|
From: | Richard Henderson |
Subject: | Re: [Qemu-devel] [PATCH for-2.5 12/30] m68k: Manage divw overflow |
Date: | Tue, 11 Aug 2015 23:03:35 -0700 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 |
On 08/09/2015 01:13 PM, Laurent Vivier wrote:
"Overflow may be detected and set before the instruction completes. If the instruction detects an overflow, it sets the overflow condition code, and the operands are unaffected."
May also implies may not. I presume this is important for matching hardware? Is there some program you know of that depends on this?
+ /* dest.l / src.w */ + + dest = DREG(insn, 9); + tcg_gen_mov_i32(QREG_DIV1, dest); + SRC_EA(env, src, OS_WORD, sign, NULL); tcg_gen_mov_i32(QREG_DIV2, src); + + /* div1 / div2 */ + if (sign) { gen_helper_divs(cpu_env, tcg_const_i32(1)); } else { gen_helper_divu(cpu_env, tcg_const_i32(1)); } + set_cc_op(s, CC_OP_FLAGS); + + l1 = gen_new_label(); + gen_jmpcc(s, 9 /* V */, l1); tmp = tcg_temp_new(); src = tcg_temp_new(); tcg_gen_ext16u_i32(tmp, QREG_DIV1); tcg_gen_shli_i32(src, QREG_DIV2, 16); - tcg_gen_or_i32(reg, tmp, src); - set_cc_op(s, CC_OP_FLAGS); + tcg_gen_or_i32(dest, tmp, src); + gen_set_label(l1);
All that said, it's possible to implement this branch inside the helper via exception. Or simply return the inputs to effect no change.
r~
[Prev in Thread] | Current Thread | [Next in Thread] |