target/loongarch: Remove cpu_fcsr0

All of the fpu operations are defined with TCG_CALL_NO_WG, but they
all modify FCSR0.  The most efficient way to fix this is to remove
cpu_fcsr0, and instead use explicit load and store operations for the
two instructions that manipulate that value.

Cc: Qi Hu <huqi@loongson.cn>
Cc: Song Gao <gaosong@loongson.cn>
Reported-by: Feiyang Chen <chenfeiyang@loongson.cn>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 target/loongarch/helper.h                    |  2 +-
 target/loongarch/fpu_helper.c                |  4 +--
 target/loongarch/translate.c                 |  3 --
 tests/tcg/loongarch64/test_fcsr.c            | 15 +++++++++
 target/loongarch/insn_trans/trans_fmov.c.inc | 33 ++++++++++----------
 tests/tcg/loongarch64/Makefile.target        |  1 +
 6 files changed, 36 insertions(+), 22 deletions(-)
 create mode 100644 tests/tcg/loongarch64/test_fcsr.c

> On Aug 7, 2022, at 01:09, Richard Henderson <richard.henderson@linaro.org> wrote:
> All of the fpu operations are defined with TCG_CALL_NO_WG, but they
> all modify FCSR0.  The most efficient way to fix this is to remove
> cpu_fcsr0, and instead use explicit load and store operations for the
> two instructions that manipulate that value.
> 
> Cc: Qi Hu <huqi@loongson.cn>
> Cc: Song Gao <gaosong@loongson.cn>
> Reported-by: Feiyang Chen <chenfeiyang@loongson.cn>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> target/loongarch/helper.h                    |  2 +-
> target/loongarch/fpu_helper.c                |  4 +--
> target/loongarch/translate.c                 |  3 --
> tests/tcg/loongarch64/test_fcsr.c            | 15 +++++++++
> target/loongarch/insn_trans/trans_fmov.c.inc | 33 ++++++++++----------
> tests/tcg/loongarch64/Makefile.target        |  1 +
> 6 files changed, 36 insertions(+), 22 deletions(-)
> create mode 100644 tests/tcg/loongarch64/test_fcsr.c
> 
> diff --git a/target/loongarch/helper.h b/target/loongarch/helper.h
> index cbbe008f32..9c01823a26 100644
> --- a/target/loongarch/helper.h
> +++ b/target/loongarch/helper.h
> @@ -91,7 +91,7 @@ DEF_HELPER_2(ftint_w_d, i64, env, i64)
> DEF_HELPER_2(frint_s, i64, env, i64)
> DEF_HELPER_2(frint_d, i64, env, i64)
> 
> -DEF_HELPER_FLAGS_2(set_rounding_mode, TCG_CALL_NO_RWG, void, env, i32)
> +DEF_HELPER_FLAGS_1(set_rounding_mode, TCG_CALL_NO_RWG, void, env)
> 
> DEF_HELPER_1(rdtime_d, i64, env)
> 
> diff --git a/target/loongarch/fpu_helper.c b/target/loongarch/fpu_helper.c
> index bd76529219..4b9637210a 100644
> --- a/target/loongarch/fpu_helper.c
> +++ b/target/loongarch/fpu_helper.c
> @@ -872,8 +872,8 @@ uint64_t helper_ftint_w_d(CPULoongArchState *env, uint64_t fj)
>     return fd;
> }
> 
> -void helper_set_rounding_mode(CPULoongArchState *env, uint32_t fcsr0)
> +void helper_set_rounding_mode(CPULoongArchState *env)
> {
> -    set_float_rounding_mode(ieee_rm[(fcsr0 >> FCSR0_RM) & 0x3],
> +    set_float_rounding_mode(ieee_rm[(env->fcsr0 >> FCSR0_RM) & 0x3],
>                             &env->fp_status);
> }
> diff --git a/target/loongarch/translate.c b/target/loongarch/translate.c
> index c9afd11420..51ba291430 100644
> --- a/target/loongarch/translate.c
> +++ b/target/loongarch/translate.c
> @@ -22,7 +22,6 @@
> /* Global register indices */
> TCGv cpu_gpr[32], cpu_pc;
> static TCGv cpu_lladdr, cpu_llval;
> -TCGv_i32 cpu_fcsr0;
> TCGv_i64 cpu_fpr[32];
> 
> #include "exec/gen-icount.h"
> @@ -266,8 +265,6 @@ void loongarch_translate_init(void)
>     }
> 
>     cpu_pc = tcg_global_mem_new(cpu_env, offsetof(CPULoongArchState, pc), "pc");
> -    cpu_fcsr0 = tcg_global_mem_new_i32(cpu_env,
> -                    offsetof(CPULoongArchState, fcsr0), "fcsr0");
>     cpu_lladdr = tcg_global_mem_new(cpu_env,
>                     offsetof(CPULoongArchState, lladdr), "lladdr");
>     cpu_llval = tcg_global_mem_new(cpu_env,
> diff --git a/tests/tcg/loongarch64/test_fcsr.c b/tests/tcg/loongarch64/test_fcsr.c
> new file mode 100644
> index 0000000000..ad3609eb99
> --- /dev/null
> +++ b/tests/tcg/loongarch64/test_fcsr.c
> @@ -0,0 +1,15 @@
> +#include <assert.h>
> +
> +int main()
> +{
> +    unsigned fcsr;
> +
> +    asm("movgr2fcsr $r0,$r0\n\t"
> +        "movgr2fr.d $f0,$r0\n\t"
> +        "fdiv.d     $f0,$f0,$f0\n\t"
> +        "movfcsr2gr %0,$r0"
> +        : "=r"(fcsr) : : "f0");
> +
> +    assert(fcsr & (16 << 16)); /* Invalid */
> +    return 0;
> +}
> diff --git a/target/loongarch/insn_trans/trans_fmov.c.inc b/target/loongarch/insn_trans/trans_fmov.c.inc
> index 24753d4568..5537e3dd35 100644
> --- a/target/loongarch/insn_trans/trans_fmov.c.inc
> +++ b/target/loongarch/insn_trans/trans_fmov.c.inc
> @@ -60,38 +60,39 @@ static bool trans_movgr2fcsr(DisasContext *ctx, arg_movgr2fcsr *a)
>     TCGv Rj = gpr_src(ctx, a->rj, EXT_NONE);
> 
>     if (mask == UINT32_MAX) {
> -        tcg_gen_extrl_i64_i32(cpu_fcsr0, Rj);
> +        tcg_gen_st32_i64(Rj, cpu_env, offsetof(CPULoongArchState, fcsr0));
>     } else {
> +        TCGv_i32 fcsr0 = tcg_temp_new_i32();
>         TCGv_i32 temp = tcg_temp_new_i32();
> 
> +        tcg_gen_ld_i32(fcsr0, cpu_env, offsetof(CPULoongArchState, fcsr0));
>         tcg_gen_extrl_i64_i32(temp, Rj);
>         tcg_gen_andi_i32(temp, temp, mask);
> -        tcg_gen_andi_i32(cpu_fcsr0, cpu_fcsr0, ~mask);
> -        tcg_gen_or_i32(cpu_fcsr0, cpu_fcsr0, temp);
> +        tcg_gen_andi_i32(fcsr0, fcsr0, ~mask);
> +        tcg_gen_or_i32(fcsr0, fcsr0, temp);
> +        tcg_gen_st_i32(fcsr0, cpu_env, offsetof(CPULoongArchState, fcsr0));
> +
>         tcg_temp_free_i32(temp);
> -
> -        /*
> -         * Install the new rounding mode to fpu_status, if changed.
> -         * Note that FCSR3 is exactly the rounding mode field.
> -         */
> -        if (mask != FCSR0_M3) {
> -            return true;
> -        }
> +        tcg_temp_free_i32(fcsr0);
>     }
> -    gen_helper_set_rounding_mode(cpu_env, cpu_fcsr0);
> 
> +    /*
> +     * Install the new rounding mode to fpu_status, if changed.
> +     * Note that FCSR3 is exactly the rounding mode field.
> +     */
> +    if (mask & FCSR0_M3) {
> +        gen_helper_set_rounding_mode(cpu_env);
> +    }
>     return true;
> }
> 
> static bool trans_movfcsr2gr(DisasContext *ctx, arg_movfcsr2gr *a)
> {
> -    TCGv_i32 temp = tcg_temp_new_i32();
>     TCGv dest = gpr_dst(ctx, a->rd, EXT_NONE);
> 
> -    tcg_gen_andi_i32(temp, cpu_fcsr0, fcsr_mask[a->fcsrs]);
> -    tcg_gen_ext_i32_i64(dest, temp);
> +    tcg_gen_ld32u_i64(dest, cpu_env, offsetof(CPULoongArchState, fcsr0));
> +    tcg_gen_andi_i64(dest, dest, fcsr_mask[a->fcsrs]);
>     gen_set_gpr(a->rd, dest, EXT_NONE);
> -    tcg_temp_free_i32(temp);
> 
>     return true;
> }
> diff --git a/tests/tcg/loongarch64/Makefile.target b/tests/tcg/loongarch64/Makefile.target
> index 0115de78ef..00030a1026 100644
> --- a/tests/tcg/loongarch64/Makefile.target
> +++ b/tests/tcg/loongarch64/Makefile.target
> @@ -15,5 +15,6 @@ LOONGARCH64_TESTS  += test_div
> LOONGARCH64_TESTS  += test_fclass
> LOONGARCH64_TESTS  += test_fpcom
> LOONGARCH64_TESTS  += test_pcadd
> +LOONGARCH64_TESTS  += test_fcsr
> 
> TESTS += $(LOONGARCH64_TESTS)
> -- 
> 2.34.1

Acked-by: Qi Hu <huqi@loongson.cn>

On 2022/8/7 上午1:08, Richard Henderson wrote:
> All of the fpu operations are defined with TCG_CALL_NO_WG, but they
> all modify FCSR0.  The most efficient way to fix this is to remove
> cpu_fcsr0, and instead use explicit load and store operations for the
> two instructions that manipulate that value.
>
> Cc: Qi Hu<huqi@loongson.cn>
> Cc: Song Gao<gaosong@loongson.cn>
> Reported-by: Feiyang Chen<chenfeiyang@loongson.cn>
> Signed-off-by: Richard Henderson<richard.henderson@linaro.org>
> ---
>   target/loongarch/helper.h                    |  2 +-
>   target/loongarch/fpu_helper.c                |  4 +--
>   target/loongarch/translate.c                 |  3 --
>   tests/tcg/loongarch64/test_fcsr.c            | 15 +++++++++
>   target/loongarch/insn_trans/trans_fmov.c.inc | 33 ++++++++++----------
>   tests/tcg/loongarch64/Makefile.target        |  1 +
>   6 files changed, 36 insertions(+), 22 deletions(-)
>   create mode 100644 tests/tcg/loongarch64/test_fcsr.c
Reviewed-by: Song Gao <gaosong@loongson.cn>

Thanks.
Song Gao