There is only one current section.

Both MCStreamer and MCObjectStreamer were maintaining a current section
variable and they were slightly out of sync. I don't think this was observable,
but was ine

There is only one current section.

Both MCStreamer and MCObjectStreamer were maintaining a current section
variable and they were slightly out of sync. I don't think this was observable,
but was inefficient and error prone.

Changing this requires a few cascading changes:

* SwitchSection has to call ChangeSection earlier for ChangeSection to see
the old section.
* With that change, ChangeSection cannot call EmitLabel, since during
ChangeSection we are still in the old section.
* When the object streamer requires a begin label, just reused the existing
generic support for begin labels instead of calling EmitLabel directly.

llvm-svn: 238357

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Delete MCSectionData.

llvm-svn: 238331

Move getSubsectionInsertionPoint to MCSection.

llvm-svn: 238320

Replace getOrCreateSectionData with registerSection.

There is now no SectionData to be created.

llvm-svn: 238208

Have getCurrentSectionData return a MCSection.

I will fix the name shortly.

llvm-svn: 238204

Store a MCSection in MCFragment.

Part of the work to merge MCSectionData into MCSection.

llvm-svn: 238160

Move HasInstructions to MCSection.

llvm-svn: 238150

Move bundle info from MCSectionData to MCSection.

llvm-svn: 238143

Stop forwarding (get|set)Aligment from MCSectionData to MCSection.

llvm-svn: 237956

Move alignment from MCSectionData to MCSection.

This starts merging MCSection and MCSectionData.

There are a few issues with the current split between MCSection and
MCSectionData.

* It optimizes t

Move alignment from MCSectionData to MCSection.

This starts merging MCSection and MCSectionData.

There are a few issues with the current split between MCSection and
MCSectionData.

* It optimizes the the not as important case. We want the production
of .o files to be really fast, but the split puts the information used
for .o emission in a separate data structure.

* The ELF/COFF/MachO hierarchy is not represented in MCSectionData,
leading to some ad-hoc ways to represent the various flags.

* It makes it harder to remember where each item is.

The attached patch starts merging the two by moving the alignment from
MCSectionData to MCSection.

Most of the patch is actually just dropping 'const', since
MCSectionData is mutable, but MCSection was not.

llvm-svn: 237936

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AsmPrinter: Compute absolute label difference directly

Create a low-overhead path for `EmitLabelDifference()` that emits a
emits an absolute number when (1) the output is an object stream and (2)
th

AsmPrinter: Compute absolute label difference directly

Create a low-overhead path for `EmitLabelDifference()` that emits a
emits an absolute number when (1) the output is an object stream and (2)
the two symbols are in the same data fragment.

This drops memory usage on Mach-O from 975 MB down to 919 MB (5.8%).
The only call is when `!doesDwarfUseRelocationsAcrossSections()` --
i.e., on Mach-O -- since otherwise an absolute offset from the start of
the section needs a relocation. (`EmitLabelDifference()` is cheaper on
ELF anyway, since it creates 1 fewer temp symbol, and it gets called far
less often. It's not clear to me if this is even a bottleneck there.)

(I'm looking at `llc` memory usage on `verify-uselistorder.lto.opt.bc`;
see r236629 for details.)

llvm-svn: 237876

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MC: Clean up method names in MCContext.

The naming was a mish-mash of old and new style. Update to be consistent
with the new. NFC.

llvm-svn: 237594

MC: Update MCCodeEmitter naming. NFC.

s/EncodeInstruction/encodeInstruction/

llvm-svn: 237469

MC: Update MCFixup naming. NFC.

s/MCFixup::Create/MCFixup::create/

llvm-svn: 237468

Use raw_pwrite_stream in the object writer/streamer.

The ELF object writer will take advantage of that in the next commit.

llvm-svn: 234950

[MC] Write padding into fragments when -mc-relax-all flag is used

Summary:
When instruction bundling is enabled and the -mc-relax-all flag is
set, we can write bundle padding directly into fragments

[MC] Write padding into fragments when -mc-relax-all flag is used

Summary:
When instruction bundling is enabled and the -mc-relax-all flag is
set, we can write bundle padding directly into fragments and avoid
creating large number of fragments significantly reducing LLVM MC
memory usage.

Test Plan: Regression test attached

Reviewers: eliben

Subscribers: jfb, mseaborn

Differential Revision: http://reviews.llvm.org/D8072

llvm-svn: 234714

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Remove dead code. NFC.

llvm-svn: 234352

Don't declare all text sections at the start of the .s

The code this patch removes was there to make sure the text sections went
before the dwarf sections. That is necessary because MachO uses offse

Don't declare all text sections at the start of the .s

The code this patch removes was there to make sure the text sections went
before the dwarf sections. That is necessary because MachO uses offsets
relative to the start of the file, so adding a section can change relaxations.

The dwarf sections were being printed at the start just to produce symbols
pointing at the start of those sections.

The underlying issue was fixed in r231898. The dwarf sections are now printed
when they are about to be used, which is after we printed the text sections.

To make sure we don't regress, the patch makes the MachO streamer assert
if CodeGen puts anything unexpected after the DWARF sections.

llvm-svn: 232842

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Split the object streamer callback in one per file format.

There are two main advantages to doing this

* Targets that only need to handle one of the formats specially don't have
to worry about th

Split the object streamer callback in one per file format.

There are two main advantages to doing this

* Targets that only need to handle one of the formats specially don't have
to worry about the others. For example, x86 now only registers a
constructor for the COFF streamer.

* Changes to the arguments passed to one format constructor will not impact
the other formats.

llvm-svn: 232699

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Add a default implementation of createObjectStreamer.

This removes duplicated code from backends that don't need to do anything
fancy.

llvm-svn: 232658

Fix uses of reserved identifiers starting with an underscore followed by an uppercase letter

This covers essentially all of llvm's headers and libs. One or two weird
cases I wasn't sure were worth/a

Fix uses of reserved identifiers starting with an underscore followed by an uppercase letter

This covers essentially all of llvm's headers and libs. One or two weird
cases I wasn't sure were worth/appropriate to fix.

llvm-svn: 232394

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Clean up static analyzer warnings.

Clang's static analyzer found several potential cases of undefined
behavior, use of un-initialized values, and potentially null pointer
dereferences in tablegen, S

Clean up static analyzer warnings.

Clang's static analyzer found several potential cases of undefined
behavior, use of un-initialized values, and potentially null pointer
dereferences in tablegen, Support, MC, and ADT. This cleans them up
with specific assertions on the assumptions of the code.

llvm-svn: 224154

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Revert r221150, as it broke sanitizer tests

llvm-svn: 221151

Emit .eh_frame with relocations to functions, rather than sections

When LLVM emits DWARF call frame information, it currently creates a local,
section-relative symbol in the code section, which is p

Emit .eh_frame with relocations to functions, rather than sections

When LLVM emits DWARF call frame information, it currently creates a local,
section-relative symbol in the code section, which is pointed to by a
relocation on the .eh_frame section. However, for C++ we emit some functions in
section groups, and the SysV ABI has some rules to make it easier to remove
these sections
(http://www.sco.com/developers/gabi/latest/ch4.sheader.html#section_group_rules):

A symbol table entry with STB_LOCAL binding that is defined relative to one
of a group's sections, and that is contained in a symbol table section that is
not part of the group, must be discarded if the group members are discarded.
References to this symbol table entry from outside the group are not allowed.

This means that we need to use the function symbol for the relocation, not a
temporary symbol.

There was a comment in the code claiming that the local symbol was used to
avoid creating a relocation, but a relocation must be created anyway as the
code and CFI are in different sections.

llvm-svn: 221150

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Attempt to fix the build after r220439

llvm-svn: 220440