Commit Graph

14981 Commits

Author SHA1 Message Date
Simon Pilgrim 9ff06a0c7e Strip UTF8 BOM that got added in rL305091
Seems my recent move to VS2017 has resulted in a few text editor issues.....

llvm-svn: 305285
2017-06-13 10:17:57 +00:00
Simon Pilgrim 2b3b717768 [X86][SSE] Refactor getTargetConstantBitsFromNode to avoid large APInts (PR32037)
Much of PR32037's compile time regression is due to getTargetConstantBitsFromNode always creating large (>64bit) APInts during the bitcasting from the source data to the destination bitwidth.

This commit avoids this bitcast stage if the data is already the correct bitwidth.

llvm-svn: 305284
2017-06-13 10:13:48 +00:00
Craig Topper 8b8767662c [AVX-512] Mark masked VPCMP instructions as commutable.
llvm-svn: 305276
2017-06-13 07:13:50 +00:00
Craig Topper e1d8103d8f [AVX-512] Mark masked version of vpcmpeq as being commutable.
llvm-svn: 305275
2017-06-13 07:13:47 +00:00
Craig Topper 42d0339257 [X86] Add masked integer compare instructions to load folding tables.
llvm-svn: 305274
2017-06-13 07:13:44 +00:00
Sanjay Patel d4765a38b4 [DAG] add helper to bind memop chains; NFCI
This step is just intended to reduce code duplication rather than change any functionality.

A follow-up would be to replace PPCTargetLowering::spliceIntoChain() usage with this new helper.

Differential Revision: https://reviews.llvm.org/D33649

llvm-svn: 305192
2017-06-12 14:41:48 +00:00
Simon Pilgrim b079c8b35b [X86][SSE] Change memop fragment to inherit from vec128load with local alignment controls
First possible step towards merging SSE/AVX memory folding pattern fragments.

Also allows us to remove the duplicate non-temporal load logic.

Differential Revision: https://reviews.llvm.org/D33902

llvm-svn: 305184
2017-06-12 10:01:27 +00:00
Craig Topper 69fead95c7 [AVX-512] Add VPCONFLICT and VPLZCNT to load folding tables.
llvm-svn: 305180
2017-06-12 04:57:31 +00:00
Sanjay Patel dcbfbb11d9 [x86] use vperm2f128 rather than vinsertf128 when there's a chance to fold a 32-byte load
I was looking closer at the x86 test diffs in D33866, and the first change seems like it 
shouldn't happen in the first place. So this patch will resolve that.

Using Agner's tables and AMD docs, vperm2f128 and vinsertf128 have identical timing for 
any given CPU model, so we should be able to interchange those without affecting perf. 
But as we can see in some of the diffs here, using vperm2f128 allows load folding, so 
we should take that opportunity to reduce code size and register pressure.

A secondary advantage is making AVX1 and AVX2 codegen more similar. Given that vperm2f128 
was introduced with AVX1, we should be selecting it in all of the same situations that we 
would with AVX2. If there's some reason that an AVX1 CPU would not want to use this 
instruction, that should be fixed up in a later pass.

Differential Revision: https://reviews.llvm.org/D33938

llvm-svn: 305171
2017-06-11 21:18:58 +00:00
Simon Pilgrim 3d37b1a277 [X86][SSE] Add support for PACKSS nodes to faux shuffle extraction
If the inputs won't saturate during packing then we can treat the PACKSS as a truncation shuffle

llvm-svn: 305091
2017-06-09 17:29:52 +00:00
Andrew V. Tischenko 8cb1d0931f Add scheduler classes to integer/float horizontal operations.
This patch will close PR32801.
Differential Revision: https://reviews.llvm.org/D33203

llvm-svn: 304986
2017-06-08 16:44:13 +00:00
Andrew V. Tischenko e0531025f8 This patch closes PR28513: an optimization of multiplication by different constants.
The initial patch was rejected: I fixed the issue and re-apply it.

llvm-svn: 304972
2017-06-08 10:20:13 +00:00
Sanjay Patel 6e8e7cc70e [x86] avoid flipping sign bits for vector icmp by using known bits
If we know that both operands of an unsigned integer vector comparison are non-negative, 
then it's safe to directly use a signed-compare-greater-than instruction (the only non-equality
integer vector compare predicate provided by SSE/AVX).

We're intentionally not changing the condition code to signed in order to preserve the
existing transforms that use min/max/psubus below here.

This should solve PR33276:
https://bugs.llvm.org/show_bug.cgi?id=33276

Differential Revision: https://reviews.llvm.org/D33862

llvm-svn: 304909
2017-06-07 13:46:34 +00:00
Simon Pilgrim 58f5be2771 [X86][SSE] Fix an issue with PEXTRW/PEXTRB indices during shuffle combining
We were checking that the index was in range of the destination vector type, not the (larger) source vector type

llvm-svn: 304894
2017-06-07 10:30:35 +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
Evgeny Stupachenko 3b88291581 Fix PR23384 (part 3 of 3)
Summary:
The patch makes instruction count the highest priority for
 LSR solution for X86 (previously registers had highest priority).

Reviewers: qcolombet

Differential Revision: http://reviews.llvm.org/D30562

From: Evgeny Stupachenko <evstupac@gmail.com>
llvm-svn: 304824
2017-06-06 20:04:16 +00:00
Anna Thomas b2a212c070 [Atomics][LoopIdiom] Recognize unordered atomic memcpy
Summary:
Expanding the loop idiom test for memcpy to also recognize
unordered atomic memcpy. The only difference for recognizing
an unordered atomic memcpy and instead of a normal memcpy is
that the loads and/or stores involved are unordered atomic operations.

Background:  http://lists.llvm.org/pipermail/llvm-dev/2017-May/112779.html

Patch by Daniel Neilson!

Reviewers: reames, anna, skatkov

Reviewed By: reames, anna

Subscribers: llvm-commits, mzolotukhin

Differential Revision: https://reviews.llvm.org/D33243

llvm-svn: 304806
2017-06-06 16:45:25 +00:00
Simon Pilgrim f7113fd270 [X86][AVX1] Split 256-bit vector non-temporal FastISel loads to keep it non-temporal (PR32744)
Extension to D33728

llvm-svn: 304798
2017-06-06 14:18:39 +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
Chandler Carruth 41ed4034dd [x86] Revert the X86FoldTablesEmitter due to more miscompiles.
In testing, we've found yet another miscompile caused by the new tables.
And this one is even less clear how to fix (we could teach it to fold
a 16-bit load instead of the 32-bit load it wants, or block folding
entirely).

Also, the approach to excluding instructions seems increasingly to not
scale well.

I have left a more detailed analysis on the review log for the original
patch (https://reviews.llvm.org/D32684) along with suggested path
forward. I will land an additional test case that I wrote which covers
the code that was miscompiling (folding into the output of `pextrw`) in
a subsequent commit to keep this a pure revert.

For each commit reverted here, I've restricted the revert to the
non-test code touching the x86 fold table emission until the last commit
where I did revert the test updates. This means the *new* test cases
added for `insertps` and `xchg` remain untouched (and continue to pass).

Reverted commits:
r304540: [X86] Don't fold into memory operands into insertps in the ...
r304347: [TableGen] Adapt more places to getValueAsString now ...
r304163: [X86] Don't fold away the memory operand of an xchg.
r304123: Don't capture a temporary std::string in a StringRef.
r304122: Resubmit "[X86] Adding new LLVM TableGen backend that ..."

Original commit was in r304088, and after a string of fixes was reverted
previously in r304121 to fix build bots, and then re-landed in r304122.

llvm-svn: 304762
2017-06-06 02:15:31 +00:00
Simon Pilgrim 807b708d13 [X86][SSE41] Non-temporal loads shouldn't be folded if it can be avoided (PR32743)
Missed SSE41 non-temporal load case in previous commit

Differential Revision: https://reviews.llvm.org/D33728

llvm-svn: 304722
2017-06-05 16:45:32 +00:00
Simon Pilgrim b2ef948628 [X86][AVX1] Split 256-bit vector non-temporal loads to keep it non-temporal (PR32744)
Differential Revision: https://reviews.llvm.org/D33728

llvm-svn: 304718
2017-06-05 16:02:01 +00:00
Simon Pilgrim a25bf0b6b9 [X86][SSE] Non-temporal loads shouldn't be folded if it can be avoided (PR32743)
Differential Revision: https://reviews.llvm.org/D33728

llvm-svn: 304717
2017-06-05 15:43:03 +00:00
Simon Pilgrim 46dd55f1e1 [X86][SSE] Change BUILD_VECTOR interleaving ordering to improve coalescing/combine opportunities
We currently generate BUILD_VECTOR as a tree of UNPCKL shuffles of the same type:

e.g. for v4f32:

Step 1: unpcklps 0, 2 ==> X: <?, ?, 2, 0>
      : unpcklps 1, 3 ==> Y: <?, ?, 3, 1>
Step 2: unpcklps X, Y ==>    <3, 2, 1, 0>

The issue is because we are not placing sequential vector elements together early enough, we fail to recognise many combinable patterns - consecutive scalar loads, extractions etc.

Instead, this patch unpacks progressively larger sequential vector elements together:

e.g. for v4f32:

Step 1: unpcklps 0, 2 ==> X: <?, ?, 1, 0>
      : unpcklps 1, 3 ==> Y: <?, ?, 3, 2>
Step 2: unpcklpd X, Y ==>    <3, 2, 1, 0>

This does mean that we are creating UNPCKL shuffle of different value types, but the relevant combines that benefit from this are quite capable of handling the additional BITCASTs that are now included in the shuffle tree.

Differential Revision: https://reviews.llvm.org/D33864

llvm-svn: 304688
2017-06-04 20:12:04 +00:00
Simon Pilgrim f93debb40c [X86][SSE] Add SCALAR_TO_VECTOR(PEXTRW/PEXTRB) support to faux shuffle combining
Generalized existing SCALAR_TO_VECTOR(EXTRACT_VECTOR_ELT) code to support AssertZext + PEXTRW/PEXTRB cases as well. 

llvm-svn: 304659
2017-06-03 11:12:57 +00:00
Sanjay Patel e737cf8500 [x86] simplify code for vector icmp pred transforms; NFCI
Organizing by transform is smaller and easier to read than a squashed switch with fall-throughs.

llvm-svn: 304611
2017-06-02 23:21:53 +00:00
Ahmed Bougacha 018a68f9e4 [X86] Correctly broadcast NaN-like integers as float on AVX.
Since r288804, we try to lower build_vectors on AVX using broadcasts of
float/double.  However, when we broadcast integer values that happen to
have a NaN float bitpattern, we lose the NaN payload, thereby changing
the integer value being broadcast.

This is caused by ConstantFP::get, to which we pass the splat i32 as
a float (by bitcasting it using bitsToFloat).  ConstantFP::get takes
a double parameter, so we end up lossily converting a single-precision
NaN to double-precision.

Instead, avoid any kinds of conversions by directly building an APFloat
from the splatted APInt.

Note that this also fixes another piece of code (broadcast of
subvectors), that currently isn't susceptible to the same problem.

Also note that we could really just use APInt and ConstantInt
throughout: the constant pool type doesn't matter much.  Still, for
consistency, use the appropriate type.

llvm-svn: 304590
2017-06-02 20:02:59 +00:00
Sanjay Patel 469014ada4 [x86] fix formatting; NFCI
llvm-svn: 304576
2017-06-02 18:14:31 +00:00
David Blaikie b6b42e018a Tidy up a bit of r304516, use SmallVector::assign rather than for loop
This might give a few better opportunities to optimize these to memcpy
rather than loops - also a few minor cleanups (StringRef-izing,
templating (to avoid std::function indirection), etc).

The SmallVector::assign(iter, iter) could be improved with the use of
SFINAE, but the (iter, iter) ctor and append(iter, iter) need it to and
don't have it - so, workaround it for now rather than bothering with the
added complexity.

(also, as noted in the added FIXME, these assign ops could potentially
be optimized better at least for non-trivially-copyable types)

llvm-svn: 304566
2017-06-02 17:24:26 +00:00
Amaury Sechet 2adb7bdbca Remove ADDC, ADDE, SUBC, SUBE and SETCCE support from the X86 backend, use the CARRY ops instead.
Summary:
As per title. This cleanup some technical debt.

Depends on D33374

Reviewers: jyknight, nemanjai, mkuper, spatel, RKSimon, zvi, bkramer

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D33390

llvm-svn: 304435
2017-06-01 16:33:08 +00:00
Zvi Rackover 7693733e80 [X86] Match bitcast of vxi1 to pmovmsk
Summary:
Add an early combine to match patterns such as:
  (i16 bitcast (v16i1 x))
  ->
  (i16 movmsk (v16i8 sext (v16i1 x)))

This combine needs to happen early enough before
type-legalization scalarizes the result of the setcc.

Reviewers: igorb, craig.topper, RKSimon

Subscribers: delena, llvm-commits

Differential Revision: https://reviews.llvm.org/D33311

llvm-svn: 304406
2017-06-01 11:27:57 +00:00
Amaury Sechet 251ea8a4f8 Do not legalize large setcc with setcce, introduce setcccarry and do it with usubo/setcccarry.
Summary:
This is a continuation of the work started in D29872 . Passing the carry down as a value rather than as a glue allows for further optimizations. Introducing setcccarry makes the use of addc/subc unecessary and we can start the removal process.

This patch only introduce the optimization strictly required to get the same level of optimization as was available before nothing more.

Reviewers: jyknight, nemanjai, mkuper, spatel, RKSimon, zvi, bkramer

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D33374

llvm-svn: 304404
2017-06-01 11:14:17 +00:00
Amaury Sechet 6506a90a70 Remove ISD::SETCC match from combineX86ADD. It's done improperly and doesn't work.
llvm-svn: 304403
2017-06-01 11:13:10 +00:00
Dehao Chen 6b737ddce7 Add LiveRangeShrink pass to shrink live range within BB.
Summary: LiveRangeShrink pass moves instruction right after the definition with the same BB if the instruction and its operands all have more than one use. This pass is inexpensive and guarantees optimal live-range within BB.

Reviewers: davidxl, wmi, hfinkel, MatzeB, andreadb

Reviewed By: MatzeB, andreadb

Subscribers: hiraditya, jyknight, sanjoy, skatkov, gberry, jholewinski, qcolombet, javed.absar, krytarowski, atrick, spatel, RKSimon, andreadb, MatzeB, mehdi_amini, mgorny, efriedma, davide, dberlin, llvm-commits

Differential Revision: https://reviews.llvm.org/D32563

llvm-svn: 304371
2017-05-31 23:25:25 +00:00
Galina Kistanova c752c4bf56 Added LLVM_FALLTHROUGH to address warning: this statement may fall through. NFC.
llvm-svn: 304355
2017-05-31 21:50:45 +00:00
Matthias Braun ac4beccaca X86FloatingPoint: Fix livein lists
After transforming FP to ST registers:
- Do not add the ST register to the livein lists, they are reserved so
  we do not need to track their liveness.
- Remove the FP registers from the livein lists, they don't have defs or
  uses anymore and so are not live.
- (The setKillFlags() call is moved to an earlier place as it relies on
   the FP registers still being present in the livein list.)

llvm-svn: 304342
2017-05-31 20:30:22 +00:00
Matthias Braun 43692a2245 X86FloatingPoint: Add some static assert, cleanup; NFC
llvm-svn: 304341
2017-05-31 20:30:17 +00:00
Galina Kistanova b2c0116e71 Added LLVM_FALLTHROUGH to address warning: this statement may fall through. NFC.
llvm-svn: 304332
2017-05-31 19:41:33 +00:00
Matthias Braun d6a36ae282 TargetMachine: Indicate whether machine verifier passes.
This adds a callback to the LLVMTargetMachine that lets target indicate
that they do not pass the machine verifier checks in all cases yet.

This is intended to be a temporary measure while the targets are fixed
allowing us to enable the machine verifier by default with
EXPENSIVE_CHECKS enabled!

Differential Revision: https://reviews.llvm.org/D33696

llvm-svn: 304320
2017-05-31 18:41:23 +00:00
Galina Kistanova 6ad77845e2 Added LLVM_FALLTHROUGH to address warning: this statement may fall through. NFC.
llvm-svn: 304312
2017-05-31 17:10:03 +00:00
Matthias Braun bcd4c68233 X86FrameLowering: No need to mark FP as live-in everywhere
The frame pointer (when used as frame pointer) is a reserved register.
We do not track liveness of reserved registers and hence do not need to
add them to the basic block livein lists.

llvm-svn: 304274
2017-05-31 02:11:10 +00:00
Matthias Braun 5e394c3d6f TargetPassConfig: Keep a reference to an LLVMTargetMachine; NFC
TargetPassConfig is not useful for targets that do not use the CodeGen
library, so we may just as well store a pointer to an
LLVMTargetMachine instead of just to a TargetMachine.

While at it, also change the constructor to take a reference instead of a
pointer as the TM must not be nullptr.

llvm-svn: 304247
2017-05-30 21:36:41 +00:00
Vedant Kumar 87aefe9042 Revert "This patch closes PR28513: an optimization of multiplication by different constants. It's implemented on DAG combiner level."
This reverts commit r304209.

I think this change is responsible for a tablgen failure in stage2 builds:

  http://green.lab.llvm.org/green/job/clang-stage2-configure-Rthinlto_build/2171/

I reproduced the failure locally (without ThinLTO), reverted the commit, rebuilt the stage1 clang, rebuilt the stage2 llvm-tblgen tool, and found that the crash disappears when the commit is reverted. Here is the stack trace:

FAILED: lib/Target/ARM/ARMGenRegisterBank.inc.tmp
cd /Volumes/Builds/pz-master-stage2-RA/lib/Target/ARM && /Volumes/Builds/pz-master-stage2-RA/bin/llvm-tblgen -gen-register-bank -I /Users/vk/llvm/lib/Target/ARM -I /Users/vk/llvm/include -I /Users/vk/llvm/lib/Target /Users/vk/llvm/lib/Target/ARM/ARM.td -o /Volumes
/Builds/pz-master-stage2-RA/lib/Target/ARM/ARMGenRegisterBank.inc.tmp
0  llvm-tblgen              0x0000000106fc9568 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 40
1  llvm-tblgen              0x0000000106fc9be6 SignalHandler(int) + 422
2  libsystem_platform.dylib 0x00000001076a7fba _sigtramp + 26
3  libsystem_platform.dylib 0x00007fff58deb468 _sigtramp + 1366570184
4  llvm-tblgen              0x0000000106e89cc7 llvm::CodeGenRegBank::getCompositeSubRegIndex(llvm::CodeGenSubRegIndex*, llvm::CodeGenSubRegIndex*) + 615
5  llvm-tblgen              0x0000000106e88be6 llvm::CodeGenRegister::computeSubRegs(llvm::CodeGenRegBank&) + 2182
6  llvm-tblgen              0x0000000106e8e9f0 llvm::CodeGenRegBank::CodeGenRegBank(llvm::RecordKeeper&) + 2192
7  llvm-tblgen              0x0000000106f384a1 llvm::EmitRegisterBank(llvm::RecordKeeper&, llvm::raw_ostream&) + 65
8  llvm-tblgen              0x0000000106f72c64 (anonymous namespace)::LLVMTableGenMain(llvm::raw_ostream&, llvm::RecordKeeper&) + 1172
9  llvm-tblgen              0x0000000106fcb15f llvm::TableGenMain(char*, bool (*)(llvm::raw_ostream&, llvm::RecordKeeper&)) + 3599
10 llvm-tblgen              0x0000000106f727a6 main + 134
11 libdyld.dylib            0x000000010733c6a5 start + 1
Stack dump:
0.      Program arguments: /Volumes/Builds/pz-master-stage2-RA/bin/llvm-tblgen -gen-register-bank -I /Users/vk/llvm/lib/Target/ARM -I /Users/vk/llvm/include -I /Users/vk/llvm/lib/Target /Users/vk/llvm/lib/Target/ARM/ARM.td -o /Volumes/Builds/pz-master-stage2-RA/lib/Target/ARM/ARMGenRegisterBank.inc.tmp
/bin/sh: line 1: 41986 Segmentation fault: 11  /Volumes/Builds/pz-master-stage2-RA/bin/llvm-tblgen -gen-register-bank -I /Users/vk/llvm/lib/Target/ARM -I /Users/vk/llvm/include -I /Users/vk/llvm/lib/Target /Users/vk/llvm/lib/Target/ARM/ARM.td -o /Volumes/Builds/pz
-master-stage2-RA/lib/Target/ARM/ARMGenRegisterBank.inc.tmp

llvm-svn: 304231
2017-05-30 19:25:22 +00:00
Craig Topper f6d4dc5b4a [SelectionDAG] Set ISD::FPOWI to Expand by default
Summary:
Currently FPOWI defaults to Legal and LegalizeDAG.cpp turns Legal into Expand for this opcode because Legal is a "lie".

This patch changes the default for this opcode to Expand and removes the hack from LegalizeDAG.cpp. It also removes all the code in the targets that set this opcode to Expand themselves since they can just rely on the default.

Reviewers: spatel, RKSimon, efriedma

Reviewed By: RKSimon

Subscribers: jfb, dschuff, sbc100, jgravelle-google, nemanjai, javed.absar, andrew.w.kaylor, llvm-commits

Differential Revision: https://reviews.llvm.org/D33530

llvm-svn: 304215
2017-05-30 15:27:55 +00:00
Andrew V. Tischenko 8b04826663 This patch closes PR28513: an optimization of multiplication by different constants.
It's implemented on DAG combiner level.

llvm-svn: 304209
2017-05-30 13:00:44 +00:00
Zachary Turner df1832cf86 Resubmit "[X86] Adding new LLVM TableGen backend that generates the X86 backend memory folding tables."
This was reverted due to buildbot breakages and I was not familiar
with this code to investigate it.  But while trying to get a
useful backtrace for the author, it turns out the fix was very
obvious.  Resubmitting this patch as is, and will submit the
fix in a followup so that the fix is not hidden in the larger
CL.

llvm-svn: 304122
2017-05-29 02:19:37 +00:00
Zachary Turner 5b199be769 Revert "[X86] Adding new LLVM TableGen backend that generates the X86 backend memory folding tables."
This reverts commit 28cb1003507f287726f43c771024a1dc102c45fe as well
as all subsequent followups.  llvm-tblgen currently segfaults with
this change, and it seems it has been broken on the bots all
day with no fixes in preparation.  See, for example:

http://lab.llvm.org:8011/builders/clang-x86-windows-msvc2015/

llvm-svn: 304121
2017-05-29 01:48:53 +00:00
Ayman Musa d9f1fe43a8 [X86] Adding new LLVM TableGen backend that generates the X86 backend memory folding tables.
X86 backend holds huge tables in order to map between the register and memory forms of each instruction.
This TableGen Backend automatically generated all these tables with the appropriate flags for each entry.

Differential Revision: https://reviews.llvm.org/D32684

llvm-svn: 304088
2017-05-28 12:55:36 +00:00
Ayman Musa 0b4f97d5e9 [X86] Adding FoldGenRegForm helper field (for memory folding tables tableGen backend) to X86Inst class and set its value for the relevant instructions.
Some register-register instructions can be encoded in 2 different ways, this happens when 2 register operands can be folded (separately). 
For example if we look at the MOV8rr and MOV8rr_REV, both instructions perform exactly the same operation, but are encoded differently. Here is the relevant information about these instructions from Intel's 64-ia-32-architectures-software-developer-manual:

Opcode  Instruction  Op/En  64-Bit Mode  Compat/Leg Mode  Description
8A /r   MOV r8,r/m8  RM     Valid        Valid            Move r/m8 to r8.
88 /r   MOV r/m8,r8  MR     Valid        Valid            Move r8 to r/m8.
Here we can see that in order to enable the folding of the output and input registers, we had to define 2 "encodings", and as a result we got 2 move 8-bit register-register instructions.

In the X86 backend, we define both of these instructions, usually one has a regular name (MOV8rr) while the other has "_REV" suffix (MOV8rr_REV), must be marked with isCodeGenOnly flag and is not emitted from CodeGen.

Automatically generating the memory folding tables relies on matching encodings of instructions, but in these cases where we want to map both memory forms of the mov 8-bit (MOV8rm & MOV8mr) to MOV8rr (not to MOV8rr_REV) we have to somehow point from the MOV8rr_REV to the "regular" appropriate instruction which in this case is MOV8rr.

This field enable this "pointing" mechanism - which is used in the TableGen backend for generating memory folding tables.

Differential Revision: https://reviews.llvm.org/D32683

llvm-svn: 304087
2017-05-28 12:39:37 +00:00
Matthias Braun ac4307c41e LivePhysRegs: Rework constructor + documentation; NFC
- Take reference instead of pointer to a TRI that cannot be nullptr.
- Improve documentation comments.

llvm-svn: 304038
2017-05-26 21:51:00 +00:00