target/arm: Remove fp checks from sve_exception_el

Instead of checking these bits in fp_exception_el and
also in sve_exception_el, document that we must compare
the results.  The only place where we have not already
checked that FP EL is zero is in rebuild_hflags_a64.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220607203306.657998-5-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 19 insertions, 39 deletions

diff --git a/target/arm/helper.c b/target/arm/helper.c
index 1bd77af7e5..4f4044c688 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6129,11 +6129,15 @@ static const ARMCPRegInfo minimal_ras_reginfo[] = {
       .access = PL2_RW, .fieldoffset = offsetof(CPUARMState, cp15.vsesr_el2) },
 };
 
-/* Return the exception level to which exceptions should be taken
- * via SVEAccessTrap.  If an exception should be routed through
- * AArch64.AdvSIMDFPAccessTrap, return 0; fp_exception_el should
- * take care of raising that exception.
- * C.f. the ARM pseudocode function CheckSVEEnabled.
+/*
+ * Return the exception level to which exceptions should be taken
+ * via SVEAccessTrap.  This excludes the check for whether the exception
+ * should be routed through AArch64.AdvSIMDFPAccessTrap.  That can easily
+ * be found by testing 0 < fp_exception_el < sve_exception_el.
+ *
+ * C.f. the ARM pseudocode function CheckSVEEnabled.  Note that the
+ * pseudocode does *not* separate out the FP trap checks, but has them
+ * all in one function.
  */
 int sve_exception_el(CPUARMState *env, int el)
 {
@@ -6151,18 +6155,6 @@ int sve_exception_el(CPUARMState *env, int el)
         case 2:
             return 1;
         }
-
-        /* Check CPACR.FPEN.  */
-        switch (FIELD_EX64(env->cp15.cpacr_el1, CPACR_EL1, FPEN)) {
-        case 1:
-            if (el != 0) {
-                break;
-            }
-            /* fall through */
-        case 0:
-        case 2:
-            return 0;
-        }
     }
 
     /*
@@ -6180,24 +6172,10 @@ int sve_exception_el(CPUARMState *env, int el)
             case 2:
                 return 2;
             }
-
-            switch (FIELD_EX32(env->cp15.cptr_el[2], CPTR_EL2, FPEN)) {
-            case 1:
-                if (el == 2 || !(hcr_el2 & HCR_TGE)) {
-                    break;
-                }
-                /* fall through */
-            case 0:
-            case 2:
-                return 0;
-            }
         } else if (arm_is_el2_enabled(env)) {
             if (FIELD_EX64(env->cp15.cptr_el[2], CPTR_EL2, TZ)) {
                 return 2;
             }
-            if (FIELD_EX64(env->cp15.cptr_el[2], CPTR_EL2, TFP)) {
-                return 0;
-            }
         }
     }
 
@@ -11168,19 +11146,21 @@ static CPUARMTBFlags rebuild_hflags_a64(CPUARMState *env, int el, int fp_el,
 
     if (cpu_isar_feature(aa64_sve, env_archcpu(env))) {
         int sve_el = sve_exception_el(env, el);
-        uint32_t zcr_len;
 
         /*
-         * If SVE is disabled, but FP is enabled,
-         * then the effective len is 0.
+         * If either FP or SVE are disabled, translator does not need len.
+         * If SVE EL > FP EL, FP exception has precedence, and translator
+         * does not need SVE EL.  Save potential re-translations by forcing
+         * the unneeded data to zero.
          */
-        if (sve_el != 0 && fp_el == 0) {
-            zcr_len = 0;
-        } else {
-            zcr_len = sve_zcr_len_for_el(env, el);
+        if (fp_el != 0) {
+            if (sve_el > fp_el) {
+                sve_el = 0;
+            }
+        } else if (sve_el == 0) {
+            DP_TBFLAG_A64(flags, VL, sve_zcr_len_for_el(env, el));
         }
         DP_TBFLAG_A64(flags, SVEEXC_EL, sve_el);
-        DP_TBFLAG_A64(flags, VL, zcr_len);
     }
 
     sctlr = regime_sctlr(env, stage1);