s390x: Improve isel for Iop_V128to64 and friends

The existing instruction selector for Iop_V128to64, Iop_V128HIto64, and
Iop_V128to32 stores the vector register on the stack and then reads the
requested integer value back from the stack into the target GPR.  This is
fairly inefficient.

Load the requested value directly from the vector register into the target
GPR instead, using S390_VEC_GET_ELEM.

diff --git a/VEX/priv/host_s390_isel.c b/VEX/priv/host_s390_isel.c
index 2f9854038da5ba8818060bfc73b01c9fd70a63ad..2000ec224059cef66f08be23b0946795e20742f9 100644 (file)
--- a/VEX/priv/host_s390_isel.c
+++ b/VEX/priv/host_s390_isel.c
@@ -1812,31 +1812,24 @@ s390_isel_int_expr_wrk(ISelEnv *env, IRExpr *expr)
          dst = newVRegI(env);
          HReg vec = s390_isel_vec_expr(env, arg);
          /* This is big-endian machine */
-         Int off;
+         Int idx;
          switch (unop) {
             case Iop_V128HIto64:
-               off = 0;
+               idx = 0;
                break;
             case Iop_V128to64:
-               off = 8;
+               idx = 1;
                break;
             case Iop_V128to32:
-               off = 12;
+               idx = 3;
                break;
             default:
                ppIROp(unop);
                vpanic("s390_isel_int_expr: unhandled V128toSMTH operation");
          }
-         s390_amode* m16_sp = s390_amode_for_stack_pointer(0);
-         s390_amode* off_sp = s390_amode_for_stack_pointer(off);
-
-         /* We could use negative displacement but vector instructions
-            require 12bit unsigned ones. So we have to allocate space on
-            stack just for one load and free it after. */
-         sub_from_SP(env, 16);
-         addInstr(env, s390_insn_store(sizeof(V128), m16_sp, vec));
-         addInstr(env, s390_insn_load(sizeof(ULong), dst, off_sp));
-         add_to_SP(env, 16);
+         s390_amode* am = s390_amode_b12(idx, s390_hreg_gpr(0));
+         addInstr(env, s390_insn_vec_amodeop(size, S390_VEC_GET_ELEM,
+                                             dst, vec, am));
          return dst;
       }