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Fix -freorder-blocks-and-partition glitch with Windows SEH

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Since GCC 8, the -freorder-blocks-and-partition pass can split a function
into hot and cold parts, thus generating 2 CIEs for a single function in
DWARF for exception purposes and doing an equivalent trick for Windows SEH.

Now the Windows system unwinder is picky when it comes to the boundary
between an active EH region and the end of the function and, therefore,
a nop may need to be added in specific cases.

gcc/
	* config/i386/winnt.c (i386_pe_seh_unwind_emit): When switching to
	the cold section, emit a nop before the directive if the previous
	active instruction can throw.
This commit is contained in:
Eric Botcazou 2021-02-12 00:16:49 +01:00
parent 5e40542f87
commit 85cefe2256
1 changed files with 4 additions and 0 deletions
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4
gcc/config/i386/winnt.c
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@ -1231,6 +1231,10 @@ i386_pe_seh_unwind_emit (FILE *asm_out_file, rtx_insn *insn)
seh = cfun->machine->seh;
if (NOTE_P (insn) && NOTE_KIND (insn) == NOTE_INSN_SWITCH_TEXT_SECTIONS)
{
/* See ix86_seh_fixup_eh_fallthru for the rationale. */
rtx_insn *prev = prev_active_insn (insn);
if (prev && !insn_nothrow_p (prev))
fputs ("\tnop\n", asm_out_file);
fputs ("\t.seh_endproc\n", asm_out_file);
seh->in_cold_section = true;
return;