From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45036) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dL0m9-0001u0-VA for qemu-devel@nongnu.org; Wed, 14 Jun 2017 01:23:30 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dL0m7-0007MO-5G for qemu-devel@nongnu.org; Wed, 14 Jun 2017 01:23:30 -0400 Received: from mail-qt0-x242.google.com ([2607:f8b0:400d:c0d::242]:34135) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1dL0m7-0007ME-0k for qemu-devel@nongnu.org; Wed, 14 Jun 2017 01:23:27 -0400 Received: by mail-qt0-x242.google.com with SMTP id o21so39043295qtb.1 for ; Tue, 13 Jun 2017 22:23:26 -0700 (PDT) Sender: Richard Henderson From: Richard Henderson Date: Tue, 13 Jun 2017 22:23:09 -0700 Message-Id: <20170614052311.13785-9-rth@twiddle.net> In-Reply-To: <20170614052311.13785-1-rth@twiddle.net> References: <20170614052311.13785-1-rth@twiddle.net> Subject: [Qemu-devel] [PULL 08/10] tcg/arm: Use ldr (literal) for goto_tb List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: peter.maydell@linaro.org 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 --- tcg/arm/tcg-target.inc.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-) diff --git a/tcg/arm/tcg-target.inc.c b/tcg/arm/tcg-target.inc.c index 42370e5..d1793ec 100644 --- a/tcg/arm/tcg-target.inc.c +++ b/tcg/arm/tcg-target.inc.c @@ -1669,14 +1669,27 @@ static inline void tcg_out_op(TCGContext *s, TCGOpcode opc, } break; case INDEX_op_goto_tb: - tcg_debug_assert(s->tb_jmp_insn_offset == 0); { /* Indirect jump method */ - intptr_t ptr = (intptr_t)(s->tb_jmp_target_addr + args[0]); - tcg_out_movi32(s, COND_AL, TCG_REG_R0, ptr & ~0xfff); - tcg_out_ld32_12(s, COND_AL, TCG_REG_PC, TCG_REG_R0, ptr & 0xfff); + intptr_t ptr, dif, dil; + TCGReg base = TCG_REG_PC; + + 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; case INDEX_op_goto_ptr: tcg_out_bx(s, COND_AL, args[0]); -- 2.9.4