s390x/tcg: Implement VECTOR FP ADD

1. We'll reuse op_vfa() for similar instructions later, prepare for
   that.
2. We'll reuse vop64_3() for other instructions later.
3. Take care of modifying the vector register only if no trap happened.
 - on traps, flags are not updated and no elements are modified
 - traps don't modify the fpc flags
 - without traps, all exceptions of all elements are merged
4. We'll reuse check_ieee_exc() later when we need the XxC flag.

We have to check for exceptions after processing each element.
Provide separate handlers for single/all element processing. We'll do
the same for all applicable FP instructions.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: David Hildenbrand <david@redhat.com>

target/s390x/Makefile.objs

@@ -2,6 +2,7 @@ obj-y += cpu.o cpu_models.o cpu_features.o gdbstub.o interrupt.o helper.o
 obj-$(CONFIG_TCG) += translate.o cc_helper.o excp_helper.o fpu_helper.o
 obj-$(CONFIG_TCG) += int_helper.o mem_helper.o misc_helper.o crypto_helper.o
 obj-$(CONFIG_TCG) += vec_helper.o vec_int_helper.o vec_string_helper.o
+obj-$(CONFIG_TCG) += vec_fpu_helper.o
 obj-$(CONFIG_SOFTMMU) += machine.o ioinst.o arch_dump.o mmu_helper.o diag.o
 obj-$(CONFIG_SOFTMMU) += sigp.o
 obj-$(CONFIG_KVM) += kvm.o

target/s390x/helper.h

@@ -249,6 +249,10 @@ DEF_HELPER_6(gvec_vstrc_cc_rt8, void, ptr, cptr, cptr, cptr, env, i32)
 DEF_HELPER_6(gvec_vstrc_cc_rt16, void, ptr, cptr, cptr, cptr, env, i32)
 DEF_HELPER_6(gvec_vstrc_cc_rt32, void, ptr, cptr, cptr, cptr, env, i32)
 
+/* === Vector Floating-Point Instructions */
+DEF_HELPER_FLAGS_5(gvec_vfa64, TCG_CALL_NO_WG, void, ptr, cptr, cptr, env, i32)
+DEF_HELPER_FLAGS_5(gvec_vfa64s, TCG_CALL_NO_WG, void, ptr, cptr, cptr, env, i32)
+
 #ifndef CONFIG_USER_ONLY
 DEF_HELPER_3(servc, i32, env, i64, i64)
 DEF_HELPER_4(diag, void, env, i32, i32, i32)

target/s390x/insn-data.def

@@ -1204,6 +1204,11 @@
 /* VECTOR STRING RANGE COMPARE */
     F(0xe78a, VSTRC,   VRR_d, V,   0, 0, 0, 0, vstrc, 0, IF_VEC)
 
+/* === Vector Floating-Point Instructions */
+
+/* VECTOR FP ADD */
+    F(0xe7e3, VFA,     VRR_c, V,   0, 0, 0, 0, vfa, 0, IF_VEC)
+
 #ifndef CONFIG_USER_ONLY
 /* COMPARE AND SWAP AND PURGE */
     E(0xb250, CSP,     RRE,   Z,   r1_32u, ra2, r1_P, 0, csp, 0, MO_TEUL, IF_PRIV)

target/s390x/translate_vx.inc.c

@@ -52,6 +52,11 @@
 #define ES_64   MO_64
 #define ES_128  4
 
+/* Floating-Point Format */
+#define FPF_SHORT       2
+#define FPF_LONG        3
+#define FPF_EXT         4
+
 static inline bool valid_vec_element(uint8_t enr, TCGMemOp es)
 {
     return !(enr & ~(NUM_VEC_ELEMENTS(es) - 1));
@@ -2538,3 +2543,27 @@ static DisasJumpType op_vstrc(DisasContext *s, DisasOps *o)
     }
     return DISAS_NEXT;
 }
+
+static DisasJumpType op_vfa(DisasContext *s, DisasOps *o)
+{
+    const uint8_t fpf = get_field(s->fields, m4);
+    const uint8_t m5 = get_field(s->fields, m5);
+    const bool se = extract32(m5, 3, 1);
+    gen_helper_gvec_3_ptr *fn;
+
+    if (fpf != FPF_LONG || extract32(m5, 0, 3)) {
+        gen_program_exception(s, PGM_SPECIFICATION);
+        return DISAS_NORETURN;
+    }
+
+    switch (s->fields->op2) {
+    case 0xe3:
+        fn = se ? gen_helper_gvec_vfa64s : gen_helper_gvec_vfa64;
+        break;
+    default:
+        g_assert_not_reached();
+    }
+    gen_gvec_3_ptr(get_field(s->fields, v1), get_field(s->fields, v2),
+                   get_field(s->fields, v3), cpu_env, 0, fn);
+    return DISAS_NEXT;
+}

target/s390x/vec_fpu_helper.c

@@ -0,0 +1,119 @@
+/*
+ * QEMU TCG support -- s390x vector floating point instruction support
+ *
+ * Copyright (C) 2019 Red Hat Inc
+ *
+ * Authors:
+ *   David Hildenbrand <david@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+#include "qemu/osdep.h"
+#include "qemu-common.h"
+#include "cpu.h"
+#include "internal.h"
+#include "vec.h"
+#include "tcg_s390x.h"
+#include "tcg/tcg-gvec-desc.h"
+#include "exec/exec-all.h"
+#include "exec/helper-proto.h"
+#include "fpu/softfloat.h"
+
+#define VIC_INVALID         0x1
+#define VIC_DIVBYZERO       0x2
+#define VIC_OVERFLOW        0x3
+#define VIC_UNDERFLOW       0x4
+#define VIC_INEXACT         0x5
+
+/* returns the VEX. If the VEX is 0, there is no trap */
+static uint8_t check_ieee_exc(CPUS390XState *env, uint8_t enr, bool XxC,
+                              uint8_t *vec_exc)
+{
+    uint8_t vece_exc = 0, trap_exc;
+    unsigned qemu_exc;
+
+    /* Retrieve and clear the softfloat exceptions */
+    qemu_exc = env->fpu_status.float_exception_flags;
+    if (qemu_exc == 0) {
+        return 0;
+    }
+    env->fpu_status.float_exception_flags = 0;
+
+    vece_exc = s390_softfloat_exc_to_ieee(qemu_exc);
+
+    /* Add them to the vector-wide s390x exception bits */
+    *vec_exc |= vece_exc;
+
+    /* Check for traps and construct the VXC */
+    trap_exc = vece_exc & env->fpc >> 24;
+    if (trap_exc) {
+        if (trap_exc & S390_IEEE_MASK_INVALID) {
+            return enr << 4 | VIC_INVALID;
+        } else if (trap_exc & S390_IEEE_MASK_DIVBYZERO) {
+            return enr << 4 | VIC_DIVBYZERO;
+        } else if (trap_exc & S390_IEEE_MASK_OVERFLOW) {
+            return enr << 4 | VIC_OVERFLOW;
+        } else if (trap_exc & S390_IEEE_MASK_UNDERFLOW) {
+            return enr << 4 | VIC_UNDERFLOW;
+        } else if (!XxC) {
+            g_assert(trap_exc & S390_IEEE_MASK_INEXACT);
+            /* inexact has lowest priority on traps */
+            return enr << 4 | VIC_INEXACT;
+        }
+    }
+    return 0;
+}
+
+static void handle_ieee_exc(CPUS390XState *env, uint8_t vxc, uint8_t vec_exc,
+                            uintptr_t retaddr)
+{
+    if (vxc) {
+        /* on traps, the fpc flags are not updated, instruction is suppressed */
+        tcg_s390_vector_exception(env, vxc, retaddr);
+    }
+    if (vec_exc) {
+        /* indicate exceptions for all elements combined */
+        env->fpc |= vec_exc << 16;
+    }
+}
+
+typedef uint64_t (*vop64_3_fn)(uint64_t a, uint64_t b, float_status *s);
+static void vop64_3(S390Vector *v1, const S390Vector *v2, const S390Vector *v3,
+                    CPUS390XState *env, bool s, vop64_3_fn fn,
+                    uintptr_t retaddr)
+{
+    uint8_t vxc, vec_exc = 0;
+    S390Vector tmp = {};
+    int i;
+
+    for (i = 0; i < 2; i++) {
+        const uint64_t a = s390_vec_read_element64(v2, i);
+        const uint64_t b = s390_vec_read_element64(v3, i);
+
+        s390_vec_write_element64(&tmp, i, fn(a, b, &env->fpu_status));
+        vxc = check_ieee_exc(env, i, false, &vec_exc);
+        if (s || vxc) {
+            break;
+        }
+    }
+    handle_ieee_exc(env, vxc, vec_exc, retaddr);
+    *v1 = tmp;
+}
+
+static uint64_t vfa64(uint64_t a, uint64_t b, float_status *s)
+{
+    return float64_add(a, b, s);
+}
+
+void HELPER(gvec_vfa64)(void *v1, const void *v2, const void *v3,
+                        CPUS390XState *env, uint32_t desc)
+{
+    vop64_3(v1, v2, v3, env, false, vfa64, GETPC());
+}
+
+void HELPER(gvec_vfa64s)(void *v1, const void *v2, const void *v3,
+                         CPUS390XState *env, uint32_t desc)
+{
+    vop64_3(v1, v2, v3, env, true, vfa64, GETPC());
+}