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.

Acked-by: Qi Hu <huqi@loongson.cn>
Reviewed-by: Song Gao <gaosong@loongson.cn>
Reported-by: Feiyang Chen <chenfeiyang@loongson.cn>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

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);
 }

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)
 

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;
 }

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,

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)

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;
+}