target/arm: Convert PMUL.8 to gvec

The gvec form will be needed for implementing SVE2.

Extend the implementation to operate on uint64_t instead of uint32_t.
Use a counted inner loop instead of terminating when op1 goes to zero,
looking toward the required implementation for ARMv8.4-DIT.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200216214232.4230-3-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/helper.h

@@ -342,7 +342,6 @@ DEF_HELPER_2(neon_sub_u8, i32, i32, i32)
 DEF_HELPER_2(neon_sub_u16, i32, i32, i32)
 DEF_HELPER_2(neon_mul_u8, i32, i32, i32)
 DEF_HELPER_2(neon_mul_u16, i32, i32, i32)
-DEF_HELPER_2(neon_mul_p8, i32, i32, i32)
 DEF_HELPER_2(neon_mull_p8, i64, i32, i32)
 
 DEF_HELPER_2(neon_tst_u8, i32, i32, i32)
@@ -696,6 +695,8 @@ DEF_HELPER_FLAGS_4(gvec_sshl_h, TCG_CALL_NO_RWG, void, ptr, ptr, ptr, i32)
 DEF_HELPER_FLAGS_4(gvec_ushl_b, TCG_CALL_NO_RWG, void, ptr, ptr, ptr, i32)
 DEF_HELPER_FLAGS_4(gvec_ushl_h, TCG_CALL_NO_RWG, void, ptr, ptr, ptr, i32)
 
+DEF_HELPER_FLAGS_4(gvec_pmul_b, TCG_CALL_NO_RWG, void, ptr, ptr, ptr, i32)
+
 #ifdef TARGET_AARCH64
 #include "helper-a64.h"
 #include "helper-sve.h"

target/arm/neon_helper.c

@@ -1131,28 +1131,6 @@ NEON_VOP(mul_u16, neon_u16, 2)
 
 /* Polynomial multiplication is like integer multiplication except the
    partial products are XORed, not added.  */
-uint32_t HELPER(neon_mul_p8)(uint32_t op1, uint32_t op2)
-{
-    uint32_t mask;
-    uint32_t result;
-    result = 0;
-    while (op1) {
-        mask = 0;
-        if (op1 & 1)
-            mask |= 0xff;
-        if (op1 & (1 << 8))
-            mask |= (0xff << 8);
-        if (op1 & (1 << 16))
-            mask |= (0xff << 16);
-        if (op1 & (1 << 24))
-            mask |= (0xff << 24);
-        result ^= op2 & mask;
-        op1 = (op1 >> 1) & 0x7f7f7f7f;
-        op2 = (op2 << 1) & 0xfefefefe;
-    }
-    return result;
-}
-
 uint64_t HELPER(neon_mull_p8)(uint32_t op1, uint32_t op2)
 {
     uint64_t result = 0;

target/arm/translate-a64.c

@@ -11169,9 +11169,10 @@ static void disas_simd_3same_int(DisasContext *s, uint32_t insn)
     case 0x13: /* MUL, PMUL */
         if (!u) { /* MUL */
             gen_gvec_fn3(s, is_q, rd, rn, rm, tcg_gen_gvec_mul, size);
-            return;
+        } else {  /* PMUL */
+            gen_gvec_op3_ool(s, is_q, rd, rn, rm, 0, gen_helper_gvec_pmul_b);
         }
-        break;
+        return;
     case 0x12: /* MLA, MLS */
         if (u) {
             gen_gvec_op3(s, is_q, rd, rn, rm, &mls_op[size]);
@@ -11301,11 +11302,6 @@ static void disas_simd_3same_int(DisasContext *s, uint32_t insn)
                 genfn = fns[size][u];
                 break;
             }
-            case 0x13: /* MUL, PMUL */
-                assert(u); /* PMUL */
-                assert(size == 0);
-                genfn = gen_helper_neon_mul_p8;
-                break;
             case 0x16: /* SQDMULH, SQRDMULH */
             {
                 static NeonGenTwoOpEnvFn * const fns[2][2] = {

target/arm/translate.c

@@ -5007,16 +5007,17 @@ static int disas_neon_data_insn(DisasContext *s, uint32_t insn)
 
         case NEON_3R_VMUL: /* VMUL */
             if (u) {
-                /* Polynomial case allows only P8 and is handled below.  */
+                /* Polynomial case allows only P8.  */
                 if (size != 0) {
                     return 1;
                 }
+                tcg_gen_gvec_3_ool(rd_ofs, rn_ofs, rm_ofs, vec_size, vec_size,
+                                   0, gen_helper_gvec_pmul_b);
             } else {
                 tcg_gen_gvec_mul(size, rd_ofs, rn_ofs, rm_ofs,
                                  vec_size, vec_size);
-                return 0;
             }
-            break;
+            return 0;
 
         case NEON_3R_VML: /* VMLA, VMLS */
             tcg_gen_gvec_3(rd_ofs, rn_ofs, rm_ofs, vec_size, vec_size,
@@ -5206,10 +5207,6 @@ static int disas_neon_data_insn(DisasContext *s, uint32_t insn)
             tmp2 = neon_load_reg(rd, pass);
             gen_neon_add(size, tmp, tmp2);
             break;
-        case NEON_3R_VMUL:
-            /* VMUL.P8; other cases already eliminated.  */
-            gen_helper_neon_mul_p8(tmp, tmp, tmp2);
-            break;
         case NEON_3R_VPMAX:
             GEN_NEON_INTEGER_OP(pmax);
             break;

target/arm/vec_helper.c

@@ -1134,3 +1134,33 @@ void HELPER(gvec_ushl_h)(void *vd, void *vn, void *vm, uint32_t desc)
     }
     clear_tail(d, opr_sz, simd_maxsz(desc));
 }
+
+/*
+ * 8x8->8 polynomial multiply.
+ *
+ * Polynomial multiplication is like integer multiplication except the
+ * partial products are XORed, not added.
+ *
+ * TODO: expose this as a generic vector operation, as it is a common
+ * crypto building block.
+ */
+void HELPER(gvec_pmul_b)(void *vd, void *vn, void *vm, uint32_t desc)
+{
+    intptr_t i, j, opr_sz = simd_oprsz(desc);
+    uint64_t *d = vd, *n = vn, *m = vm;
+
+    for (i = 0; i < opr_sz / 8; ++i) {
+        uint64_t nn = n[i];
+        uint64_t mm = m[i];
+        uint64_t rr = 0;
+
+        for (j = 0; j < 8; ++j) {
+            uint64_t mask = (nn & 0x0101010101010101ull) * 0xff;
+            rr ^= mm & mask;
+            mm = (mm << 1) & 0xfefefefefefefefeull;
+            nn >>= 1;
+        }
+        d[i] = rr;
+    }
+    clear_tail(d, opr_sz, simd_maxsz(desc));
+}