Commit Graph

3 Commits

Author SHA1 Message Date
Martin Storsjö afb4e0f289 [AArch64] Omit SEH directives for the epilogue if none are needed
For these cases, we already omit the prologue directives, if
(!AFI->hasStackFrame() && !windowsRequiresStackProbe && !NumBytes).

When writing the epilogue (after the prolog has been written), if
the function doesn't have the WinCFI flag set (i.e. if no prologue
was generated), assume that no epilogue will be needed either,
and don't emit any epilog start pseudo instruction. After completing
the epilogue, make sure that it actually matched the prologue.

Previously, when epilogue start/end was generated, but no prologue,
the unwind info for such functions actually was huge; 12 bytes xdata
(4 bytes header, 4 bytes for one non-folded epilogue header, 4 bytes
for padded opcodes) and 8 bytes pdata. Because the epilog consisted of
one opcode (end) but the prolog was empty (no .seh_endprologue), the
epilogue couldn't be folded into the prologue, and thus couldn't be
considered for packed form either.

On a 6.5 MB DLL with 110 KB pdata and 166 KB xdata, this gets rid of
38 KB pdata and 62 KB xdata.

Differential Revision: https://reviews.llvm.org/D88641
2020-10-02 09:12:56 +03:00
Martin Storsjö 5b86d130e2 [AArch64] Generate and parse SEH assembly directives
This ensures that you get the same output regardless if generating
code directly to an object file or if generating assembly and
assembling that.

Add implementations of the EmitARM64WinCFI*() methods in
AArch64TargetAsmStreamer, and fill in one blank in MCAsmStreamer.

Add corresponding directive handlers in AArch64AsmParser and
COFFAsmParser.

Some SEH directive names have been picked to match the prior art
for SEH assembly directives for x86_64, e.g. the spelling of
".seh_startepilogue" matching the preexisting ".seh_endprologue".

For the directives for saving registers, the exact spelling
from the arm64 documentation is picked, e.g. ".seh_save_reg" (to follow
that naming for all the other ones, e.g. ".seh_save_fregp_x"), while
the corresponding one for x86_64 is plain ".seh_savereg" without the
second underscore.

Directives in the epilogues have the same names as in prologues,
e.g. .seh_savereg, even though the registers are restored, not
saved, at that point.

Differential Revision: https://reviews.llvm.org/D86529
2020-08-29 15:15:22 +03:00
Martin Storsjo 4ed18e5ef5 [AArch64] Handle lowering lround on windows, where long is 32 bit
Differential Revision: https://reviews.llvm.org/D62108

llvm-svn: 361192
2019-05-20 19:53:28 +00:00