On Fri, Nov 11, 2016 at 12:11:49AM -0500, David Edelsohn wrote:
> On Thu, Nov 10, 2016 at 6:47 PM, Dominik Vogt <v...@linux.vnet.ibm.com> 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.)
>
> Please also update the ASCII pictures above the rs6000_stack_info()
> function in rs6000.c to show / describe the new padding for alignment.
Like in the new patch? (Please double check that I got this right
in all three cases).
Ciao
Dominik ^_^ ^_^
--
Dominik Vogt
IBM Germany
gcc/ChangeLog
* config/rs6000/rs6000.c (rs6000_stack_info): PR/77359: Properly align
local variables in functions calling alloca. Also update the ASCII
drawings
* config/rs6000/rs6000.h (STARTING_FRAME_OFFSET, STACK_DYNAMIC_OFFSET):
PR/77359: Likewise.
* config/rs6000/aix.h (STARTING_FRAME_OFFSET, STACK_DYNAMIC_OFFSET):
PR/77359: Copy AIX specific versions of the rs6000.h macros to aix.h.
>From a80234c45173bebbfa07e810ff534c60591a8b76 Mon Sep 17 00:00:00 2001
From: Dominik Vogt <v...@linux.vnet.ibm.com>
Date: Fri, 28 Oct 2016 12:59:55 +0100
Subject: [PATCH] PR/77359: Properly align local variables in functions
calling alloca.
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 | 35 +++++++++++++++++++++++++++++++++++
gcc/config/rs6000/rs6000.c | 24 +++++++++++++++++++-----
gcc/config/rs6000/rs6000.h | 26 ++++++++++++++++++--------
3 files changed, 72 insertions(+), 13 deletions(-)
diff --git a/gcc/config/rs6000/aix.h b/gcc/config/rs6000/aix.h
index b254236..f6eb122 100644
--- a/gcc/config/rs6000/aix.h
+++ b/gcc/config/rs6000/aix.h
@@ -40,6 +40,41 @@
#undef STACK_BOUNDARY
#define STACK_BOUNDARY 128
+/* Offset within stack frame to start allocating local variables at.
+ If FRAME_GROWS_DOWNWARD, this is the offset to the END of the
+ first local allocated. Otherwise, it is the offset to the BEGINNING
+ of the first local allocated.
+
+ 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.
+
+ 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 \
+ (FRAME_GROWS_DOWNWARD
\
+ ? 0 \
+ : (cfun->calls_alloca \
+ ? RS6000_ALIGN (crtl->outgoing_args_size + RS6000_SAVE_AREA, 16) \
+ : (RS6000_ALIGN (crtl->outgoing_args_size, 16) + RS6000_SAVE_AREA)))
+
+/* Offset from the stack pointer register to an item dynamically
+ allocated on the stack, e.g., by `alloca'.
+
+ 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.
+
+ 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)
+
#undef TARGET_IEEEQUAD
#define TARGET_IEEEQUAD 0
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index f9e4739..4f3b886 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -25781,7 +25781,7 @@ rs6000_savres_strategy (rs6000_stack_t *info,
+---------------------------------------+
| saved TOC pointer | 20 40
+---------------------------------------+
- | Parameter save area (P) | 24 48
+ | Parameter save area (+padding*) (P) | 24 48
+---------------------------------------+
| Alloca space (A) | 24+P etc.
+---------------------------------------+
@@ -25802,6 +25802,9 @@ rs6000_savres_strategy (rs6000_stack_t *info,
old SP->| back chain to caller's caller |
+---------------------------------------+
+ * If the alloca area is present, the parameter save area is
+ padded so that the former starts 16-byte aligned.
+
The required alignment for AIX configurations is two words (i.e., 8
or 16 bytes).
@@ -25816,7 +25819,7 @@ rs6000_savres_strategy (rs6000_stack_t *info,
+---------------------------------------+
| Saved TOC pointer | 24
+---------------------------------------+
- | Parameter save area (P) | 32
+ | Parameter save area (+padding*) (P) | 32
+---------------------------------------+
| Alloca space (A) | 32+P
+---------------------------------------+
@@ -25833,6 +25836,8 @@ rs6000_savres_strategy (rs6000_stack_t *info,
old SP->| back chain to caller's caller | 32+P+A+L+W+Y+G+F
+---------------------------------------+
+ * If the alloca area is present, the parameter save area is
+ padded so that the former starts 16-byte aligned.
V.4 stack frames look like:
@@ -25841,7 +25846,7 @@ rs6000_savres_strategy (rs6000_stack_t *info,
+---------------------------------------+
| caller's saved LR | 4
+---------------------------------------+
- | Parameter save area (P) | 8
+ | Parameter save area (+padding*) (P) | 8
+---------------------------------------+
| Alloca space (A) | 8+P
+---------------------------------------+
@@ -25870,6 +25875,10 @@ rs6000_savres_strategy (rs6000_stack_t *info,
old SP->| back chain to caller's caller |
+---------------------------------------+
+ * If the alloca area is present and the required alignment is
+ 16 bytes, the parameter save area is padded so that the
+ alloca area starts 16-byte aligned.
+
The required alignment for V.4 is 16 bytes, or 8 bytes if -meabi is
given. (But note below and in sysv4.h that we require only 8 and
may round up the size of our stack frame anyways. The historical
@@ -26004,8 +26013,13 @@ rs6000_stack_info (void)
info->reg_size = reg_size;
info->fixed_size = RS6000_SAVE_AREA;
info->vars_size = RS6000_ALIGN (get_frame_size (), 8);
- info->parm_size = RS6000_ALIGN (crtl->outgoing_args_size,
- TARGET_ALTIVEC ? 16 : 8);
+ if (cfun->calls_alloca)
+ info->parm_size =
+ RS6000_ALIGN (crtl->outgoing_args_size + info->fixed_size,
+ STACK_BOUNDARY / BITS_PER_UNIT) - info->fixed_size;
+ else
+ info->parm_size = RS6000_ALIGN (crtl->outgoing_args_size,
+ TARGET_ALTIVEC ? 16 : 8);
if (FRAME_GROWS_DOWNWARD)
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..afda416 100644
--- a/gcc/config/rs6000/rs6000.h
+++ b/gcc/config/rs6000/rs6000.h
@@ -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 \
- : (RS6000_ALIGN (crtl->outgoing_args_size, \
- (TARGET_ALTIVEC || TARGET_VSX) ? 16 : 8) \
- + RS6000_SAVE_AREA))
+ : (cfun->calls_alloca \
+ ? (RS6000_ALIGN (crtl->outgoing_args_size + RS6000_SAVE_AREA, \
+ (TARGET_ALTIVEC || TARGET_VSX) ? 16 : 8 )) \
+ : (RS6000_ALIGN (crtl->outgoing_args_size, \
+ (TARGET_ALTIVEC || TARGET_VSX) ? 16 : 8) \
+ + RS6000_SAVE_AREA)))
/* Offset from the stack pointer register to an item dynamically
allocated on the stack, e.g., by `alloca'.
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'). */
#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, \
+ (TARGET_ALTIVEC || TARGET_VSX) ? 16 : 8)
/* If we generate an insn to push BYTES bytes,
this says how many the stack pointer really advances by.
--
2.3.0
