[PATCH GCC][3/4]Add support for constant operand in pattern (convert (op:s (convert@2 @0) (convert?@3 @1)))

[Bin Cheng]

Hi,
This is an update patch for 
https://gcc.gnu.org/ml/gcc-patches/2016-10/msg00738.html .  In this version, 
existing pattern (convert (op:s (convert@2 @0) (convert?@3 @1))) is extended.  
It allows narrowing of arithmetic operation which has constant integer as its 
second operand.  It also simplifies next patch handling cond_expr.
Bootstrap and test on x86_64 and AArch64 for whole patch set.  Is it OK?

Thanks,
bin

2016-10-21  Bin Cheng  <bin.ch...@arm.com>

        * match.pd ((convert (op:s (convert@2 @0) (convert?@3 @1)))): Add
        support for constant operand for OP.

gcc/testsuite/ChangeLog
2016-10-21  Bin Cheng  <bin.ch...@arm.com>

        * gcc.dg/fold-narrowbopcst-1.c: New test.
diff --git a/gcc/match.pd b/gcc/match.pd
index a8a6b85..86fb544 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -3335,7 +3335,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
    operation and convert the result to the desired type.  */
 (for op (plus minus)
   (simplify
-    (convert (op:s (convert@2 @0) (convert@3 @1)))
+    (convert (op:s (convert@2 @0) (convert?@3 @1)))
     (if (INTEGRAL_TYPE_P (type)
         /* We check for type compatibility between @0 and @1 below,
            so there's no need to check that @1/@3 are integral types.  */
@@ -3351,12 +3351,17 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
         && TYPE_PRECISION (type) == GET_MODE_PRECISION (TYPE_MODE (type))
         /* The inner conversion must be a widening conversion.  */
         && TYPE_PRECISION (TREE_TYPE (@2)) > TYPE_PRECISION (TREE_TYPE (@0))
-        && types_match (@0, @1)
-        && types_match (@0, type))
+        && types_match (@0, type)
+        && (types_match (@0, @1)
+            /* Or the second operand must be constant integer.  */
+            || (@3 == @1
+                && types_match (@1, @2)
+                && TREE_CODE (@1) == INTEGER_CST)))
       (if (TYPE_OVERFLOW_WRAPS (TREE_TYPE (@0)))
-       (convert (op @0 @1))
+       (convert (op @0 (convert:type @1)))
        (with { tree utype = unsigned_type_for (TREE_TYPE (@0)); }
-        (convert (op (convert:utype @0) (convert:utype @1))))))))
+        (convert (op (convert:utype @0)
+                     (convert:utype (convert:type @1)))))))))
 
 /* This is another case of narrowing, specifically when there's an outer
    BIT_AND_EXPR which masks off bits outside the type of the innermost
diff --git a/gcc/testsuite/gcc.dg/fold-narrowbopcst-1.c 
b/gcc/testsuite/gcc.dg/fold-narrowbopcst-1.c
new file mode 100644
index 0000000..8a33677
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fold-narrowbopcst-1.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -fdump-tree-optimized" } */
+
+int foo1 (unsigned char a[], unsigned int x)
+{
+  unsigned int i;
+  for (i = 0; i < 1000; i++)
+    {
+      x = a[i];
+      a[i] = (unsigned char)(x >= 100 ? x - 100 : 0);
+    }
+  return x;
+}
+/* { dg-final { scan-tree-dump " = _.* \\+ 156" "optimized" } } */