Commit Graph

250 Commits

Author SHA1 Message Date
Craig Topper ebf52e80c1 [X86] Correct the Defs, Uses, hasSideEffects, mayLoad, mayStore for XCHG and XADD instructions.
I don't think we emit any of these from codegen except for using XCHG16ar as 2 byte NOP.

llvm-svn: 330298
2018-04-18 22:07:53 +00:00
Keith Wyss 3d86823f3d [XRay] Typed event logging intrinsic
Summary:
Add an LLVM intrinsic for type discriminated event logging with XRay.
Similar to the existing intrinsic for custom events, but also accepts
a type tag argument to allow plugins to be aware of different types
and semantically interpret logged events they know about without
choking on those they don't.

Relies on a symbol defined in compiler-rt patch D43668. I may wait
to submit before I can see demo everything working together including
a still to come clang patch.

Reviewers: dberris, pelikan, eizan, rSerge, timshen

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D45633

llvm-svn: 330219
2018-04-17 21:30:29 +00:00
David Blaikie 6054e650ff Move TargetLoweringObjectFile from CodeGen to Target to fix layering
It's implemented in Target & include from other Target headers, so the
header should be in Target.

llvm-svn: 328392
2018-03-23 23:58:19 +00:00
Craig Topper f27016f3de [X86] Move the AC_EVEX_2_VEX AsmComments enum to X86InstrInfo.h from X86InstComments.h.
X86InstComments.h is used by tools that only have the MC layer. We shouldn't be importing a file from CodeGen into this.

X86InstrInfo.h isn't a great place, but I couldn't find a better one.

llvm-svn: 327202
2018-03-10 05:15:22 +00:00
Simon Pilgrim 90fd0622b6 [X86][MMX] Improve handling of 64-bit MMX constants
64-bit MMX constant generation usually ends up lowering into SSE instructions before being spilled/reloaded as a MMX type.

This patch bitcasts the constant to a double value to allow correct loading directly to the MMX register.

I've added MMX constant asm comment support to improve testing, it's better to always print the double values as hex constants as MMX is mainly an integer unit (and even with 3DNow! its just floats).

Differential Revision: https://reviews.llvm.org/D43616

llvm-svn: 326497
2018-03-01 22:22:31 +00:00
Chandler Carruth c58f2166ab Introduce the "retpoline" x86 mitigation technique for variant #2 of the speculative execution vulnerabilities disclosed today, specifically identified by CVE-2017-5715, "Branch Target Injection", and is one of the two halves to Spectre..
Summary:
First, we need to explain the core of the vulnerability. Note that this
is a very incomplete description, please see the Project Zero blog post
for details:
https://googleprojectzero.blogspot.com/2018/01/reading-privileged-memory-with-side.html

The basis for branch target injection is to direct speculative execution
of the processor to some "gadget" of executable code by poisoning the
prediction of indirect branches with the address of that gadget. The
gadget in turn contains an operation that provides a side channel for
reading data. Most commonly, this will look like a load of secret data
followed by a branch on the loaded value and then a load of some
predictable cache line. The attacker then uses timing of the processors
cache to determine which direction the branch took *in the speculative
execution*, and in turn what one bit of the loaded value was. Due to the
nature of these timing side channels and the branch predictor on Intel
processors, this allows an attacker to leak data only accessible to
a privileged domain (like the kernel) back into an unprivileged domain.

The goal is simple: avoid generating code which contains an indirect
branch that could have its prediction poisoned by an attacker. In many
cases, the compiler can simply use directed conditional branches and
a small search tree. LLVM already has support for lowering switches in
this way and the first step of this patch is to disable jump-table
lowering of switches and introduce a pass to rewrite explicit indirectbr
sequences into a switch over integers.

However, there is no fully general alternative to indirect calls. We
introduce a new construct we call a "retpoline" to implement indirect
calls in a non-speculatable way. It can be thought of loosely as
a trampoline for indirect calls which uses the RET instruction on x86.
Further, we arrange for a specific call->ret sequence which ensures the
processor predicts the return to go to a controlled, known location. The
retpoline then "smashes" the return address pushed onto the stack by the
call with the desired target of the original indirect call. The result
is a predicted return to the next instruction after a call (which can be
used to trap speculative execution within an infinite loop) and an
actual indirect branch to an arbitrary address.

On 64-bit x86 ABIs, this is especially easily done in the compiler by
using a guaranteed scratch register to pass the target into this device.
For 32-bit ABIs there isn't a guaranteed scratch register and so several
different retpoline variants are introduced to use a scratch register if
one is available in the calling convention and to otherwise use direct
stack push/pop sequences to pass the target address.

This "retpoline" mitigation is fully described in the following blog
post: https://support.google.com/faqs/answer/7625886

We also support a target feature that disables emission of the retpoline
thunk by the compiler to allow for custom thunks if users want them.
These are particularly useful in environments like kernels that
routinely do hot-patching on boot and want to hot-patch their thunk to
different code sequences. They can write this custom thunk and use
`-mretpoline-external-thunk` *in addition* to `-mretpoline`. In this
case, on x86-64 thu thunk names must be:
```
  __llvm_external_retpoline_r11
```
or on 32-bit:
```
  __llvm_external_retpoline_eax
  __llvm_external_retpoline_ecx
  __llvm_external_retpoline_edx
  __llvm_external_retpoline_push
```
And the target of the retpoline is passed in the named register, or in
the case of the `push` suffix on the top of the stack via a `pushl`
instruction.

There is one other important source of indirect branches in x86 ELF
binaries: the PLT. These patches also include support for LLD to
generate PLT entries that perform a retpoline-style indirection.

The only other indirect branches remaining that we are aware of are from
precompiled runtimes (such as crt0.o and similar). The ones we have
found are not really attackable, and so we have not focused on them
here, but eventually these runtimes should also be replicated for
retpoline-ed configurations for completeness.

For kernels or other freestanding or fully static executables, the
compiler switch `-mretpoline` is sufficient to fully mitigate this
particular attack. For dynamic executables, you must compile *all*
libraries with `-mretpoline` and additionally link the dynamic
executable and all shared libraries with LLD and pass `-z retpolineplt`
(or use similar functionality from some other linker). We strongly
recommend also using `-z now` as non-lazy binding allows the
retpoline-mitigated PLT to be substantially smaller.

When manually apply similar transformations to `-mretpoline` to the
Linux kernel we observed very small performance hits to applications
running typical workloads, and relatively minor hits (approximately 2%)
even for extremely syscall-heavy applications. This is largely due to
the small number of indirect branches that occur in performance
sensitive paths of the kernel.

When using these patches on statically linked applications, especially
C++ applications, you should expect to see a much more dramatic
performance hit. For microbenchmarks that are switch, indirect-, or
virtual-call heavy we have seen overheads ranging from 10% to 50%.

However, real-world workloads exhibit substantially lower performance
impact. Notably, techniques such as PGO and ThinLTO dramatically reduce
the impact of hot indirect calls (by speculatively promoting them to
direct calls) and allow optimized search trees to be used to lower
switches. If you need to deploy these techniques in C++ applications, we
*strongly* recommend that you ensure all hot call targets are statically
linked (avoiding PLT indirection) and use both PGO and ThinLTO. Well
tuned servers using all of these techniques saw 5% - 10% overhead from
the use of retpoline.

We will add detailed documentation covering these components in
subsequent patches, but wanted to make the core functionality available
as soon as possible. Happy for more code review, but we'd really like to
get these patches landed and backported ASAP for obvious reasons. We're
planning to backport this to both 6.0 and 5.0 release streams and get
a 5.0 release with just this cherry picked ASAP for distros and vendors.

This patch is the work of a number of people over the past month: Eric, Reid,
Rui, and myself. I'm mailing it out as a single commit due to the time
sensitive nature of landing this and the need to backport it. Huge thanks to
everyone who helped out here, and everyone at Intel who helped out in
discussions about how to craft this. Also, credit goes to Paul Turner (at
Google, but not an LLVM contributor) for much of the underlying retpoline
design.

Reviewers: echristo, rnk, ruiu, craig.topper, DavidKreitzer

Subscribers: sanjoy, emaste, mcrosier, mgorny, mehdi_amini, hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D41723

llvm-svn: 323155
2018-01-22 22:05:25 +00:00
Andrew V. Tischenko 22f0742dda Fix for bug PR35549 - Repeated schedule comments.
Differential Revision: https://reviews.llvm.org/D40960

llvm-svn: 320837
2017-12-15 18:13:05 +00:00
Michael Zolotukhin ad24af7f58 Remove redundant includes from lib/Target/X86.
llvm-svn: 320636
2017-12-13 21:31:19 +00:00
Francis Visoiu Mistrih 9d7bb0cb40 [CodeGen] Print register names in lowercase in both MIR and debug output
As part of the unification of the debug format and the MIR format,
always print registers as lowercase.

* Only debug printing is affected. It now follows MIR.

Differential Revision: https://reviews.llvm.org/D40417

llvm-svn: 319187
2017-11-28 17:15:09 +00:00
David Blaikie b3bde2ea50 Fix a bunch more layering of CodeGen headers that are in Target
All these headers already depend on CodeGen headers so moving them into
CodeGen fixes the layering (since CodeGen depends on Target, not the
other way around).

llvm-svn: 318490
2017-11-17 01:07:10 +00:00
Reid Kleckner 9cdd4df81a [codeview] Implement FPO data assembler directives
Summary:
This adds a set of new directives that describe 32-bit x86 prologues.
The directives are limited and do not expose the full complexity of
codeview FPO data. They are merely a convenience for the compiler to
generate more readable assembly so we don't need to generate tons of
labels in CodeGen. If our prologue emission changes in the future, we
can change the set of available directives to suit our needs. These are
modelled after the .seh_ directives, which use a different format that
interacts with exception handling.

The directives are:
  .cv_fpo_proc _foo
  .cv_fpo_pushreg ebp/ebx/etc
  .cv_fpo_setframe ebp/esi/etc
  .cv_fpo_stackalloc 200
  .cv_fpo_endprologue
  .cv_fpo_endproc
  .cv_fpo_data _foo

I tried to follow the implementation of ARM EHABI CFI directives by
sinking most directives out of MCStreamer and into X86TargetStreamer.
This helps avoid polluting non-X86 code with WinCOFF specific logic.

I used cdb to confirm that this can show locals in parent CSRs in a few
cases, most importantly the one where we use ESI as a frame pointer,
i.e. the one in http://crbug.com/756153#c28

Once we have cdb integration in debuginfo-tests, we can add integration
tests there.

Reviewers: majnemer, hans

Subscribers: aemerson, mgorny, kristof.beyls, llvm-commits, hiraditya

Differential Revision: https://reviews.llvm.org/D38776

llvm-svn: 315513
2017-10-11 21:24:33 +00:00
Craig Topper c16a472966 Revert r314249 "Recommit r314151 "[X86] Make all the NOREX CodeGenOnly instructions into postRA pseudos like the NOREX version of TEST."""
This caused PR34751

llvm-svn: 314339
2017-09-27 20:34:17 +00:00
Craig Topper 7f0eeb428b Recommit r314151 "[X86] Make all the NOREX CodeGenOnly instructions into postRA pseudos like the NOREX version of TEST.""
The late MOV8rr_NOREX that caused the crash has been removed.

llvm-svn: 314249
2017-09-26 21:35:09 +00:00
Benjamin Kramer 4b2113a303 Revert "[X86] Make all the NOREX CodeGenOnly instructions into postRA pseudos like the NOREX version of TEST."
Makes llc crash. This reverts commit r314151.

llvm-svn: 314199
2017-09-26 10:25:27 +00:00
Craig Topper d830f276c1 [X86] Make all the NOREX CodeGenOnly instructions into postRA pseudos like the NOREX version of TEST.
llvm-svn: 314151
2017-09-25 21:14:55 +00:00
Dean Michael Berris ebc1659016 [XRay][CodeGen] Use PIC-friendly code in XRay sleds and remove synthetic references in .text
Summary:
This is a re-roll of D36615 which uses PLT relocations in the back-end
to the call to __xray_CustomEvent() when building in -fPIC and
-fxray-instrument mode.

Reviewers: pcc, djasper, bkramer

Subscribers: sdardis, javed.absar, llvm-commits

Differential Revision: https://reviews.llvm.org/D37373

llvm-svn: 312466
2017-09-04 05:34:58 +00:00
Daniel Jasper c0a976d417 Revert r311525: "[XRay][CodeGen] Use PIC-friendly code in XRay sleds; remove synthetic references in .text"
Breaks builds internally. Will forward repo instructions to author.

llvm-svn: 312243
2017-08-31 15:17:17 +00:00
Dean Michael Berris 0884b73220 [XRay][CodeGen] Use PIC-friendly code in XRay sleds; remove synthetic references in .text
Summary:
This change achieves two things:

  - Redefine the Custom Event handling instrumentation points emitted by
    the compiler to not require dynamic relocation of references to the
    __xray_CustomEvent trampoline.

  - Remove the synthetic reference we emit at the end of a function that
    we used to keep auxiliary sections alive in favour of SHF_LINK_ORDER
    associated with the section where the function is defined.

To achieve the custom event handling change, we've had to introduce the
concept of sled versioning -- this will need to be supported by the
runtime to allow us to understand how to turn on/off the new version of
the custom event handling sleds. That change has to land first before we
change the way we write the sleds.

To remove the synthetic reference, we rely on a relatively new linker
feature that preserves the sections that are associated with each other.
This allows us to limit the effects on the .text section of ELF
binaries.

Because we're still using absolute references that are resolved at
runtime for the instrumentation map (and function index) maps, we mark
these sections write-able. In the future we can re-define the entries in
the map to use relative relocations instead that can be statically
determined by the linker. That change will be a bit more invasive so we
defer this for later.

Depends on D36816.

Reviewers: dblaikie, echristo, pcc

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D36615

llvm-svn: 311525
2017-08-23 04:49:41 +00:00
Craig Topper ad140cfb68 [X86] Add comment string for broadcast loads from the constant pool.
Summary:
When broadcasting from the constant pool its useful to print out the final vector similar to what we do for normal moves from the constant pool.

I changed only a couple tests that were broadcast focused. One of them had been previously hand tweaked after running the script so that it could check the constant pool declaration. But I think this patch makes that unnecessary now since we can check the comment instead.

Reviewers: spatel, RKSimon, zvi

Reviewed By: spatel

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D34923

llvm-svn: 307062
2017-07-04 05:46:11 +00:00
Hiroshi Inoue bb703e8960 fix trivial typos; NFC
suport -> support

llvm-svn: 306968
2017-07-02 03:24:54 +00:00
Zachary Turner 264b5d9e88 Move Object format code to lib/BinaryFormat.
This creates a new library called BinaryFormat that has all of
the headers from llvm/Support containing structure and layout
definitions for various types of binary formats like dwarf, coff,
elf, etc as well as the code for identifying a file from its
magic.

Differential Revision: https://reviews.llvm.org/D33843

llvm-svn: 304864
2017-06-07 03:48:56 +00:00
Chandler Carruth 6bda14b313 Sort the remaining #include lines in include/... and lib/....
I did this a long time ago with a janky python script, but now
clang-format has built-in support for this. I fed clang-format every
line with a #include and let it re-sort things according to the precise
LLVM rules for include ordering baked into clang-format these days.

I've reverted a number of files where the results of sorting includes
isn't healthy. Either places where we have legacy code relying on
particular include ordering (where possible, I'll fix these separately)
or where we have particular formatting around #include lines that
I didn't want to disturb in this patch.

This patch is *entirely* mechanical. If you get merge conflicts or
anything, just ignore the changes in this patch and run clang-format
over your #include lines in the files.

Sorry for any noise here, but it is important to keep these things
stable. I was seeing an increasing number of patches with irrelevant
re-ordering of #include lines because clang-format was used. This patch
at least isolates that churn, makes it easy to skip when resolving
conflicts, and gets us to a clean baseline (again).

llvm-svn: 304787
2017-06-06 11:49:48 +00:00
Dean Michael Berris 9bcaed867a [XRay] Custom event logging intrinsic
This patch introduces an LLVM intrinsic and a target opcode for custom event
logging in XRay. Initially, its use case will be to allow users of XRay to log
some type of string ("poor man's printf"). The target opcode compiles to a noop
sled large enough to enable calling through to a runtime-determined relative
function call. At runtime, when X-Ray is enabled, the sled is replaced by
compiler-rt with a trampoline to the logic for creating the custom log entries.

Future patches will implement the compiler-rt parts and clang-side support for
emitting the IR corresponding to this intrinsic.

Reviewers: timshen, dberris

Subscribers: igorb, pelikan, rSerge, timshen, echristo, dberris, llvm-commits

Differential Revision: https://reviews.llvm.org/D27503

llvm-svn: 302405
2017-05-08 05:45:21 +00:00
Andrew V. Tischenko 75745d0c3e This patch closes PR#32216: Better testing of schedule model instruction latencies/throughputs.
The details are here: https://reviews.llvm.org/D30941

llvm-svn: 300311
2017-04-14 07:44:23 +00:00
Craig Topper 811756b4dc [X86][XOP] Reduce the size of a multiclass by moving more stuff to parameters instead of doing 128-bit and 256-bit simultaneously.
This requires some instructions to be renamed to move the Y earlier in the instruction name. The new names are more consistent with other instructions.

llvm-svn: 295579
2017-02-18 22:53:43 +00:00
Hans Wennborg a468601e0e [X86] Re-enable conditional tail calls and fix PR31257.
This reverts r294348, which removed support for conditional tail calls
due to the PR above. It fixes the PR by marking live registers as
implicitly used and defined by the now predicated tailcall. This is
similar to how IfConversion predicates instructions.

Differential Revision: https://reviews.llvm.org/D29856

llvm-svn: 295262
2017-02-16 00:04:05 +00:00
Hans Wennborg 819e3e02a9 [X86] Disable conditional tail calls (PR31257)
They are currently modelled incorrectly (as calls, which clobber
registers, confusing e.g. Machine Copy Propagation).

Reverting until we figure out the proper solution.

llvm-svn: 294348
2017-02-07 20:37:45 +00:00
Sanjoy Das 2f63cbcc0c [ImplicitNullCheck] Extend Implicit Null Check scope by using stores
Summary:
This change allows usage of store instruction for implicit null check.

Memory Aliasing Analisys is not used and change conservatively supposes
that any store and load may access the same memory. As a result
re-ordering of store-store, store-load and load-store is prohibited.

Patch by Serguei Katkov!

Reviewers: reames, sanjoy

Reviewed By: sanjoy

Subscribers: atrick, llvm-commits

Differential Revision: https://reviews.llvm.org/D29400

llvm-svn: 294338
2017-02-07 19:19:49 +00:00
Peter Collingbourne dc5e583687 X86: Produce @ABS8 symbol modifiers for absolute symbols in range [0,128).
Differential Revision: https://reviews.llvm.org/D28689

llvm-svn: 293844
2017-02-02 00:32:03 +00:00
Nirav Dave a7c041d147 [X86] Implement -mfentry
Summary: Insert calls to __fentry__ at function entry.

Reviewers: hfinkel, craig.topper

Subscribers: mgorny, llvm-commits

Differential Revision: https://reviews.llvm.org/D28000

llvm-svn: 293648
2017-01-31 17:00:27 +00:00
Matthias Braun 8c209aa877 Cleanup dump() functions.
We had various variants of defining dump() functions in LLVM. Normalize
them (this should just consistently implement the things discussed in
http://lists.llvm.org/pipermail/cfe-dev/2014-January/034323.html

For reference:
- Public headers should just declare the dump() method but not use
  LLVM_DUMP_METHOD or #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
- The definition of a dump method should look like this:
  #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
  LLVM_DUMP_METHOD void MyClass::dump() {
    // print stuff to dbgs()...
  }
  #endif

llvm-svn: 293359
2017-01-28 02:02:38 +00:00
Dean Michael Berris f7e7b938ea [XRay] Merge instrumentation point table emission code into AsmPrinter.
Summary:
No need to have this per-architecture.  While there, unify 32-bit ARM's
behaviour with what changed elsewhere and start function names lowercase
as per the coding standards.  Individual entry emission code goes to the
entry's own class.

Fully tested on amd64, cross-builds on both ARMs and PowerPC.

Reviewers: dberris

Subscribers: aemerson, llvm-commits

Differential Revision: https://reviews.llvm.org/D28209

llvm-svn: 290858
2017-01-03 04:30:21 +00:00
Gadi Haber 19c4fc5e62 This is a large patch for X86 AVX-512 of an optimization for reducing code size by encoding EVEX AVX-512 instructions using the shorter VEX encoding when possible.
There are cases of AVX-512 instructions that have two possible encodings. This is the case with instructions that use vector registers with low indexes of 0 - 15 and do not use the zmm registers or the mask k registers.
The EVEX encoding prefix requires 4 bytes whereas the VEX prefix can take only up to 3 bytes. Consequently, using the VEX encoding for these instructions results in a code size reduction of ~2 bytes even though it is compiled with the AVX-512 features enabled.

Reviewers: Craig Topper, Zvi Rackoover, Elena Demikhovsky 
Differential Revision: https://reviews.llvm.org/D27901

llvm-svn: 290663
2016-12-28 10:12:48 +00:00
Craig Topper d4091494d3 [X86] Invert an 'if' and early out to fix a weird indentation. NFCI
llvm-svn: 287909
2016-11-25 02:29:24 +00:00
Craig Topper a46936185a [X86] Size a SmallVector to the worst case mask size for a 512-bit shuffle. NFCI
llvm-svn: 287908
2016-11-25 02:29:21 +00:00
Kuba Mracek 06995e866b [xray] Add XRay support for Mach-O in CodeGen
Currently, XRay only supports emitting the XRay table (xray_instr_map) on ELF binaries. Let's add Mach-O support.

Differential Revision: https://reviews.llvm.org/D26983

llvm-svn: 287734
2016-11-23 02:07:04 +00:00
Simon Pilgrim ca3072ac58 [X86][AVX512] Add mask/maskz writemask support to constant pool shuffle decode commentx
llvm-svn: 284488
2016-10-18 15:45:37 +00:00
Craig Topper 175a415e78 [AVX-512] Add support for decoding shuffle mask from constant pool for masked VPERMILPS/PD.
llvm-svn: 284450
2016-10-18 03:36:52 +00:00
Craig Topper 1f5178ff9f [X86] Fix shuffle decoding assertions to print the right number of required operands. Update the checks themselves to be >= to the same number instead of > one less than the required number.
llvm-svn: 284365
2016-10-17 06:41:18 +00:00
Hans Wennborg c4b1d20ba2 Win64: Don't emit unwind info for "leaf" functions (PR30337)
According to MSDN (see the PR), functions which don't touch any callee-saved
registers (including %rsp) don't need any unwind info.

This patch makes LLVM not emit unwind info for such functions, to save
binary size.

Differential Revision: https://reviews.llvm.org/D24748

llvm-svn: 282185
2016-09-22 19:50:05 +00:00
Dean Michael Berris 4640154446 [XRay] ARM 32-bit no-Thumb support in LLVM
This is a port of XRay to ARM 32-bit, without Thumb support yet. The XRay instrumentation support is moving up to AsmPrinter.
This is one of 3 commits to different repositories of XRay ARM port. The other 2 are:

https://reviews.llvm.org/D23932 (Clang test)
https://reviews.llvm.org/D23933 (compiler-rt)

Differential Revision: https://reviews.llvm.org/D23931

llvm-svn: 281878
2016-09-19 00:54:35 +00:00
Eric Christopher a808f2981e Remove unused function getMang().
llvm-svn: 281707
2016-09-16 07:32:58 +00:00
Hans Wennborg 6ecf619be9 X86: Fold tail calls into conditional branches also for 64-bit (PR26302)
This extends the optimization in r280832 to also work for 64-bit. The only
quirk is that we can't do this for 64-bit Windows (yet).

Differential Revision: https://reviews.llvm.org/D24423

llvm-svn: 281113
2016-09-09 22:37:27 +00:00
Hans Wennborg c39ef776fc Win64: Don't use REX prefix for direct tail calls
The REX prefix should be used on indirect jmps, but not direct ones.
For direct jumps, the unwinder looks at the offset to determine if
it's inside the current function.

Differential Revision: https://reviews.llvm.org/D24359

llvm-svn: 281003
2016-09-08 23:35:10 +00:00
Renato Golin 049f387112 Revert "[XRay] ARM 32-bit no-Thumb support in LLVM"
And associated commits, as they broke the Thumb bots.

This reverts commit r280935.
This reverts commit r280891.
This reverts commit r280888.

llvm-svn: 280967
2016-09-08 17:10:39 +00:00
Dean Michael Berris 17d94e279e [XRay] ARM 32-bit no-Thumb support in LLVM
This is a port of XRay to ARM 32-bit, without Thumb support yet. The XRay instrumentation support is moving up to AsmPrinter.
This is one of 3 commits to different repositories of XRay ARM port. The other 2 are:

1. https://reviews.llvm.org/D23932 (Clang test)
2. https://reviews.llvm.org/D23933 (compiler-rt)

Differential Revision: https://reviews.llvm.org/D23931

llvm-svn: 280888
2016-09-08 00:19:04 +00:00
Hans Wennborg 75e25f6812 X86: Fold tail calls into conditional branches where possible (PR26302)
When branching to a block that immediately tail calls, it is possible to fold
the call directly into the branch if the call is direct and there is no stack
adjustment, saving one byte.

Example:

  define void @f(i32 %x, i32 %y) {
  entry:
    %p = icmp eq i32 %x, %y
    br i1 %p, label %bb1, label %bb2
  bb1:
    tail call void @foo()
    ret void
  bb2:
    tail call void @bar()
    ret void
  }

before:

  f:
          movl    4(%esp), %eax
          cmpl    8(%esp), %eax
          jne     .LBB0_2
          jmp     foo
  .LBB0_2:
          jmp     bar

after:

  f:
          movl    4(%esp), %eax
          cmpl    8(%esp), %eax
          jne     bar
  .LBB0_1:
          jmp     foo

I don't expect any significant size savings from this (on a Clang bootstrap I
saw 288 bytes), but it does make the code a little tighter.

This patch only does 32-bit, but 64-bit would work similarly.

Differential Revision: https://reviews.llvm.org/D24108

llvm-svn: 280832
2016-09-07 17:52:14 +00:00
Dean Michael Berris e8ae5baaf7 [XRay] Detect and emit sleds for sibling/tail calls
Summary:
This change promotes the 'isTailCall(...)' member function to
TargetInstrInfo as a query interface for determining on a per-target
basis whether a given MachineInstr is a tail call instruction. We build
upon this in the XRay instrumentation pass to emit special sleds for
tail call optimisations, where we emit the correct kind of sled.

The tail call sleds look like a mix between the function entry and
function exit sleds. Form-wise, the sled comes before the "jmp"
instruction that implements the tail call similar to how we do it for
the function entry sled. Functionally, because we know this is a tail
call, it behaves much like an exit sled -- i.e. at runtime we may use
the exit trampolines instead of a different kind of trampoline.

A follow-up change to recognise these sleds will be done in compiler-rt,
so that we can start intercepting these initially as exits, but also
have the option to have different log entries to more accurately reflect
that this is actually a tail call.

Reviewers: echristo, rSerge, majnemer

Subscribers: mehdi_amini, dberris, llvm-commits

Differential Revision: https://reviews.llvm.org/D23986

llvm-svn: 280334
2016-09-01 01:29:13 +00:00
Philip Reames e83c4b30ca [stackmaps] More extraction of common code [NFCI]
General cleanup before starting to work on the part I want to actually change.

llvm-svn: 279586
2016-08-23 23:33:29 +00:00
Dean Michael Berris 1dd1ca9727 [XRay] Synthesize a reference to the xray_instr_map
Without the synthesized reference to a symbol in the xray_instr_map,
linker section garbage collection will helpfully remove the whole
xray_instr_map section from the final executable (or archive). This will
cause the runtime to not be able to identify the sleds and hot-patch the
calls/jumps into the runtime trampolines.

This change adds a reference from the text section at the end of the
function to keep around the associated xray_instr_map section as well.

We also make sure that we catch this reference in the test.

Reviewers: chandlerc, echristo, majnemer, mehdi_amini

Subscribers: mehdi_amini, llvm-commits, dberris

Differential Revision: https://reviews.llvm.org/D23398

llvm-svn: 279204
2016-08-19 04:44:30 +00:00