[PULL 24/42] target/ppc: overhauled and moved logic of storing fpscr

[David Gibson <david@gibson.dropbear.id.au>]

From: "Bruno Larsen (billionai)" <bruno.larsen@eldorado.org.br>

Followed the suggested overhaul to store_fpscr logic, and moved it to
cpu.c where it can be accessed in !TCG builds.

The overhaul was suggested because storing a value to fpscr should
never raise an exception, so we could remove all the mess that happened
with POWERPC_EXCP_FP.

We also moved fpscr_set_rounding_mode into cpu.c as it could now be moved
there, and it is needed when a value for the fpscr is being stored
directly.

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Bruno Larsen (billionai) <bruno.larsen@eldorado.org.br>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20210527163522.23019-1-bruno.larsen@eldorado.org.br>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 target/ppc/cpu.c        |  43 ++++++++
 target/ppc/cpu.h        |  12 +-
 target/ppc/fpu_helper.c | 238 +++-------------------------------------
 target/ppc/gdbstub.c    |   6 +-
 4 files changed, 65 insertions(+), 234 deletions(-)

diff --git a/target/ppc/cpu.c b/target/ppc/cpu.c
index c8e87e30f1..19d67b5b07 100644
--- a/target/ppc/cpu.c
+++ b/target/ppc/cpu.c
@@ -25,6 +25,7 @@
 #include "fpu/softfloat-helpers.h"
 #include "mmu-hash64.h"
 #include "helper_regs.h"
+#include "sysemu/tcg.h"
 
 target_ulong cpu_read_xer(CPUPPCState *env)
 {
@@ -109,3 +110,45 @@ void ppc_store_lpcr(PowerPCCPU *cpu, target_ulong val)
     /* The gtse bit affects hflags */
     hreg_compute_hflags(env);
 }
+
+static inline void fpscr_set_rounding_mode(CPUPPCState *env)
+{
+    int rnd_type;
+
+    /* Set rounding mode */
+    switch (fpscr_rn) {
+    case 0:
+        /* Best approximation (round to nearest) */
+        rnd_type = float_round_nearest_even;
+        break;
+    case 1:
+        /* Smaller magnitude (round toward zero) */
+        rnd_type = float_round_to_zero;
+        break;
+    case 2:
+        /* Round toward +infinite */
+        rnd_type = float_round_up;
+        break;
+    default:
+    case 3:
+        /* Round toward -infinite */
+        rnd_type = float_round_down;
+        break;
+    }
+    set_float_rounding_mode(rnd_type, &env->fp_status);
+}
+
+void ppc_store_fpscr(CPUPPCState *env, target_ulong val)
+{
+    val &= ~(FP_VX | FP_FEX);
+    if (val & FPSCR_IX) {
+        val |= FP_VX;
+    }
+    if ((val >> FPSCR_XX) & (val >> FPSCR_XE) & 0x1f) {
+        val |= FP_FEX;
+    }
+    env->fpscr = val;
+    if (tcg_enabled()) {
+        fpscr_set_rounding_mode(env);
+    }
+}
diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
index b0934d9be4..b7ae4902e4 100644
--- a/target/ppc/cpu.h
+++ b/target/ppc/cpu.h
@@ -675,11 +675,11 @@ enum {
 #define fpscr_ni     (((env->fpscr) >> FPSCR_NI)     & 0x1)
 #define fpscr_rn     (((env->fpscr) >> FPSCR_RN0)    & 0x3)
 /* Invalid operation exception summary */
-#define fpscr_ix ((env->fpscr) & ((1 << FPSCR_VXSNAN) | (1 << FPSCR_VXISI)  | \
-                                  (1 << FPSCR_VXIDI)  | (1 << FPSCR_VXZDZ)  | \
-                                  (1 << FPSCR_VXIMZ)  | (1 << FPSCR_VXVC)   | \
-                                  (1 << FPSCR_VXSOFT) | (1 << FPSCR_VXSQRT) | \
-                                  (1 << FPSCR_VXCVI)))
+#define FPSCR_IX     ((1 << FPSCR_VXSNAN) | (1 << FPSCR_VXISI)  | \
+                      (1 << FPSCR_VXIDI)  | (1 << FPSCR_VXZDZ)  | \
+                      (1 << FPSCR_VXIMZ)  | (1 << FPSCR_VXVC)   | \
+                      (1 << FPSCR_VXSOFT) | (1 << FPSCR_VXSQRT) | \
+                      (1 << FPSCR_VXCVI))
 /* exception summary */
 #define fpscr_ex  (((env->fpscr) >> FPSCR_XX) & 0x1F)
 /* enabled exception summary */
@@ -1332,7 +1332,7 @@ void cpu_ppc_set_vhyp(PowerPCCPU *cpu, PPCVirtualHypervisor *vhyp);
 #endif
 #endif
 
-void store_fpscr(CPUPPCState *env, uint64_t arg, uint32_t mask);
+void ppc_store_fpscr(CPUPPCState *env, target_ulong val);
 void helper_hfscr_facility_check(CPUPPCState *env, uint32_t bit,
                                  const char *caller, uint32_t cause);
 
diff --git a/target/ppc/fpu_helper.c b/target/ppc/fpu_helper.c
index a4a283df2b..c4896cecc8 100644
--- a/target/ppc/fpu_helper.c
+++ b/target/ppc/fpu_helper.c
@@ -383,247 +383,35 @@ static inline void float_inexact_excp(CPUPPCState *env)
     }
 }
 
-static inline void fpscr_set_rounding_mode(CPUPPCState *env)
-{
-    int rnd_type;
-
-    /* Set rounding mode */
-    switch (fpscr_rn) {
-    case 0:
-        /* Best approximation (round to nearest) */
-        rnd_type = float_round_nearest_even;
-        break;
-    case 1:
-        /* Smaller magnitude (round toward zero) */
-        rnd_type = float_round_to_zero;
-        break;
-    case 2:
-        /* Round toward +infinite */
-        rnd_type = float_round_up;
-        break;
-    default:
-    case 3:
-        /* Round toward -infinite */
-        rnd_type = float_round_down;
-        break;
-    }
-    set_float_rounding_mode(rnd_type, &env->fp_status);
-}
-
 void helper_fpscr_clrbit(CPUPPCState *env, uint32_t bit)
 {
-    int prev;
-
-    prev = (env->fpscr >> bit) & 1;
-    env->fpscr &= ~(1 << bit);
-    if (prev == 1) {
-        switch (bit) {
-        case FPSCR_RN1:
-        case FPSCR_RN0:
-            fpscr_set_rounding_mode(env);
-            break;
-        case FPSCR_VXSNAN:
-        case FPSCR_VXISI:
-        case FPSCR_VXIDI:
-        case FPSCR_VXZDZ:
-        case FPSCR_VXIMZ:
-        case FPSCR_VXVC:
-        case FPSCR_VXSOFT:
-        case FPSCR_VXSQRT:
-        case FPSCR_VXCVI:
-            if (!fpscr_ix) {
-                /* Set VX bit to zero */
-                env->fpscr &= ~FP_VX;
-            }
-            break;
-        case FPSCR_OX:
-        case FPSCR_UX:
-        case FPSCR_ZX:
-        case FPSCR_XX:
-        case FPSCR_VE:
-        case FPSCR_OE:
-        case FPSCR_UE:
-        case FPSCR_ZE:
-        case FPSCR_XE:
-            if (!fpscr_eex) {
-                /* Set the FEX bit */
-                env->fpscr &= ~FP_FEX;
-            }
-            break;
-        default:
-            break;
-        }
+    uint32_t mask = 1u << bit;
+    if (env->fpscr & mask) {
+        ppc_store_fpscr(env, env->fpscr & ~(target_ulong)mask);
     }
 }
 
 void helper_fpscr_setbit(CPUPPCState *env, uint32_t bit)
 {
-    CPUState *cs = env_cpu(env);
-    int prev;
-
-    prev = (env->fpscr >> bit) & 1;
-    env->fpscr |= 1 << bit;
-    if (prev == 0) {
-        switch (bit) {
-        case FPSCR_VX:
-            env->fpscr |= FP_FX;
-            if (fpscr_ve) {
-                goto raise_ve;
-            }
-            break;
-        case FPSCR_OX:
-            env->fpscr |= FP_FX;
-            if (fpscr_oe) {
-                goto raise_oe;
-            }
-            break;
-        case FPSCR_UX:
-            env->fpscr |= FP_FX;
-            if (fpscr_ue) {
-                goto raise_ue;
-            }
-            break;
-        case FPSCR_ZX:
-            env->fpscr |= FP_FX;
-            if (fpscr_ze) {
-                goto raise_ze;
-            }
-            break;
-        case FPSCR_XX:
-            env->fpscr |= FP_FX;
-            if (fpscr_xe) {
-                goto raise_xe;
-            }
-            break;
-        case FPSCR_VXSNAN:
-        case FPSCR_VXISI:
-        case FPSCR_VXIDI:
-        case FPSCR_VXZDZ:
-        case FPSCR_VXIMZ:
-        case FPSCR_VXVC:
-        case FPSCR_VXSOFT:
-        case FPSCR_VXSQRT:
-        case FPSCR_VXCVI:
-            env->fpscr |= FP_VX;
-            env->fpscr |= FP_FX;
-            if (fpscr_ve != 0) {
-                goto raise_ve;
-            }
-            break;
-        case FPSCR_VE:
-            if (fpscr_vx != 0) {
-            raise_ve:
-                env->error_code = POWERPC_EXCP_FP;
-                if (fpscr_vxsnan) {
-                    env->error_code |= POWERPC_EXCP_FP_VXSNAN;
-                }
-                if (fpscr_vxisi) {
-                    env->error_code |= POWERPC_EXCP_FP_VXISI;
-                }
-                if (fpscr_vxidi) {
-                    env->error_code |= POWERPC_EXCP_FP_VXIDI;
-                }
-                if (fpscr_vxzdz) {
-                    env->error_code |= POWERPC_EXCP_FP_VXZDZ;
-                }
-                if (fpscr_vximz) {
-                    env->error_code |= POWERPC_EXCP_FP_VXIMZ;
-                }
-                if (fpscr_vxvc) {
-                    env->error_code |= POWERPC_EXCP_FP_VXVC;
-                }
-                if (fpscr_vxsoft) {
-                    env->error_code |= POWERPC_EXCP_FP_VXSOFT;
-                }
-                if (fpscr_vxsqrt) {
-                    env->error_code |= POWERPC_EXCP_FP_VXSQRT;
-                }
-                if (fpscr_vxcvi) {
-                    env->error_code |= POWERPC_EXCP_FP_VXCVI;
-                }
-                goto raise_excp;
-            }
-            break;
-        case FPSCR_OE:
-            if (fpscr_ox != 0) {
-            raise_oe:
-                env->error_code = POWERPC_EXCP_FP | POWERPC_EXCP_FP_OX;
-                goto raise_excp;
-            }
-            break;
-        case FPSCR_UE:
-            if (fpscr_ux != 0) {
-            raise_ue:
-                env->error_code = POWERPC_EXCP_FP | POWERPC_EXCP_FP_UX;
-                goto raise_excp;
-            }
-            break;
-        case FPSCR_ZE:
-            if (fpscr_zx != 0) {
-            raise_ze:
-                env->error_code = POWERPC_EXCP_FP | POWERPC_EXCP_FP_ZX;
-                goto raise_excp;
-            }
-            break;
-        case FPSCR_XE:
-            if (fpscr_xx != 0) {
-            raise_xe:
-                env->error_code = POWERPC_EXCP_FP | POWERPC_EXCP_FP_XX;
-                goto raise_excp;
-            }
-            break;
-        case FPSCR_RN1:
-        case FPSCR_RN0:
-            fpscr_set_rounding_mode(env);
-            break;
-        default:
-            break;
-        raise_excp:
-            /* Update the floating-point enabled exception summary */
-            env->fpscr |= FP_FEX;
-            /* We have to update Rc1 before raising the exception */
-            cs->exception_index = POWERPC_EXCP_PROGRAM;
-            break;
-        }
+    uint32_t mask = 1u << bit;
+    if (!(env->fpscr & mask)) {
+        ppc_store_fpscr(env, env->fpscr | mask);
     }
 }
 
-void helper_store_fpscr(CPUPPCState *env, uint64_t arg, uint32_t mask)
+void helper_store_fpscr(CPUPPCState *env, uint64_t val, uint32_t nibbles)
 {
-    CPUState *cs = env_cpu(env);
-    target_ulong prev, new;
+    target_ulong mask = 0;
     int i;
 
-    prev = env->fpscr;
-    new = (target_ulong)arg;
-    new &= ~(FP_FEX | FP_VX);
-    new |= prev & (FP_FEX | FP_VX);
+    /* TODO: push this extension back to translation time */
     for (i = 0; i < sizeof(target_ulong) * 2; i++) {
-        if (mask & (1 << i)) {
-            env->fpscr &= ~(0xFLL << (4 * i));
-            env->fpscr |= new & (0xFLL << (4 * i));
+        if (nibbles & (1 << i)) {
+            mask |= (target_ulong) 0xf << (4 * i);
         }
     }
-    /* Update VX and FEX */
-    if (fpscr_ix != 0) {
-        env->fpscr |= FP_VX;
-    } else {
-        env->fpscr &= ~FP_VX;
-    }
-    if ((fpscr_ex & fpscr_eex) != 0) {
-        env->fpscr |= FP_FEX;
-        cs->exception_index = POWERPC_EXCP_PROGRAM;
-        /* XXX: we should compute it properly */
-        env->error_code = POWERPC_EXCP_FP;
-    } else {
-        env->fpscr &= ~FP_FEX;
-    }
-    fpscr_set_rounding_mode(env);
-}
-
-void store_fpscr(CPUPPCState *env, uint64_t arg, uint32_t mask)
-{
-    helper_store_fpscr(env, arg, mask);
+    val = (val & mask) | (env->fpscr & ~mask);
+    ppc_store_fpscr(env, val);
 }
 
 static void do_float_check_status(CPUPPCState *env, uintptr_t raddr)
diff --git a/target/ppc/gdbstub.c b/target/ppc/gdbstub.c
index 308b98fc90..09ff1328d4 100644
--- a/target/ppc/gdbstub.c
+++ b/target/ppc/gdbstub.c
@@ -271,7 +271,7 @@ int ppc_cpu_gdb_write_register(CPUState *cs, uint8_t *mem_buf, int n)
             break;
         case 70:
             /* fpscr */
-            store_fpscr(env, ldtul_p(mem_buf), 0xffffffff);
+            ppc_store_fpscr(env, ldtul_p(mem_buf));
             break;
         }
     }
@@ -321,7 +321,7 @@ int ppc_cpu_gdb_write_register_apple(CPUState *cs, uint8_t *mem_buf, int n)
             break;
         case 70 + 32:
             /* fpscr */
-            store_fpscr(env, ldq_p(mem_buf), 0xffffffff);
+            ppc_store_fpscr(env, ldq_p(mem_buf));
             break;
         }
     }
@@ -474,7 +474,7 @@ static int gdb_set_float_reg(CPUPPCState *env, uint8_t *mem_buf, int n)
     }
     if (n == 32) {
         ppc_maybe_bswap_register(env, mem_buf, 4);
-        store_fpscr(env, ldl_p(mem_buf), 0xffffffff);
+        ppc_store_fpscr(env, ldl_p(mem_buf));
         return 4;
     }
     return 0;
-- 
2.31.1