diff mbox

PR77359: Properly align local variables in functions calling alloca.

Message ID 20161111085821.GA6100@linux.vnet.ibm.com
State New
Headers show

Commit Message

Dominik Vogt Nov. 11, 2016, 8:58 a.m. UTC 
On Thu, Nov 10, 2016 at 06:17:57PM -0600, Segher Boessenkool wrote:
> On Fri, Nov 11, 2016 at 12:47:02AM +0100, Dominik Vogt wrote:
> > On Thu, Nov 03, 2016 at 11:40:44AM +0100, Dominik Vogt wrote:
> > > The attached patch fixes the stack layout problems on AIX and
> > > Power as described here:
> > > 
> > >   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77359
> > > 
> > > The patch has been bootstrapped on AIX (32 Bit) and bootstrappend
> > > and regression tested on Power (biarch).  It needs more testing
> > > that I cannot do with the hardware available to me.
> > > 
> > > If the patch is good, this one can be re-applied:
> > > 
> > >   https://gcc.gnu.org/ml/gcc-patches/2016-07/msg01730.html
> > >   https://gcc.gnu.org/ml/gcc-patches/2016-08/msg01616.html
> > 
> > So, is this patch in order to be committed?  (Assuming that a
> > followup patch will clean up the rs6000.h+aix.h quirks.)
> 
> You say it needs more testing -- what testing?

Regression testing on AIX (David has done this in reply to the
original message), possibly also on 32-Bit Power, if that is a
reasonable target.

> (And it needs to be posted to gcc-patches@ of course).

This discussion was originally on gcc-patches, but somehow it got
removed from the recipient list.

> > > +   : (cfun->calls_alloca						\
> > > +      ? RS6000_ALIGN (crtl->outgoing_args_size + RS6000_SAVE_AREA, 16)	\
> > > +      : (RS6000_ALIGN (crtl->outgoing_args_size, 16) + RS6000_SAVE_AREA)))
> 
> Maybe you can make the comment explain these last two lines as well...  It
> seems to me you want to align STARTING_FRAME_OFFSET if calls_alloca?

Done.

> Also add a comment for the one in rs6000.h?

Done.

> > > +   RS6000_ALIGN (crtl->outgoing_args_size + (STACK_POINTER_OFFSET), 16)
> 
> You don't need parens around STACK_POINTER_OFFSET.

Done.

New patch attached (added more comments and removed parentheses;
not re-tested).  (The first attachment is a diff between the two
patches.)

Ciao

Dominik ^_^  ^_^

Comments

Segher Boessenkool Nov. 11, 2016, 8:17 p.m. UTC | #1 
On Fri, Nov 11, 2016 at 09:58:21AM +0100, Dominik Vogt wrote:
> > You say it needs more testing -- what testing?
> 
> Regression testing on AIX (David has done this in reply to the
> original message), possibly also on 32-Bit Power, if that is a
> reasonable target.

It is.  I'll test powerpc64-linux -m32, and a crosscompiler for
powerpc-linux.

Thanks for the patch.  Please apply to trunk.  Does it need backports
later?


Segher
Dominik Vogt Nov. 15, 2016, 9:42 a.m. UTC | #2 
On Fri, Nov 11, 2016 at 02:17:58PM -0600, Segher Boessenkool wrote:
> On Fri, Nov 11, 2016 at 09:58:21AM +0100, Dominik Vogt wrote:
> > > You say it needs more testing -- what testing?
> > 
> > Regression testing on AIX (David has done this in reply to the
> > original message), possibly also on 32-Bit Power, if that is a
> > reasonable target.
> 
> It is.  I'll test powerpc64-linux -m32, and a crosscompiler for
> powerpc-linux.
> 
> Thanks for the patch.  Please apply to trunk.  Does it need backports
> later?

Depends on whether the Power/AIX folks think backports are
necessary.  We'll apply the patch to trunk; if a backport is
desired later, David or someone else from IBM could do that (i.e.
it's not necessary that our department commits further patches).

Ciao

Dominik ^_^  ^_^
diff mbox

Patch

--- old/0001-PR77359-Properly-align-local-variables-in-functions-.patch	2016-11-11 09:52:16.535439142 +0100
+++ new/0001-PR77359-Properly-align-local-variables-in-functions-.patch	2016-11-11 09:50:03.715439142 +0100
@@ -1,4 +1,4 @@ 
-From bd36042fd82e29204d2f10c180b9e7c27281eef2 Mon Sep 17 00:00:00 2001
+From faae30210f584bba92ab96aac479ae8f253e59b7 Mon Sep 17 00:00:00 2001
 From: Dominik Vogt <vogt@linux.vnet.ibm.com>
 Date: Fri, 28 Oct 2016 12:59:55 +0100
 Subject: [PATCH 1/2] PR77359: Properly align local variables in functions
@@ -7,16 +7,16 @@ 
 See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77359 for a discussion of the
 problem and the fix.
 ---
- gcc/config/rs6000/aix.h    | 27 +++++++++++++++++++++++++++
+ gcc/config/rs6000/aix.h    | 35 +++++++++++++++++++++++++++++++++++
  gcc/config/rs6000/rs6000.c |  9 +++++++--
- gcc/config/rs6000/rs6000.h | 14 ++++++++------
- 3 files changed, 42 insertions(+), 8 deletions(-)
+ gcc/config/rs6000/rs6000.h | 26 ++++++++++++++++++--------
+ 3 files changed, 60 insertions(+), 10 deletions(-)
 
 diff --git a/gcc/config/rs6000/aix.h b/gcc/config/rs6000/aix.h
-index b254236..7773517 100644
+index b254236..f6eb122 100644
 --- a/gcc/config/rs6000/aix.h
 +++ b/gcc/config/rs6000/aix.h
-@@ -40,6 +40,33 @@
+@@ -40,6 +40,41 @@
  #undef  STACK_BOUNDARY
  #define STACK_BOUNDARY 128
  
@@ -27,7 +27,12 @@ 
 +
 +   On the RS/6000, the frame pointer is the same as the stack pointer,
 +   except for dynamic allocations.  So we start after the fixed area and
-+   outgoing parameter area.  */
++   outgoing parameter area.
++
++   If the function uses dynamic stack space (CALLS_ALLOCA is set), that
++   space needs to be aligned to STACK_BOUNDARY, i.e. the sum of the
++   sizes of the fixed area and the parameter area must be a multiple of
++   STACK_BOUNDARY.  */
 +
 +#undef STARTING_FRAME_OFFSET
 +#define STARTING_FRAME_OFFSET						\
@@ -42,10 +47,13 @@ 
 +
 +   The default value for this macro is `STACK_POINTER_OFFSET' plus the
 +   length of the outgoing arguments.  The default is correct for most
-+   machines.  See `function.c' for details.  */
++   machines.  See `function.c' for details.
++
++   This value must be a multiple of STACK_BOUNDARY (hard coded in
++   `emit-rtl.c').  */
 +#undef STACK_DYNAMIC_OFFSET
 +#define STACK_DYNAMIC_OFFSET(FUNDECL)					\
-+   RS6000_ALIGN (crtl->outgoing_args_size + (STACK_POINTER_OFFSET), 16)
++   RS6000_ALIGN (crtl->outgoing_args_size + STACK_POINTER_OFFSET, 16)
 +
  #undef  TARGET_IEEEQUAD
  #define TARGET_IEEEQUAD 0
@@ -71,10 +79,21 @@ 
      info->vars_size
        += RS6000_ALIGN (info->fixed_size + info->vars_size + info->parm_size,
 diff --git a/gcc/config/rs6000/rs6000.h b/gcc/config/rs6000/rs6000.h
-index 4b83abd..c11dc1b 100644
+index 4b83abd..afda416 100644
 --- a/gcc/config/rs6000/rs6000.h
 +++ b/gcc/config/rs6000/rs6000.h
-@@ -1728,9 +1728,12 @@ extern enum reg_class rs6000_constraints[RS6000_CONSTRAINT_MAX];
+@@ -1723,25 +1723,35 @@ extern enum reg_class rs6000_constraints[RS6000_CONSTRAINT_MAX];
+ 
+    On the RS/6000, the frame pointer is the same as the stack pointer,
+    except for dynamic allocations.  So we start after the fixed area and
+-   outgoing parameter area.  */
++   outgoing parameter area.
++
++   If the function uses dynamic stack space (CALLS_ALLOCA is set), that
++   space needs to be aligned to STACK_BOUNDARY, i.e. the sum of the
++   sizes of the fixed area and the parameter area must be a multiple of
++   STACK_BOUNDARY.  */
+ 
  #define STARTING_FRAME_OFFSET						\
    (FRAME_GROWS_DOWNWARD							\
     ? 0									\
@@ -90,14 +109,19 @@ 
  
  /* Offset from the stack pointer register to an item dynamically
     allocated on the stack, e.g., by `alloca'.
-@@ -1739,9 +1742,8 @@ extern enum reg_class rs6000_constraints[RS6000_CONSTRAINT_MAX];
+ 
+    The default value for this macro is `STACK_POINTER_OFFSET' plus the
     length of the outgoing arguments.  The default is correct for most
-    machines.  See `function.c' for details.  */
+-   machines.  See `function.c' for details.  */
++   machines.  See `function.c' for details.
++
++   This value must be a multiple of STACK_BOUNDARY (hard coded in
++   `emit-rtl.c').  */
  #define STACK_DYNAMIC_OFFSET(FUNDECL)					\
 -  (RS6000_ALIGN (crtl->outgoing_args_size,				\
 -		 (TARGET_ALTIVEC || TARGET_VSX) ? 16 : 8)		\
 -   + (STACK_POINTER_OFFSET))
-+  RS6000_ALIGN (crtl->outgoing_args_size + (STACK_POINTER_OFFSET),	\
++  RS6000_ALIGN (crtl->outgoing_args_size + STACK_POINTER_OFFSET,	\
 +		(TARGET_ALTIVEC || TARGET_VSX) ? 16 : 8)
  
  /* If we generate an insn to push BYTES bytes,