Re: [PATCH][AArch64] Cleanup move immediate code

[Wilco Dijkstra <Wilco.Dijkstra@arm.com>]

Hi Richard,

> -      scalar_int_mode imode = (mode == HFmode
> -                            ? SImode
> -                            : int_mode_for_mode (mode).require ());
> +      machine_mode imode = (mode == DFmode) ? DImode : SImode;

> It looks like this might mishandle DDmode, if not now then in the future.
> Seems safer to use known_eq (GET_MODE_SIZE (mode), 8)

I've changed that, but it does not matter for the narrow modes as the result
will be identical - only DDmode might get costed incorrectly.

> Sorry for not noticing last time, but: rather than have
> aarch64_zeroextended_move_imm (which is quite a complicated test),
> could we just add an extra (default off) parameter to aarch64_move_imm
> that suppresses the (val >> 32) == 0 test?

That makes things more complicated again - ultimately I'd like to get rid of the
mode parameter since most callers use a fixed mode, and ones that don't are
now creating and passing fake modes... I've change it like aarch64_move_imm
and call aarch64_is_movz twice to check it is not a 64-bit MOVZ/MOVN.

Cheers,
Wilco

v3: Use aarch64_is_movz, use known_eq

Simplify, refactor and improve various move immediate functions.
Allow 32-bit MOVI/N as a valid 64-bit immediate which removes special
cases in aarch64_internal_mov_immediate.  Add new constraint so the movdi
pattern only needs a single alternative for move immediate.

Passes bootstrap and regress, OK for commit?

gcc/ChangeLog:

	* config/aarch64/aarch64.cc (aarch64_bitmask_imm): Use unsigned type.
        (aarch64_zeroextended_move_imm): New function.
        (aarch64_move_imm): Refactor, assert mode is SImode or DImode.
        (aarch64_internal_mov_immediate): Assert mode is SImode or DImode.
        Simplify special cases.
        (aarch64_uimm12_shift): Simplify code.
        (aarch64_clamp_to_uimm12_shift): Likewise.
        (aarch64_movw_imm): Rename to aarch64_is_movz.
        (aarch64_float_const_rtx_p): Pass either SImode or DImode to
        aarch64_internal_mov_immediate.
        (aarch64_rtx_costs): Likewise.
        * config/aarch64/aarch64.md (movdi_aarch64): Merge 'N' and 'M'
        constraints into single 'O'.
        (mov<mode>_aarch64): Likewise.
        * config/aarch64/aarch64-protos.h (aarch64_move_imm): Use unsigned.
        (aarch64_bitmask_imm): Likewise.
        (aarch64_uimm12_shift): Likewise.
        (aarch64_zeroextended_move_imm): New prototype.
        * config/aarch64/constraints.md: Add 'O' for 32/64-bit immediates,
        limit 'N' to 64-bit only moves.

---

diff --git a/gcc/config/aarch64/aarch64-protos.h b/gcc/config/aarch64/aarch64-protos.h
index 4be93c93c26e091f878bc8e4cf06e90888405fb2..8bce6ec7599edcc2e6a1d8006450f35c0ce7f61f 100644
--- a/gcc/config/aarch64/aarch64-protos.h
+++ b/gcc/config/aarch64/aarch64-protos.h
@@ -756,7 +756,7 @@ void aarch64_post_cfi_startproc (void);
 poly_int64 aarch64_initial_elimination_offset (unsigned, unsigned);
 int aarch64_get_condition_code (rtx);
 bool aarch64_address_valid_for_prefetch_p (rtx, bool);
-bool aarch64_bitmask_imm (HOST_WIDE_INT val, machine_mode);
+bool aarch64_bitmask_imm (unsigned HOST_WIDE_INT val, machine_mode);
 unsigned HOST_WIDE_INT aarch64_and_split_imm1 (HOST_WIDE_INT val_in);
 unsigned HOST_WIDE_INT aarch64_and_split_imm2 (HOST_WIDE_INT val_in);
 bool aarch64_and_bitmask_imm (unsigned HOST_WIDE_INT val_in, machine_mode mode);
@@ -793,7 +793,7 @@ bool aarch64_masks_and_shift_for_bfi_p (scalar_int_mode, unsigned HOST_WIDE_INT,
 					unsigned HOST_WIDE_INT,
 					unsigned HOST_WIDE_INT);
 bool aarch64_zero_extend_const_eq (machine_mode, rtx, machine_mode, rtx);
-bool aarch64_move_imm (HOST_WIDE_INT, machine_mode);
+bool aarch64_move_imm (unsigned HOST_WIDE_INT, machine_mode);
 machine_mode aarch64_sve_int_mode (machine_mode);
 opt_machine_mode aarch64_sve_pred_mode (unsigned int);
 machine_mode aarch64_sve_pred_mode (machine_mode);
@@ -843,8 +843,9 @@ bool aarch64_sve_float_arith_immediate_p (rtx, bool);
 bool aarch64_sve_float_mul_immediate_p (rtx);
 bool aarch64_split_dimode_const_store (rtx, rtx);
 bool aarch64_symbolic_address_p (rtx);
-bool aarch64_uimm12_shift (HOST_WIDE_INT);
+bool aarch64_uimm12_shift (unsigned HOST_WIDE_INT);
 int aarch64_movk_shift (const wide_int_ref &, const wide_int_ref &);
+bool aarch64_zeroextended_move_imm (unsigned HOST_WIDE_INT);
 bool aarch64_use_return_insn_p (void);
 const char *aarch64_output_casesi (rtx *);
 
diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index a73741800c963ee6605fd2cfa918f4399da4bfdf..00269632eeb52c29ba2011c4c82274968b850d71 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -5625,12 +5625,10 @@ aarch64_bitmask_imm (unsigned HOST_WIDE_INT val)
 
 /* Return true if VAL is a valid bitmask immediate for MODE.  */
 bool
-aarch64_bitmask_imm (HOST_WIDE_INT val_in, machine_mode mode)
+aarch64_bitmask_imm (unsigned HOST_WIDE_INT val, machine_mode mode)
 {
   if (mode == DImode)
-    return aarch64_bitmask_imm (val_in);
-
-  unsigned HOST_WIDE_INT val = val_in;
+    return aarch64_bitmask_imm (val);
 
   if (mode == SImode)
     return aarch64_bitmask_imm ((val & 0xffffffff) | (val << 32));
@@ -5669,51 +5667,58 @@ aarch64_check_bitmask (unsigned HOST_WIDE_INT val,
 }
 
 
-/* Return true if val is an immediate that can be loaded into a
-   register by a MOVZ instruction.  */
-static bool
-aarch64_movw_imm (HOST_WIDE_INT val, scalar_int_mode mode)
+/* Return true if VAL is a valid MOVZ immediate.  */
+static inline bool
+aarch64_is_movz (unsigned HOST_WIDE_INT val)
 {
-  if (GET_MODE_SIZE (mode) > 4)
-    {
-      if ((val & (((HOST_WIDE_INT) 0xffff) << 32)) == val
-	   || (val & (((HOST_WIDE_INT) 0xffff) << 48)) == val)
-	return 1;
-    }
-  else
-    {
-      /* Ignore sign extension.  */
-      val &= (HOST_WIDE_INT) 0xffffffff;
-    }
-  return ((val & (((HOST_WIDE_INT) 0xffff) << 0)) == val
-	  || (val & (((HOST_WIDE_INT) 0xffff) << 16)) == val);
+  return (val >> (ctz_hwi (val) & 48)) < 65536;
 }
 
 
-/* Return true if VAL is an immediate that can be loaded into a
-   register in a single instruction.  */
+/* Return true if immediate VAL can only be created by using a 32-bit
+   zero-extended move immediate, not by a 64-bit move.  */
 bool
-aarch64_move_imm (HOST_WIDE_INT val, machine_mode mode)
+aarch64_zeroextended_move_imm (unsigned HOST_WIDE_INT val)
 {
-  scalar_int_mode int_mode;
-  if (!is_a <scalar_int_mode> (mode, &int_mode))
+  if (aarch64_is_movz (val) || aarch64_is_movz (~val))
     return false;
 
-  if (aarch64_movw_imm (val, int_mode) || aarch64_movw_imm (~val, int_mode))
-    return 1;
-  return aarch64_bitmask_imm (val, int_mode);
+  return !aarch64_bitmask_imm (val);
+}
+
+
+/* Return true if VAL is an immediate that can be created by a single
+   MOV instruction.  */
+bool
+aarch64_move_imm (unsigned HOST_WIDE_INT val, machine_mode mode)
+{
+  gcc_assert (mode == SImode || mode == DImode);
+
+  if (val < 65536)
+    return true;
+
+  unsigned HOST_WIDE_INT mask =
+    (val >> 32) == 0 || mode == SImode ? 0xffffffff : HOST_WIDE_INT_M1U;
+
+  if (aarch64_is_movz (val & mask) || aarch64_is_movz (~val & mask))
+    return true;
+
+  val = (val & mask) | ((val << 32) & ~mask);
+  return aarch64_bitmask_imm (val);
 }
 
 
 static int
 aarch64_internal_mov_immediate (rtx dest, rtx imm, bool generate,
-				scalar_int_mode mode)
+				machine_mode mode)
 {
   int i;
   unsigned HOST_WIDE_INT val, val2, mask;
   int one_match, zero_match;
   int num_insns;
 
+  gcc_assert (mode == SImode || mode == DImode);
+
   val = INTVAL (imm);
 
   if (aarch64_move_imm (val, mode))
@@ -5723,31 +5728,6 @@ aarch64_internal_mov_immediate (rtx dest, rtx imm, bool generate,
       return 1;
     }
 
-  /* Check to see if the low 32 bits are either 0xffffXXXX or 0xXXXXffff
-     (with XXXX non-zero). In that case check to see if the move can be done in
-     a smaller mode.  */
-  val2 = val & 0xffffffff;
-  if (mode == DImode
-      && aarch64_move_imm (val2, SImode)
-      && (((val >> 32) & 0xffff) == 0 || (val >> 48) == 0))
-    {
-      if (generate)
-	emit_insn (gen_rtx_SET (dest, GEN_INT (val2)));
-
-      /* Check if we have to emit a second instruction by checking to see
-	 if any of the upper 32 bits of the original DI mode value is set.  */
-      if (val == val2)
-	return 1;
-
-      i = (val >> 48) ? 48 : 32;
-
-      if (generate)
-	 emit_insn (gen_insv_immdi (dest, GEN_INT (i),
-				    GEN_INT ((val >> i) & 0xffff)));
-
-      return 2;
-    }
-
   if ((val >> 32) == 0 || mode == SImode)
     {
       if (generate)
@@ -5771,24 +5751,31 @@ aarch64_internal_mov_immediate (rtx dest, rtx imm, bool generate,
   one_match = ((~val & mask) == 0) + ((~val & (mask << 16)) == 0) +
     ((~val & (mask << 32)) == 0) + ((~val & (mask << 48)) == 0);
 
+  /* Try a bitmask immediate and a movk to generate the immediate
+     in 2 instructions.  */
+
   if (zero_match < 2 && one_match < 2)
     {
-      /* Try emitting a bitmask immediate with a movk replacing 16 bits.
-	 For a 64-bit bitmask try whether changing 16 bits to all ones or
-	 zeroes creates a valid bitmask.  To check any repeated bitmask,
-	 try using 16 bits from the other 32-bit half of val.  */
-
       for (i = 0; i < 64; i += 16)
-	if (aarch64_check_bitmask (val, val2, mask << i))
-	  {
-	    if (generate)
-	      {
-		emit_insn (gen_rtx_SET (dest, GEN_INT (val2)));
-		emit_insn (gen_insv_immdi (dest, GEN_INT (i),
-					   GEN_INT ((val >> i) & 0xffff)));
-	      }
-	    return 2;
-	  }
+	{
+	  if (aarch64_check_bitmask (val, val2, mask << i))
+	    break;
+
+	  val2 = val & ~(mask << i);
+	  if ((val2 >> 32) == 0 && aarch64_move_imm (val2, DImode))
+	    break;
+	}
+
+      if (i != 64)
+	{
+	  if (generate)
+	    {
+	      emit_insn (gen_rtx_SET (dest, GEN_INT (val2)));
+	      emit_insn (gen_insv_immdi (dest, GEN_INT (i),
+					 GEN_INT ((val >> i) & 0xffff)));
+	    }
+	  return 2;
+	}
     }
 
   /* Try a bitmask plus 2 movk to generate the immediate in 3 instructions.  */
@@ -5857,26 +5844,24 @@ aarch64_mov128_immediate (rtx imm)
 /* Return true if val can be encoded as a 12-bit unsigned immediate with
    a left shift of 0 or 12 bits.  */
 bool
-aarch64_uimm12_shift (HOST_WIDE_INT val)
+aarch64_uimm12_shift (unsigned HOST_WIDE_INT val)
 {
-  return ((val & (((HOST_WIDE_INT) 0xfff) << 0)) == val
-	  || (val & (((HOST_WIDE_INT) 0xfff) << 12)) == val
-	  );
+  return val < 4096 || (val & 0xfff000) == val;
 }
 
 /* Returns the nearest value to VAL that will fit as a 12-bit unsigned immediate
    that can be created with a left shift of 0 or 12.  */
 static HOST_WIDE_INT
-aarch64_clamp_to_uimm12_shift (HOST_WIDE_INT val)
+aarch64_clamp_to_uimm12_shift (unsigned HOST_WIDE_INT val)
 {
   /* Check to see if the value fits in 24 bits, as that is the maximum we can
      handle correctly.  */
-  gcc_assert ((val & 0xffffff) == val);
+  gcc_assert (val < 0x1000000);
 
-  if (((val & 0xfff) << 0) == val)
+  if (val < 4096)
     return val;
 
-  return val & (0xfff << 12);
+  return val & 0xfff000;
 }
 
 
@@ -7024,8 +7009,7 @@ aarch64_expand_mov_immediate (rtx dest, rtx imm)
       return;
     }
 
-  aarch64_internal_mov_immediate (dest, imm, true,
-				  as_a <scalar_int_mode> (mode));
+  aarch64_internal_mov_immediate (dest, imm, true, mode);
 }
 
 /* Return the MEM rtx that provides the canary value that should be used
@@ -11197,9 +11181,7 @@ aarch64_float_const_rtx_p (rtx x)
       && SCALAR_FLOAT_MODE_P (mode)
       && aarch64_reinterpret_float_as_int (x, &ival))
     {
-      scalar_int_mode imode = (mode == HFmode
-			       ? SImode
-			       : int_mode_for_mode (mode).require ());
+      machine_mode imode = known_eq (GET_MODE_SIZE (mode), 8) ? DImode : SImode;
       int num_instr = aarch64_internal_mov_immediate
 			(NULL_RTX, gen_int_mode (ival, imode), false, imode);
       return num_instr < 3;
@@ -13857,10 +13839,10 @@ aarch64_rtx_costs (rtx x, machine_mode mode, int outer ATTRIBUTE_UNUSED,
 	     proportionally expensive to the number of instructions
 	     required to build that constant.  This is true whether we
 	     are compiling for SPEED or otherwise.  */
-	  if (!is_a <scalar_int_mode> (mode, &int_mode))
-	    int_mode = word_mode;
+	  machine_mode imode = known_le (GET_MODE_SIZE (mode), 4)
+				? SImode : DImode;
 	  *cost = COSTS_N_INSNS (aarch64_internal_mov_immediate
-				 (NULL_RTX, x, false, int_mode));
+				 (NULL_RTX, x, false, imode));
 	}
       return true;
 
@@ -13876,9 +13858,8 @@ aarch64_rtx_costs (rtx x, machine_mode mode, int outer ATTRIBUTE_UNUSED,
 	  bool succeed = aarch64_reinterpret_float_as_int (x, &ival);
 	  gcc_assert (succeed);
 
-	  scalar_int_mode imode = (mode == HFmode
-				   ? SImode
-				   : int_mode_for_mode (mode).require ());
+	  machine_mode imode = known_eq (GET_MODE_SIZE (mode), 8)
+				? DImode : SImode;
 	  int ncost = aarch64_internal_mov_immediate
 		(NULL_RTX, gen_int_mode (ival, imode), false, imode);
 	  *cost += COSTS_N_INSNS (ncost);
diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
index 76b6898ca048c559ff7f7fba78119161b3d382f6..5694a1efea1df8e532520475140c8748b54e3d89 100644
--- a/gcc/config/aarch64/aarch64.md
+++ b/gcc/config/aarch64/aarch64.md
@@ -1309,16 +1309,15 @@ (define_insn_and_split "*movsi_aarch64"
 )
 
 (define_insn_and_split "*movdi_aarch64"
-  [(set (match_operand:DI 0 "nonimmediate_operand" "=r,k,r,r,r,r,r, r,w, m,m,   r,  r,  r, w,r,w, w")
-	(match_operand:DI 1 "aarch64_mov_operand"  " r,r,k,N,M,n,Usv,m,m,rZ,w,Usw,Usa,Ush,rZ,w,w,Dd"))]
+  [(set (match_operand:DI 0 "nonimmediate_operand" "=r,k,r,r,r,r, r,w, m,m,   r,  r,  r, w,r,w, w")
+	(match_operand:DI 1 "aarch64_mov_operand"  " r,r,k,O,n,Usv,m,m,rZ,w,Usw,Usa,Ush,rZ,w,w,Dd"))]
   "(register_operand (operands[0], DImode)
     || aarch64_reg_or_zero (operands[1], DImode))"
   "@
    mov\\t%x0, %x1
    mov\\t%0, %x1
    mov\\t%x0, %1
-   mov\\t%x0, %1
-   mov\\t%w0, %1
+   * return aarch64_zeroextended_move_imm (INTVAL (operands[1])) ? \"mov\\t%w0, %1\" : \"mov\\t%x0, %1\";
    #
    * return aarch64_output_sve_cnt_immediate (\"cnt\", \"%x0\", operands[1]);
    ldr\\t%x0, %1
@@ -1340,11 +1339,11 @@ (define_insn_and_split "*movdi_aarch64"
        DONE;
     }"
   ;; The "mov_imm" type for CNTD is just a placeholder.
-  [(set_attr "type" "mov_reg,mov_reg,mov_reg,mov_imm,mov_imm,mov_imm,mov_imm,
+  [(set_attr "type" "mov_reg,mov_reg,mov_reg,mov_imm,mov_imm,mov_imm,
 		     load_8,load_8,store_8,store_8,load_8,adr,adr,f_mcr,f_mrc,
 		     fmov,neon_move")
-   (set_attr "arch"   "*,*,*,*,*,*,sve,*,fp,*,fp,*,*,*,fp,fp,fp,simd")
-   (set_attr "length" "4,4,4,4,4,*,  4,4, 4,4, 4,8,4,4, 4, 4, 4,   4")]
+   (set_attr "arch"   "*,*,*,*,*,sve,*,fp,*,fp,*,*,*,fp,fp,fp,simd")
+   (set_attr "length" "4,4,4,4,*,  4,4, 4,4, 4,8,4,4, 4, 4, 4,   4")]
 )
 
 (define_insn "insv_imm<mode>"
@@ -1508,7 +1507,7 @@ (define_insn "*mov<mode>_aarch64"
 
 (define_insn "*mov<mode>_aarch64"
   [(set (match_operand:DFD 0 "nonimmediate_operand" "=w, w  ,?r,w,w  ,w  ,w,m,r,m ,r,r")
-	(match_operand:DFD 1 "general_operand"      "Y , ?rY, w,w,Ufc,Uvi,m,w,m,rY,r,N"))]
+	(match_operand:DFD 1 "general_operand"      "Y , ?rY, w,w,Ufc,Uvi,m,w,m,rY,r,O"))]
   "TARGET_FLOAT && (register_operand (operands[0], <MODE>mode)
     || aarch64_reg_or_fp_zero (operands[1], <MODE>mode))"
   "@
@@ -1523,7 +1522,7 @@ (define_insn "*mov<mode>_aarch64"
    ldr\\t%x0, %1
    str\\t%x1, %0
    mov\\t%x0, %x1
-   mov\\t%x0, %1"
+   * return aarch64_zeroextended_move_imm (INTVAL (operands[1])) ? \"mov\\t%w0, %1\" : \"mov\\t%x0, %1\";"
   [(set_attr "type" "neon_move,f_mcr,f_mrc,fmov,fconstd,neon_move,\
 		     f_loadd,f_stored,load_8,store_8,mov_reg,\
 		     fconstd")
diff --git a/gcc/config/aarch64/constraints.md b/gcc/config/aarch64/constraints.md
index 29efb6c0cff7574c9b239ef358acaca96dd75d03..6168295814c3ce4b6f65030cddfd08172b6febd8 100644
--- a/gcc/config/aarch64/constraints.md
+++ b/gcc/config/aarch64/constraints.md
@@ -106,6 +106,12 @@ (define_constraint "M"
 
 (define_constraint "N"
  "A constant that can be used with a 64-bit MOV immediate operation."
+ (and (match_code "const_int")
+      (match_test "aarch64_move_imm (ival, DImode)")
+      (match_test "!aarch64_zeroextended_move_imm (ival)")))
+
+(define_constraint "O"
+ "A constant that can be used with a 32 or 64-bit MOV immediate operation."
  (and (match_code "const_int")
       (match_test "aarch64_move_imm (ival, DImode)")))