This adds a loop rerolling pass: the opposite of (partial) loop unrolling. The
transformation aims to take loops like this:
for (int i = 0; i < 3200; i += 5) {
a[i] += alpha * b[i];
a[i + 1] += alpha * b[i + 1];
a[i + 2] += alpha * b[i + 2];
a[i + 3] += alpha * b[i + 3];
a[i + 4] += alpha * b[i + 4];
}
and turn them into this:
for (int i = 0; i < 3200; ++i) {
a[i] += alpha * b[i];
}
and loops like this:
for (int i = 0; i < 500; ++i) {
x[3*i] = foo(0);
x[3*i+1] = foo(0);
x[3*i+2] = foo(0);
}
and turn them into this:
for (int i = 0; i < 1500; ++i) {
x[i] = foo(0);
}
There are two motivations for this transformation:
1. Code-size reduction (especially relevant, obviously, when compiling for
code size).
2. Providing greater choice to the loop vectorizer (and generic unroller) to
choose the unrolling factor (and a better ability to vectorize). The loop
vectorizer can take vector lengths and register pressure into account when
choosing an unrolling factor, for example, and a pre-unrolled loop limits that
choice. This is especially problematic if the manual unrolling was optimized
for a machine different from the current target.
The current implementation is limited to single basic-block loops only. The
rerolling recognition should work regardless of how the loop iterations are
intermixed within the loop body (subject to dependency and side-effect
constraints), but the significant restriction is that the order of the
instructions in each iteration must be identical. This seems sufficient to
capture all current use cases.
This pass is not currently enabled by default at any optimization level.
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stack traces by default if you use PrettyStackTraceProgram, so that existing LLVM-based
tools will continue to get it without any changes.
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linkonce_odr_auto_hide was in incomplete attempt to implement a way
for the linker to hide symbols that are known to be available in every
TU and whose addresses are not relevant for a particular DSO.
It was redundant in that it all its uses are equivalent to
linkonce_odr+unnamed_addr. Unlike those, it has never been connected
to clang or llvm's optimizers, so it was effectively dead.
Given that nothing produces it, this patch just nukes it
(other than the llvm-c enum value).
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Objective-C data structures.
This is allows tools such as darwin's otool(1) that uses the
LLVM disassembler take a pointer value being loaded by
an instruction and add a comment to what it is being referenced
to make following disassembly of Objective-C programs
more readable.
For example disassembling the Mac OS X TextEdit app one
will see comments like the following:
movq 0x20684(%rip), %rsi ## Objc selector ref: standardUserDefaults
movq 0x21985(%rip), %rdi ## Objc class ref: _OBJC_CLASS_$_NSUserDefaults
movq 0x1d156(%rip), %r14 ## Objc message: +[NSUserDefaults standardUserDefaults]
leaq 0x23615(%rip), %rdx ## Objc cfstring ref: @"SelectLinePanel"
callq 0x10001386c ## Objc message: -[[%rdi super] initWithWindowNibName:]
These diffs also include putting quotes around C strings
in literal pools and uses "symbol address" in the comment
when adding a symbol name to the comment to tell these
types of references apart:
leaq 0x4f(%rip), %rax ## literal pool for: "Hello world"
movq 0x1c3ea(%rip), %rax ## literal pool symbol address: ___stack_chk_guard
Of course the easy changes are in the LLVM disassembler and
the hard work is up to the implementer of the SymbolLookUp()
call back.
rdar://10602439
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There are two ways one could implement hiding of linkonce_odr symbols in LTO:
* LLVM tells the linker which symbols can be hidden if not used from native
files.
* The linker tells LLVM which symbols are not used from other object files,
but will be put in the dso symbol table if present.
GOLD's API is the second option. It was implemented almost 1:1 in llvm by
passing the list down to internalize.
LLVM already had partial support for the first option. It is also very similar
to how ld64 handles hiding these symbols when *not* doing LTO.
This patch then
* removes the APIs for the DSO list.
* marks LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN all linkonce_odr unnamed_addr
global values and other linkonce_odr whose address is not used.
* makes the gold plugin responsible for handling the API mismatch.
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This reverts commit r193255 and instead creates an lto_bool_t typedef
that points to bool, _Bool, or unsigned char depending on what is
available. Only recent versions of MSVC provide a stdbool.h header.
Reviewers: rafael.espindola
Differential Revision: http://llvm-reviews.chandlerc.com/D2019
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All of the Core API functions have versions which accept explicit context, in
addition to ones which work on global context. This commit adds functions
which accept explicit context to the Target API for consistency.
Patch by Peter Zotov
Differential Revision: http://llvm-reviews.chandlerc.com/D1912
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I expose the API with some caveats:
- The C++ API involves a traditional void* opaque pointer for the fatal
error callback. The C API doesn’t do this. I don’t think that the void*
opaque pointer makes any sense since this is a global callback - there will
only be one of them. So if you need to pass some data to your callback,
just put it in a global variable.
- The bindings will ignore the gen_crash_diag boolean. I ignore it because
(1) I don’t know what it does, (2) it’s not documented AFAIK, and (3) I
couldn’t imagine any use for it. I made the gut call that it probably
wasn’t important enough to expose through the C API.
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This new library will be linked in when using the "all-targets"
component and contains the LLVMInitializeAll* functions.
This means that those functions will exist as real symbols in
the shared library, and can therefore can be called from
bindings that are using ffi the shared library.
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This reverts commit r192316. The original change introduced circular
dependencies between libTarget and backends. That would broke a build unless
link everything into one big binary.
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Making them proper functions defined in the (shared)lib instead of
static inlines defined in the header files makes it possible to
actually distribute a binary compiled against the shared library
without having to worry about getting undefined symbol errors when
calling e.g LLVMInitializeAllTargetInfos because the shared library on
the other system was compiled with different targets.
Differential Revision: http://llvm-reviews.chandlerc.com/D1714
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Generalize the API so we can distinguish symbols that are needed just for a DSO
symbol table from those that are used from some native .o.
The symbols that are only wanted for the dso symbol table can be dropped if
llvm can prove every other dso has a copy (linkonce_odr) and the address is not
important (unnamed_addr).
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disassembled output alongside the instructions.
E.g., on a vector shuffle operation with a memory operand, disassembled
outputs are:
* Without the option:
vpshufd $-0x79, (%rsp), %xmm0
* With the option:
vpshufd $-0x79, (%rsp), %xmm0 ## Latency: 5
The printed latency is extracted from the schedule model available in the
disassembler context. Thus, this option has no effect if there is not a
scheduling model for the target.
This boils down to one may need to specify the CPU string, so that this
option could have an effect.
Note: Latency < 2 are not printed.
This part of <rdar://problem/14687488>.
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It's useful for the memory managers that are allocating a section to know what the name of the section is.
At a minimum, this is useful for low-level debugging - it's customary for JITs to be able to tell you what
memory they allocated, and as part of any such dump, they should be able to tell you some meta-data about
what each allocation is for. This allows clients that supply their own memory managers to do this.
Additionally, we also envision the SectionName being useful for passing meta-data from within LLVM to an LLVM
client.
This changes both the C and C++ APIs, and all of the clients of those APIs within LLVM. I'm assuming that
it's safe to change the C++ API because that API is allowed to change. I'm assuming that it's safe to change
the C API because we haven't shipped the API in a release yet (LLVM 3.3 doesn't include the MCJIT memory
management C API).
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comments issued with verbose assembly.
E.g., on a vector shuffle operation, disassembled output are:
* Without the option:
vpshufd $-0x79, (%rsp), %xmm0
* With the option:
vpshufd $-0x79, (%rsp), %xmm0 ## xmm0 = mem[3,1,0,2]
This part of <rdar://problem/14687488>.
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----
Add new API lto_codegen_compile_parallel().
This API is proposed by Nick Kledzik. The semantic is:
--------------------------------------------------------------------------
Generate code for merged module into an array of native object files. On
success returns a pointer to an array of NativeObjectFile. The count
parameter returns the number of elements in the array. Each element is
a pointer/length for a generated mach-o/ELF buffer. The buffer is owned
by the lto_code_gen_t and will be freed when lto_codegen_dispose() is called,
or lto_codegen_compile() is called again. On failure, returns NULL
(check lto_get_error_message() for details).
extern const struct NativeObjectFile*
lto_codegen_compile_parallel(lto_code_gen_t cg, size_t *count);
---------------------------------------------------------------------------
This API is currently only called on OSX platform. Linux or other Unixes
using GNU gold are not supposed to call this function, because on these systems,
object files are fed back to linker via disk file instead of memory buffer.
In this commit, lto_codegen_compile_parallel() simply calls
lto_codegen_compile() to return a single object file. In the near future,
this function is the entry point for compilation with partition. Linker can
blindly call this function even if partition is turned off; in this case,
compiler will return only one object file.
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