On 11/3/20 11:16 AM, Richard Biener wrote:
> On Tue, 3 Nov 2020, Bernd Edlinger wrote:
>
>>
>>
>> On 11/3/20 10:34 AM, Richard Biener wrote:
>>> On Mon, 2 Nov 2020, Bernd Edlinger wrote:
>>>
>>>> On 11/2/20 3:07 PM, Richard Biener wrote:
>>>>> On Mon, 2 Nov 2020, Bernd Edlinger wrote:
>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> this makes sure that stack allocated SSA_NAMEs are
>>>>>> at least MODE_ALIGNED. Also increase the MEM_ALIGN
>>>>>> for the corresponding rtl objects.
>>>>>>
>>>>>>
>>>>>> Tested on x86_64-pc-linux-gnu and arm-none-eabi.
>>>>>>
>>>>>> OK for trunk?
>>>>>
>>>>>
>>>>> @@ -1022,6 +1030,14 @@ expand_one_stack_var_at (tree decl, rtx base,
>>>>> unsigned base_align,
>>>>> }
>>>>>
>>>>> set_rtl (decl, x);
>>>>> +
>>>>> + if (TREE_CODE (decl) == SSA_NAME
>>>>> + && GET_MODE (x) != BLKmode
>>>>> + && MEM_ALIGN (x) < GET_MODE_ALIGNMENT (GET_MODE (x)))
>>>>> + {
>>>>> + gcc_checking_assert (GET_MODE_ALIGNMENT (GET_MODE (x)) <=
>>>>> base_align);
>>>>> + set_mem_align (x, GET_MODE_ALIGNMENT (GET_MODE (x)));
>>>>> + }
>>>>> }
>>>>>
>>>>>
>>>>> I wonder whether we cannot "fix" set_rtl to not call
>>>>> set_mem_attributes in this path, maybe directly call
>>>>> set_mem_align there instead? That is, the preceeding
>>>>> code for ! SSA_NAME already tries to adjust alignment
>>>>> to honor that of the actual stack slot - IMHO the
>>>>> non-SSA and SSA cases should be merged after this
>>>>> patch, but maybe simply by calling set_mem_align
>>>>> instead of doing the DECL_ALIGN frobbing and do
>>>>> the alignment compute also for SSA_NAMEs?
>>>>>
>>>>> The other pieces look OK but the above is a bit ugly
>>>>> at the moment.
>>>>>
>>>>
>>>> Hmm, how about this?
>>>
>>> That would work for me. Guess removing the DECL_ALIGN frobbing
>>> in the != SSA_NAME path didn't work out or you didn't try out
>>> of caution?
>>>
>>
>> I didn't try, since it felt simply more correct this way,
>> and get_object_alignment would probably give a different
>> answer since it uses DECL_ALIGN too.
>
> OK, I see.
>
> Richard.
>
Ok, good.
So this is what I will commit shortly.
Thanks
Bernd.
From e281da96736655c42296806162d1b979dd368544 Mon Sep 17 00:00:00 2001
From: Bernd Edlinger <[email protected]>
Date: Sun, 1 Nov 2020 07:32:20 +0100
Subject: [PATCH] Fix PR97205
This makes sure that stack allocated SSA_NAMEs are
at least MODE_ALIGNED. Also increase the MEM_ALIGN
for the corresponding rtl objects.
gcc:
2020-11-03 Bernd Edlinger <[email protected]>
PR target/97205
* cfgexpand.c (align_local_variable): Make SSA_NAMEs
at least MODE_ALIGNED.
(expand_one_stack_var_at): Increase MEM_ALIGN for SSA_NAMEs.
testsuite:
2020-11-03 Bernd Edlinger <[email protected]>
PR target/97205
* gcc.c-torture/compile/pr97205.c: New test.
---
gcc/cfgexpand.c | 43 ++++++++++++++++-----------
gcc/testsuite/gcc.c-torture/compile/pr97205.c | 7 +++++
2 files changed, 33 insertions(+), 17 deletions(-)
create mode 100644 gcc/testsuite/gcc.c-torture/compile/pr97205.c
diff --git a/gcc/cfgexpand.c b/gcc/cfgexpand.c
index f3f17d3..6c41a7e 100644
--- a/gcc/cfgexpand.c
+++ b/gcc/cfgexpand.c
@@ -366,7 +366,15 @@ align_local_variable (tree decl, bool really_expand)
unsigned int align;
if (TREE_CODE (decl) == SSA_NAME)
- align = TYPE_ALIGN (TREE_TYPE (decl));
+ {
+ tree type = TREE_TYPE (decl);
+ machine_mode mode = TYPE_MODE (type);
+
+ align = TYPE_ALIGN (type);
+ if (mode != BLKmode
+ && align < GET_MODE_ALIGNMENT (mode))
+ align = GET_MODE_ALIGNMENT (mode);
+ }
else
{
align = LOCAL_DECL_ALIGNMENT (decl);
@@ -999,20 +1007,21 @@ expand_one_stack_var_at (tree decl, rtx base, unsigned base_align,
x = plus_constant (Pmode, base, offset);
x = gen_rtx_MEM (TREE_CODE (decl) == SSA_NAME
? TYPE_MODE (TREE_TYPE (decl))
- : DECL_MODE (SSAVAR (decl)), x);
+ : DECL_MODE (decl), x);
+
+ /* Set alignment we actually gave this decl if it isn't an SSA name.
+ If it is we generate stack slots only accidentally so it isn't as
+ important, we'll simply set the alignment directly on the MEM. */
+
+ if (base == virtual_stack_vars_rtx)
+ offset -= frame_phase;
+ align = known_alignment (offset);
+ align *= BITS_PER_UNIT;
+ if (align == 0 || align > base_align)
+ align = base_align;
if (TREE_CODE (decl) != SSA_NAME)
{
- /* Set alignment we actually gave this decl if it isn't an SSA name.
- If it is we generate stack slots only accidentally so it isn't as
- important, we'll simply use the alignment that is already set. */
- if (base == virtual_stack_vars_rtx)
- offset -= frame_phase;
- align = known_alignment (offset);
- align *= BITS_PER_UNIT;
- if (align == 0 || align > base_align)
- align = base_align;
-
/* One would think that we could assert that we're not decreasing
alignment here, but (at least) the i386 port does exactly this
via the MINIMUM_ALIGNMENT hook. */
@@ -1022,6 +1031,8 @@ expand_one_stack_var_at (tree decl, rtx base, unsigned base_align,
}
set_rtl (decl, x);
+
+ set_mem_align (x, align);
}
class stack_vars_data
@@ -1327,13 +1338,11 @@ expand_one_stack_var_1 (tree var)
{
tree type = TREE_TYPE (var);
size = tree_to_poly_uint64 (TYPE_SIZE_UNIT (type));
- byte_align = TYPE_ALIGN_UNIT (type);
}
else
- {
- size = tree_to_poly_uint64 (DECL_SIZE_UNIT (var));
- byte_align = align_local_variable (var, true);
- }
+ size = tree_to_poly_uint64 (DECL_SIZE_UNIT (var));
+
+ byte_align = align_local_variable (var, true);
/* We handle highly aligned variables in expand_stack_vars. */
gcc_assert (byte_align * BITS_PER_UNIT <= MAX_SUPPORTED_STACK_ALIGNMENT);
diff --git a/gcc/testsuite/gcc.c-torture/compile/pr97205.c b/gcc/testsuite/gcc.c-torture/compile/pr97205.c
new file mode 100644
index 0000000..6600011
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/pr97205.c
@@ -0,0 +1,7 @@
+int a;
+typedef __attribute__((aligned(2))) int x;
+int f ()
+{
+ x b = a;
+ return b;
+}
--
1.9.1
