From: Eric Botcazou <ebotcazou@adacore.com>
Date: Wed, 25 Oct 2023 15:52:38 +0000 (+0200)
Subject: ada: Fix miscompilation of loop over boolean range
X-Git-Tag: basepoints/gcc-15~4474
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=4649c079409ec6cb67cd2cca0df81877e53c78b4;p=thirdparty%2Fgcc.git

ada: Fix miscompilation of loop over boolean range

The optimized form generated in this case turns out to be problematic.

gcc/ada/

	* gcc-interface/trans.cc (Loop_Statement_to_gnu): Always use the
	simpler form for a loop with a boolean iteration variable.
---

diff --git a/gcc/ada/gcc-interface/trans.cc b/gcc/ada/gcc-interface/trans.cc
index c7d91628f80c..9c418beda964 100644
--- a/gcc/ada/gcc-interface/trans.cc
+++ b/gcc/ada/gcc-interface/trans.cc
@@ -3021,7 +3021,9 @@ Loop_Statement_to_gnu (Node_Id gnat_node)
 	}
 
       /* We use two different strategies to translate the loop, depending on
-	 whether optimization is enabled.
+	 whether optimization is enabled, except for the very peculiar case
+	 of a loop running over a boolean type where we use the simpler form
+	 in order to avoid manipulating negative values in a boolean context.
 
 	 If it is, we generate the canonical loop form expected by the loop
 	 optimizer and the loop vectorizer, which is the do-while form:
@@ -3067,7 +3069,9 @@ Loop_Statement_to_gnu (Node_Id gnat_node)
 
 	 which works in all cases.  */
 
-      if (optimize && !optimize_debug)
+      if (optimize
+	  && !optimize_debug
+	  && TREE_CODE (gnu_base_type) != BOOLEAN_TYPE)
 	{
 	  /* We can use the do-while form directly if GNU_FIRST-1 doesn't
 	     overflow.  */