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Date: Thu, 14 Mar 2024 14:44:03 +0100
From: Leah Neukirchen <leah@...u.org>
To: lixing <lixing@...ngson.cn>
Cc: musl@...ts.openwall.com
Subject: Re: loongarch64 atomics not working?
lixing <lixing@...ngson.cn> writes:
> we checked the objdump binaries for -Os and -O2, the a_cas_p implement
> looks ok for both.
>
> Also, we cross build the musl and mksh with -Os, the binary hang with
> qemu user mode emulation , but not hang in the real hardware.
>
> so, maybe this is a qemu problem, we will let our qemu guys to check
> this problem.
Pretty surely it's a bug in QEMU. qemu 8.1.5 works with mksh.Os,
qemu 8.2.1 hangs. I have bisected the issue down to:
commit c5af6628f4be5d30800233e59ba3842ca19a12e6 (HEAD)
Author: Jiajie Chen <c@....je>
Date: Tue Aug 22 09:13:52 2023 +0200
target/loongarch: Extract make_address_i() helper
Reverting this hunk fixes it:
diff --git a/target/loongarch/insn_trans/trans_atomic.c.inc b/target/loongarch/insn_trans/trans_atomic.c.inc
index fbc081448d..bff3e7a74c 100644
--- a/target/loongarch/insn_trans/trans_atomic.c.inc
+++ b/target/loongarch/insn_trans/trans_atomic.c.inc
@@ -7,8 +7,9 @@ static bool gen_ll(DisasContext *ctx, arg_rr_i *a, MemOp mop)
{
TCGv dest = gpr_dst(ctx, a->rd, EXT_NONE);
TCGv src1 = gpr_src(ctx, a->rj, EXT_NONE);
- TCGv t0 = make_address_i(ctx, src1, a->imm);
+ TCGv t0 = tcg_temp_new();
+ tcg_gen_addi_tl(t0, src1, a->imm);
tcg_gen_qemu_ld_i64(dest, t0, ctx->mem_idx, mop);
tcg_gen_st_tl(t0, cpu_env, offsetof(CPULoongArchState, lladdr));
tcg_gen_st_tl(dest, cpu_env, offsetof(CPULoongArchState, llval));
I think the issue is that make_address_i optimizes the addition away
if a->imm is zero, but that's just from looking at the code for 15min.
hth,
--
Leah Neukirchen <leah@...u.org> https://leahneukirchen.org/
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