https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97822
--- Comment #14 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to Werner Zeh from comment #7)
> The analysis has shown that the observed behavior was introduced with commit
> 122f9da15d1db58bd5f96a8a49d81d529ca07a1e between version 7 and 8.
>
> Looking deeper into this change, you see the following change made in
> gcc/config/i386/i386.c:
> 1 static inline bool
> 2 fp_valid_at (HOST_WIDE_INT cfa_offset)
> 3 {
> 4 const struct machine_frame_state &fs = cfun->machine->fs;
> 5 - return fs.fp_valid && !(fs.sp_valid && fs.sp_realigned
> 6 - && cfa_offset > fs.sp_realigned_offset);
> 7 + if (fs.sp_realigned && cfa_offset > fs.sp_realigned_fp_last)
> 8 + {
> 9 + /* Validate that the cfa_offset isn't in a "no-man's land". */
> 10 + gcc_assert (cfa_offset >= fs.sp_realigned_offset);
> 11 + return false;
> 12 + }
> 13 + return fs.fp_valid;
> 14 }
>
> The problem is that this change modified the condition in line 5 to line 7,
> which removed the term fs.sp_valid.
I think the above analysis is correct. Also, in ix86_expand_prologue we have
the following comment:
/* SEH unwind emit doesn't currently support REG_CFA_EXPRESSION, which
is needed to describe where a register is saved using a realigned
stack pointer, so we need to invalidate the stack pointer for that
target. */
if (TARGET_SEH)
m->fs.sp_valid = false;
This is Werner's proposed change in a patch form:
--cut here--
diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
index 722c1713a6d..f5283c2c6b7 100644
--- a/gcc/config/i386/i386.cc
+++ b/gcc/config/i386/i386.cc
@@ -7403,7 +7403,7 @@ static inline bool
fp_valid_at (HOST_WIDE_INT cfa_offset)
{
const struct machine_frame_state &fs = cfun->machine->fs;
- if (fs.sp_realigned && cfa_offset > fs.sp_realigned_fp_last)
+ if (fs.sp_valid && fs.sp_realigned && cfa_offset > fs.sp_realigned_fp_last)
{
/* Validate that the cfa_offset isn't in a "no-man's land". */
gcc_assert (cfa_offset >= fs.sp_realigned_offset);
--cut here--
@Jonathan, can you please bootstrap and regression test the patch on MingW? I
will test it on linux, but according to the above comment I expect it will not
make any impact on non-SEH target.
@Werner, can you please post the patch following [1] to gcc-patches@ mailing
list for eventual approval by MingW maintainer? The patch submission needs your
Signed-off-By: tag.
[1] https://gcc.gnu.org/contribute.html
