MATCH: Move `a <= CST1 ? MAX<a, CST2> : a` optimization to match

This moves the `a <= CST1 ? MAX<a, CST2> : a` optimization
from phiopt to match. It just adds a new pattern to match.pd.

There is one more change needed before being able to remove
minmax_replacement from phiopt.

A few notes on the testsuite changes:
* phi-opt-5.c is now able to optimize at phiopt1 so remove
the xfail.
* pr66726-4.c can be optimized during fold before phiopt1
so need to change the scanning.
* pr66726-5.c needs two phiopt passes currently to optimize
to the right thing, it needed 2 phiopt passes before, the cast
from int to unsigned char is the reason.
* pr66726-6.c is what the original pr66726-4.c was testing
before the fold was able to optimize it.

OK? Bootstrapped and tested on x86_64-linux-gnu.

gcc/ChangeLog:

	* match.pd (`(a CMP CST1) ? max<a,CST2> : a`): New
	pattern.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/phi-opt-5.c: Remove last xfail.
	* gcc.dg/tree-ssa/pr66726-4.c: Change how scanning
	works.
	* gcc.dg/tree-ssa/pr66726-5.c: New test.
	* gcc.dg/tree-ssa/pr66726-6.c: New test.

5 files changed, 68 insertions, 2 deletions

diff --git a/gcc/match.pd b/gcc/match.pd
index 577f4ba..aae3649 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -5036,6 +5036,24 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
      (if (code == MAX_EXPR)
       (minmax (max @1 @2) @4)))))))
 
+/* Optimize (a CMP CST1) ? max<a,CST2> : a */
+(for cmp    (gt  ge  lt  le)
+     minmax (min min max max)
+ (simplify
+  (cond (cmp @0 @1) (minmax:c@2 @0 @3) @4)
+   (with
+    {
+      tree_code code = minmax_from_comparison (cmp, @0, @1, @0, @4);
+    }
+    (if ((cmp == LT_EXPR || cmp == LE_EXPR)
+	 && code == MIN_EXPR
+         && integer_nonzerop (fold_build2 (LE_EXPR, boolean_type_node, @3, @1)))
+     (min @2 @4)
+     (if ((cmp == GT_EXPR || cmp == GE_EXPR)
+	  && code == MAX_EXPR
+          && integer_nonzerop (fold_build2 (GE_EXPR, boolean_type_node, @3, @1)))
+      (max @2 @4))))))
+
 /* X != C1 ? -X : C2 simplifies to -X when -C1 == C2.  */
 (simplify
  (cond (ne @0 INTEGER_CST@1) (negate@3 @0) INTEGER_CST@2)
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-5.c b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-5.c
index 5f78a1ba..e78d9d8 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-5.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-5.c
@@ -39,7 +39,7 @@ float repl2 (float vary)
 
 /* phiopt1 confused by predictors.  */
 /* { dg-final { scan-tree-dump "vary.*MAX_EXPR.*0\\.0" "phiopt1" } } */
-/* { dg-final { scan-tree-dump "vary.*MIN_EXPR.*1\\.0" "phiopt1" { xfail *-*-* } } } */
+/* { dg-final { scan-tree-dump "vary.*MIN_EXPR.*1\\.0" "phiopt1" } } */
 /* { dg-final { scan-tree-dump "vary.*MAX_EXPR.*0\\.0" "phiopt2"} } */
 /* { dg-final { scan-tree-dump "vary.*MIN_EXPR.*1\\.0" "phiopt2"} } */
 
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr66726-4.c b/gcc/testsuite/gcc.dg/tree-ssa/pr66726-4.c
index 4e43522..930ad5f 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/pr66726-4.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr66726-4.c
@@ -9,4 +9,7 @@ foo (unsigned char *p, int i)
   *p = SAT (i);
 }
 
-/* { dg-final { scan-tree-dump-times "COND_EXPR .*and PHI .*converted to straightline code" 1 "phiopt1" } } */
+/* fold could optimize SAT before phiopt1 so only match on the
+   MIN/MAX here.  */
+/* { dg-final { scan-tree-dump-times "= MIN_EXPR" 1 "phiopt1" } } */
+/* { dg-final { scan-tree-dump-times "= MAX_EXPR" 1 "phiopt1" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr66726-5.c b/gcc/testsuite/gcc.dg/tree-ssa/pr66726-5.c
new file mode 100644
index 0000000..4b5066c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr66726-5.c
@@ -0,0 +1,28 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-phiopt1-details -fdump-tree-phiopt2-details -fdump-tree-optimized" } */
+
+#define SAT(x) (x < 0 ? 0 : (x > 255 ? 255 : x))
+
+unsigned char
+foo (unsigned char *p, int i)
+{
+  if (i < 0)
+    return 0;
+  {
+    int t;
+    if (i > 255)
+      t = 255;
+    else
+      t = i;
+    return t;
+  }
+}
+
+/* Because of the way PHIOPT works, it only does the merging of BBs after it is done so we get the case were we can't
+   optimize the above until phiopt2 right now.  */
+/* { dg-final { scan-tree-dump-times "COND_EXPR .*and PHI .*converted to straightline code" 2 "phiopt1" { xfail *-*-* } } } */
+/* { dg-final { scan-tree-dump-times "COND_EXPR .*and PHI .*converted to straightline code" 0 "phiopt2" { xfail *-*-* } } } */
+/* { dg-final { scan-tree-dump-times "= MIN_EXPR" 1 "phiopt1" } } */
+/* { dg-final { scan-tree-dump-times "= MAX_EXPR" 1 "phiopt1" { xfail *-*-* } } } */
+/* { dg-final { scan-tree-dump-times "= MIN_EXPR" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "= MAX_EXPR" 1 "optimized"  } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr66726-6.c b/gcc/testsuite/gcc.dg/tree-ssa/pr66726-6.c
new file mode 100644
index 0000000..5c6b499
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr66726-6.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-phiopt1-details" } */
+
+
+unsigned char
+foo1 (unsigned char *p, int i)
+{
+  if (i < 0)
+    return 0;
+  {
+    int t = i > 255 ? 255 : i;
+    return t;
+  }
+}
+/* testing to see if moving the cast out of the conditional. */
+
+/* { dg-final { scan-tree-dump-times "COND_EXPR .*and PHI .*converted to straightline code" 1 "phiopt1" } } */