Richard Sandiford <richard.sandif...@linaro.org> writes:
> Richard Biener <richard.guent...@gmail.com> writes:
>> On Fri, Dec 15, 2017 at 1:48 AM, Richard Sandiford
>> <richard.sandif...@linaro.org> wrote:
>>> Richard Biener <richard.guent...@gmail.com> writes:
>>>> On Mon, Nov 20, 2017 at 10:02 PM, Richard Sandiford
>>>> <richard.sandif...@linaro.org> wrote:
>>>>> Richard Biener <richard.guent...@gmail.com> writes:
>>>>>> On Thu, Oct 26, 2017 at 2:06 PM, Richard Biener
>>>>>> <richard.guent...@gmail.com> wrote:
>>>>>>> On Mon, Oct 23, 2017 at 1:25 PM, Richard Sandiford
>>>>>>> <richard.sandif...@linaro.org> wrote:
>>>>>>>> This patch adds a stub helper routine to provide the mode
>>>>>>>> of a scalar shift amount, given the mode of the values
>>>>>>>> being shifted.
>>>>>>>>
>>>>>>>> One long-standing problem has been to decide what this mode
>>>>>>>> should be for arbitrary rtxes (as opposed to those directly
>>>>>>>> tied to a target pattern).  Is it the mode of the shifted
>>>>>>>> elements?  Is it word_mode?  Or maybe QImode?  Is it whatever
>>>>>>>> the corresponding target pattern says?  (In which case what
>>>>>>>> should the mode be when the target doesn't have a pattern?)
>>>>>>>>
>>>>>>>> For now the patch picks word_mode, which should be safe on
>>>>>>>> all targets but could perhaps become suboptimal if the helper
>>>>>>>> routine is used more often than it is in this patch.  As it
>>>>>>>> stands the patch does not change the generated code.
>>>>>>>>
>>>>>>>> The patch also adds a helper function that constructs rtxes
>>>>>>>> for constant shift amounts, again given the mode of the value
>>>>>>>> being shifted.  As well as helping with the SVE patches, this
>>>>>>>> is one step towards allowing CONST_INTs to have a real mode.
>>>>>>>
>>>>>>> I think gen_shift_amount_mode is flawed and while encapsulating
>>>>>>> constant shift amount RTX generation into a gen_int_shift_amount
>>>>>>> looks good to me I'd rather have that ??? in this function (and
>>>>>>> I'd use the mode of the RTX shifted, not word_mode...).
>>>>>
>>>>> OK.  I'd gone for word_mode because that's what expand_binop uses
>>>>> for CONST_INTs:
>>>>>
>>>>>       op1_mode = (GET_MODE (op1) != VOIDmode
>>>>>                   ? as_a <scalar_int_mode> (GET_MODE (op1))
>>>>>                   : word_mode);
>>>>>
>>>>> But using the inner mode should be fine too.  The patch below does that.
>>>>>
>>>>>>> In the end it's up to insn recognizing to convert the op to the
>>>>>>> expected mode and for generic RTL it's us that should decide
>>>>>>> on the mode -- on GENERIC the shift amount has to be an
>>>>>>> integer so why not simply use a mode that is large enough to
>>>>>>> make the constant fit?
>>>>>
>>>>> ...but I can do that instead if you think it's better.
>>>>>
>>>>>>> Just throwing in some comments here, RTL isn't my primary
>>>>>>> expertise.
>>>>>>
>>>>>> To add a little bit - shift amounts is maybe the only(?) place
>>>>>> where a modeless CONST_INT makes sense!  So "fixing"
>>>>>> that first sounds backwards.
>>>>>
>>>>> But even here they have a mode conceptually, since out-of-range shift
>>>>> amounts are target-defined rather than undefined.  E.g. if the target
>>>>> interprets the shift amount as unsigned, then for a shift amount
>>>>> (const_int -1) it matters whether the mode is QImode (and so we're
>>>>> shifting by 255) or HImode (and so we're shifting by 65535.
>>>>
>>>> I think RTL is well-defined (at least I hope so ...) and machine 
>>>> constraints
>>>> need to be modeled explicitely (like embedding an implicit bit_and in
>>>> shift patterns).
>>>
>>> Well, RTL is well-defined in the sense that if you have
>>>
>>>   (ashift X (foo:HI ...))
>>>
>>> then the shift amount must be interpreted as HImode rather than some
>>> other mode.  The problem here is to define a default choice of mode for
>>> const_ints, in cases where the shift is being created out of the blue.
>>>
>>> Whether the shift amount is effectively signed or unsigned isn't defined
>>> by RTL without SHIFT_COUNT_TRUNCATED, since the choice only matters for
>>> out-of-range values, and the behaviour for out-of-range RTL shifts is
>>> specifically treated as target-defined without SHIFT_COUNT_TRUNCATED.
>>>
>>> I think the revised patch does implement your suggestion of using the
>>> integer equivalent of the inner mode as the default, but we need to
>>> decide whether to go with it, go with the original word_mode approach
>>> (taken from existing expand_binop code) or something else.  Something
>>> else could include the widest supported integer mode, so that we never
>>> change the value.
>>
>> I guess it's pretty arbitrary what we choose (but we might need to adjust
>> targets?).  For something like this an appealing choice would be sth
>> that is host and target idependent, like [u]int32_t or given CONST_INT
>> is always 64bits now and signed int64_t aka HOST_WIDE_INT (bad
>> name now).  That means it's the "infinite precision" thing that fits
>> into CONST_INT ;)
>
> Sounds OK to me.  How about the attached?

Taking MAX_FIXED_MODE_SIZE into account was bogus, since we'd then just
fail to find a mode.  This version has survived the full cross-target
testing.  Also bootstrapped & regression-tested on aarch64-linux-gnu,
x86_64-linux-gnu and powerpc64-linux-gnu.  OK to install?

At this stage this is the patch that is holding up the rest of the
approved ones.

Thanks,
Richard


2017-12-19  Richard Sandiford  <richard.sandif...@linaro.org>
            Alan Hayward  <alan.hayw...@arm.com>
            David Sherwood  <david.sherw...@arm.com>

gcc/
        * emit-rtl.h (gen_int_shift_amount): Declare.
        * emit-rtl.c (gen_int_shift_amount): New function.
        * asan.c (asan_emit_stack_protection): Use gen_int_shift_amount
        instead of GEN_INT.
        * calls.c (shift_return_value): Likewise.
        * cse.c (fold_rtx): Likewise.
        * dse.c (find_shift_sequence): Likewise.
        * expmed.c (init_expmed_one_mode, store_bit_field_1, expand_shift_1)
        (expand_shift, expand_smod_pow2): Likewise.
        * lower-subreg.c (shift_cost): Likewise.
        * optabs.c (expand_superword_shift, expand_doubleword_mult)
        (expand_unop, expand_binop, shift_amt_for_vec_perm_mask)
        (expand_vec_perm_var): Likewise.
        * simplify-rtx.c (simplify_unary_operation_1): Likewise.
        (simplify_binary_operation_1): Likewise.
        * combine.c (try_combine, find_split_point, force_int_to_mode)
        (simplify_shift_const_1, simplify_shift_const): Likewise.
        (change_zero_ext): Likewise.  Use simplify_gen_binary.

Index: gcc/emit-rtl.h
===================================================================
--- gcc/emit-rtl.h      2017-12-16 14:23:26.068200011 +0000
+++ gcc/emit-rtl.h      2017-12-19 19:09:23.877365740 +0000
@@ -369,6 +369,7 @@ extern void set_reg_attrs_for_parm (rtx,
 extern void set_reg_attrs_for_decl_rtl (tree t, rtx x);
 extern void adjust_reg_mode (rtx, machine_mode);
 extern int mem_expr_equal_p (const_tree, const_tree);
+extern rtx gen_int_shift_amount (machine_mode, HOST_WIDE_INT);
 
 extern bool need_atomic_barrier_p (enum memmodel, bool);
 
Index: gcc/emit-rtl.c
===================================================================
--- gcc/emit-rtl.c      2017-12-16 14:23:26.068200011 +0000
+++ gcc/emit-rtl.c      2017-12-19 19:09:23.877365740 +0000
@@ -6418,6 +6418,22 @@ need_atomic_barrier_p (enum memmodel mod
     }
 }
 
+/* Return a constant shift amount for shifting a value of mode MODE
+   by VALUE bits.  */
+
+rtx
+gen_int_shift_amount (machine_mode, HOST_WIDE_INT value)
+{
+  /* Use a 64-bit mode, to avoid any truncation.
+
+     ??? Perhaps this should be automatically derived from the .md files
+     instead, or perhaps have a target hook.  */
+  scalar_int_mode shift_mode = (BITS_PER_UNIT == 8
+                               ? DImode
+                               : int_mode_for_size (64, 0).require ());
+  return gen_int_mode (value, shift_mode);
+}
+
 /* Initialize fields of rtl_data related to stack alignment.  */
 
 void
Index: gcc/asan.c
===================================================================
--- gcc/asan.c  2017-12-16 14:23:26.065200853 +0000
+++ gcc/asan.c  2017-12-19 19:09:23.867366133 +0000
@@ -1386,7 +1386,7 @@ asan_emit_stack_protection (rtx base, rt
   TREE_ASM_WRITTEN (id) = 1;
   emit_move_insn (mem, expand_normal (build_fold_addr_expr (decl)));
   shadow_base = expand_binop (Pmode, lshr_optab, base,
-                             GEN_INT (ASAN_SHADOW_SHIFT),
+                             gen_int_shift_amount (Pmode, ASAN_SHADOW_SHIFT),
                              NULL_RTX, 1, OPTAB_DIRECT);
   shadow_base
     = plus_constant (Pmode, shadow_base,
Index: gcc/calls.c
===================================================================
--- gcc/calls.c 2017-12-16 14:23:26.066200572 +0000
+++ gcc/calls.c 2017-12-19 19:09:23.868366094 +0000
@@ -2900,15 +2900,17 @@ shift_return_value (machine_mode mode, b
   HOST_WIDE_INT shift;
 
   gcc_assert (REG_P (value) && HARD_REGISTER_P (value));
-  shift = GET_MODE_BITSIZE (GET_MODE (value)) - GET_MODE_BITSIZE (mode);
+  machine_mode value_mode = GET_MODE (value);
+  shift = GET_MODE_BITSIZE (value_mode) - GET_MODE_BITSIZE (mode);
   if (shift == 0)
     return false;
 
   /* Use ashr rather than lshr for right shifts.  This is for the benefit
      of the MIPS port, which requires SImode values to be sign-extended
      when stored in 64-bit registers.  */
-  if (!force_expand_binop (GET_MODE (value), left_p ? ashl_optab : ashr_optab,
-                          value, GEN_INT (shift), value, 1, OPTAB_WIDEN))
+  if (!force_expand_binop (value_mode, left_p ? ashl_optab : ashr_optab,
+                          value, gen_int_shift_amount (value_mode, shift),
+                          value, 1, OPTAB_WIDEN))
     gcc_unreachable ();
   return true;
 }
Index: gcc/cse.c
===================================================================
--- gcc/cse.c   2017-12-16 14:23:26.067200292 +0000
+++ gcc/cse.c   2017-12-19 19:09:23.874365858 +0000
@@ -3611,9 +3611,9 @@ fold_rtx (rtx x, rtx_insn *insn)
                      || INTVAL (const_arg1) < 0))
                {
                  if (SHIFT_COUNT_TRUNCATED)
-                   canon_const_arg1 = GEN_INT (INTVAL (const_arg1)
-                                               & (GET_MODE_UNIT_BITSIZE (mode)
-                                                  - 1));
+                   canon_const_arg1 = gen_int_shift_amount
+                     (mode, (INTVAL (const_arg1)
+                             & (GET_MODE_UNIT_BITSIZE (mode) - 1)));
                  else
                    break;
                }
@@ -3660,9 +3660,9 @@ fold_rtx (rtx x, rtx_insn *insn)
                      || INTVAL (inner_const) < 0))
                {
                  if (SHIFT_COUNT_TRUNCATED)
-                   inner_const = GEN_INT (INTVAL (inner_const)
-                                          & (GET_MODE_UNIT_BITSIZE (mode)
-                                             - 1));
+                   inner_const = gen_int_shift_amount
+                     (mode, (INTVAL (inner_const)
+                             & (GET_MODE_UNIT_BITSIZE (mode) - 1)));
                  else
                    break;
                }
@@ -3692,7 +3692,8 @@ fold_rtx (rtx x, rtx_insn *insn)
                  /* As an exception, we can turn an ASHIFTRT of this
                     form into a shift of the number of bits - 1.  */
                  if (code == ASHIFTRT)
-                   new_const = GEN_INT (GET_MODE_UNIT_BITSIZE (mode) - 1);
+                   new_const = gen_int_shift_amount
+                     (mode, GET_MODE_UNIT_BITSIZE (mode) - 1);
                  else if (!side_effects_p (XEXP (y, 0)))
                    return CONST0_RTX (mode);
                  else
Index: gcc/dse.c
===================================================================
--- gcc/dse.c   2017-12-16 14:23:26.068200011 +0000
+++ gcc/dse.c   2017-12-19 19:09:23.875365819 +0000
@@ -1642,8 +1642,9 @@ find_shift_sequence (int access_size,
                                     store_mode, byte);
          if (ret && CONSTANT_P (ret))
            {
+             rtx shift_rtx = gen_int_shift_amount (new_mode, shift);
              ret = simplify_const_binary_operation (LSHIFTRT, new_mode,
-                                                    ret, GEN_INT (shift));
+                                                    ret, shift_rtx);
              if (ret && CONSTANT_P (ret))
                {
                  byte = subreg_lowpart_offset (read_mode, new_mode);
@@ -1679,7 +1680,8 @@ find_shift_sequence (int access_size,
         of one dsp where the cost of these two was not the same.  But
         this really is a rare case anyway.  */
       target = expand_binop (new_mode, lshr_optab, new_reg,
-                            GEN_INT (shift), new_reg, 1, OPTAB_DIRECT);
+                            gen_int_shift_amount (new_mode, shift),
+                            new_reg, 1, OPTAB_DIRECT);
 
       shift_seq = get_insns ();
       end_sequence ();
Index: gcc/expmed.c
===================================================================
--- gcc/expmed.c        2017-12-16 14:23:26.069199731 +0000
+++ gcc/expmed.c        2017-12-19 19:09:23.879365662 +0000
@@ -223,7 +223,8 @@ init_expmed_one_mode (struct init_expmed
          PUT_MODE (all->zext, wider_mode);
          PUT_MODE (all->wide_mult, wider_mode);
          PUT_MODE (all->wide_lshr, wider_mode);
-         XEXP (all->wide_lshr, 1) = GEN_INT (mode_bitsize);
+         XEXP (all->wide_lshr, 1)
+           = gen_int_shift_amount (wider_mode, mode_bitsize);
 
          set_mul_widen_cost (speed, wider_mode,
                              set_src_cost (all->wide_mult, wider_mode, speed));
@@ -910,12 +911,14 @@ store_bit_field_1 (rtx str_rtx, unsigned
             to make sure that for big-endian machines the higher order
             bits are used.  */
          if (new_bitsize < BITS_PER_WORD && BYTES_BIG_ENDIAN && !backwards)
-           value_word = simplify_expand_binop (word_mode, lshr_optab,
-                                               value_word,
-                                               GEN_INT (BITS_PER_WORD
-                                                        - new_bitsize),
-                                               NULL_RTX, true,
-                                               OPTAB_LIB_WIDEN);
+           {
+             int shift = BITS_PER_WORD - new_bitsize;
+             rtx shift_rtx = gen_int_shift_amount (word_mode, shift);
+             value_word = simplify_expand_binop (word_mode, lshr_optab,
+                                                 value_word, shift_rtx,
+                                                 NULL_RTX, true,
+                                                 OPTAB_LIB_WIDEN);
+           }
 
          if (!store_bit_field_1 (op0, new_bitsize,
                                  bitnum + bit_offset,
@@ -2366,8 +2369,9 @@ expand_shift_1 (enum tree_code code, mac
       if (CONST_INT_P (op1)
          && ((unsigned HOST_WIDE_INT) INTVAL (op1) >=
              (unsigned HOST_WIDE_INT) GET_MODE_BITSIZE (scalar_mode)))
-       op1 = GEN_INT ((unsigned HOST_WIDE_INT) INTVAL (op1)
-                      % GET_MODE_BITSIZE (scalar_mode));
+       op1 = gen_int_shift_amount (mode,
+                                   (unsigned HOST_WIDE_INT) INTVAL (op1)
+                                   % GET_MODE_BITSIZE (scalar_mode));
       else if (GET_CODE (op1) == SUBREG
               && subreg_lowpart_p (op1)
               && SCALAR_INT_MODE_P (GET_MODE (SUBREG_REG (op1)))
@@ -2384,7 +2388,8 @@ expand_shift_1 (enum tree_code code, mac
       && IN_RANGE (INTVAL (op1), GET_MODE_BITSIZE (scalar_mode) / 2 + left,
                   GET_MODE_BITSIZE (scalar_mode) - 1))
     {
-      op1 = GEN_INT (GET_MODE_BITSIZE (scalar_mode) - INTVAL (op1));
+      op1 = gen_int_shift_amount (mode, (GET_MODE_BITSIZE (scalar_mode)
+                                        - INTVAL (op1)));
       left = !left;
       code = left ? LROTATE_EXPR : RROTATE_EXPR;
     }
@@ -2464,8 +2469,8 @@ expand_shift_1 (enum tree_code code, mac
              if (op1 == const0_rtx)
                return shifted;
              else if (CONST_INT_P (op1))
-               other_amount = GEN_INT (GET_MODE_BITSIZE (scalar_mode)
-                                       - INTVAL (op1));
+               other_amount = gen_int_shift_amount
+                 (mode, GET_MODE_BITSIZE (scalar_mode) - INTVAL (op1));
              else
                {
                  other_amount
@@ -2538,8 +2543,9 @@ expand_shift_1 (enum tree_code code, mac
 expand_shift (enum tree_code code, machine_mode mode, rtx shifted,
              int amount, rtx target, int unsignedp)
 {
-  return expand_shift_1 (code, mode,
-                        shifted, GEN_INT (amount), target, unsignedp);
+  return expand_shift_1 (code, mode, shifted,
+                        gen_int_shift_amount (mode, amount),
+                        target, unsignedp);
 }
 
 /* Likewise, but return 0 if that cannot be done.  */
@@ -3857,7 +3863,7 @@ expand_smod_pow2 (scalar_int_mode mode,
        {
          HOST_WIDE_INT masklow = (HOST_WIDE_INT_1 << logd) - 1;
          signmask = force_reg (mode, signmask);
-         shift = GEN_INT (GET_MODE_BITSIZE (mode) - logd);
+         shift = gen_int_shift_amount (mode, GET_MODE_BITSIZE (mode) - logd);
 
          /* Use the rtx_cost of a LSHIFTRT instruction to determine
             which instruction sequence to use.  If logical right shifts
Index: gcc/lower-subreg.c
===================================================================
--- gcc/lower-subreg.c  2017-12-16 14:23:26.069199731 +0000
+++ gcc/lower-subreg.c  2017-12-19 19:09:23.879365662 +0000
@@ -141,7 +141,7 @@ shift_cost (bool speed_p, struct cost_rt
   PUT_CODE (rtxes->shift, code);
   PUT_MODE (rtxes->shift, mode);
   PUT_MODE (rtxes->source, mode);
-  XEXP (rtxes->shift, 1) = GEN_INT (op1);
+  XEXP (rtxes->shift, 1) = gen_int_shift_amount (mode, op1);
   return set_src_cost (rtxes->shift, mode, speed_p);
 }
 
Index: gcc/optabs.c
===================================================================
--- gcc/optabs.c        2017-12-16 14:23:26.070199450 +0000
+++ gcc/optabs.c        2017-12-19 19:09:23.882365544 +0000
@@ -431,8 +431,9 @@ expand_superword_shift (optab binoptab,
       if (binoptab != ashr_optab)
        emit_move_insn (outof_target, CONST0_RTX (word_mode));
       else
-       if (!force_expand_binop (word_mode, binoptab,
-                                outof_input, GEN_INT (BITS_PER_WORD - 1),
+       if (!force_expand_binop (word_mode, binoptab, outof_input,
+                                gen_int_shift_amount (word_mode,
+                                                      BITS_PER_WORD - 1),
                                 outof_target, unsignedp, methods))
          return false;
     }
@@ -789,7 +790,8 @@ expand_doubleword_mult (machine_mode mod
 {
   int low = (WORDS_BIG_ENDIAN ? 1 : 0);
   int high = (WORDS_BIG_ENDIAN ? 0 : 1);
-  rtx wordm1 = umulp ? NULL_RTX : GEN_INT (BITS_PER_WORD - 1);
+  rtx wordm1 = (umulp ? NULL_RTX
+               : gen_int_shift_amount (word_mode, BITS_PER_WORD - 1));
   rtx product, adjust, product_high, temp;
 
   rtx op0_high = operand_subword_force (op0, high, mode);
@@ -1190,7 +1192,7 @@ expand_binop (machine_mode mode, optab b
       unsigned int bits = GET_MODE_PRECISION (int_mode);
 
       if (CONST_INT_P (op1))
-        newop1 = GEN_INT (bits - INTVAL (op1));
+       newop1 = gen_int_shift_amount (int_mode, bits - INTVAL (op1));
       else if (targetm.shift_truncation_mask (int_mode) == bits - 1)
         newop1 = negate_rtx (GET_MODE (op1), op1);
       else
@@ -1412,7 +1414,7 @@ expand_binop (machine_mode mode, optab b
 
       /* Apply the truncation to constant shifts.  */
       if (double_shift_mask > 0 && CONST_INT_P (op1))
-       op1 = GEN_INT (INTVAL (op1) & double_shift_mask);
+       op1 = gen_int_mode (INTVAL (op1) & double_shift_mask, op1_mode);
 
       if (op1 == CONST0_RTX (op1_mode))
        return op0;
@@ -1522,7 +1524,7 @@ expand_binop (machine_mode mode, optab b
       else
        {
          rtx into_temp1, into_temp2, outof_temp1, outof_temp2;
-         rtx first_shift_count, second_shift_count;
+         HOST_WIDE_INT first_shift_count, second_shift_count;
          optab reverse_unsigned_shift, unsigned_shift;
 
          reverse_unsigned_shift = (left_shift ^ (shift_count < BITS_PER_WORD)
@@ -1533,20 +1535,24 @@ expand_binop (machine_mode mode, optab b
 
          if (shift_count > BITS_PER_WORD)
            {
-             first_shift_count = GEN_INT (shift_count - BITS_PER_WORD);
-             second_shift_count = GEN_INT (2 * BITS_PER_WORD - shift_count);
+             first_shift_count = shift_count - BITS_PER_WORD;
+             second_shift_count = 2 * BITS_PER_WORD - shift_count;
            }
          else
            {
-             first_shift_count = GEN_INT (BITS_PER_WORD - shift_count);
-             second_shift_count = GEN_INT (shift_count);
+             first_shift_count = BITS_PER_WORD - shift_count;
+             second_shift_count = shift_count;
            }
+         rtx first_shift_count_rtx
+           = gen_int_shift_amount (word_mode, first_shift_count);
+         rtx second_shift_count_rtx
+           = gen_int_shift_amount (word_mode, second_shift_count);
 
          into_temp1 = expand_binop (word_mode, unsigned_shift,
-                                    outof_input, first_shift_count,
+                                    outof_input, first_shift_count_rtx,
                                     NULL_RTX, unsignedp, next_methods);
          into_temp2 = expand_binop (word_mode, reverse_unsigned_shift,
-                                    into_input, second_shift_count,
+                                    into_input, second_shift_count_rtx,
                                     NULL_RTX, unsignedp, next_methods);
 
          if (into_temp1 != 0 && into_temp2 != 0)
@@ -1559,10 +1565,10 @@ expand_binop (machine_mode mode, optab b
            emit_move_insn (into_target, inter);
 
          outof_temp1 = expand_binop (word_mode, unsigned_shift,
-                                     into_input, first_shift_count,
+                                     into_input, first_shift_count_rtx,
                                      NULL_RTX, unsignedp, next_methods);
          outof_temp2 = expand_binop (word_mode, reverse_unsigned_shift,
-                                     outof_input, second_shift_count,
+                                     outof_input, second_shift_count_rtx,
                                      NULL_RTX, unsignedp, next_methods);
 
          if (inter != 0 && outof_temp1 != 0 && outof_temp2 != 0)
@@ -2802,25 +2808,29 @@ expand_unop (machine_mode mode, optab un
 
          if (optab_handler (rotl_optab, mode) != CODE_FOR_nothing)
            {
-             temp = expand_binop (mode, rotl_optab, op0, GEN_INT (8), target,
-                                  unsignedp, OPTAB_DIRECT);
+             temp = expand_binop (mode, rotl_optab, op0,
+                                  gen_int_shift_amount (mode, 8),
+                                  target, unsignedp, OPTAB_DIRECT);
              if (temp)
                return temp;
             }
 
          if (optab_handler (rotr_optab, mode) != CODE_FOR_nothing)
            {
-             temp = expand_binop (mode, rotr_optab, op0, GEN_INT (8), target,
-                                  unsignedp, OPTAB_DIRECT);
+             temp = expand_binop (mode, rotr_optab, op0,
+                                  gen_int_shift_amount (mode, 8),
+                                  target, unsignedp, OPTAB_DIRECT);
              if (temp)
                return temp;
            }
 
          last = get_last_insn ();
 
-         temp1 = expand_binop (mode, ashl_optab, op0, GEN_INT (8), NULL_RTX,
+         temp1 = expand_binop (mode, ashl_optab, op0,
+                               gen_int_shift_amount (mode, 8), NULL_RTX,
                                unsignedp, OPTAB_WIDEN);
-         temp2 = expand_binop (mode, lshr_optab, op0, GEN_INT (8), NULL_RTX,
+         temp2 = expand_binop (mode, lshr_optab, op0,
+                               gen_int_shift_amount (mode, 8), NULL_RTX,
                                unsignedp, OPTAB_WIDEN);
          if (temp1 && temp2)
            {
@@ -5402,7 +5412,7 @@ shift_amt_for_vec_perm_mask (rtx sel)
        return NULL_RTX;
     }
 
-  return GEN_INT (first * bitsize);
+  return gen_int_shift_amount (GET_MODE (sel), first * bitsize);
 }
 
 /* A subroutine of expand_vec_perm for expanding one vec_perm insn.  */
@@ -5572,7 +5582,8 @@ expand_vec_perm (machine_mode mode, rtx
                                   NULL, 0, OPTAB_DIRECT);
       else
        sel = expand_simple_binop (selmode, ASHIFT, sel,
-                                  GEN_INT (exact_log2 (u)),
+                                  gen_int_shift_amount (selmode,
+                                                        exact_log2 (u)),
                                   NULL, 0, OPTAB_DIRECT);
       gcc_assert (sel != NULL);
 
Index: gcc/simplify-rtx.c
===================================================================
--- gcc/simplify-rtx.c  2017-12-16 14:23:26.070199450 +0000
+++ gcc/simplify-rtx.c  2017-12-19 19:09:23.884365465 +0000
@@ -1165,7 +1165,8 @@ simplify_unary_operation_1 (enum rtx_cod
          if (STORE_FLAG_VALUE == 1)
            {
              temp = simplify_gen_binary (ASHIFTRT, inner, XEXP (op, 0),
-                                         GEN_INT (isize - 1));
+                                         gen_int_shift_amount (inner,
+                                                               isize - 1));
              if (int_mode == inner)
                return temp;
              if (GET_MODE_PRECISION (int_mode) > isize)
@@ -1175,7 +1176,8 @@ simplify_unary_operation_1 (enum rtx_cod
          else if (STORE_FLAG_VALUE == -1)
            {
              temp = simplify_gen_binary (LSHIFTRT, inner, XEXP (op, 0),
-                                         GEN_INT (isize - 1));
+                                         gen_int_shift_amount (inner,
+                                                               isize - 1));
              if (int_mode == inner)
                return temp;
              if (GET_MODE_PRECISION (int_mode) > isize)
@@ -2672,7 +2674,8 @@ simplify_binary_operation_1 (enum rtx_co
        {
          val = wi::exact_log2 (rtx_mode_t (trueop1, mode));
          if (val >= 0)
-           return simplify_gen_binary (ASHIFT, mode, op0, GEN_INT (val));
+           return simplify_gen_binary (ASHIFT, mode, op0,
+                                       gen_int_shift_amount (mode, val));
        }
 
       /* x*2 is x+x and x*(-1) is -x */
@@ -3296,7 +3299,8 @@ simplify_binary_operation_1 (enum rtx_co
       /* Convert divide by power of two into shift.  */
       if (CONST_INT_P (trueop1)
          && (val = exact_log2 (UINTVAL (trueop1))) > 0)
-       return simplify_gen_binary (LSHIFTRT, mode, op0, GEN_INT (val));
+       return simplify_gen_binary (LSHIFTRT, mode, op0,
+                                   gen_int_shift_amount (mode, val));
       break;
 
     case DIV:
@@ -3416,10 +3420,12 @@ simplify_binary_operation_1 (enum rtx_co
          && IN_RANGE (INTVAL (trueop1),
                       GET_MODE_UNIT_PRECISION (mode) / 2 + (code == ROTATE),
                       GET_MODE_UNIT_PRECISION (mode) - 1))
-       return simplify_gen_binary (code == ROTATE ? ROTATERT : ROTATE,
-                                   mode, op0,
-                                   GEN_INT (GET_MODE_UNIT_PRECISION (mode)
-                                            - INTVAL (trueop1)));
+       {
+         int new_amount = GET_MODE_UNIT_PRECISION (mode) - INTVAL (trueop1);
+         rtx new_amount_rtx = gen_int_shift_amount (mode, new_amount);
+         return simplify_gen_binary (code == ROTATE ? ROTATERT : ROTATE,
+                                     mode, op0, new_amount_rtx);
+       }
 #endif
       /* FALLTHRU */
     case ASHIFTRT:
@@ -3460,8 +3466,8 @@ simplify_binary_operation_1 (enum rtx_co
              == GET_MODE_BITSIZE (inner_mode) - GET_MODE_BITSIZE (int_mode))
          && subreg_lowpart_p (op0))
        {
-         rtx tmp = GEN_INT (INTVAL (XEXP (SUBREG_REG (op0), 1))
-                            + INTVAL (op1));
+         rtx tmp = gen_int_shift_amount
+           (inner_mode, INTVAL (XEXP (SUBREG_REG (op0), 1)) + INTVAL (op1));
          tmp = simplify_gen_binary (code, inner_mode,
                                     XEXP (SUBREG_REG (op0), 0),
                                     tmp);
@@ -3472,7 +3478,8 @@ simplify_binary_operation_1 (enum rtx_co
        {
          val = INTVAL (op1) & (GET_MODE_UNIT_PRECISION (mode) - 1);
          if (val != INTVAL (op1))
-           return simplify_gen_binary (code, mode, op0, GEN_INT (val));
+           return simplify_gen_binary (code, mode, op0,
+                                       gen_int_shift_amount (mode, val));
        }
       break;
 
Index: gcc/combine.c
===================================================================
--- gcc/combine.c       2017-12-16 14:23:26.067200292 +0000
+++ gcc/combine.c       2017-12-19 19:09:23.873365897 +0000
@@ -3804,8 +3804,9 @@ try_combine (rtx_insn *i3, rtx_insn *i2,
              && INTVAL (XEXP (*split, 1)) > 0
              && (i = exact_log2 (UINTVAL (XEXP (*split, 1)))) >= 0)
            {
+             rtx i_rtx = gen_int_shift_amount (split_mode, i);
              SUBST (*split, gen_rtx_ASHIFT (split_mode,
-                                            XEXP (*split, 0), GEN_INT (i)));
+                                            XEXP (*split, 0), i_rtx));
              /* Update split_code because we may not have a multiply
                 anymore.  */
              split_code = GET_CODE (*split);
@@ -3819,8 +3820,10 @@ try_combine (rtx_insn *i3, rtx_insn *i2,
              && (i = exact_log2 (UINTVAL (XEXP (XEXP (*split, 0), 1)))) >= 0)
            {
              rtx nsplit = XEXP (*split, 0);
+             rtx i_rtx = gen_int_shift_amount (GET_MODE (nsplit), i);
              SUBST (XEXP (*split, 0), gen_rtx_ASHIFT (GET_MODE (nsplit),
-                                            XEXP (nsplit, 0), GEN_INT (i)));
+                                                      XEXP (nsplit, 0),
+                                                      i_rtx));
              /* Update split_code because we may not have a multiply
                 anymore.  */
              split_code = GET_CODE (*split);
@@ -5088,12 +5091,12 @@ find_split_point (rtx *loc, rtx_insn *in
                                      GET_MODE (XEXP (SET_SRC (x), 0))))))
            {
              machine_mode mode = GET_MODE (XEXP (SET_SRC (x), 0));
-
+             rtx pos_rtx = gen_int_shift_amount (mode, pos);
              SUBST (SET_SRC (x),
                     gen_rtx_NEG (mode,
                                  gen_rtx_LSHIFTRT (mode,
                                                    XEXP (SET_SRC (x), 0),
-                                                   GEN_INT (pos))));
+                                                   pos_rtx)));
 
              split = find_split_point (&SET_SRC (x), insn, true);
              if (split && split != &SET_SRC (x))
@@ -5151,11 +5154,11 @@ find_split_point (rtx *loc, rtx_insn *in
            {
              unsigned HOST_WIDE_INT mask
                = (HOST_WIDE_INT_1U << len) - 1;
+             rtx pos_rtx = gen_int_shift_amount (mode, pos);
              SUBST (SET_SRC (x),
                     gen_rtx_AND (mode,
                                  gen_rtx_LSHIFTRT
-                                 (mode, gen_lowpart (mode, inner),
-                                  GEN_INT (pos)),
+                                 (mode, gen_lowpart (mode, inner), pos_rtx),
                                  gen_int_mode (mask, mode)));
 
              split = find_split_point (&SET_SRC (x), insn, true);
@@ -5164,14 +5167,15 @@ find_split_point (rtx *loc, rtx_insn *in
            }
          else
            {
+             int left_bits = GET_MODE_PRECISION (mode) - len - pos;
+             int right_bits = GET_MODE_PRECISION (mode) - len;
              SUBST (SET_SRC (x),
                     gen_rtx_fmt_ee
                     (unsignedp ? LSHIFTRT : ASHIFTRT, mode,
                      gen_rtx_ASHIFT (mode,
                                      gen_lowpart (mode, inner),
-                                     GEN_INT (GET_MODE_PRECISION (mode)
-                                              - len - pos)),
-                     GEN_INT (GET_MODE_PRECISION (mode) - len)));
+                                     gen_int_shift_amount (mode, left_bits)),
+                     gen_int_shift_amount (mode, right_bits)));
 
              split = find_split_point (&SET_SRC (x), insn, true);
              if (split && split != &SET_SRC (x))
@@ -8952,10 +8956,11 @@ force_int_to_mode (rtx x, scalar_int_mod
          /* Must be more sign bit copies than the mask needs.  */
          && ((int) num_sign_bit_copies (XEXP (x, 0), GET_MODE (XEXP (x, 0)))
              >= exact_log2 (mask + 1)))
-       x = simplify_gen_binary (LSHIFTRT, xmode, XEXP (x, 0),
-                                GEN_INT (GET_MODE_PRECISION (xmode)
-                                         - exact_log2 (mask + 1)));
-
+       {
+         int nbits = GET_MODE_PRECISION (xmode) - exact_log2 (mask + 1);
+         x = simplify_gen_binary (LSHIFTRT, xmode, XEXP (x, 0),
+                                  gen_int_shift_amount (xmode, nbits));
+       }
       goto shiftrt;
 
     case ASHIFTRT:
@@ -10448,7 +10453,7 @@ simplify_shift_const_1 (enum rtx_code co
 {
   enum rtx_code orig_code = code;
   rtx orig_varop = varop;
-  int count;
+  int count, log2;
   machine_mode mode = result_mode;
   machine_mode shift_mode;
   scalar_int_mode tmode, inner_mode, int_mode, int_varop_mode, int_result_mode;
@@ -10651,13 +10656,11 @@ simplify_shift_const_1 (enum rtx_code co
             is cheaper.  But it is still better on those machines to
             merge two shifts into one.  */
          if (CONST_INT_P (XEXP (varop, 1))
-             && exact_log2 (UINTVAL (XEXP (varop, 1))) >= 0)
+             && (log2 = exact_log2 (UINTVAL (XEXP (varop, 1)))) >= 0)
            {
-             varop
-               = simplify_gen_binary (ASHIFT, GET_MODE (varop),
-                                      XEXP (varop, 0),
-                                      GEN_INT (exact_log2 (
-                                               UINTVAL (XEXP (varop, 1)))));
+             rtx log2_rtx = gen_int_shift_amount (GET_MODE (varop), log2);
+             varop = simplify_gen_binary (ASHIFT, GET_MODE (varop),
+                                          XEXP (varop, 0), log2_rtx);
              continue;
            }
          break;
@@ -10665,13 +10668,11 @@ simplify_shift_const_1 (enum rtx_code co
        case UDIV:
          /* Similar, for when divides are cheaper.  */
          if (CONST_INT_P (XEXP (varop, 1))
-             && exact_log2 (UINTVAL (XEXP (varop, 1))) >= 0)
+             && (log2 = exact_log2 (UINTVAL (XEXP (varop, 1)))) >= 0)
            {
-             varop
-               = simplify_gen_binary (LSHIFTRT, GET_MODE (varop),
-                                      XEXP (varop, 0),
-                                      GEN_INT (exact_log2 (
-                                               UINTVAL (XEXP (varop, 1)))));
+             rtx log2_rtx = gen_int_shift_amount (GET_MODE (varop), log2);
+             varop = simplify_gen_binary (LSHIFTRT, GET_MODE (varop),
+                                          XEXP (varop, 0), log2_rtx);
              continue;
            }
          break;
@@ -10806,10 +10807,10 @@ simplify_shift_const_1 (enum rtx_code co
 
              mask_rtx = gen_int_mode (nonzero_bits (varop, int_varop_mode),
                                       int_result_mode);
-
+             rtx count_rtx = gen_int_shift_amount (int_result_mode, count);
              mask_rtx
                = simplify_const_binary_operation (code, int_result_mode,
-                                                  mask_rtx, GEN_INT (count));
+                                                  mask_rtx, count_rtx);
 
              /* Give up if we can't compute an outer operation to use.  */
              if (mask_rtx == 0
@@ -10865,9 +10866,10 @@ simplify_shift_const_1 (enum rtx_code co
              if (code == ASHIFTRT && int_mode != int_result_mode)
                break;
 
+             rtx count_rtx = gen_int_shift_amount (int_result_mode, count);
              rtx new_rtx = simplify_const_binary_operation (code, int_mode,
                                                             XEXP (varop, 0),
-                                                            GEN_INT (count));
+                                                            count_rtx);
              varop = gen_rtx_fmt_ee (code, int_mode, new_rtx, XEXP (varop, 1));
              count = 0;
              continue;
@@ -10933,7 +10935,7 @@ simplify_shift_const_1 (enum rtx_code co
              && (new_rtx = simplify_const_binary_operation
                  (code, int_result_mode,
                   gen_int_mode (INTVAL (XEXP (varop, 1)), int_result_mode),
-                  GEN_INT (count))) != 0
+                  gen_int_shift_amount (int_result_mode, count))) != 0
              && CONST_INT_P (new_rtx)
              && merge_outer_ops (&outer_op, &outer_const, GET_CODE (varop),
                                  INTVAL (new_rtx), int_result_mode,
@@ -11076,7 +11078,7 @@ simplify_shift_const_1 (enum rtx_code co
              && (new_rtx = simplify_const_binary_operation
                  (ASHIFT, int_result_mode,
                   gen_int_mode (INTVAL (XEXP (varop, 1)), int_result_mode),
-                  GEN_INT (count))) != 0
+                  gen_int_shift_amount (int_result_mode, count))) != 0
              && CONST_INT_P (new_rtx)
              && merge_outer_ops (&outer_op, &outer_const, PLUS,
                                  INTVAL (new_rtx), int_result_mode,
@@ -11097,7 +11099,7 @@ simplify_shift_const_1 (enum rtx_code co
              && (new_rtx = simplify_const_binary_operation
                  (code, int_result_mode,
                   gen_int_mode (INTVAL (XEXP (varop, 1)), int_result_mode),
-                  GEN_INT (count))) != 0
+                  gen_int_shift_amount (int_result_mode, count))) != 0
              && CONST_INT_P (new_rtx)
              && merge_outer_ops (&outer_op, &outer_const, XOR,
                                  INTVAL (new_rtx), int_result_mode,
@@ -11152,12 +11154,12 @@ simplify_shift_const_1 (enum rtx_code co
                      - GET_MODE_UNIT_PRECISION (GET_MODE (varop)))))
            {
              rtx varop_inner = XEXP (varop, 0);
-
-             varop_inner
-               = gen_rtx_LSHIFTRT (GET_MODE (varop_inner),
-                                   XEXP (varop_inner, 0),
-                                   GEN_INT
-                                   (count + INTVAL (XEXP (varop_inner, 1))));
+             int new_count = count + INTVAL (XEXP (varop_inner, 1));
+             rtx new_count_rtx = gen_int_shift_amount (GET_MODE (varop_inner),
+                                                       new_count);
+             varop_inner = gen_rtx_LSHIFTRT (GET_MODE (varop_inner),
+                                             XEXP (varop_inner, 0),
+                                             new_count_rtx);
              varop = gen_rtx_TRUNCATE (GET_MODE (varop), varop_inner);
              count = 0;
              continue;
@@ -11209,7 +11211,8 @@ simplify_shift_const_1 (enum rtx_code co
     x = NULL_RTX;
 
   if (x == NULL_RTX)
-    x = simplify_gen_binary (code, shift_mode, varop, GEN_INT (count));
+    x = simplify_gen_binary (code, shift_mode, varop,
+                            gen_int_shift_amount (shift_mode, count));
 
   /* If we were doing an LSHIFTRT in a wider mode than it was originally,
      turn off all the bits that the shift would have turned off.  */
@@ -11271,7 +11274,8 @@ simplify_shift_const (rtx x, enum rtx_co
     return tem;
 
   if (!x)
-    x = simplify_gen_binary (code, GET_MODE (varop), varop, GEN_INT (count));
+    x = simplify_gen_binary (code, GET_MODE (varop), varop,
+                            gen_int_shift_amount (GET_MODE (varop), count));
   if (GET_MODE (x) != result_mode)
     x = gen_lowpart (result_mode, x);
   return x;
@@ -11462,8 +11466,9 @@ change_zero_ext (rtx pat)
          if (BITS_BIG_ENDIAN)
            start = GET_MODE_PRECISION (inner_mode) - size - start;
 
-         if (start)
-           x = gen_rtx_LSHIFTRT (inner_mode, XEXP (x, 0), GEN_INT (start));
+         if (start != 0)
+           x = gen_rtx_LSHIFTRT (inner_mode, XEXP (x, 0),
+                                 gen_int_shift_amount (inner_mode, start));
          else
            x = XEXP (x, 0);
          if (mode != inner_mode)

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