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tcg/arm: Use ldr (literal) for goto_tb 

The new placement of the TB means that we can use one insn
to load the goto_tb destination directly from the TB.

Signed-off-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Richard Henderson 2017-06-05 19:42:51 -04:00
parent 9c39b94f14
commit 308714e6bc
1 changed files with 18 additions and 5 deletions
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21
tcg/arm/tcg-target.inc.c
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@ -1669,14 +1669,27 @@ static inline void tcg_out_op(TCGContext *s, TCGOpcode opc,
} }
break; break;
case INDEX_op_goto_tb: case INDEX_op_goto_tb:
tcg_debug_assert(s->tb_jmp_insn_offset == 0);
{ {
/* Indirect jump method */ /* Indirect jump method */
intptr_t ptr = (intptr_t)(s->tb_jmp_target_addr + args[0]); intptr_t ptr, dif, dil;
tcg_out_movi32(s, COND_AL, TCG_REG_R0, ptr & ~0xfff); TCGReg base = TCG_REG_PC;
tcg_out_ld32_12(s, COND_AL, TCG_REG_PC, TCG_REG_R0, ptr & 0xfff);
tcg_debug_assert(s->tb_jmp_insn_offset == 0);
ptr = (intptr_t)(s->tb_jmp_target_addr + args[0]);
dif = ptr - ((intptr_t)s->code_ptr + 8);
dil = sextract32(dif, 0, 12);
if (dif != dil) {
/* The TB is close, but outside the 12 bits addressable by
the load. We can extend this to 20 bits with a sub of a
shifted immediate from pc. In the vastly unlikely event
the code requires more than 1MB, we'll use 2 insns and
be no worse off. */
base = TCG_REG_R0;
tcg_out_movi32(s, COND_AL, base, ptr - dil);
} }
tcg_out_ld32_12(s, COND_AL, TCG_REG_PC, base, dil);
s->tb_jmp_reset_offset[args[0]] = tcg_current_code_size(s); s->tb_jmp_reset_offset[args[0]] = tcg_current_code_size(s);
}
break; break;
case INDEX_op_goto_ptr: case INDEX_op_goto_ptr:
tcg_out_bx(s, COND_AL, args[0]); tcg_out_bx(s, COND_AL, args[0]);