[PATCH, i386]: Fix addcarry<mode>/subborrow<mode> patterns

[Jakub Jelinek <jakub at redhat dot com>]

On Mon, Oct 23, 2017 at 09:03:33PM +0200, Uros Bizjak wrote:
> >> As for addcarry/subborrow, the problem is that we expect in the pr67317*
> >> tests that combine is able to notice that the CF setter sets CF to
> >> unconditional 0 and matches the pattern.  With the patch I wrote
> >> we end up with the combiner trying to match an insn where the CCC
> >> is set from a TImode comparison:
> >> (parallel [
> >>         (set (reg:CC 17 flags)
> >>             (compare:CC (zero_extend:TI (plus:DI (reg/v:DI 92 [ a ])
> >>                         (reg/v:DI 94 [ c ])))
> >>                 (zero_extend:TI (reg/v:DI 94 [ c ]))))
> >>         (set (reg:DI 98)
> >>             (plus:DI (reg/v:DI 92 [ a ])
> >>                 (reg/v:DI 94 [ c ])))
> >>     ])
> >> So, either we need a define_insn_and_split pattern that would deal with
> >> that (for UNSPEC it would be the same thing, have a define_insn_and_split
> >> that would replace the (ltu...) with (const_int 0)), or perhaps be smarter
> >> during expansion, if we see the first argument is constant 0, expand it
> >> like a normal add instruction with CC setter.

This patch fixes the addcarry/subborrow patterns and deals with the
pr67317* regressions by special casing the first argument 0 case already
at expansion rather than waiting for combine.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2017-10-24  Jakub Jelinek  <jakub@redhat.com>

	PR target/82628
	* config/i386/i386.md (addcarry<mode>, subborrow<mode>): Change
	patterns to better describe from which operation the CF is computed.
	(addcarry<mode>_0, subborrow<mode>_0): New patterns.
	* config/i386/i386.c (ix86_expand_builtin) <case handlecarry>: Pass
	one LTU with [DT]Imode and another one with [SD]Imode.  If arg0
	is 0, use _0 suffixed expanders instead of emitting a comparison
	before it.

--- gcc/config/i386/i386.c.jj	2017-10-23 12:52:20.711575924 +0200
+++ gcc/config/i386/i386.c	2017-10-23 15:59:07.379391029 +0200
@@ -35050,10 +35050,10 @@ ix86_expand_builtin (tree exp, rtx targe
 		     machine_mode mode, int ignore)
 {
   size_t i;
-  enum insn_code icode;
+  enum insn_code icode, icode2;
   tree fndecl = TREE_OPERAND (CALL_EXPR_FN (exp), 0);
   tree arg0, arg1, arg2, arg3, arg4;
-  rtx op0, op1, op2, op3, op4, pat, insn;
+  rtx op0, op1, op2, op3, op4, pat, pat2, insn;
   machine_mode mode0, mode1, mode2, mode3, mode4;
   unsigned int fcode = DECL_FUNCTION_CODE (fndecl);
 
@@ -36028,22 +36028,34 @@ rdseed_step:
 
     case IX86_BUILTIN_SBB32:
       icode = CODE_FOR_subborrowsi;
+      icode2 = CODE_FOR_subborrowsi_0;
       mode0 = SImode;
+      mode1 = DImode;
+      mode2 = CCmode;
       goto handlecarry;
 
     case IX86_BUILTIN_SBB64:
       icode = CODE_FOR_subborrowdi;
+      icode2 = CODE_FOR_subborrowdi_0;
       mode0 = DImode;
+      mode1 = TImode;
+      mode2 = CCmode;
       goto handlecarry;
 
     case IX86_BUILTIN_ADDCARRYX32:
       icode = CODE_FOR_addcarrysi;
+      icode2 = CODE_FOR_addcarrysi_0;
       mode0 = SImode;
+      mode1 = DImode;
+      mode2 = CCCmode;
       goto handlecarry;
 
     case IX86_BUILTIN_ADDCARRYX64:
       icode = CODE_FOR_addcarrydi;
+      icode2 = CODE_FOR_addcarrydi_0;
       mode0 = DImode;
+      mode1 = TImode;
+      mode2 = CCCmode;
 
     handlecarry:
       arg0 = CALL_EXPR_ARG (exp, 0); /* unsigned char c_in.  */
@@ -36052,7 +36064,8 @@ rdseed_step:
       arg3 = CALL_EXPR_ARG (exp, 3); /* unsigned int *sum_out.  */
 
       op1 = expand_normal (arg0);
-      op1 = copy_to_mode_reg (QImode, convert_to_mode (QImode, op1, 1));
+      if (!integer_zerop (arg0))
+	op1 = copy_to_mode_reg (QImode, convert_to_mode (QImode, op1, 1));
 
       op2 = expand_normal (arg1);
       if (!register_operand (op2, mode0))
@@ -36069,21 +36082,31 @@ rdseed_step:
 	  op4 = copy_addr_to_reg (op4);
 	}
 
-      /* Generate CF from input operand.  */
-      emit_insn (gen_addqi3_cconly_overflow (op1, constm1_rtx));
-
-      /* Generate instruction that consumes CF.  */
       op0 = gen_reg_rtx (mode0);
+      if (integer_zerop (arg0))
+	{
+	  /* If arg0 is 0, optimize right away into add or sub
+	     instruction that sets CCCmode flags.  */
+	  op1 = gen_rtx_REG (mode2, FLAGS_REG);
+	  emit_insn (GEN_FCN (icode2) (op0, op2, op3));
+	}
+      else
+	{
+	  /* Generate CF from input operand.  */
+	  emit_insn (gen_addqi3_cconly_overflow (op1, constm1_rtx));
 
-      op1 = gen_rtx_REG (CCCmode, FLAGS_REG);
-      pat = gen_rtx_LTU (mode0, op1, const0_rtx);
-      emit_insn (GEN_FCN (icode) (op0, op2, op3, op1, pat));
+	  /* Generate instruction that consumes CF.  */
+	  op1 = gen_rtx_REG (CCCmode, FLAGS_REG);
+	  pat = gen_rtx_LTU (mode1, op1, const0_rtx);
+	  pat2 = gen_rtx_LTU (mode0, op1, const0_rtx);
+	  emit_insn (GEN_FCN (icode) (op0, op2, op3, op1, pat, pat2));
+	}
 
       /* Return current CF value.  */
       if (target == 0)
         target = gen_reg_rtx (QImode);
 
-      PUT_MODE (pat, QImode);
+      pat = gen_rtx_LTU (QImode, op1, const0_rtx);
       emit_insn (gen_rtx_SET (target, pat));
 
       /* Store the result.  */
--- gcc/config/i386/i386.md.jj	2017-10-23 12:52:20.701576051 +0200
+++ gcc/config/i386/i386.md	2017-10-23 15:53:36.013585636 +0200
@@ -6840,15 +6840,19 @@ (define_insn "*addsi3_carry_zext"
 (define_insn "addcarry<mode>"
   [(set (reg:CCC FLAGS_REG)
 	(compare:CCC
-	  (plus:SWI48
+	  (zero_extend:<DWI>
 	    (plus:SWI48
-	      (match_operator:SWI48 4 "ix86_carry_flag_operator"
-	       [(match_operand 3 "flags_reg_operand") (const_int 0)])
-	      (match_operand:SWI48 1 "nonimmediate_operand" "%0"))
-	    (match_operand:SWI48 2 "nonimmediate_operand" "rm"))
-	  (match_dup 1)))
+	      (plus:SWI48
+		(match_operator:SWI48 5 "ix86_carry_flag_operator"
+		  [(match_operand 3 "flags_reg_operand") (const_int 0)])
+		(match_operand:SWI48 1 "nonimmediate_operand" "%0"))
+	      (match_operand:SWI48 2 "nonimmediate_operand" "rm")))
+	  (plus:<DWI>
+	    (zero_extend:<DWI> (match_dup 2))
+	    (match_operator:<DWI> 4 "ix86_carry_flag_operator"
+	      [(match_dup 3) (const_int 0)]))))
    (set (match_operand:SWI48 0 "register_operand" "=r")
-	(plus:SWI48 (plus:SWI48 (match_op_dup 4
+	(plus:SWI48 (plus:SWI48 (match_op_dup 5
 				 [(match_dup 3) (const_int 0)])
 				(match_dup 1))
 		    (match_dup 2)))]
@@ -6859,6 +6863,18 @@ (define_insn "addcarry<mode>"
    (set_attr "pent_pair" "pu")
    (set_attr "mode" "<MODE>")])
 
+(define_expand "addcarry<mode>_0"
+  [(parallel
+     [(set (reg:CCC FLAGS_REG)
+	   (compare:CCC
+	     (plus:SWI48
+	       (match_operand:SWI48 1 "nonimmediate_operand")
+	       (match_operand:SWI48 2 "x86_64_general_operand"))
+	     (match_dup 1)))
+      (set (match_operand:SWI48 0 "register_operand")
+	   (plus:SWI48 (match_dup 1) (match_dup 2)))])]
+  "ix86_binary_operator_ok (PLUS, <MODE>mode, operands)")
+
 (define_insn "sub<mode>3_carry"
   [(set (match_operand:SWI 0 "nonimmediate_operand" "=<r>m,<r>")
 	(minus:SWI
@@ -6941,15 +6957,18 @@ (define_insn "sub<mode>3_carry_ccgz"
 (define_insn "subborrow<mode>"
   [(set (reg:CCC FLAGS_REG)
 	(compare:CCC
-	  (match_operand:SWI48 1 "nonimmediate_operand" "0")
-	  (plus:SWI48
-	    (match_operator:SWI48 4 "ix86_carry_flag_operator"
-	     [(match_operand 3 "flags_reg_operand") (const_int 0)])
-	    (match_operand:SWI48 2 "nonimmediate_operand" "rm"))))
+	  (zero_extend:<DWI>
+	    (match_operand:SWI48 1 "nonimmediate_operand" "0"))
+	  (plus:<DWI>
+	    (match_operator:<DWI> 4 "ix86_carry_flag_operator"
+	      [(match_operand 3 "flags_reg_operand") (const_int 0)])
+	    (zero_extend:<DWI>
+	      (match_operand:SWI48 2 "nonimmediate_operand" "rm")))))
    (set (match_operand:SWI48 0 "register_operand" "=r")
-	(minus:SWI48 (minus:SWI48 (match_dup 1)
-				  (match_op_dup 4
-				   [(match_dup 3) (const_int 0)]))
+	(minus:SWI48 (minus:SWI48
+		       (match_dup 1)
+		       (match_operator:SWI48 5 "ix86_carry_flag_operator"
+			 [(match_dup 3) (const_int 0)]))
 		     (match_dup 2)))]
   "ix86_binary_operator_ok (MINUS, <MODE>mode, operands)"
   "sbb{<imodesuffix>}\t{%2, %0|%0, %2}"
@@ -6957,6 +6976,16 @@ (define_insn "subborrow<mode>"
    (set_attr "use_carry" "1")
    (set_attr "pent_pair" "pu")
    (set_attr "mode" "<MODE>")])
+
+(define_expand "subborrow<mode>_0"
+  [(parallel
+     [(set (reg:CC FLAGS_REG)
+	   (compare:CC
+	     (match_operand:SWI48 1 "nonimmediate_operand")
+	     (match_operand:SWI48 2 "<general_operand>")))
+      (set (match_operand:SWI48 0 "register_operand")
+	   (minus:SWI48 (match_dup 1) (match_dup 2)))])]
+  "ix86_binary_operator_ok (MINUS, <MODE>mode, operands)")
 
 ;; Overflow setting add instructions
 


	Jakub