re PR target/87913 (max(n, 1) code generation)

2018-11-08  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/87913
	* tree-ssa-phiopt.c (minmax_replacement): Turn EQ/NE compares
	of extreme values to ordered comparisons.

	* gcc.dg/tree-ssa/phi-opt-20.c: New testcase.

From-SVN: r265909

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index decc5a0..270180f 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2018-11-08  Richard Biener  <rguenther@suse.de>
+
+       PR tree-optimization/87913
+       * tree-ssa-phiopt.c (minmax_replacement): Turn EQ/NE compares
+       of extreme values to ordered comparisons.
+
 2018-11-07  Sandra Loosemore  <sandra@codesourcery.com>
 
        PR middle-end/42726

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index e719c31..5edc17e 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2018-11-08  Richard Biener  <rguenther@suse.de>
+
+       PR tree-optimization/87913
+       * gcc.dg/tree-ssa/phi-opt-20.c: New testcase.
+
 2018-11-08  Chenghua Xu  <paul.hua.gm@gmail.com>
 
        * gcc.target/mips/mips.exp (mips-dg-options):

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-20.c b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-20.c
new file mode 100644 (file)
index 0000000..c310308
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-20.c
@@ -0,0 +1,25 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-phiopt1" } */
+
+unsigned int f(unsigned int num)
+{
+  return num < 1 ? 1 : num;
+}
+
+unsigned int g(unsigned int num)
+{
+  return num > (unsigned)__INT_MAX__ * 2 ? (unsigned)__INT_MAX__ * 2 : num;
+}
+
+int h(int num)
+{
+  return num < -__INT_MAX__ ? -__INT_MAX__ : num;
+}
+
+int i(int num)
+{
+  return num > __INT_MAX__-1 ? __INT_MAX__-1 : num;
+}
+
+/* { dg-final { scan-tree-dump-times "MAX_EXPR" 2 "phiopt1" } } */
+/* { dg-final { scan-tree-dump-times "MIN_EXPR" 2 "phiopt1" } } */

diff --git a/gcc/tree-ssa-phiopt.c b/gcc/tree-ssa-phiopt.c
index 0784510..64039e2 100644 (file)
--- a/gcc/tree-ssa-phiopt.c
+++ b/gcc/tree-ssa-phiopt.c
@@ -1204,7 +1204,7 @@ minmax_replacement (basic_block cond_bb, basic_block middle_bb,
                    edge e0, edge e1, gimple *phi,
                    tree arg0, tree arg1)
 {
-  tree result, type;
+  tree result, type, rhs;
   gcond *cond;
   gassign *new_stmt;
   edge true_edge, false_edge;
@@ -1220,6 +1220,25 @@ minmax_replacement (basic_block cond_bb, basic_block middle_bb,
 
   cond = as_a <gcond *> (last_stmt (cond_bb));
   cmp = gimple_cond_code (cond);
+  rhs = gimple_cond_rhs (cond);
+
+  /* Turn EQ/NE of extreme values to order comparisons.  */
+  if ((cmp == NE_EXPR || cmp == EQ_EXPR)
+      && TREE_CODE (rhs) == INTEGER_CST)
+    {
+      if (wi::eq_p (wi::to_wide (rhs), wi::min_value (TREE_TYPE (rhs))))
+       {
+         cmp = (cmp == EQ_EXPR) ? LT_EXPR : GE_EXPR;
+         rhs = wide_int_to_tree (TREE_TYPE (rhs),
+                                 wi::min_value (TREE_TYPE (rhs)) + 1);
+       }
+      else if (wi::eq_p (wi::to_wide (rhs), wi::max_value (TREE_TYPE (rhs))))
+       {
+         cmp = (cmp == EQ_EXPR) ? GT_EXPR : LE_EXPR;
+         rhs = wide_int_to_tree (TREE_TYPE (rhs),
+                                 wi::max_value (TREE_TYPE (rhs)) - 1);
+       }
+    }
 
   /* This transformation is only valid for order comparisons.  Record which
      operand is smaller/larger if the result of the comparison is true.  */
@@ -1228,7 +1247,7 @@ minmax_replacement (basic_block cond_bb, basic_block middle_bb,
   if (cmp == LT_EXPR || cmp == LE_EXPR)
     {
       smaller = gimple_cond_lhs (cond);
-      larger = gimple_cond_rhs (cond);
+      larger = rhs;
       /* If we have smaller < CST it is equivalent to smaller <= CST-1.
         Likewise smaller <= CST is equivalent to smaller < CST+1.  */
       if (TREE_CODE (larger) == INTEGER_CST)
@@ -1255,7 +1274,7 @@ minmax_replacement (basic_block cond_bb, basic_block middle_bb,
     }
   else if (cmp == GT_EXPR || cmp == GE_EXPR)
     {
-      smaller = gimple_cond_rhs (cond);
+      smaller = rhs;
       larger = gimple_cond_lhs (cond);
       /* If we have larger > CST it is equivalent to larger >= CST+1.
         Likewise larger >= CST is equivalent to larger > CST-1.  */