Re: [PATCH GCC][1/4]Simplify (convert1 (minmax ((convert2 (x) c)))) into minmax (x c)

[Bin.Cheng]

On Wed, Oct 26, 2016 at 3:10 PM, Bin.Cheng <amker.ch...@gmail.com> wrote:
> On Wed, Oct 26, 2016 at 3:04 PM, Marc Glisse <marc.gli...@inria.fr> wrote:
>> On Wed, 26 Oct 2016, Bin.Cheng wrote:
>>
>>> Thanks for reviewing, updated patch attached.  Is it OK?
>>
>>
>> +/* (convert (minmax ((convert (x) c)))) -> minmax (x c) if x is promoted
>> +   and the outer convert demotes the expression back to x's type.  */
>> +(for minmax (min max)
>> + (simplify
>> +  (convert (minmax@0 (convert @1) INTEGER_CST@2))
>> +  (if (types_match (@1, type) && int_fits_type_p (@2, type)
>> +       && TYPE_PRECISION (TREE_TYPE (@0)) > TYPE_PRECISION (TREE_TYPE
>> (@1)))
>> +   (minmax @1 (convert @2)))))
>>
>> Don't you have a problem if @1 is signed but not @0?
>> (int)max((unsigned long)(-2),3ul)
>> seems to satisfy your conditions, but is not the same as
>> max(-2,3)
> Ah, yes.  I falsely removed sign check from the original patch.  Will
> update that.
>
Here it is.  Sorry for the mistake.

Thanks,
bin

diff --git a/gcc/match.pd b/gcc/match.pd
index 767d23a..73bee34 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -1337,6 +1337,17 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
        && TYPE_MIN_VALUE (type)
        && operand_equal_p (@1, TYPE_MIN_VALUE (type), OEP_ONLY_CONST))
    @0)))
+
+/* (convert (minmax ((convert (x) c)))) -> minmax (x c) if x is promoted
+   and the outer convert demotes the expression back to x's type.  */
+(for minmax (min max)
+ (simplify
+  (convert (minmax@0 (convert @1) INTEGER_CST@2))
+  (if (types_match (@1, type) && int_fits_type_p (@2, type)
+       && TYPE_SIGN (TREE_TYPE (@0)) == TYPE_SIGN (type)
+       && TYPE_PRECISION (TREE_TYPE (@0)) > TYPE_PRECISION (type))
+   (minmax @1 (convert @2)))))
+
 (for minmax (FMIN FMAX)
  /* If either argument is NaN, return the other one.  Avoid the
     transformation if we get (and honor) a signalling NaN.  */
diff --git a/gcc/testsuite/gcc.dg/fold-convmaxconv-1.c 
b/gcc/testsuite/gcc.dg/fold-convmaxconv-1.c
new file mode 100644
index 0000000..3ffff8b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fold-convmaxconv-1.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-optimized" } */
+
+int foo (short a[], int x)
+{
+  unsigned int i;
+  for (i = 0; i < 1000; i++)
+    {
+      x = a[i];
+      a[i] = (x <= 0 ? 0 : x);
+    }
+  return x;
+}
+
+/* { dg-final { scan-tree-dump-not " = MAX_EXPR <x_\[0-9\]*" "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/fold-convminconv-1.c 
b/gcc/testsuite/gcc.dg/fold-convminconv-1.c
new file mode 100644
index 0000000..f4a048e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fold-convminconv-1.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-optimized" } */
+
+int foo (unsigned short a[], unsigned int x)
+{
+  unsigned int i;
+  for (i = 0; i < 1000; i++)
+    {
+      x = a[i];
+      a[i] = (x >= 255 ? 255 : x);
+    }
+  return x;
+}
+
+/* { dg-final { scan-tree-dump-not " = MIN_EXPR <x_\[0-9\]*" "optimized" } } */