[CodeGenPrepare] Cut off FindAllMemoryUses if there are too many uses.
This avoids excessive compile time. The case I'm looking at is
Function.cpp from an old version of LLVM that still had the giant
memcmp string matcher in it. Before r308322 this compiled in about 2
minutes, after it, clang takes infinite* time to compile it. With
this patch we're at 5 min, which is still bad but this is a
pathological case.
The cut off at 20 uses was chosen by looking at other cut-offs in LLVM
for user scanning. It's probably too high, but does the job and is
very unlikely to regress anything.
Fixes PR33900.
* I'm impatient and aborted after 15 minutes, on the bug report it was
killed after 2h.
Pull in r308986 from upstream llvm trunk (by Simon Pilgrim):
[X86][CGP] Reduce memcmp() expansion to 2 load pairs (PR33914)
D35067/rL308322 attempted to support up to 4 load pairs for memcmp
inlining which resulted in regressions for some optimized libc memcmp
implementations (PR33914).
Until we can match these more optimal cases, this patch reduces the
memcmp expansion to a maximum of 2 load pairs (which matches what we
do for -Os).
This patch should be considered for the 5.0.0 release branch as well
Differential Revision: https://reviews.llvm.org/D35830
These fix a hang (or extremely long compile time) when building older
LLVM ports.
Reported by: antoine
PR: 219139
Add ISD::EH_DWARF_CFA, simplify @llvm.eh.dwarf.cfa on Mips, fix on
PowerPC
LLVM has an @llvm.eh.dwarf.cfa intrinsic, used to lower the
GCC-compatible __builtin_dwarf_cfa() builtin. As pointed out in
PR26761, this is currently broken on PowerPC (and likely on ARM as
well). Currently, @llvm.eh.dwarf.cfa is lowered using:
ADD(FRAMEADDR, FRAME_TO_ARGS_OFFSET)
where FRAME_TO_ARGS_OFFSET defaults to the constant zero. On x86,
FRAME_TO_ARGS_OFFSET is lowered to 2*SlotSize. This setup, however,
does not work for PowerPC. Because of the way that the stack layout
works, the canonical frame address is not exactly (FRAMEADDR +
FRAME_TO_ARGS_OFFSET) on PowerPC (there is a lower save-area offset
as well), so it is not just a matter of implementing
FRAME_TO_ARGS_OFFSET for PowerPC (unless we redefine its semantics --
We can do that, since it is currently used only for
@llvm.eh.dwarf.cfa lowering, but the better to directly lower the CFA
construct itself (since it can be easily represented as a
fixed-offset FrameIndex)). Mips currently does this, but by using a
custom lowering for ADD that specifically recognizes the (FRAMEADDR,
FRAME_TO_ARGS_OFFSET) pattern.
This change introduces a ISD::EH_DWARF_CFA node, which by default
expands using the existing logic, but can be directly lowered by the
target. Mips is updated to use this method (which simplifies its
implementation, and I suspect makes it more robust), and updates
PowerPC to do the same.
Fixes PR26761.
Differential Revision: https://reviews.llvm.org/D24038
[DwarfDebug] Move MergeValues to .cpp, NFC
Pull in r257979 from upstream llvm trunk, by Keno Fischer:
[DwarfDebug] Don't merge DebugLocEntries if their pieces overlap
Summary:
Later in DWARF emission we check that DebugLocEntries have
non-overlapping pieces, so we should create any such entries
by merging here.
Fixes PR26163.
Reviewers: aprantl
Differential Revision: http://reviews.llvm.org/D16249
Again, these will be merged to the official release_38 branch soon, but
we need them ASAP.
be merged to the official release_38 branch soon, but we need it ASAP):
Stop increasing alignment of externally-visible globals on ELF
platforms.
With ELF, the alignment of a global variable in a shared library will
get copied into an executables linked against it, if the executable even
accesss the variable. So, it's not possible to implicitly increase
alignment based on access patterns, or you'll break existing binaries.
This happened to affect libc++'s std::cout symbol, for example. See
thread: http://thread.gmane.org/gmane.comp.compilers.clang.devel/45311
(This is a re-commit of r257719, without the bug reported in
PR26144. I've tweaked the code to not assert-fail in
enforceKnownAlignment when computeKnownBits doesn't recurse far enough
to find the underlying Alloca/GlobalObject value.)
Differential Revision: http://reviews.llvm.org/D16145
from upstream clang trunk, which sets the default debug tuning back to
gdb. The lldb debug tuning is not yet grokked completely by our ELF
manipulation tools.
