[Polly][Docs] Fix wrong claim about optimization levels.

Thanks Justin Paston-Cooper for the report.

diff --git a/polly/docs/UsingPollyWithClang.rst b/polly/docs/UsingPollyWithClang.rst
index b6f3705..d203324 100644 (file)
--- a/polly/docs/UsingPollyWithClang.rst
+++ b/polly/docs/UsingPollyWithClang.rst
@@ -21,7 +21,8 @@ Optimizing with Polly
 =====================
 
 Optimizing with Polly is as easy as adding -O3 -mllvm -polly to your compiler
-flags (Polly is only available at -O3).
+flags (Polly is not available unless optimizations are enabled, such as
+-O1,-O2,-O3; Optimizing for size with -Os or -Oz is not recommended).
 
 .. code-block:: console