From 85cefe22564c4b7c1159a544fa692a24e0c71870 Mon Sep 17 00:00:00 2001 From: Eric Botcazou Date: Fri, 12 Feb 2021 00:16:49 +0100 Subject: [PATCH] Fix -freorder-blocks-and-partition glitch with Windows SEH 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. --- gcc/config/i386/winnt.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/gcc/config/i386/winnt.c b/gcc/config/i386/winnt.c index 962c88e3c1b..adc3f36f13b 100644 --- a/gcc/config/i386/winnt.c +++ b/gcc/config/i386/winnt.c @@ -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; -- 2.30.2