From: Richard Henderson <richard.henderson@linaro.org>
To: Alistair Francis <alistair.francis@wdc.com>,
qemu-devel@nongnu.org, qemu-riscv@nongnu.org
Cc: alistair23@gmail.com, bmeng.cn@gmail.com, palmer@dabbelt.com
Subject: Re: [PATCH v2 8/9] target/riscv: Consolidate RV32/64 32-bit instructions
Date: Tue, 13 Apr 2021 20:42:51 -0700 [thread overview]
Message-ID: <77d3d314-a03e-e081-04c0-a22447fd2658@linaro.org> (raw)
In-Reply-To: <058e2779f8bcd25816bc2338a44ab6f1b2d549db.1618356725.git.alistair.francis@wdc.com>
On 4/13/21 4:34 PM, Alistair Francis wrote:
> -#ifndef CONFIG_USER_ONLY
> -# ifdef TARGET_RISCV32
> -# define is_32bit(ctx) true
> -# else
> +#ifdef TARGET_RISCV32
> +# define is_32bit(ctx) true
> +#else
> static inline bool is_32bit(DisasContext *ctx)
> {
> - return !(ctx->misa & RV64);
> + return (ctx->misa & RV32) == RV32;
Why the change here? Also note the previous comment about fixing this to false
for TARGET_RISCV64 && CONFIG_USER_ONLY.
> static bool trans_fcvt_l_d(DisasContext *ctx, arg_fcvt_l_d *a)
> {
> REQUIRE_FPU;
> REQUIRE_EXT(ctx, RVD);
> + REQUIRE_64BIT(ctx);
I think you should always put the 64-bit check first.
That way, on TARGET_RISCV32, the entire function folds away.
>
> - TCGv t0 = tcg_temp_new();
> + TCGv_i64 t0 = tcg_temp_new_i64();
> gen_set_rm(ctx, a->rm);
> gen_helper_fcvt_l_d(t0, cpu_env, cpu_fpr[a->rs1]);
> - gen_set_gpr(a->rd, t0);
> - tcg_temp_free(t0);
> + gen_set_gpr(a->rd, (TCGv) t0);
So... I really don't like the cast.
This is fixable one of two ways.
(1) Change the real helper to use target_ulong.
(2) Use the gen_helper_* stubs that I talked about in reply to v1.
> @@ -390,8 +390,9 @@ static bool trans_fmv_x_d(DisasContext *ctx, arg_fmv_x_d *a)
> {
> REQUIRE_FPU;
> REQUIRE_EXT(ctx, RVD);
> + REQUIRE_64BIT(ctx);
>
> - gen_set_gpr(a->rd, cpu_fpr[a->rs1]);
> + gen_set_gpr(a->rd, (TCGv) cpu_fpr[a->rs1]);
This one's different, and might be worth
#ifdef TARGET_RISCV64
gen_set_gpr
#else
qemu_build_not_reached
#endif
> +++ b/target/riscv/insn_trans/trans_rvf.c.inc
> @@ -303,11 +303,11 @@ static bool trans_fmv_x_w(DisasContext *ctx, arg_fmv_x_w *a)
>
> TCGv t0 = tcg_temp_new();
>
> -#if defined(TARGET_RISCV64)
> - tcg_gen_ext32s_tl(t0, cpu_fpr[a->rs1]);
> -#else
> - tcg_gen_extrl_i64_i32(t0, cpu_fpr[a->rs1]);
> -#endif
> + if (!is_32bit(ctx)) {
> + tcg_gen_ext32s_tl((TCGv) t0, (TCGv) cpu_fpr[a->rs1]);
> + } else {
> + tcg_gen_extrl_i64_i32((TCGv_i32) t0, cpu_fpr[a->rs1]);
> + }
I think you should leave this ifdef alone. The ifdef has determined the size
of target_ulong and thus the size of TCGv, and thus the correct move to use.
If TARGET_RISCV64 and is_32bit, the high bits are ignored; the fact that they
happen to be copies of the sign bit is irrelevant.
r~
next prev parent reply other threads:[~2021-04-14 3:44 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-13 23:32 [PATCH v2 0/9] RISC-V: Steps towards running 32-bit guests on Alistair Francis
2021-04-13 23:33 ` [PATCH v2 1/9] target/riscv: Remove the hardcoded RVXLEN macro Alistair Francis
2021-04-14 7:59 ` Bin Meng
2021-04-13 23:33 ` [PATCH v2 2/9] target/riscv: Remove the hardcoded SSTATUS_SD macro Alistair Francis
2021-04-14 7:59 ` Bin Meng
2021-04-13 23:33 ` [PATCH v2 3/9] target/riscv: Remove the hardcoded HGATP_MODE macro Alistair Francis
2021-04-14 7:59 ` Bin Meng
2021-04-13 23:33 ` [PATCH v2 4/9] target/riscv: Remove the hardcoded MSTATUS_SD macro Alistair Francis
2021-04-14 3:13 ` Richard Henderson
2021-04-13 23:34 ` [PATCH v2 5/9] target/riscv: Remove the hardcoded SATP_MODE macro Alistair Francis
2021-04-14 3:14 ` Richard Henderson
2021-04-14 8:00 ` Bin Meng
2021-04-13 23:34 ` [PATCH v2 6/9] target/riscv: Remove the unused HSTATUS_WPRI macro Alistair Francis
2021-04-14 8:00 ` Bin Meng
2021-04-13 23:34 ` [PATCH v2 7/9] target/riscv: Remove an unused CASE_OP_32_64 macro Alistair Francis
2021-04-14 8:00 ` Bin Meng
2021-04-13 23:34 ` [PATCH v2 8/9] target/riscv: Consolidate RV32/64 32-bit instructions Alistair Francis
2021-04-14 3:42 ` Richard Henderson [this message]
2021-04-22 2:01 ` Alistair Francis
2021-04-13 23:34 ` [PATCH v2 9/9] target/riscv: Consolidate RV32/64 16-bit instructions Alistair Francis
2021-04-14 3:57 ` Richard Henderson
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