb_bl_ind(asm_thumb_t *as, void *fun_ptr, uint fun_id, uint reg_temp) {
@ -370,8 +372,8 @@ void asm_thumb_bl_ind(asm_thumb_t *as, void *fun_ptr, uint fun_id, uint reg_temp
asm_thumb_op16(as, ASM_THUMB_FORMAT_9_10_ENCODE(ASM_THUMB_FORMAT_9_LDR | ASM_THUMB_FORMAT_9_WORD_TRANSFER, reg_temp, ASM_THUMB_REG_R7, fun_id));
asm_thumb_op16(as, OP_BLX(reg_temp));
} else {
// load ptr to function into register using immediate; 6 bytes
asm_thumb_mov_reg_i32(as, reg_temp, (mp_uint_t)fun_ptr);
// load ptr to function from table, indexed by fun_id using wide load; 6 bytes
asm_thumb_op32(as, OP_LDR_W_HI(ASM_THUMB_REG_R7), OP_LDR_W_LO(reg_temp, fun_id << 2));
asm_thumb_op16(as, OP_BLX(reg_temp));
}
}