x86: Emit LAHF/SAHF instead of PUSHF/POPF

NaCl's sandbox doesn't allow PUSHF/POPF out of security concerns (priviledged emulators have forgotten to mask system bits in the past, and EFLAGS's DF bit

x86: Emit LAHF/SAHF instead of PUSHF/POPF

NaCl's sandbox doesn't allow PUSHF/POPF out of security concerns (priviledged emulators have forgotten to mask system bits in the past, and EFLAGS's DF bit is a constant source of hilarity). Commit r220529 fixed PR20376 by saving cmpxchg's flags result using EFLAGS, this commit now generated LAHF/SAHF instead, for all of x86 (not just NaCl) because it leads to an overall performance gain over PUSHF/POPF.

As with the previous patch this code generation is pretty bad because it occurs very later, after register allocation, and in many cases it rematerializes flags which were already available (e.g. already in a register through SETE). Fortunately it's somewhat rare that this code needs to fire.

I did [[ https://github.com/jfbastien/benchmark-x86-flags | a bit of benchmarking ]], the results on an Intel Haswell E5-2690 CPU at 2.9GHz are:

| Time per call (ms) | Runtime (ms) | Benchmark |
| 0.000012514 | 6257 | sete.i386 |
| 0.000012810 | 6405 | sete.i386-fast |
| 0.000010456 | 5228 | sete.x86-64 |
| 0.000010496 | 5248 | sete.x86-64-fast |
| 0.000012906 | 6453 | lahf-sahf.i386 |
| 0.000013236 | 6618 | lahf-sahf.i386-fast |
| 0.000010580 | 5290 | lahf-sahf.x86-64 |
| 0.000010304 | 5152 | lahf-sahf.x86-64-fast |
| 0.000028056 | 14028 | pushf-popf.i386 |
| 0.000027160 | 13580 | pushf-popf.i386-fast |
| 0.000023810 | 11905 | pushf-popf.x86-64 |
| 0.000026468 | 13234 | pushf-popf.x86-64-fast |

Clearly `PUSHF`/`POPF` are suboptimal. It doesn't really seems to be worth teaching LLVM about individual flags, at least not for this purpose.

Reviewers: rnk, jvoung, t.p.northover

Subscribers: llvm-commits

Differential revision: http://reviews.llvm.org/D6629

llvm-svn: 244503

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Revert "Fix MO's analyzePhysReg, it was confusing sub- and super-registers. Problem pointed out by Michael Hordijk."

I mistakenly committed the patch for D6629, and was trying to commit another. Rev

Revert "Fix MO's analyzePhysReg, it was confusing sub- and super-registers. Problem pointed out by Michael Hordijk."

I mistakenly committed the patch for D6629, and was trying to commit another. Reverting until it gets proper signoff.

llvm-svn: 244121

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Fix MO's analyzePhysReg, it was confusing sub- and super-registers. Problem pointed out by Michael Hordijk.

llvm-svn: 244120

[ARM] Pass a callback to FunctionPass constructors to enable skipping execution
on a per-function basis.

Previously some of the passes were conditionally added to ARM's pass pipeline
based on the ta

[ARM] Pass a callback to FunctionPass constructors to enable skipping execution
on a per-function basis.

Previously some of the passes were conditionally added to ARM's pass pipeline
based on the target machine's subtarget. This patch makes changes to add those
passes unconditionally and execute them conditonally based on the predicate
functor passed to the pass constructors. This enables running different sets of
passes for different functions in the module.

rdar://problem/20542263

Differential Revision: http://reviews.llvm.org/D8717

llvm-svn: 239325

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Update SetVector to rely on the underlying set's insert to return a pair<iterator, bool>

This is to be consistent with StringSet and ultimately with the standard
library's associative container inse

Update SetVector to rely on the underlying set's insert to return a pair<iterator, bool>

This is to be consistent with StringSet and ultimately with the standard
library's associative container insert function.

This lead to updating SmallSet::insert to return pair<iterator, bool>,
and then to update SmallPtrSet::insert to return pair<iterator, bool>,
and then to update all the existing users of those functions...

llvm-svn: 222334

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Have MachineInstrBundle use the MachineFunction for subtarget
access rather than the TargetMachine.

llvm-svn: 219662

Remove the TargetMachine forwards for TargetSubtargetInfo based
information and update all callers. No functional change.

llvm-svn: 214781

[C++11] Add 'override' keyword to virtual methods that override their base class.

llvm-svn: 203220

[C++11] Replace llvm::next and llvm::prior with std::next and std::prev.

Remove the old functions.

llvm-svn: 202636

Move an assertion so it doesn't dereference end().

The R600 target has test cases that exercises this code.

llvm-svn: 171538

Use the new MI bundling API in MachineInstrBundle itself.

The new API is higher level than just manipulating the bundle flags
directly, and the setIsInsideBundle() function will disappear soon.

llv

Use the new MI bundling API in MachineInstrBundle itself.

The new API is higher level than just manipulating the bundle flags
directly, and the setIsInsideBundle() function will disappear soon.

llvm-svn: 170159

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Use the new script to sort the includes of every file under lib.

Sooooo many of these had incorrect or strange main module includes.
I have manually inspected all of these, and fixed the main module

Use the new script to sort the includes of every file under lib.

Sooooo many of these had incorrect or strange main module includes.
I have manually inspected all of these, and fixed the main module
include to be the nearest plausible thing I could find. If you own or
care about any of these source files, I encourage you to take some time
and check that these edits were sensible. I can't have broken anything
(I strictly added headers, and reordered them, never removed), but they
may not be the headers you'd really like to identify as containing the
API being implemented.

Many forward declarations and missing includes were added to a header
files to allow them to parse cleanly when included first. The main
module rule does in fact have its merits. =]

llvm-svn: 169131

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Fix physical register liveness calculations:

+ Take account of clobbers
+ Give outputs priority over inputs since they happen later.

llvm-svn: 168360

Increase the static sizes of some SmallSets. finalizeBundle() is very frequently called for some backends, and growing into an std::set is overkill for these numbers.

llvm-svn: 164044

whitespace

llvm-svn: 164043

Add an analyzePhysReg() function to MachineOperandIteratorBase that analyses an instruction's use of a physical register, analogous to analyzeVirtReg.

Rename RegInfo to VirtRegInfo so as not to be c

Add an analyzePhysReg() function to MachineOperandIteratorBase that analyses an instruction's use of a physical register, analogous to analyzeVirtReg.

Rename RegInfo to VirtRegInfo so as not to be confused with the new PhysRegInfo.

llvm-svn: 163694

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Switch all register list clients to the new MC*Iterator interface.

No functional change intended.

Sorry for the churn. The iterator classes are supposed to help avoid
giant commits like this one in

Switch all register list clients to the new MC*Iterator interface.

No functional change intended.

Sorry for the churn. The iterator classes are supposed to help avoid
giant commits like this one in the future. The TableGen-produced
register lists are getting quite large, and it may be necessary to
change the table representation.

This makes it possible to do so without changing all clients (again).

llvm-svn: 157854

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Avoid finalizeBundles infinite looping.

llvm-svn: 152089

Convert more GenRegisterInfo tables from unsigned to uint16_t to reduce static data size.

llvm-svn: 152016

Add an analyzeVirtReg() function.

This function does more or less the same as
MI::readsWritesVirtualRegister(), but it supports bundles as well.

It also determines if any constraint requires readin

Add an analyzeVirtReg() function.

This function does more or less the same as
MI::readsWritesVirtualRegister(), but it supports bundles as well.

It also determines if any constraint requires reading and writing
operands to use the same register. Most clients want to know.

Use the more modern MO.readsReg() instead of trying to sort out undefs
and partial redefines. Stop supporting the extra full <imp-def> operand
as an alternative to <def,undef> sub-register defines.

llvm-svn: 151690

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Codegen pass definition cleanup. No functionality.

Moving toward a uniform style of pass definition to allow easier target configuration.
Globally declare Pass ID.
Globally declare pass initializer.

Codegen pass definition cleanup. No functionality.

Moving toward a uniform style of pass definition to allow easier target configuration.
Globally declare Pass ID.
Globally declare pass initializer.
Use INITIALIZE_PASS consistently.
Add a call to the initializer from CodeGen.cpp.
Remove redundant "createPass" functions and "getPassName" methods.

While cleaning up declarations, cleaned up comments (sorry for large diff).

llvm-svn: 150100

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More bundle related API additions.

llvm-svn: 148465

Enhance finalizeBundle to return end of bundle iterator because it makes sense.

llvm-svn: 148462

- Slight change to finalizeBundle() interface. LastMI is not exclusive (pointing
to instruction right after the last instruction in the bundle.
- Add a finalizeBundle() variant that doesn't specify

- Slight change to finalizeBundle() interface. LastMI is not exclusive (pointing
to instruction right after the last instruction in the bundle.
- Add a finalizeBundle() variant that doesn't specify LastMI. Instead, the code
will find the last instruction in the bundle by following the 'InsideBundle'
marker. This is useful in case bundles are formed early (i.e. during MI
scheduling) but finalized later (i.e. after register allocator has finished
rewriting virtual registers with physical registers).

llvm-svn: 148444

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Rename Finalizebundle to finalizeBundle to conform to coding guideline.

llvm-svn: 148440