20426 Commits

Author SHA1 Message Date
Gerolf Hoflehner
69bf036617 [DAGCombiner] Follow coding convention for function name (NFC)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267745 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-27 17:27:16 +00:00
Nico Weber
f519b2d36d Revert r267649, it caused PR27539.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267723 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-27 15:16:54 +00:00
Cong Hou
283390a068 Detects the SAD pattern on X86 so that much better code will be emitted once the pattern is matched.
Differential revision: http://reviews.llvm.org/D14840



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267649 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-27 01:29:18 +00:00
Quentin Colombet
7ec26d4fef [MachineInstrBundle] Actually set the PartialDeadDef flag only when the register
is defined!

The users were checking the proper thing (Defined + PartialDeadDef), but the
information may have been wrong for other use cases, so fix that.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267641 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-27 00:16:29 +00:00
Quentin Colombet
1b369e43d3 [MachineBasicBlock] Take advantage of the partially dead information.
Thanks to that information we wouldn't lie on a register being live whereas it
is not.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267622 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-26 23:14:29 +00:00
Quentin Colombet
b62e24784c [MachineInstrBundle] Improvement the recognition of dead definitions.
Now, it is possible to know that partial definitions are dead definitions and
recognize that clobbered registers are also dead.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267621 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-26 23:14:24 +00:00
Ahmed Bougacha
fb52dfa04d [CodeGen] Add getBuildVector and getSplatBuildVector helpers. NFCI.
Differential Revision: http://reviews.llvm.org/D17176

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267606 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-26 21:15:30 +00:00
Krzysztof Parzyszek
87d4b8c4a1 [Tail duplication] Handle source registers with subregisters
When a block is tail-duplicated, the PHI nodes from that block are
replaced with appropriate COPY instructions. When those PHI nodes
contained use operands with subregisters, the subregisters were
dropped from the COPY instructions, resulting in incorrect code.

Keep track of the subregister information and use this information
when remapping instructions from the duplicated block.

Differential Revision: http://reviews.llvm.org/D19337


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267583 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-26 18:36:34 +00:00
Sanjay Patel
6f5aa79cda [CodeGenPrepare] use branch weight metadata to decide if a select should be turned into a branch
This is part of solving PR27344:
https://llvm.org/bugs/show_bug.cgi?id=27344

CGP should undo the SimplifyCFG transform for the same reason that earlier patches have used this
same mechanism: it's possible that passes between SimplifyCFG and CGP may be able to optimize the
IR further with a select in place.

For the TLI hook default, >99% taken or not taken is chosen as the default threshold for a highly
predictable branch. Even the most limited HW branch predictors will be correct on this branch almost
all the time, so even a massive mispredict penalty perf loss would be overcome by the win from all
the times the branch was predicted correctly.

As a follow-up, we could make the default target hook less conservative by using the SchedMachineModel's
MispredictPenalty. Or we could just let targets override the default by implementing the hook with that
and other target-specific options. Note that trying to statically determine mispredict rates for 
close-to-balanced profile weight data is generally impossible if the HW is sufficiently advanced. Ie, 
50/50 taken/not-taken might still be 100% predictable.

Finally, note that this patch as-is will not solve PR27344 because the current __builtin_unpredictable()
branch weight default values are 4 and 64. A proposal to change that is in D19435.

Differential Revision: http://reviews.llvm.org/D19488



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267572 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-26 17:11:17 +00:00
Sanjay Patel
e59120290f [CodeGenPrepare] don't convert an unpredictable select into control flow
Suggested in the review of D19488:
http://reviews.llvm.org/D19488



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267504 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-26 00:47:39 +00:00
Marcin Koscielnicki
e7311dc60e [PR27390] [CodeGen] Reject indexed loads in CombinerDAG.
visitAND, when folding and (load) forgets to check which output of
an indexed load is involved, happily folding the updated address
output on the following testcase:

target datalayout = "e-m:e-i64:64-n32:64"
target triple = "powerpc64le-unknown-linux-gnu"

%typ = type { i32, i32 }

define signext i32 @_Z8access_pP1Tc(%typ* %p, i8 zeroext %type) {
  %b = getelementptr inbounds %typ, %typ* %p, i64 0, i32 1
  %1 = load i32, i32* %b, align 4
  %2 = ptrtoint i32* %b to i64
  %3 = and i64 %2, -35184372088833
  %4 = inttoptr i64 %3 to i32*
  %_msld = load i32, i32* %4, align 4
  %zzz = add i32 %1,  %_msld
  ret i32 %zzz
}

Fix this by checking ResNo.

I've found a few more places that currently neglect to check for
indexed load, and tightened them up as well, but I don't have test
cases for them.  In fact, they might not be triggerable at all,
at least with current targets.  Still, better safe than sorry.

Differential Revision: http://reviews.llvm.org/D19202

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267420 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-25 15:43:44 +00:00
David Majnemer
e7edf2d8d2 [WinEH] Update SplitAnalysis::computeLastSplitPoint to cope with multiple EH successors
We didn't have logic to correctly handle CFGs where there was more than
one EH-pad successor (these are novel with WinEH).
There were situations where a register was live in one exceptional
successor but not another but the code as written would only consider
the first exceptional successor it found.

This resulted in split points which were insufficiently early if an
invoke was present.

This fixes PR27501.

N.B.  This removes getLandingPadSuccessor.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267412 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-25 14:31:32 +00:00
Gerolf Hoflehner
3f71db1efb [MachineCombiner] Support for floating-point FMA on ARM64 (re-commit r267098)
The original patch caused crashes because it could derefence a null pointer
for SelectionDAGTargetInfo for targets that do not define it.

Evaluates fmul+fadd -> fmadd combines and similar code sequences in the
machine combiner. It adds support for float and double similar to the existing
integer implementation. The key features are:

- DAGCombiner checks whether it should combine greedily or let the machine
combiner do the evaluation. This is only supported on ARM64.
- It gives preference to throughput over latency: the heuristic used is
to combine always in loops. The targets decides whether the machine
combiner should optimize for throughput or latency.
- Supports for fmadd, f(n)msub, fmla, fmls patterns
- On by default at O3 ffast-math



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267328 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-24 05:14:01 +00:00
Craig Topper
c0f92c94ab [CodeGen] Teach DAG combine to fold select_cc seteq X, 0, sizeof(X), ctlz_zero_undef(X) -> ctlz(X). InstCombine already does this for IR and X86 pattern matches this during isel.
A follow up commit will remove the X86 patterns to allow this to be tested.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267325 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-24 04:38:32 +00:00
Duncan P. N. Exon Smith
de7484036b DebugInfo: Remove MDString-based type references
Eliminate DITypeIdentifierMap and make DITypeRef a thin wrapper around
DIType*.  It is no longer legal to refer to a DICompositeType by its
'identifier:', and DIBuilder no longer retains all types with an
'identifier:' automatically.

Aside from the bitcode upgrade, this is mainly removing logic to resolve
an MDString-based reference to an actualy DIType.  The commits leading
up to this have made the implicit type map in DICompileUnit's
'retainedTypes:' field superfluous.

This does not remove DITypeRef, DIScopeRef, DINodeRef, and
DITypeRefArray, or stop using them in DI-related metadata.  Although as
of this commit they aren't serving a useful purpose, there are patchces
under review to reuse them for CodeView support.

The tests in LLVM were updated with deref-typerefs.sh, which is attached
to the thread "[RFC] Lazy-loading of debug info metadata":

  http://lists.llvm.org/pipermail/llvm-dev/2016-April/098318.html

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267296 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-23 21:08:00 +00:00
Sanjay Patel
7ceecf02a1 replace duplicated static functions for profile metadata access with BranchInst member function; NFCI
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267295 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-23 20:01:22 +00:00
Craig Topper
1886c8e29a [CodeGen] When promoting CTTZ operations to larger type, don't insert a select to detect if the input is zero to return the original size instead of the extended size. Instead just set the first bit in the zero extended part.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267280 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-23 05:20:47 +00:00
Andrew Kaylor
1e455c5cfb Re-commit optimization bisect support (r267022) without new pass manager support.
The original commit was reverted because of a buildbot problem with LazyCallGraph::SCC handling (not related to the OptBisect handling).

Differential Revision: http://reviews.llvm.org/D19172



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267231 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-22 22:06:11 +00:00
Peter Collingbourne
74eabdd998 Introduce llvm.load.relative intrinsic.
This intrinsic takes two arguments, ``%ptr`` and ``%offset``. It loads
a 32-bit value from the address ``%ptr + %offset``, adds ``%ptr`` to that
value and returns it. The constant folder specifically recognizes the form of
this intrinsic and the constant initializers it may load from; if a loaded
constant initializer is known to have the form ``i32 trunc(x - %ptr)``,
the intrinsic call is folded to ``x``.

LLVM provides that the calculation of such a constant initializer will
not overflow at link time under the medium code model if ``x`` is an
``unnamed_addr`` function. However, it does not provide this guarantee for
a constant initializer folded into a function body. This intrinsic can be
used to avoid the possibility of overflows when loading from such a constant.

Differential Revision: http://reviews.llvm.org/D18367

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267223 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-22 21:18:02 +00:00
Matt Arsenault
6217a62bc0 TLI: Only iterate over integer vector types
Instead of iterating over all vectors and skipping integers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267220 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-22 21:16:17 +00:00
Matt Arsenault
87d1190761 DAGCombiner: Relax alignment restriction when changing store type
If the target allows the alignment, this should be OK.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267217 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-22 21:01:41 +00:00
Peter Collingbourne
5011913625 CodeGen: Use PLT relocations for relative references to unnamed_addr functions.
The relative vtable ABI (PR26723) needs PLT relocations to refer to virtual
functions defined in other DSOs. The unnamed_addr attribute means that the
function's address is not significant, so we're allowed to substitute it
with the address of a PLT entry.

Also includes a bonus feature: addends for COFF image-relative references.

Differential Revision: http://reviews.llvm.org/D17938

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267211 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-22 20:40:10 +00:00
Matt Arsenault
625291533e DAGCombiner: Relax alignment restriction when changing load type
If the target allows the alignment, this should still be OK.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267209 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-22 20:21:36 +00:00
Matthias Braun
bc2216cab2 MachineScheduler: Move code to initialize a Candidate out of tryCandidate(); NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267191 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-22 19:10:15 +00:00
Matthias Braun
14c1739a3e MachineScheduler: Limit the size of the ready list.
Avoid quadratic complexity in unusually large basic blocks by limiting
the size of the ready lists.

Differential Revision: http://reviews.llvm.org/D19349

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267189 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-22 19:09:17 +00:00
Tom Stellard
bfad27b7b8 PostRAHazardRecocgnizer: Fix unused-private-field warning
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267160 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-22 15:11:08 +00:00
Tom Stellard
fbbc621bb4 CodeGen: Add a stand-alone hazard recognizer pass
Summary:
This new pass allows targets to use the hazard recognizer without having
to also run one of the schedulers.  This is useful when compiling with
optimizations disabled for targets that still need noop hazards
to be handled correctly.

Reviewers: hfinkel, atrick

Subscribers: arsenm, llvm-commits

Differential Revision: http://reviews.llvm.org/D18594

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267156 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-22 14:43:50 +00:00
Eric Liu
2321e6017b Fix -Wunused-variable in non-asserts build.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267128 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-22 09:50:31 +00:00
Daniel Sanders
c4f4f71fb7 Revert r267098 - [MachineCombiner] Support for floating-point FMA on ARM64
It introduced buildbot failures on clang-cmake-mips, clang-ppc64le-linux, among others.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267127 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-22 09:37:26 +00:00
Vedant Kumar
8866d94a61 Revert "Initial implementation of optimization bisect support."
This reverts commit r267022, due to an ASan failure:

  http://lab.llvm.org:8080/green/job/clang-stage2-cmake-RgSan_check/1549

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267115 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-22 06:51:37 +00:00
Nicolai Haehnle
3441786e27 AMDGPU/SI: add llvm.amdgcn.ps.live intrinsic
Summary:
This intrinsic returns true if the current thread belongs to a live pixel
and false if it belongs to a pixel that we are executing only for derivative
computation. It will be used by Mesa to implement gl_HelperInvocation.

Note that for pixels that are killed during the shader, this implementation
also returns true, but it doesn't matter because those pixels are always
disabled in the EXEC mask.

This unearthed a corner case in the instruction verifier, which complained
about a v_cndmask 0, 1, exec, exec<imp-use> instruction. That's stupid but
correct code, so make the verifier accept it as such.

Reviewers: arsenm, tstellarAMD

Subscribers: arsenm, llvm-commits

Differential Revision: http://reviews.llvm.org/D19191

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267102 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-22 04:04:08 +00:00
Gerolf Hoflehner
7c23aa2d8c [MachineCombiner] Support for floating-point FMA on ARM64
Evaluates fmul+fadd -> fmadd combines and similar code sequences in the
machine combiner. It adds support for float and double similar to the existing
integer implementation. The key features are:

- DAGCombiner checks whether it should combine greedily or let the machine
combiner do the evaluation. This is only supported on ARM64.
- It gives preference to throughput over latency: the heuristic used is
to combine always in loops. The targets decides whether the machine
combiner should optimize for throughput or latency.
- Supports for fmadd, f(n)msub, fmla, fmls patterns
- On by default at O3 ffast-math



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267098 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-22 02:15:19 +00:00
David Blaikie
259641db60 Fix more -Wunused-variable in non-asserts build.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267077 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-21 23:24:09 +00:00
David Blaikie
12098d3b4a Fix some -Wunused-variable warnings in non-asserts builds.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267073 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-21 22:53:33 +00:00
Derek Schuff
4913b3f2cf Improve error message reporting for MachineFunctionProperties
When printing the properties required by a pass, only print the
properties that are set, and not those that are clear (only properties
that are set are verified, clear properties are "don't-care").

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267070 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-21 22:19:24 +00:00
Quentin Colombet
f2cd15729a [MachineBasicBlock] Make the pass argument truly mandatory when
splitting edges.

MachineBasicBlock::SplitCriticalEdges will crash if a nullptr would have
been passed for the Pass argument. Do not allow that by turning this
argument into a reference.
The alternative would have been to make the Pass a truly optional
argument, but although this is easy to do, I was afraid users using it
like this would not be aware the livness information, dominator tree and
such would silently be broken.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267052 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-21 21:01:13 +00:00
Quentin Colombet
e4d168d65f [MachineBasicBlock] Refactor SplitCriticalEdge to expose a query API.
Introduce canSplitCriticalEdge, so that clients can now query whether or
not a critical edge can be split without actually needing to split it.
This may be useful when gathering information for cost models for
instance.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267046 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-21 20:46:27 +00:00
Quentin Colombet
0e156ed701 [RegisterBankInfo] Change the API for the verify methods.
Return bool instead of void so that it is natural to put the calls into
asserts.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267033 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-21 18:34:43 +00:00
Matt Arsenault
193934bd68 LegalizeDAG: Move unaligned load/store expansion to TLI
When custom lowered, this is not called if the store is custom
lowered. Move it to be a utility function so targets can
easily expand unaligned accesses when custom lowering.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267029 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-21 18:19:11 +00:00
Quentin Colombet
99b0ca43ae [RegisterBankInfo] Change the representation of the partial mappings.
Instead of holding a mask, hold two value: the start index and the
length of the mapping. This is a more compact representation, although
less powerful. That being said, arbitrary masks would not have worked
for the generic so do not allow them in the first place.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267025 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-21 18:09:34 +00:00
Matt Arsenault
88c88b2b19 DAGCombiner: Reduce 64-bit BFE pattern to pattern on 32-bit component
If the extracted bits are restricted to the upper half or lower half,
this can be truncated.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267024 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-21 18:03:06 +00:00
Andrew Kaylor
c852398cbc Initial implementation of optimization bisect support.
This patch implements a optimization bisect feature, which will allow optimizations to be selectively disabled at compile time in order to track down test failures that are caused by incorrect optimizations.

The bisection is enabled using a new command line option (-opt-bisect-limit).  Individual passes that may be skipped call the OptBisect object (via an LLVMContext) to see if they should be skipped based on the bisect limit.  A finer level of control (disabling individual transformations) can be managed through an addition OptBisect method, but this is not yet used.

The skip checking in this implementation is based on (and replaces) the skipOptnoneFunction check.  Where that check was being called, a new call has been inserted in its place which checks the bisect limit and the optnone attribute.  A new function call has been added for module and SCC passes that behaves in a similar way.

Differential Revision: http://reviews.llvm.org/D19172



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267022 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-21 17:58:54 +00:00
Amjad Aboud
1268621b54 Fixed Dwarf debug info emission to skip DILexicalBlockFile entries.
Before this fix, DILexicalBlockFile entries were skipped only in some cases and were not in other cases.

Differential Revision: http://reviews.llvm.org/D18724


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@267004 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-21 16:58:49 +00:00
Craig Topper
3655b0c31f [SelectionDAG] Teach LegalizeVectorOps to directly Expand CTTZ_ZERO_UNDEF/CTLZ_ZERO_UNDEF to CTTZ/CTLZ directly if those ops are Legal/Custom instead of deferring it to LegalizeOps.
This is needed to support CTTZ/CTLZ Custom correctly since LegalizeOps would be too late to do the custom lowering.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266951 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-21 04:43:57 +00:00
Matthias Braun
d396215071 MachineSched: Cleanup; NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266946 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-21 01:54:13 +00:00
Mehdi Amini
7ecb5827ca ScoreboardHazardRecognizer: unbreak TSAN by moving a static mutated variable to a member
From: Mehdi Amini <mehdi.amini@apple.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266837 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-20 00:21:24 +00:00
Tim Shen
ac94d4bd34 [PPC, SSP] Support PowerPC Linux stack protection.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266809 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-19 20:14:52 +00:00
Tim Shen
e7221e673c [SSP, 2/2] Create llvm.stackguard() intrinsic and lower it to LOAD_STACK_GUARD
With this change, ideally IR pass can always generate llvm.stackguard
call to get the stack guard; but for now there are still IR form stack
guard customizations around (see getIRStackGuard()). Future SSP
customization should go through LOAD_STACK_GUARD.

There is a behavior change: stack guard values are not CSEed anymore,
since we should never reuse the value in case that it has been spilled (and
corrupted). See ssp-guard-spill.ll. This also cause the change of stack
size and codegen in X86 and AArch64 test cases.

Ideally we'd like to know if the guard created in llvm.stackprotector() gets
spilled or not. If the value is spilled, discard the value and reload
stack guard; otherwise reuse the value. This can be done by teaching
register allocator to know how to rematerialize LOAD_STACK_GUARD and
force a rematerialization (which seems hard), or check for spilling in
expandPostRAPseudo. It only makes sense when the stack guard is a global
variable, which requires more instructions to load. Anyway, this seems to go out
of the scope of the current patch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266806 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-19 19:40:37 +00:00
Sanjoy Das
a1ff4a6198 Add a description for the PatchableFunction pass; NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266721 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-19 06:25:02 +00:00
Sanjoy Das
151328540e Introduce a "patchable-function" function attribute
Summary:
The `"patchable-function"` attribute can be used by an LLVM client to
influence LLVM's code generation in ways that makes the generated code
easily patchable at runtime (for instance, to redirect control).
Right now only one patchability scheme is supported,
`"prologue-short-redirect"`, but this can be expanded in the future.

Reviewers: joker.eph, rnk, echristo, dberris

Subscribers: joker.eph, echristo, mcrosier, llvm-commits

Differential Revision: http://reviews.llvm.org/D19046

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266715 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-19 05:24:47 +00:00