[arm] Early expansion of usubvdi4.

This patch adds early expansion of usubvdi4, allowing us to handle some
constants in place, which previously we were unable to do.

	* config/arm/arm.md (usubvdi4): Allow registers or integers for
	incoming operands.  Early split the calculation into SImode
	operations.
	(usubvsi3_borrow): New insn pattern.
	(usubvsi3_borrow_imm): Likewise.

From-SVN: r277188

gcc/ChangeLog

 2019-10-18  Richard Earnshaw  <rearnsha@arm.com>
 
+	* config/arm/arm.md (usubvdi4): Allow registers or integers for
+	incoming operands.  Early split the calculation into SImode
+	operations.
+	(usubvsi3_borrow): New insn pattern.
+	(usubvsi3_borrow_imm): Likewise.
+
+2019-10-18  Richard Earnshaw  <rearnsha@arm.com>
+
 	* config/arm/arm.md (usubv<mode>4): Delete expansion.
 	(usubvsi4): New pattern.  Allow some immediate values for inputs.
 	(usubvdi4): New pattern.

gcc/config/arm/arm.md

@@ -1390,13 +1390,81 @@
 
 (define_expand "usubvdi4"
   [(match_operand:DI 0 "s_register_operand")
-   (match_operand:DI 1 "s_register_operand")
-   (match_operand:DI 2 "s_register_operand")
+   (match_operand:DI 1 "reg_or_int_operand")
+   (match_operand:DI 2 "reg_or_int_operand")
    (match_operand 3 "")]
   "TARGET_32BIT"
 {
-  emit_insn (gen_subdi3_compare1 (operands[0], operands[1], operands[2]));
-  arm_gen_unlikely_cbranch (LTU, CCmode, operands[3]);
+  rtx lo_result, hi_result;
+  rtx lo_op1, hi_op1, lo_op2, hi_op2;
+  lo_result = gen_lowpart (SImode, operands[0]);
+  hi_result = gen_highpart (SImode, operands[0]);
+  machine_mode mode = CCmode;
+
+  if (CONST_INT_P (operands[1]) && CONST_INT_P (operands[2]))
+    {
+      /* If both operands are constants we can decide the result statically.  */
+      wi::overflow_type overflow;
+      wide_int val = wi::sub (rtx_mode_t (operands[1], DImode),
+			      rtx_mode_t (operands[2], DImode),
+			      UNSIGNED, &overflow);
+      emit_move_insn (operands[0], GEN_INT (val.to_shwi ()));
+      if (overflow != wi::OVF_NONE)
+	emit_jump_insn (gen_jump (operands[3]));
+      DONE;
+    }
+  else if (CONST_INT_P (operands[1]))
+    {
+      arm_decompose_di_binop (operands[2], operands[1], &lo_op2, &hi_op2,
+			      &lo_op1, &hi_op1);
+      if (const_ok_for_arm (INTVAL (lo_op1)))
+	{
+	  emit_insn (gen_rsb_imm_compare (lo_result, lo_op1, lo_op2,
+					  GEN_INT (~UINTVAL (lo_op1))));
+	  /* We could potentially use RSC here in Arm state, but not
+	     in Thumb, so it's probably not worth the effort of handling
+	     this.  */
+	  hi_op1 = force_reg (SImode, hi_op1);
+	  mode = CC_RSBmode;
+	  goto highpart;
+	}
+      operands[1] = force_reg (DImode, operands[1]);
+    }
+
+  arm_decompose_di_binop (operands[1], operands[2], &lo_op1, &hi_op1,
+			  &lo_op2, &hi_op2);
+  if (lo_op2 == const0_rtx)
+    {
+      emit_move_insn (lo_result, lo_op1);
+      if (!arm_add_operand (hi_op2, SImode))
+        hi_op2 = force_reg (SImode, hi_op2);
+      emit_insn (gen_usubvsi4 (hi_result, hi_op1, hi_op2, operands[3]));
+      DONE;
+    }
+
+  if (CONST_INT_P (lo_op2) && !arm_addimm_operand (lo_op2, SImode))
+    lo_op2 = force_reg (SImode, lo_op2);
+  if (CONST_INT_P (lo_op2))
+    emit_insn (gen_cmpsi2_addneg (lo_result, lo_op1, lo_op2,
+				  GEN_INT (-INTVAL (lo_op2))));
+  else
+    emit_insn (gen_subsi3_compare1 (lo_result, lo_op1, lo_op2));
+
+ highpart:
+  if (!arm_not_operand (hi_op2, SImode))
+    hi_op2 = force_reg (SImode, hi_op2);
+  rtx ccreg = gen_rtx_REG (mode, CC_REGNUM);
+  if (CONST_INT_P (hi_op2))
+    emit_insn (gen_usubvsi3_borrow_imm (hi_result, hi_op1, hi_op2,
+					GEN_INT (UINTVAL (hi_op2) & 0xffffffff),
+					gen_rtx_LTU (SImode, ccreg, const0_rtx),
+					gen_rtx_LTU (DImode, ccreg,
+						     const0_rtx)));
+  else
+    emit_insn (gen_usubvsi3_borrow (hi_result, hi_op1, hi_op2,
+				    gen_rtx_LTU (SImode, ccreg, const0_rtx),
+				    gen_rtx_LTU (DImode, ccreg, const0_rtx)));
+  arm_gen_unlikely_cbranch (LTU, CC_Bmode, operands[3]);
 
   DONE;
 })
@@ -1825,6 +1893,43 @@
    (set_attr "type" "alus_imm")]
 )
 
+(define_insn "usubvsi3_borrow"
+  [(set (reg:CC_B CC_REGNUM)
+	(compare:CC_B
+	 (zero_extend:DI (match_operand:SI 1 "s_register_operand" "0,r"))
+	 (plus:DI (match_operand:DI 4 "arm_borrow_operation" "")
+	          (zero_extend:DI
+		   (match_operand:SI 2 "s_register_operand" "l,r")))))
+   (set (match_operand:SI 0 "s_register_operand" "=l,r")
+	(minus:SI (match_dup 1)
+		  (plus:SI (match_operand:SI 3 "arm_borrow_operation" "")
+			   (match_dup 2))))]
+  "TARGET_32BIT"
+  "sbcs%?\\t%0, %1, %2"
+  [(set_attr "conds" "set")
+   (set_attr "arch" "t2,*")
+   (set_attr "length" "2,4")]
+)
+
+(define_insn "usubvsi3_borrow_imm"
+  [(set (reg:CC_B CC_REGNUM)
+	(compare:CC_B
+	 (zero_extend:DI (match_operand:SI 1 "s_register_operand" "r,r"))
+	 (plus:DI (match_operand:DI 5 "arm_borrow_operation" "")
+		  (match_operand:DI 3 "const_int_operand" "n,n"))))
+   (set (match_operand:SI 0 "s_register_operand" "=r,r")
+	(minus:SI (match_dup 1)
+		  (plus:SI (match_operand:SI 4 "arm_borrow_operation" "")
+			   (match_operand:SI 2 "arm_adcimm_operand" "I,K"))))]
+  "TARGET_32BIT
+   && (UINTVAL (operands[2]) & 0xffffffff) == UINTVAL (operands[3])"
+  "@
+  sbcs%?\\t%0, %1, %2
+  adcs%?\\t%0, %1, #%B2"
+  [(set_attr "conds" "set")
+   (set_attr "type" "alus_imm")]
+)
+
 (define_expand "subsf3"
   [(set (match_operand:SF           0 "s_register_operand")
 	(minus:SF (match_operand:SF 1 "s_register_operand")