Key Locker provides a mechanism to encrypt and decrypt data with an AES key without having access
to the raw key value by converting AES keys into “handles”. These handles can be used to perform the
same encryption and decryption operations as the original AES keys, but they only work on the current
system and only until they are revoked. If software revokes Key Locker handles (e.g., on a reboot),
then any previous handles can no longer be used.
Reviewed By: craig.topper
Differential Revision: https://reviews.llvm.org/D88398
Support -march=sapphirerapids for x86.
Compare with Icelake Server, it includes 14 more new features. They are
amxtile, amxint8, amxbf16, avx512bf16, avx512vp2intersect, cldemote,
enqcmd, movdir64b, movdiri, ptwrite, serialize, shstk, tsxldtrk, waitpkg.
Reviewed By: craig.topper
Differential Revision: https://reviews.llvm.org/D86503
This is preparation for making clang default to -mtune=generic when no -march is specified. This will allow the default tuning to be "generic" even though our default march is "pentium4" or "x86-64".
To avoid llc lit test regressions, if no mcpu is specified, I've defaulted tune to use i586 to match the old tuning settings of no CPU. Some tests explicitly used -mcpu=generic which I've removed so they instead get this default of architecture features from generic and tune from i586.
I updated one llvm-mca test to check a different CPU since generic has a scheduler model now
Differential Revision: https://reviews.llvm.org/D86312
This patch implements initial backend support for a -mtune CPU controlled by a "tune-cpu" function attribute. If the attribute is not present X86 will use the resolved CPU from target-cpu attribute or command line.
This patch adds MC layer support a tune CPU. Each CPU now has two sets of features stored in their GenSubtargetInfo.inc tables . These features lists are passed separately to the Processor and ProcessorModel classes in tablegen. The tune list defaults to an empty list to avoid changes to non-X86. This annoyingly increases the size of static tables on all target as we now store 24 more bytes per CPU. I haven't quantified the overall impact, but I can if we're concerned.
One new test is added to X86 to show a few tuning features with mismatched tune-cpu and target-cpu/target-feature attributes to demonstrate independent control. Another new test is added to demonstrate that the scheduler model follows the tune CPU.
I have not added a -mtune to llc/opt or MC layer command line yet. With no attributes we'll just use the -mcpu for both. MC layer tools will always follow the normal CPU for tuning.
Differential Revision: https://reviews.llvm.org/D85165
After the recent change to the tuning settings for pentium4 to improve our default 32-bit behavior, I've decided to see about implementing -mtune support. This way we could have a default architecture CPU of "pentium4" or "x86-64" and a default tuning cpu of "generic". And we could change our "pentium4" tuning settings back to what they were before.
As a step to supporting this, this patch separates all of the features lists for the CPUs into 2 lists. I'm using the Proc class and a new ProcModel class to concat the 2 lists before passing to the target independent ProcessorModel. Future work to truly support mtune would change ProcessorModel to take 2 lists separately. I've diffed the X86GenSubtargetInfo.inc file before and after this patch to ensure that the final feature list for the CPUs isn't changed.
Differential Revision: https://reviews.llvm.org/D84879
We already had CMPXCH8B feature on this CPU for the frontend so
this doesn't have much effect.
The FeatureSlowUAMem16 only matters if someone compiles with
-march=lakemont -msse which doesn't make sense, but is consistent
with all our pre-sse4.2 CPUs. Maybe the feature flag should be
FeatureFastUAMem16 and set on the newer CPUs instead.
As briefly discussed in IRC with @craig.topper,
the pass is disabled basically since it's original introduction (nov 2018)
due to known correctness issues (miscompilations),
and there hasn't been much work done to fix that.
While i won't promise that i will "fix" the pass,
i have looked at it previously, and i'm sure i won't try to fix it
if that requires actually fixing this existing code.
Reviewed By: craig.topper
Differential Revision: https://reviews.llvm.org/D84775
Feature64Bit is only used by a check in the X86Subtarget
constructor to ensure that the CPU selected supports 64-bit mode
when the triple is for 64-bit mode.
'generic' is the default CPU in llc and so needs to be able to
pass this check. Previously we did this by detecting the name and
adding the feature to the feature string. But there doesn't seem
to be any reason we can't just add the feature to the CPU directly.
We deprecated mpx feature in 10.0. I left this feature flag
in case someone still had IR files containing the feature
in a target-feature attribute. At the time I think I thought it
would fail the test if the feature couldn't be found. Further
review suggests that at worst it prints a message to
stderr about ignoring the feature.
SAHF/LAHF instructions are always available in 32-bit mode. Early
64-bit capable CPUs made the undefined opcodes in 64-bit mode. This
was changed on later CPUs.
We have a feature flag to control our usage of these instructions.
This feature flag is hooked up to a clang command line option
-msahf/-mno-sahf specifically to give control of the 64-bit mode
behavior.
In the backend X86Subtarget constructor we were explicitly forcing
+sahf into the feature flag string if we were not compiling for
64-bit mode. This was intended to make the predicates always allow
the instructions outside of 64-bit mode. Unfortunately, the way
it was placed into the string allowed -mno-sahf from clang to disable
SAHF instructions in 32-bit mode. This causes an assertion to fire
if you compile a floating point comparison with something like
"-march=pentium -mno-sahf" as our floating point comparison
handling on CPUs that don't support FCOMI/FUCOMI instructions
requires SAHF.
To fix this, this commit restricts the feature flag to only apply to
64-bit mode by ignoring the flag outside 64-bit mode in
X86Subtarget::hasLAHFSAHF(). This way we don't need to mess with
the feature string at all.
I meant to do this in D83913, but missed it while updating the
feature list.
Interestingly I think this is disabling the postRA scheduler. But
it does match our default 64-bit behavior.
Reviewed By: echristo
Differential Revision: https://reviews.llvm.org/D83996
Alternative to D83897. I believe the big change here is that I removed slow unaligned memory 16
Down side that it may adversely effect tuning if someone explicitly targets -march=pentium4 and expects pentium4 tuned code. Of course pentium4 is so old our default behavior with the previous settings may not have been the best either.
Reviewed By: echristo, RKSimon
Differential Revision: https://reviews.llvm.org/D83913
This patch creates a clang flag to enable SESES. This flag also ensures that
lvi-cfi is on when using seses via clang.
SESES should use lvi-cfi to mitigate returns and indirect branches.
The flag to enable the SESES functionality only without lvi-cfi is now
-x86-seses-enable-without-lvi-cfi to warn users part of the mitigation is not
enabled if they use this flag. This is useful in case folks want to see the
cost of SESES separate from the LVI-CFI.
Reviewed By: sconstab
Differential Revision: https://reviews.llvm.org/D79910
These features implicitly enabled XSAVE in the frontend, but not
the backend. Disabling XSAVE in the frontend disabled XSAVEOPT, but
not the other 2. Nothing happened in the backend.
The PREFETCHW instruction was originally part of the 3DNow. But
it was given its own CPUID bit on later CPUs just before 3DNow
was deprecated.
We were setting the -mprfchw flag if -m3dnow was passed or the CPU
supported 3dnow unless -mno-prfchw was passed. But -march=native
on a CPU without the PRFCHW CPUID bit set will pass -mno-prfchw.
So -march=k8 will behave differently than -march=native on a K8
for example.
So remove this implicit setting from the frontend and instead
enable the backend to use PREFETCHW if 3dnow OR prfchw is enabled.
Also enable PRFCHW flag on amdfam10/barcelona which seems to be
where this CPUID bit was introduced. That CPU also supported
3dnow.
The PREFETCHW instruction was originally part of the 3DNow. But
it was given its own CPUID bit on later CPUs just before 3DNow
was deprecated.
We were setting the -mprfchw flag if -m3dnow was passed or the CPU
supported 3dnow unless -mno-prfchw was passed. But -march=native
on a CPU without the PRFCHW CPUID bit set will pass -mno-prfchw.
So -march=k8 will behave differently than -march=native on a K8
for example.
So remove this implicit setting from the frontend and instead
enable the backend to use PREFETCHW if 3dnow OR prfchw is enabled.
Also enable PRFCHW flag on amdfam10/barcelona which seems to be
where this CPUID bit was introduced. That CPU also supported
3dnow.
Adds a new data structure, ImmutableGraph, and uses RDF to find LVI gadgets and add them to a MachineGadgetGraph.
More specifically, a new X86 machine pass finds Load Value Injection (LVI) gadgets consisting of a load from memory (i.e., SOURCE), and any operation that may transmit the value loaded from memory over a covert channel, or use the value loaded from memory to determine a branch/call target (i.e., SINK).
Also adds a new target feature to X86: +lvi-load-hardening
The feature can be added via the clang CLI using -mlvi-hardening.
Differential Revision: https://reviews.llvm.org/D75936
This is currently enabled for Intel big cores from Sandy Bridge onward, as well as Atom, Silvermont, and KNL, due to 64-bit division being so slow on these cores. AMD cores can do this in hardware (use 32-bit division based on input operand width), so it's not a win there. But since the majority of x86 CPUs benefit from this optimization, and since the potential upside is significantly greater than the downside, we should enable this for the generic x86-64 target.
Patch By: @atdt
Reviewed By: @craig.topper, @RKSimon
Differential Revision: https://reviews.llvm.org/D75567
Adds a new data structure, ImmutableGraph, and uses RDF to find LVI gadgets and add them to a MachineGadgetGraph.
More specifically, a new X86 machine pass finds Load Value Injection (LVI) gadgets consisting of a load from memory (i.e., SOURCE), and any operation that may transmit the value loaded from memory over a covert channel, or use the value loaded from memory to determine a branch/call target (i.e., SINK).
Also adds a new target feature to X86: +lvi-load-hardening
The feature can be added via the clang CLI using -mlvi-hardening.
Differential Revision: https://reviews.llvm.org/D75936
This pass replaces each indirect call/jump with a direct call to a thunk that looks like:
lfence
jmpq *%r11
This ensures that if the value in register %r11 was loaded from memory, then
the value in %r11 is (architecturally) correct prior to the jump.
Also adds a new target feature to X86: +lvi-cfi
("cfi" meaning control-flow integrity)
The feature can be added via clang CLI using -mlvi-cfi.
This is an alternate implementation to https://reviews.llvm.org/D75934 That merges the thunk insertion functionality with the existing X86 retpoline code.
Differential Revision: https://reviews.llvm.org/D76812
Back in D42616, we switched our default nop length from 15 to 10 bytes because some platforms have painful decode stalls when encountering multiple instruction prefixes. (10 byte long nops come from the fact that prefixes are used to pad after 8 bytes, and some platforms have issues w/more than two prefixes.)
Based on Agner's guides, it appears to be the case that modern Intel (SandyBridge and later) can decode an arbitrary number of prefixes without issue. Intel's guide only provides up to 9 bytes; I read that as providing a safe default for all their chips. Older chips and Atom series have serious decode stalls. I can't find a conclusive reference beyond those two.
Differential Revision: https://reviews.llvm.org/D75945
Lets us remove another SLM proc family flag usage.
This is NFC, but we should probably check whether atom/glm/knl? should be using this flag as well...
The patch gives out the details of the znver2 scheduler model.
There are few improvements with respect to execution units, latencies and
throughput when compared with znver1.
The tests that were present for znver1 for llvm-mca tool were replicated.
The latencies, execution units, timeline and throughput information are updated for znver2.
Reviewers: craig.topper, Simon Pilgrim
Differential Revision: https://reviews.llvm.org/D66088
-mvzeroupper will force the vzeroupper insertion pass to run on
CPUs that normally wouldn't. -mno-vzeroupper disables it on CPUs
where it normally runs.
To support this with the default feature handling in clang, we
need a vzeroupper feature flag in X86.td. Since this flag has
the opposite polarity of the fast-partial-ymm-or-zmm-write we
used to use to disable the pass, we now need to add this new
flag to every CPU except KNL/KNM and BTVER2 to keep identical
behavior.
Remove -fast-partial-ymm-or-zmm-write which is no longer used.
Differential Revision: https://reviews.llvm.org/D69786
PTEST and especially the MOVMSK instructions are slow on Knights Landing
or later. As a bonus, this patch increases instruction parallelism by
emitting:
KORTEST(PCMPNEQ(a, b), PCMPNEQ(c, d)) == 0
Instead of:
KORTEST(AND(PCMPEQ(a, b), PCMPEQ(c, d))) == ~0
https://reviews.llvm.org/D69157
Summary:
This allows enabling useaa on the command-line and will allow enabling the
feature on a per-CPU basis where benchmarking shows improvements.
This is modelled after the ARM/AArch64 target.
Reviewers: RKSimon, andreadb, craig.topper
Subscribers: javed.absar, kristof.beyls, hiraditya, ychen, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D67266
llvm-svn: 371989
AVX512 instructions can cause a frequency drop on these CPUs. This
can negate the performance gains from using wider vectors. Enabling
prefer-vector-width=256 will prevent generation of zmm registers
unless explicit 512 bit operations are used in the original source
code.
I believe gcc and icc both do something similar to this by default.
Differential Revision: https://reviews.llvm.org/D67259
llvm-svn: 371694
Summary:
Similar to the previous prefer-256-bit flag. We might want to
enable this by default some CPUs. This just starts the initial
work to implement and prove that it effects TTI's vector width.
Reviewers: RKSimon, echristo, spatel, atdt
Reviewed By: RKSimon
Subscribers: lebedev.ri, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D67311
llvm-svn: 371319
-Deprecate -mmpx and -mno-mpx command line options
-Remove CPUID detection of mpx for -march=native
-Remove MPX from all CPUs
-Remove MPX preprocessor define
I've left the "mpx" string in the backend so we don't fail on old IR, but its not connected to anything.
gcc has also deprecated these command line options. https://www.phoronix.com/scan.php?page=news_item&px=GCC-Patch-To-Drop-MPX
Differential Revision: https://reviews.llvm.org/D66669
llvm-svn: 370393
Support -march=tigerlake for x86.
Compare with Icelake Client, It include 4 more new features ,they are
avx512vp2intersect, movdiri, movdir64b, shstk.
Patch by Xiang Zhang (xiangzhangllvm)
Differential Revision: https://reviews.llvm.org/D65840
llvm-svn: 368543
This fixes znver1 so that it properly enables CMPXHG8B. We can
probably remove explicit CMPXCHG8B from CPUs that also have
CMPXCHG16B, but keeping this simple to allow cherry pick to 9.0.
Fixes PR42935.
llvm-svn: 368324
Summary:
Cleans X86.td's Barcelona entry to be more like the others,
by moving the features out of the `Proc<>`, thus potentially
making it possible to inherit from them.
Split off from D63628
Reviewers: craig.topper, RKSimon
Reviewed By: craig.topper
Subscribers: hiraditya, jfb, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D65791
llvm-svn: 368061
D61068 handled vector shifts, this patch does the same for scalars where there are similar number of pipes for shifts as bit ops - this is true almost entirely for AMD targets where the scalar ALUs are well balanced.
This combine avoids AND immediate mask which usually means we reduce encoding size.
Some tests show use of (slow, scaled) LEA instead of SHL in some cases, but thats due to particular shift immediates - shift+mask generate these just as easily.
Differential Revision: https://reviews.llvm.org/D61830
llvm-svn: 360684
Wang, Pengfei