Commit Graph

380 Commits

Author SHA1 Message Date
Matthias Braun
8ac056b9dd Enable MachineVerifier in debug mode for X86, ARM, AArch64, Mips.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224075 91177308-0d34-0410-b5e6-96231b3b80d8
2014-12-11 23:18:03 +00:00
Matthias Braun
5b17297b3d [CodeGen] Add print and verify pass after each MachineFunctionPass by default
Previously print+verify passes were added in a very unsystematic way, which is
annoying when debugging as you miss intermediate steps and allows bugs to stay
unnotice when no verification is performed.

To make this change practical I added the possibility to explicitely disable
verification. I used this option on all places where no verification was
performed previously (because alot of places actually don't pass the
MachineVerifier).
In the long term these problems should be fixed properly and verification
enabled after each pass. I'll enable some more verification in subsequent
commits.

This is the 2nd attempt at this after realizing that PassManager::add() may
actually delete the pass.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224059 91177308-0d34-0410-b5e6-96231b3b80d8
2014-12-11 21:26:47 +00:00
Rafael Espindola
428923cfe2 This reverts commit r224043 and r224042.
check-llvm was failing.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224045 91177308-0d34-0410-b5e6-96231b3b80d8
2014-12-11 20:03:57 +00:00
Matthias Braun
e9256e340b Enable machineverifier in debug mode for X86, ARM, AArch64, Mips
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224043 91177308-0d34-0410-b5e6-96231b3b80d8
2014-12-11 19:42:09 +00:00
Matthias Braun
71f56c4aac [CodeGen] Add print and verify pass after each MachineFunctionPass by default
Previously print+verify passes were added in a very unsystematic way, which is
annoying when debugging as you miss intermediate steps and allows bugs to stay
unnotice when no verification is performed.

To make this change practical I added the possibility to explicitely disable
verification. I used this option on all places where no verification was
performed previously (because alot of places actually don't pass the
MachineVerifier).
In the long term these problems should be fixed properly and verification
enabled after each pass. I'll enable some more verification in subsequent
commits.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224042 91177308-0d34-0410-b5e6-96231b3b80d8
2014-12-11 19:42:05 +00:00
Reid Kleckner
d12434058d Add out of line virtual destructors to all LLVMTargetMachine subclasses
These recently all grew a unique_ptr<TargetLoweringObjectFile> member in
r221878.  When anyone calls a virtual method of a class, clang-cl
requires all virtual methods to be semantically valid. This includes the
implicit virtual destructor, which triggers instantiation of the
unique_ptr destructor, which fails because the type being deleted is
incomplete.

This is just part of the ongoing saga of PR20337, which is affecting
Blink as well. Because the MSVC ABI doesn't have key functions, we end
up referencing the vtable and implicit destructor on any virtual call
through a class. We don't actually end up emitting the dtor, so it'd be
good if we could avoid this unneeded type completion work.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222480 91177308-0d34-0410-b5e6-96231b3b80d8
2014-11-20 23:37:18 +00:00
Aditya Nandakumar
847729d19a This patch changes the ownership of TLOF from TargetLoweringBase to TargetMachine so that different subtargets could share the TLOF effectively
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221878 91177308-0d34-0410-b5e6-96231b3b80d8
2014-11-13 09:26:31 +00:00
Eric Christopher
e6f32be8df Add subtarget caches to aarch64, arm, ppc, and x86.
These will make it easier to test further changes to the
code generation and optimization pipelines as those are
moved to subtargets initialized with target feature and
target cpu.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219106 91177308-0d34-0410-b5e6-96231b3b80d8
2014-10-06 06:45:36 +00:00
Robin Morisset
5c16c4e45a [X86] Use the generic AtomicExpandPass instead of X86AtomicExpandPass
This required a new hook called hasLoadLinkedStoreConditional to know whether
to expand atomics to LL/SC (ARM, AArch64, in a future patch Power) or to
CmpXchg (X86).

Apart from that, the new code in AtomicExpandPass is mostly moved from
X86AtomicExpandPass. The main result of this patch is to get rid of that
pass, which had lots of code duplicated with AtomicExpandPass.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217928 91177308-0d34-0410-b5e6-96231b3b80d8
2014-09-17 00:06:58 +00:00
Eric Christopher
d5dd8ce2a5 Reinstate "Nuke the old JIT."
Approved by Jim Grosbach, Lang Hames, Rafael Espindola.

This reinstates commits r215111, 215115, 215116, 215117, 215136.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216982 91177308-0d34-0410-b5e6-96231b3b80d8
2014-09-02 22:28:02 +00:00
Eric Christopher
d0ba0f6dd1 Move some X86 subtarget configuration onto the subtarget that's being
created.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215271 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-09 01:07:25 +00:00
Eric Christopher
aa5b9c0f6f Temporarily Revert "Nuke the old JIT." as it's not quite ready to
be deleted. This will be reapplied as soon as possible and before
the 3.6 branch date at any rate.

Approved by Jim Grosbach, Lang Hames, Rafael Espindola.

This reverts commits r215111, 215115, 215116, 215117, 215136.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215154 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-07 22:02:54 +00:00
Rafael Espindola
875710a2fd Nuke the old JIT.
I am sure we will be finding bits and pieces of dead code for years to
come, but this is a good start.

Thanks to Lang Hames for making MCJIT a good replacement!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215111 91177308-0d34-0410-b5e6-96231b3b80d8
2014-08-07 14:21:18 +00:00
Tim Northover
5c8b83eb7a X86: expand atomics in IR instead of as MachineInstrs.
The logic for expanding atomics that aren't natively supported in
terms of cmpxchg loops is much simpler to express at the IR level. It
also allows the normal optimisations and CodeGen improvements to help
out with atomics, instead of using a limited set of possible
instructions..

rdar://problem/13496295

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212119 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-01 18:53:31 +00:00
Eric Christopher
fdea941583 Move all of the x86 subtarget initialized variables down into the x86 subtarget
from the x86 target machine. Should be no functional change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210479 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-09 17:08:19 +00:00
Saleem Abdulrasool
aa53e49779 X86: simplify data layout calculation
X86Subtarget::isTargetCygMing || X86Subtarget::isTargetKnownWindowsMSVC is
equivalent to all Windows environments.  Simplify the check to isOSWindows.
NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210431 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-08 19:08:36 +00:00
Eric Christopher
7fe88820e3 Replace the use of TargetMachine with a tiny bool variable.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210386 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-06 23:26:48 +00:00
Eric Christopher
df2f80d909 Remove all local variables from X86SelectionDAGInfo, the DAG has
all of the ones we were stashing away on startup.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210385 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-06 23:26:43 +00:00
Eric Christopher
38ee55ddfa Remove X86Subtarget from the X86FrameLowering constructor since
we can just pass in the values we already know and we're not
caching the subtarget anymore.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210292 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-05 22:10:58 +00:00
Eric Christopher
6d18c24e99 Remove duplicate copy of InstrItineraryData from the TargetMachine,
it's already on the subtarget.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210289 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-05 21:42:54 +00:00
Eric Christopher
1e135990c7 Remove uses of the TargetMachine from X86FrameLowering.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210223 91177308-0d34-0410-b5e6-96231b3b80d8
2014-06-05 00:09:05 +00:00
Eric Christopher
26bbeece29 Avoid using subtarget features when adding X86 specific passes to
the pass pipeline.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209382 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-22 01:46:02 +00:00
Eric Christopher
42854e57a9 Rename createGlobalBaseRegPass -> createX86GlobalBaseRegPass to make
it obvious that it's a target specific pass.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209380 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-22 01:45:57 +00:00
Eric Christopher
189fe78e2f Make early if conversion dependent upon the subtarget and add
a subtarget hook to enable. Unconditionally add to the pass pipeline
for targets that might want to use it. No functional change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209340 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-21 23:40:26 +00:00
Alexey Volkov
0d0bab5168 [X86] Tune LEA usage for Silvermont
According to Intel Software Optimization Manual on Silvermont in some cases LEA
is better to be replaced with ADD instructions:
"The rule of thumb for ADDs and LEAs is that it is justified to use LEA
with a valid index and/or displacement for non-destructive destination purposes
(especially useful for stack offset cases), or to use a SCALE.
Otherwise, ADD(s) are preferable."

Differential Revision: http://reviews.llvm.org/D3826


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209198 91177308-0d34-0410-b5e6-96231b3b80d8
2014-05-20 08:55:50 +00:00
Yaron Keren
64b2297786 Patch by Vadim Chugunov
Win64 stack unwinder gets confused when execution flow "falls through" after
a call to 'noreturn' function. This fixes the "missing epilogue" problem by 
emitting a trap instruction for IR 'unreachable' on x86_x64-pc-windows.

A secondary use for it would be for anyone wanting to make double-sure that
'noreturn' functions, indeed, do not return.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206684 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-19 13:47:43 +00:00
Yaron Keren
bec4ff5781 isTargetWindows() renamed to isTargetKnownWindowsMSVC()
to reflect its current functionality.

Based on Takumi NAKAMURA suggestion.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@205338 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-01 18:15:34 +00:00
Craig Topper
59ae7294ef Prune includes in X86 target.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204216 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-19 06:53:25 +00:00
Craig Topper
f2c9fef815 [C++11] Add 'override' keyword to virtual methods that override their base class.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203378 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-09 07:44:38 +00:00
David Woodhouse
476136e951 [x86] Kill gratuitous X86_{32,64}TargetMachine subclasses, use X86TargetMachine
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198720 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-08 00:08:50 +00:00
Rafael Espindola
8e0f67dcec Make the llvm mangler depend only on DataLayout.
Before this patch any program that wanted to know the final symbol name of a
GlobalValue had to link with Target.

This patch implements a compromise solution where the mangler uses DataLayout.
This way, any tool that already links with Target (llc, clang) gets the exact
behavior as before and new IR files can be mangled without linking with Target.

With this patch the mangler is constructed with just a DataLayout and DataLayout
is extended to include the information the Mangler needs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198438 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-03 19:21:54 +00:00
Rafael Espindola
33cc3f81c1 Remove the 's' DataLayout specification
During the years there have been some attempts at figuring out how to
align byval arguments. A look at the commit log suggests that they
were

* Use the ABI alignment.
* When that was not sufficient for x86-64, I added the 's' specification to
  DataLayout.
* When that was not sufficient Evan added the virtual getByValTypeAlignment.
* When even that was not sufficient, we just got the FE to add the alignment
  to the byval.

This patch is just a simple cleanup that removes my first attempt at fixing the
problem. I also added an AArch64 implementation of getByValTypeAlignment to
make sure this patch is a nop. I also left the 's' parsing for backward
compatibility.

I will send a short email to llvmdev about the change for anyone maintaining
an out of tree target.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198287 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-01 22:29:43 +00:00
Rafael Espindola
960ede2e1d Synchronize the NaCl DataLayout strings with the ones in clang.
Patch by Derek Schuff.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197640 91177308-0d34-0410-b5e6-96231b3b80d8
2013-12-19 00:44:37 +00:00
Rafael Espindola
c4bc055bb4 One last cleanup of LLVM's DataLayout strings.
Produce them in the same order on every target. The order is that of
getStringRepresentation: e|E-i*-f*-v*-a*-s*-n*-S*.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197411 91177308-0d34-0410-b5e6-96231b3b80d8
2013-12-16 19:31:14 +00:00
Rafael Espindola
ea53c6ae30 The preferred alignment defaults to the abi alignment. Omit if it is the same.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197400 91177308-0d34-0410-b5e6-96231b3b80d8
2013-12-16 18:01:51 +00:00
Rafael Espindola
7ef5520e8c On DataLayout, omit the default of p:64:64:64.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197397 91177308-0d34-0410-b5e6-96231b3b80d8
2013-12-16 17:15:29 +00:00
Rafael Espindola
48c2927021 Assume defaults to produce smaller datalayout strings.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197249 91177308-0d34-0410-b5e6-96231b3b80d8
2013-12-13 17:56:11 +00:00
Rafael Espindola
9e9622d63e Refactor the computation of the x86 datalayout.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196976 91177308-0d34-0410-b5e6-96231b3b80d8
2013-12-10 22:05:32 +00:00
Nadav Rotem
fe16848601 Mark some command line flags as hidden
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193013 91177308-0d34-0410-b5e6-96231b3b80d8
2013-10-18 23:38:13 +00:00
NAKAMURA Takumi
d5a2eb0925 X86TargetMachine.cpp: Clarify to emit GOT in i686-{cygming|win32}-elf for mcjit.
I suppose all "lli -use-mcjit i686-*" should require GOT, (and to fail.)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188856 91177308-0d34-0410-b5e6-96231b3b80d8
2013-08-21 02:37:25 +00:00
Bill Wendling
ea44281d5d Access the TargetLoweringInfo from the TargetMachine object instead of caching it. The TLI may change between functions. No functionality change.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184349 91177308-0d34-0410-b5e6-96231b3b80d8
2013-06-19 20:51:24 +00:00
Rafael Espindola
4a971705bc Remove the MachineMove class.
It was just a less powerful and more confusing version of
MCCFIInstruction. A side effect is that, since MCCFIInstruction uses
dwarf register numbers, calls to getDwarfRegNum are pushed out, which
should allow further simplifications.

I left the MachineModuleInfo::addFrameMove interface unchanged since
this patch was already fairly big.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181680 91177308-0d34-0410-b5e6-96231b3b80d8
2013-05-13 01:16:13 +00:00
Preston Gurd
d6ac8e9a03 This patch adds the X86FixupLEAs pass, which will reduce instruction
latency for certain models of the Intel Atom family, by converting
instructions into their equivalent LEA instructions, when it is both
useful and possible to do so.




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180573 91177308-0d34-0410-b5e6-96231b3b80d8
2013-04-25 20:29:37 +00:00
Eli Bendersky
a5597f0eaf In this patch, we teach X86_64TargetMachine that it has a ILP32
(defined by the x32 ABI) mode, in which case its pointers are 32-bits
in size. This knowledge is also added to X86RegisterInfo that now
returns the appropriate registers in getPointerRegClass.

There are many outcomes to this change. In order to keep the patches
separate and manageable, we start by focusing on some simple testable
cases. The patch adds a test with passing a pointer to a function -
focusing on the difference between the two data models for x86-64.
Another test is added for handling of 'sret' arguments (and
functionality is added in X86ISelLowering to make it work).

A note on naming: the "x32 ABI" document refers to the AMD64
architecture (in LLVM it's distinguished by being is64Bits() in the
x86 subtarget) with two variations: the LP64 (default) data model, and
the ILP32 data model. This patch adds predicates to the subtarget
which are consistent with this naming scheme.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173503 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-25 22:07:43 +00:00
Jakob Stoklund Olesen
02c6325a45 Provide a place for targets to insert ILP optimization passes.
Move the early if-conversion pass into this group.

ILP optimizations usually need to find the right balance between
register pressure and ILP using the MachineTraceMetrics analysis to
identify critical paths and estimate other costs. Such passes should run
together so they can share dominator tree and loop info analyses.

Besides if-conversion, future passes to run here here could include
expression height reduction and ARM's MLxExpansion pass.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172687 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-17 00:58:38 +00:00
Preston Gurd
c7b902e7fe Pad Short Functions for Intel Atom
The current Intel Atom microarchitecture has a feature whereby
when a function returns early then it is slightly faster to execute
a sequence of NOP instructions to wait until the return address is ready,
as opposed to simply stalling on the ret instruction until
the return address is ready.

When compiling for X86 Atom only, this patch will run a pass,
called "X86PadShortFunction" which will add NOP instructions where less
than four cycles elapse between function entry and return.

It includes tests.

This patch has been updated to address Nadav's review comments
- Optimize only at >= O1 and don't do optimization if -Os is set
- Stores MachineBasicBlock* instead of BBNum
- Uses DenseMap instead of std::map
- Fixes placement of braces

Patch by Andy Zhang.




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171879 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-08 18:27:24 +00:00
Chandler Carruth
aeef83c6af Switch TargetTransformInfo from an immutable analysis pass that requires
a TargetMachine to construct (and thus isn't always available), to an
analysis group that supports layered implementations much like
AliasAnalysis does. This is a pretty massive change, with a few parts
that I was unable to easily separate (sorry), so I'll walk through it.

The first step of this conversion was to make TargetTransformInfo an
analysis group, and to sink the nonce implementations in
ScalarTargetTransformInfo and VectorTargetTranformInfo into
a NoTargetTransformInfo pass. This allows other passes to add a hard
requirement on TTI, and assume they will always get at least on
implementation.

The TargetTransformInfo analysis group leverages the delegation chaining
trick that AliasAnalysis uses, where the base class for the analysis
group delegates to the previous analysis *pass*, allowing all but tho
NoFoo analysis passes to only implement the parts of the interfaces they
support. It also introduces a new trick where each pass in the group
retains a pointer to the top-most pass that has been initialized. This
allows passes to implement one API in terms of another API and benefit
when some other pass above them in the stack has more precise results
for the second API.

The second step of this conversion is to create a pass that implements
the TargetTransformInfo analysis using the target-independent
abstractions in the code generator. This replaces the
ScalarTargetTransformImpl and VectorTargetTransformImpl classes in
lib/Target with a single pass in lib/CodeGen called
BasicTargetTransformInfo. This class actually provides most of the TTI
functionality, basing it upon the TargetLowering abstraction and other
information in the target independent code generator.

The third step of the conversion adds support to all TargetMachines to
register custom analysis passes. This allows building those passes with
access to TargetLowering or other target-specific classes, and it also
allows each target to customize the set of analysis passes desired in
the pass manager. The baseline LLVMTargetMachine implements this
interface to add the BasicTTI pass to the pass manager, and all of the
tools that want to support target-aware TTI passes call this routine on
whatever target machine they end up with to add the appropriate passes.

The fourth step of the conversion created target-specific TTI analysis
passes for the X86 and ARM backends. These passes contain the custom
logic that was previously in their extensions of the
ScalarTargetTransformInfo and VectorTargetTransformInfo interfaces.
I separated them into their own file, as now all of the interface bits
are private and they just expose a function to create the pass itself.
Then I extended these target machines to set up a custom set of analysis
passes, first adding BasicTTI as a fallback, and then adding their
customized TTI implementations.

The fourth step required logic that was shared between the target
independent layer and the specific targets to move to a different
interface, as they no longer derive from each other. As a consequence,
a helper functions were added to TargetLowering representing the common
logic needed both in the target implementation and the codegen
implementation of the TTI pass. While technically this is the only
change that could have been committed separately, it would have been
a nightmare to extract.

The final step of the conversion was just to delete all the old
boilerplate. This got rid of the ScalarTargetTransformInfo and
VectorTargetTransformInfo classes, all of the support in all of the
targets for producing instances of them, and all of the support in the
tools for manually constructing a pass based around them.

Now that TTI is a relatively normal analysis group, two things become
straightforward. First, we can sink it into lib/Analysis which is a more
natural layer for it to live. Second, clients of this interface can
depend on it *always* being available which will simplify their code and
behavior. These (and other) simplifications will follow in subsequent
commits, this one is clearly big enough.

Finally, I'm very aware that much of the comments and documentation
needs to be updated. As soon as I had this working, and plausibly well
commented, I wanted to get it committed and in front of the build bots.
I'll be doing a few passes over documentation later if it sticks.

Commits to update DragonEgg and Clang will be made presently.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171681 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-07 01:37:14 +00:00
Nadav Rotem
5d1f5c1737 Revert revision 171524. Original message:
URL: http://llvm.org/viewvc/llvm-project?rev=171524&view=rev
Log:
The current Intel Atom microarchitecture has a feature whereby when a function
returns early then it is slightly faster to execute a sequence of NOP
instructions to wait until the return address is ready,
as opposed to simply stalling on the ret instruction
until the return address is ready.

When compiling for X86 Atom only, this patch will run a pass, called
"X86PadShortFunction" which will add NOP instructions where less than four
cycles elapse between function entry and return.

It includes tests.

Patch by Andy Zhang.




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171603 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-05 05:42:48 +00:00
Preston Gurd
dd30b47175 The current Intel Atom microarchitecture has a feature whereby when a function
returns early then it is slightly faster to execute a sequence of NOP
instructions to wait until the return address is ready,
as opposed to simply stalling on the ret instruction
until the return address is ready.

When compiling for X86 Atom only, this patch will run a pass, called
"X86PadShortFunction" which will add NOP instructions where less than four
cycles elapse between function entry and return.

It includes tests.

Patch by Andy Zhang.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171524 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-04 20:54:54 +00:00
Richard Smith
ba836a2e80 Fix use-before-construction of X86TargetLowering.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170654 91177308-0d34-0410-b5e6-96231b3b80d8
2012-12-20 04:04:17 +00:00