Since GCC 8, the -freorder-blocks-and-partition pass can split a function into
hot and cold parts, thus generating 2 FDEs for a single function in DWARF for
exception purposes and doing an equivalent trick for Windows SEH on x86-64.
Now the Windows system unwinder does not support arbitrarily large frames and
there is even a hard limit on the encoding of the CFI, which changes the stack
allocation strategy when it is topped and which must be reflected everywhere.
I overlooked that when implementing the -freorder-blocks-and-partition support
back in 2018 and this results in an ICE when gigantic frames, like e.g. in the
attached Ada testcase.
Bootstrapped on x86-64/Windows, applied on all active branches as obvious.
2021-04-19 Eric Botcazou <ebotca...@adacore.com>
* config/i386/winnt.c (i386_pe_seh_cold_init): Properly deal with
frames larger than the SEH maximum frame size.
2021-04-19 Eric Botcazou <ebotca...@adacore.com>
* gnat.dg/opt92.adb: New test.
--
Eric Botcazou
diff --git a/gcc/config/i386/winnt.c b/gcc/config/i386/winnt.c
index cc121965294..b66263ad243 100644
--- a/gcc/config/i386/winnt.c
+++ b/gcc/config/i386/winnt.c
@@ -921,15 +921,17 @@ i386_pe_seh_cold_init (FILE *f, const char *name)
/* In the normal case, the frame pointer is near the bottom of the frame
so we can do the full stack allocation and set it afterwards. There
- is an exception when the function accesses prior frames so, in this
- case, we need to pre-allocate a small chunk before setting it. */
- if (crtl->accesses_prior_frames)
- alloc_offset = seh->cfa_offset;
- else
+ is an exception if the function overflows the SEH maximum frame size
+ or accesses prior frames so, in this case, we need to pre-allocate a
+ small chunk of stack before setting it. */
+ offset = seh->sp_offset - INCOMING_FRAME_SP_OFFSET;
+ if (offset < SEH_MAX_FRAME_SIZE && !crtl->accesses_prior_frames)
alloc_offset = seh->sp_offset;
+ else
+ alloc_offset = MIN (seh->cfa_offset + 240, seh->sp_offset);
offset = alloc_offset - INCOMING_FRAME_SP_OFFSET;
- if (offset > 0 && offset < SEH_MAX_FRAME_SIZE)
+ if (offset > 0)
fprintf (f, "\t.seh_stackalloc\t" HOST_WIDE_INT_PRINT_DEC "\n", offset);
for (int regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
@@ -958,7 +960,7 @@ i386_pe_seh_cold_init (FILE *f, const char *name)
fprintf (f, ", " HOST_WIDE_INT_PRINT_DEC "\n", offset);
}
- if (crtl->accesses_prior_frames)
+ if (alloc_offset != seh->sp_offset)
{
offset = seh->sp_offset - alloc_offset;
if (offset > 0 && offset < SEH_MAX_FRAME_SIZE)
-- { dg-do compile { target { lp64 || llp64 } } }
-- { dg-options "-O2 -gnatws" }
procedure Main is
subtype Int64 is Long_Long_Integer;
type Arr is array (Int64 range <>) of Boolean;
Pow : constant := 10;
procedure Compute (B : in out Arr) is
Factor : Int64 := 3;
Num : Int64;
begin
while Factor <= 10 ** (Pow / 2) loop
Num := Factor;
while Num < 10 ** Pow loop
if B (Num) then
Factor := Num;
exit;
end if;
Num := Num + 2;
end loop;
Num := Factor * Factor;
while Num < 10 ** Pow loop
B (Num) := False;
Num := Num + Factor * 2;
end loop;
Factor := Factor + 2;
end loop;
end;
B : Arr (1 .. 10 ** Pow) := (others => True);
begin
Compute (B);
end;