[PATCH, i386]: Improve STV conversion of shifts

[Uros Bizjak]

Attached patch improves costing for STV shifts and corrects reject
condition for out of range shift count operands.

2019-08-28  Uroš Bizjak  <ubiz...@gmail.com>

    * config/i386/i386-features.c
    (general_scalar_chain::compute_convert_gain):
    Correct cost for double-word shifts.
    (general_scalar_to_vector_candidate_p): Reject count operands
    greater or equal to mode bitsize.

Bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.

Committed to mainline SVN.

Uros.

diff --git a/gcc/config/i386/i386-features.c b/gcc/config/i386/i386-features.c
index 6eb1482a9f01..766ec355e07b 100644
--- a/gcc/config/i386/i386-features.c
+++ b/gcc/config/i386/i386-features.c
@@ -549,11 +549,18 @@ general_scalar_chain::compute_convert_gain ()
               || GET_CODE (src) == ASHIFTRT
               || GET_CODE (src) == LSHIFTRT)
        {
+         if (m == 2)
+           {
+             if (INTVAL (XEXP (src, 1)) >= 32)
+               igain += ix86_cost->add;
+             else
+               igain += ix86_cost->shift_const;
+           }
+
+         igain += ix86_cost->shift_const - ix86_cost->sse_op;
+
          if (CONST_INT_P (XEXP (src, 0)))
            igain -= vector_const_cost (XEXP (src, 0));
-         igain += m * ix86_cost->shift_const - ix86_cost->sse_op;
-         if (INTVAL (XEXP (src, 1)) >= 32)
-           igain -= COSTS_N_INSNS (1);
        }
       else if (GET_CODE (src) == PLUS
               || GET_CODE (src) == MINUS
@@ -1325,7 +1332,7 @@ general_scalar_to_vector_candidate_p (rtx_insn *insn, 
enum machine_mode mode)
     case ASHIFT:
     case LSHIFTRT:
       if (!CONST_INT_P (XEXP (src, 1))
-         || !IN_RANGE (INTVAL (XEXP (src, 1)), 0, 63))
+         || !IN_RANGE (INTVAL (XEXP (src, 1)), 0, GET_MODE_BITSIZE (mode)-1))
        return false;
       break;