re PR tree-optimization/89518 (missed optimisation for array address calculations)

2019-05-03  Richard Biener  <rguenther@suse.de>

	PR middle-end/89518
	* match.pd: Add pattern to optimize (A / B) * B + (A % B) to A.

	* gcc.dg/pr89518.c: New testcase.

From-SVN: r270846

gcc/ChangeLog

 2019-05-03  Richard Biener  <rguenther@suse.de>
 
+	PR middle-end/89518
+	* match.pd: Add pattern to optimize (A / B) * B + (A % B) to A.
+
+2019-05-03  Richard Biener  <rguenther@suse.de>
+
 	PR middle-end/87314
 	* match.pd (cmp (convert1?@2 addr@0) (convert2? addr@1)):
 	Handle STRING_CST vs DECL or STRING_CST.

gcc/match.pd

@@ -2736,6 +2736,13 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
   (mult (convert1? (exact_div @0 @@1)) (convert2? @1))
   (convert @0))
 
+/* Simplify (A / B) * B + (A % B) -> A.  */
+(for div (trunc_div ceil_div floor_div round_div)
+     mod (trunc_mod ceil_mod floor_mod round_mod)
+  (simplify
+   (plus:c (mult:c (div @0 @1) @1) (mod @0 @1))
+   @0))
+
 /* ((X /[ex] A) +- B) * A  -->  X +- A * B.  */
 (for op (plus minus)
  (simplify

gcc/testsuite/ChangeLog

 2019-05-03  Richard Biener  <rguenther@suse.de>
 
+	PR middle-end/89518
+	* gcc.dg/pr89518.c: New testcase.
+
+2019-05-03  Richard Biener  <rguenther@suse.de>
+
 	PR middle-end/87314
 	* gcc.dg/pr87314-1.c: New testcase.
 

gcc/testsuite/gcc.dg/pr89518.c

+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-original" } */
+
+unsigned foo (unsigned a, unsigned b)
+{
+  return a/b * b + a%b;
+}
+
+int bar (int a, int b)
+{
+  return a/b * b + a%b;
+}
+
+/* { dg-final { scan-tree-dump-times "return a;" 2 "original" } } */