The following enables final value replacement for floating point
expressions if -funsafe-math-optimizations is set (that's the
flag the reassoc pass controls similar transforms on).
Bootstrapped / tested on x86_64-unknown-linux-gnu, queued for GCC 8.
Richard.
2017-02-14 Richard Biener <rguent...@suse.de>
PR tree-optimization/79460
* tree-scalar-evolution.c (final_value_replacement_loop): Also
allow final value replacement of floating point expressions.
* gcc.dg/tree-ssa/sccp-3.c: New testcase.
Index: gcc/tree-scalar-evolution.c
===================================================================
--- gcc/tree-scalar-evolution.c (revision 245417)
+++ gcc/tree-scalar-evolution.c (working copy)
@@ -3718,8 +3718,10 @@ final_value_replacement_loop (struct loo
continue;
}
- if (!POINTER_TYPE_P (TREE_TYPE (def))
- && !INTEGRAL_TYPE_P (TREE_TYPE (def)))
+ if (! (POINTER_TYPE_P (TREE_TYPE (def))
+ || INTEGRAL_TYPE_P (TREE_TYPE (def))
+ || (FLOAT_TYPE_P (TREE_TYPE (def))
+ && flag_unsafe_math_optimizations)))
{
gsi_next (&psi);
continue;
Index: gcc/testsuite/gcc.dg/tree-ssa/sccp-3.c
===================================================================
--- gcc/testsuite/gcc.dg/tree-ssa/sccp-3.c (nonexistent)
+++ gcc/testsuite/gcc.dg/tree-ssa/sccp-3.c (working copy)
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -funsafe-math-optimizations -fdump-tree-sccp" } */
+
+float f(float x[])
+{
+ float p = 1.0;
+ for (int i = 0; i < 200; i++)
+ p += 1;
+ return p;
+}
+
+/* { dg-final { scan-tree-dump "final value replacement.* = 2.01e\\+2;" "sccp"
} } */
