diff mbox

stack adjustment is unsigned

Message ID 2c5076c5-ef4a-1b9a-337a-e90e965af93f@acm.org
State New
Headers show

Commit Message

Nathan Sidwell May 1, 2017, 10:23 p.m. UTC 
I happened to notice that stack adjustment code was confusingly testing for an 
unsigned value being > 0.  In this case unadjusted_alignment is of type unsigned 
HOST_WIDE_INT, so the 'else' portion of the has no effect.

This patch simplifies the adjustment to be less confusing (IMHO).

booted and tested on x86_64-linux-gnu, ok?

Comments

Jeff Law May 1, 2017, 10:57 p.m. UTC | #1 
On 05/01/2017 04:23 PM, Nathan Sidwell wrote:
> I happened to notice that stack adjustment code was confusingly testing 
> for an unsigned value being > 0.  In this case unadjusted_alignment is 
> of type unsigned HOST_WIDE_INT, so the 'else' portion of the has no effect.
> 
> This patch simplifies the adjustment to be less confusing (IMHO).
> 
> booted and tested on x86_64-linux-gnu, ok?
> 
OK I guess.  It's not obvious what would happen with a wrong direction 
target, but the one we've got (PA) doesn't use this code because it's an 
ACCUMULATE_OUTGOING_ARGS target.

It appears that the size passed in would always be positive (it's a size 
after all), but I couldn't guarantee that without a lot more auditing.

Jeff
diff mbox

Patch

Index: gcc/calls.c
===================================================================
--- gcc/calls.c	(revision 247416)
+++ gcc/calls.c	(working copy)
@@ -2644,13 +2644,8 @@  combine_pending_stack_adjustment_and_cal
   adjustment = pending_stack_adjust;
   /* Push enough additional bytes that the stack will be aligned
      after the arguments are pushed.  */
-  if (preferred_unit_stack_boundary > 1)
-    {
-      if (unadjusted_alignment > 0)
-	adjustment -= preferred_unit_stack_boundary - unadjusted_alignment;
-      else
-	adjustment += unadjusted_alignment;
-    }
+  if (preferred_unit_stack_boundary > 1 && unadjusted_alignment)
+    adjustment -= preferred_unit_stack_boundary - unadjusted_alignment;
 
   /* Now, sets ARGS_SIZE->CONSTANT so that we pop the right number of
      bytes after the call.  The right number is the entire