Revert "DebugInfo: Fully integrate ctor type homing into 'limited' debug info"

Reverting to simplify some Google-internal rollout issues. Will recommit
in a week or two.

This reverts commit 517bbc6

Revert "DebugInfo: Fully integrate ctor type homing into 'limited' debug info"

Reverting to simplify some Google-internal rollout issues. Will recommit
in a week or two.

This reverts commit 517bbc64dbe493644eff8d55fd9566435e930520.

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DebugInfo: Fully integrate ctor type homing into 'limited' debug info

Simplify debug info back to just "limited" or "full" by rolling the ctor
type homing fully into the "limited" debug info.

Also

DebugInfo: Fully integrate ctor type homing into 'limited' debug info

Simplify debug info back to just "limited" or "full" by rolling the ctor
type homing fully into the "limited" debug info.

Also fix a bug I found along the way that was causing ctor type homing
to kick in even when something could be vtable homed (where vtable
homing is stronger/more effective than ctor homing) - fixing at the same
time as it keeps the tests (that were testing only "limited non ctor"
homing and now test ctor homing) passing.

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[DebugInfo] Switch to using constructor homing (-debug-info-kind=constructor) by default when debug info is enabled

Constructor homing reduces the amount of class type info that is emitted
by emitti

[DebugInfo] Switch to using constructor homing (-debug-info-kind=constructor) by default when debug info is enabled

Constructor homing reduces the amount of class type info that is emitted
by emitting conmplete type info for a class only when a constructor for
that class is emitted.

This will mainly reduce the amount of duplicate debug info in object
files. In Chrome enabling ctor homing decreased total build directory sizes
by about 30%.

It's also expected that some class types (such as unused classes)
will no longer be emitted in the debug info. This is fine, since we wouldn't
expect to need these types when debugging.

In some cases (e.g. libc++, https://reviews.llvm.org/D98750), classes
are used without calling the constructor. Since this is technically
undefined behavior, enabling constructor homing should be fine.
However Clang now has an attribute
`__attribute__((standalone_debug))` that can be used on classes to
ignore ctor homing.

Bug: https://bugs.llvm.org/show_bug.cgi?id=46537

Differential Revision: https://reviews.llvm.org/D106084

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Make -f[no-]split-dwarf-inlining CC1 default align with driver default (no inlining)

This makes CC1 and driver defaults consistent.
In addition, for more common cases (-g is specified without -gspli

Make -f[no-]split-dwarf-inlining CC1 default align with driver default (no inlining)

This makes CC1 and driver defaults consistent.
In addition, for more common cases (-g is specified without -gsplit-dwarf), users will not see -fno-split-dwarf-inlining in CC1 options.

Verified that the below is still true:

* `clang -g` => `splitDebugInlining: false` in DICompileUnit
* `clang -g -gsplit-dwarf` => `splitDebugInlining: false` in DICompileUnit
* `clang -g -gsplit-dwarf -fsplit-dwarf-inlining` => no `splitDebugInlining: false`

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D97706

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[Driver] -gsplit-dwarf: Produce .dwo regardless of -gN for IR input

This generalizes D94647 to IR input, as suggested by @tejohnson.
Ideally the driver should just forward split dwarf options, but d

[Driver] -gsplit-dwarf: Produce .dwo regardless of -gN for IR input

This generalizes D94647 to IR input, as suggested by @tejohnson.
Ideally the driver should just forward split dwarf options, but doing this currently will cause `clang -gsplit-dwarf -c a.c` to create a .dwo with just `.strtab`.

Reviewed By: dblaikie, tejohnson

Differential Revision: https://reviews.llvm.org/D94655

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[Driver] -gsplit-dwarf: Produce .dwo regardless of -gN for -fthinlto-index=

-g is an IR generation option while -gsplit-dwarf is an object file generation option.
For -gsplit-dwarf in the backend ph

[Driver] -gsplit-dwarf: Produce .dwo regardless of -gN for -fthinlto-index=

-g is an IR generation option while -gsplit-dwarf is an object file generation option.
For -gsplit-dwarf in the backend phase of a distributed ThinLTO (-fthinlto-index=) which does object file generation and no IR generation, -g should not be needed.

This patch makes `-fthinlto-index= -gsplit-dwarf` emit .dwo even in the absence of -g.
This should fix https://crbug.com/1158215 after D80391.

```
// Distributed ThinLTO usage
clang -g -O2 -c -flto=thin -fthin-link-bitcode=a.indexing.o a.c
clang -g -O2 -c -flto=thin -fthin-link-bitcode=b.indexing.o b.c
clang -fuse-ld=lld -Wl,--thinlto-index-only=a.rsp -Wl,--thinlto-prefix-replace=';lto/' -Wl,--thinlto-object-suffix-replace='.indexing.o;.o' a.indexing.o b.indexing.o
clang -gsplit-dwarf -O2 -c -fthinlto-index=lto/a.o.thinlto.bc a.o -o lto/a.o
clang -gsplit-dwarf -O2 -c -fthinlto-index=lto/b.o.thinlto.bc b.o -o lto/b.o
clang -fuse-ld=lld @a.rsp -o exe
```

Note: for implicit regular/Thin LTO, .dwo emission works without this patch:
`clang -flto=thin -gsplit-dwarf a.o b.o` passes `-plugin-opt=dwo_dir=` to the linker.
The linker forwards the option to LTO. LTOBackend.cpp emits `$dwo_dir/[01234].dwo`.

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D94647

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Fix split-debug.c test on Windows

[Driver] Add -gno-split-dwarf which can disable debug fission

Currently when -gsplit-dwarf is specified (could be buried in a build system),
there is no convenient way to cancel debug fission withou

[Driver] Add -gno-split-dwarf which can disable debug fission

Currently when -gsplit-dwarf is specified (could be buried in a build system),
there is no convenient way to cancel debug fission without affecting the debug
information amount (all of -g0, -g1 -fsplit-dwarf-inlining and -gline-directives-only
can, but they affect the debug information amount).

Reviewed By: #debug-info, dblaikie

Differential Revision: https://reviews.llvm.org/D92809

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[Driver] Don't make -gsplit-dwarf imply -g2

RFC: http://lists.llvm.org/pipermail/cfe-dev/2020-May/065430.html
Agreement from GCC: https://sourceware.org/pipermail/gcc-patches/2020-May/545688.html

g

[Driver] Don't make -gsplit-dwarf imply -g2

RFC: http://lists.llvm.org/pipermail/cfe-dev/2020-May/065430.html
Agreement from GCC: https://sourceware.org/pipermail/gcc-patches/2020-May/545688.html

g_flags_Group options generally don't affect the amount of debugging
information. -gsplit-dwarf is an exception. Its order dependency with
other gN_Group options make it inconvenient in a build system:

* -g0 -gsplit-dwarf -> level 2
-gsplit-dwarf "upgrades" the amount of debugging information despite
the previous intention (-g0) to drop debugging information
* -g1 -gsplit-dwarf -> level 2
-gsplit-dwarf "upgrades" the amount of debugging information.
* If we have a higher-level -gN, -gN -gsplit-dwarf will supposedly decrease the
amount of debugging information. This happens with GCC -g3.

The non-orthogonality has confused many users. GCC 11 will change the semantics
(-gsplit-dwarf no longer implies -g2) despite the backwards compatibility break.
This patch matches its behavior.

New semantics:

* If there is a g_Group, allow split DWARF if useful
(none of: -g0, -gline-directives-only, -g1 -fno-split-dwarf-inlining)
* Otherwise, no-op.

To restore the original behavior, replace -gsplit-dwarf with -gsplit-dwarf -g.

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D80391

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[test] Rewrite split-debug.c

Use generic ELF target triples.
Add missing coverage: -gsplit-dwarf=split -g -fsplit-dwarf-inlining
Reorganize and add comments.
Test -gno-pubnames

Support dwarf fission for wasm object files

Initial support for dwarf fission sections (-gsplit-dwarf) on wasm.
The most interesting change is support for writing 2 files (.o and .dwo) in the
wasm o

Support dwarf fission for wasm object files

Initial support for dwarf fission sections (-gsplit-dwarf) on wasm.
The most interesting change is support for writing 2 files (.o and .dwo) in the
wasm object writer. My approach moves object-writing logic into its own function
and calls it twice, swapping out the endian::Writer (W) in between calls.
It also splits the import-preparation step into its own function (and skips it when writing a dwo).

Differential Revision: https://reviews.llvm.org/D85685

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Revert "Switch to using -debug-info-kind=constructor as default (from =limited)"

This reverts commit 227db86a1b7dd6f96f7df14890fcd071bc4fe1f5.

Causing debug info errors in google3 LTO builds; also

Revert "Switch to using -debug-info-kind=constructor as default (from =limited)"

This reverts commit 227db86a1b7dd6f96f7df14890fcd071bc4fe1f5.

Causing debug info errors in google3 LTO builds; also causes a
debuginfo-test failure.

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Switch to using -debug-info-kind=constructor as default (from =limited)

Summary:
-debug-info-kind=constructor reduces the amount of class debug info that
is emitted; this patch switches to using thi

Switch to using -debug-info-kind=constructor as default (from =limited)

Summary:
-debug-info-kind=constructor reduces the amount of class debug info that
is emitted; this patch switches to using this as the default.

Constructor homing emits the complete type info for a class only when the
constructor is emitted, so it is expected that there will be some classes that
are not defined in the debug info anymore because they are never constructed,
and we shouldn't need debug info for these classes.

I compared the PDB files for clang, and there are 273 class types that are defined with `=limited`
but not with `=constructor` (out of ~60,000 total class types).
We've looked at a number of the types that are no longer defined with =constructor. The vast
majority of cases are something like class A is used as a parameter in a member function of
some other class B, which is emitted. But the function that uses class A is never called, and class A
is never constructed, and therefore isn't emitted in the debug info.

Bug: https://bugs.llvm.org/show_bug.cgi?id=46537

Subscribers: aprantl, cfe-commits, lldb-commits

Tags: #clang, #lldb

Differential Revision: https://reviews.llvm.org/D79147

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[DWARF5][SplitDwarf] Set default state for -fsplit-dwarf-inlining to be false.

The -fsplit-dwarf-inlining option does not conform to DWARF5 standard.
It creates children for Skeleton compilation

[DWARF5][SplitDwarf] Set default state for -fsplit-dwarf-inlining to be false.

The -fsplit-dwarf-inlining option does not conform to DWARF5 standard.
It creates children for Skeleton compilation unit. We need default behavior
to be DWARF5 compatible. Thus set default state for -fsplit-dwarf-inlining
into "false".

Differential Revision: https://reviews.llvm.org/D71304

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[Clang] Remove unused -split-dwarf and obsolete -enable-split-dwarf

Summary:
The changes in D59673 made the choice redundant, since we can achieve
single-file split DWARF just by not setting an outp

[Clang] Remove unused -split-dwarf and obsolete -enable-split-dwarf

Summary:
The changes in D59673 made the choice redundant, since we can achieve
single-file split DWARF just by not setting an output file name.
Like llc we can also derive whether to enable Split DWARF from whether
-split-dwarf-file is set, so we don't need the flag at all anymore.

The test CodeGen/split-debug-filename.c distinguished between having set
or not set -enable-split-dwarf with -split-dwarf-file, but we can
probably just always emit the metadata into the IR.

The flag -split-dwarf wasn't used at all anymore.

Reviewers: dblaikie, echristo

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D63167

llvm-svn: 364479

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[Clang] Harmonize Split DWARF options with llc

Summary:
With Split DWARF the resulting object file (then called skeleton CU)
contains the file name of another ("DWO") file with the debug info.
This

[Clang] Harmonize Split DWARF options with llc

Summary:
With Split DWARF the resulting object file (then called skeleton CU)
contains the file name of another ("DWO") file with the debug info.
This can be a problem for remote compilation, as it will contain the
name of the file on the compilation server, not on the client.

To use Split DWARF with remote compilation, one needs to either

* make sure only relative paths are used, and mirror the build directory
structure of the client on the server,
* inject the desired file name on the client directly.

Since llc already supports the latter solution, we're just copying that
over. We allow setting the actual output filename separately from the
value of the DW_AT_[GNU_]dwo_name attribute in the skeleton CU.

Fixes PR40276.

Reviewers: dblaikie, echristo, tejohnson

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D59673

llvm-svn: 363496

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[Clang] Rename -split-dwarf-file to -split-dwarf-output

Summary:
This is the first in a series of changes trying to align clang -cc1
flags for Split DWARF with those of llc. The unfortunate side eff

[Clang] Rename -split-dwarf-file to -split-dwarf-output

Summary:
This is the first in a series of changes trying to align clang -cc1
flags for Split DWARF with those of llc. The unfortunate side effect of
having -split-dwarf-output for single file Split DWARF will disappear
again in a subsequent change.

The change is the result of a discussion in D59673.

Reviewers: dblaikie, echristo

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D63130

llvm-svn: 363494

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[Driver] Simplify -g level computation and its interaction with -gsplit-dwarf

Summary:
When -gsplit-dwarf is used together with other -g options, in most cases
the computed debug info level is decid

[Driver] Simplify -g level computation and its interaction with -gsplit-dwarf

Summary:
When -gsplit-dwarf is used together with other -g options, in most cases
the computed debug info level is decided by the last -g option, with one
special case (see below). This patch drops that special case and thus
makes it easy to reason about:

// If a lower debug level -g comes after -gsplit-dwarf, in some cases
// -gsplit-dwarf is cancelled.
-gsplit-dwarf -g0 => 0
-gsplit-dwarf -gline-directives-only => DebugDirectivesOnly
-gsplit-dwarf -gmlt -fsplit-dwarf-inlining => 1
-gsplit-dwarf -gmlt -fno-split-dwarf-inlining => 1 + split

// If -gsplit-dwarf comes after -g options, with this patch, the net
// effect is 2 + split for all combinations
-g0 -gsplit-dwarf => 2 + split
-gline-directives-only -gsplit-dwarf => 2 + split
-gmlt -gsplit-dwarf -fsplit-dwarf-inlining => 2 + split
-gmlt -gsplit-dwarf -fno-split-dwarf-inlining => 1 + split (before) 2 + split (after)

The last case has been changed. In general, if the user intends to lower
debug info level, place that -g option after -gsplit-dwarf.

Some context:

In gcc, the last of -gsplit-dwarf -g0 -g1 -g2 -g3 -ggdb[0-3] -gdwarf-*
... decides the debug info level (-gsplit-dwarf -gdwarf-* have level 2).
It is a bit unfortunate that -gsplit-dwarf -gdwarf-* ... participate in
the level computation but that is the status quo.

Reviewers: dblaikie, echristo, probinson

Reviewed By: dblaikie, probinson

Subscribers: probinson, aprantl, jdoerfert, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D59923

llvm-svn: 358544

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[AMDGPU] Switch default DWARF version to 5

Effectively reverts r337612. The issues that cropped up with the last
attempt appear to have gone away.

Differential Revision: https://reviews.llvm.org/D5

[AMDGPU] Switch default DWARF version to 5

Effectively reverts r337612. The issues that cropped up with the last
attempt appear to have gone away.

Differential Revision: https://reviews.llvm.org/D59008

llvm-svn: 357285

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[Driver] Allow -gsplit-dwarf on ELF OSes other than Linux and Fuchsia

In gcc, -gsplit-dwarf is handled in gcc/gcc.c as a spec
(ASM_FINAL_SPEC): objcopy --extract-dwo + objcopy --strip-dwo. In
gcc/op

[Driver] Allow -gsplit-dwarf on ELF OSes other than Linux and Fuchsia

In gcc, -gsplit-dwarf is handled in gcc/gcc.c as a spec
(ASM_FINAL_SPEC): objcopy --extract-dwo + objcopy --strip-dwo. In
gcc/opts.c, -gsplit_dwarf has the same semantic of a -g. Except for the
availability of the external command 'objcopy', nothing precludes the
feature working on other ELF OSes. llvm doesn't use objcopy, so it doesn't
have to exclude other OSes.

llvm-svn: 357150

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[Clang] - Add '-gsplit-dwarf[=split,=single]' version for '-gsplit-dwarf' option.

The DWARF5 specification says(Appendix F.1):

"The sections that do not require relocation, however, can be
written

[Clang] - Add '-gsplit-dwarf[=split,=single]' version for '-gsplit-dwarf' option.

The DWARF5 specification says(Appendix F.1):

"The sections that do not require relocation, however, can be
written to the relocatable object (.o) file but ignored by the
linker or they can be written to a separate DWARF object (.dwo)
file that need not be accessed by the linker."

The first part describes a single file split DWARF feature and there
is no way to trigger this behavior atm.
Fortunately, no many changes are required to keep *.dwo sections
in a .o, the patch does that.

Differential revision: https://reviews.llvm.org/D52296

llvm-svn: 346837

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Reland r332885, "CodeGen, Driver: Start using direct split dwarf emission in clang."

As well as two follow-on commits r332906, r332911 with a fix for
test clang/test/CodeGen/split-debug-filename.c.

Reland r332885, "CodeGen, Driver: Start using direct split dwarf emission in clang."

As well as two follow-on commits r332906, r332911 with a fix for
test clang/test/CodeGen/split-debug-filename.c.

llvm-svn: 333013

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Revert "CodeGen, Driver: Start using direct split dwarf emission in clang."

This reverts commit r332885 as it broke several greendragon buildbots.

llvm-svn: 332973

CodeGen, Driver: Start using direct split dwarf emission in clang.

Fixes PR37466.

Differential Revision: https://reviews.llvm.org/D47093

llvm-svn: 332885

Enable -fno-split-dwarf-inlining even when -gsplit-dwarf isn't specified.

Since -gsplit-dwarf is specified on a backend compile (in ThinLTO
parlance) it isn't passed during the frontend compile (bec

Enable -fno-split-dwarf-inlining even when -gsplit-dwarf isn't specified.

Since -gsplit-dwarf is specified on a backend compile (in ThinLTO
parlance) it isn't passed during the frontend compile (because no ELF
object/dwo file is produced then), yet the -fno-split-dwarf-inlining
value needs to be encoded in the LLVM DebugInfo metadata to have
effect...

So let it be specified & it'll be silently ignored if -gsplit-dwarf
isn't used in the end, otherwise it'll be used on a per-cu basis
depending on where it's specified in the frontend compile actions.

llvm-svn: 301684

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