This patch builds on some existing code to do CFG reconstruction from
a disassembled binary:
- MCModule represents the binary, and has a list of MCAtoms.
- MCAtom represents either disassembled instructions (MCTextAtom), or
contiguous data (MCDataAtom), and covers a specific range of addresses.
- MCBasicBlock and MCFunction form the reconstructed CFG. An MCBB is
backed by an MCTextAtom, and has the usual successors/predecessors.
- MCObjectDisassembler creates a module from an ObjectFile using a
disassembler. It first builds an atom for each section. It can also
construct the CFG, and this splits the text atoms into basic blocks.
MCModule and MCAtom were only sketched out; MCFunction and MCBB were
implemented under the experimental "-cfg" llvm-objdump -macho option.
This cleans them up for further use; llvm-objdump -d -cfg now generates
graphviz files for each function found in the binary.
In the future, MCObjectDisassembler may be the right place to do
"intelligent" disassembly: for example, handling constant islands is just
a matter of splitting the atom, using information that may be available
in the ObjectFile. Also, better initial atom formation than just using
sections is possible using symbols (and things like Mach-O's
function_starts load command).
This brings two minor regressions in llvm-objdump -macho -cfg:
- The printing of a relocation's referenced symbol.
- An annotation on loop BBs, i.e., which are their own successor.
Relocation printing is replaced by the MCSymbolizer; the basic CFG
annotation will be superseded by more related functionality.
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This is a basic first step towards symbolization of disassembled
instructions. This used to be done using externally provided (C API)
callbacks. This patch introduces:
- the MCSymbolizer class, that mimics the same functions that were used
in the X86 and ARM disassemblers to symbolize immediate operands and
to annotate loads based off PC (for things like c string literals).
- the MCExternalSymbolizer class, which implements the old C API.
- the MCRelocationInfo class, which provides a way for targets to
translate relocations (either object::RelocationRef, or disassembler
C API VariantKinds) to MCExprs.
- the MCObjectSymbolizer class, which does symbolization using what it
finds in an object::ObjectFile. This makes simple symbolization (with
no fancy relocation stuff) work for all object formats!
- x86-64 Mach-O and ELF MCRelocationInfos.
- A basic ARM Mach-O MCRelocationInfo, that provides just enough to
support the C API VariantKinds.
Most of what works in otool (the only user of the old symbolization API
that I know of) for x86-64 symbolic disassembly (-tvV) works, namely:
- symbol references: call _foo; jmp 15 <_foo+50>
- relocations: call _foo-_bar; call _foo-4
- __cf?string: leaq 193(%rip), %rax ## literal pool for "hello"
Stub support is the main missing part (because libObject doesn't know,
among other things, about mach-o indirect symbols).
As for the MCSymbolizer API, instead of relying on the disassemblers
to call the tryAdding* methods, maybe this could be done automagically
using InstrInfo? For instance, even though PC-relative LEAs are used
to get the address of string literals in a typical Mach-O file, a MOV
would be used in an ELF file. And right now, the explicit symbolization
only recognizes PC-relative LEAs. InstrInfo should have already have
most of what is needed to know what to symbolize, so this can
definitely be improved.
I'd also like to remove object::RelocationRef::getValueString (it seems
only used by relocation printing in objdump), as simply printing the
created MCExpr is definitely enough (and cleaner than string concats).
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Now that there is no longer any distinction between symbolLo
and symbolHi operands in either printing, encoding, or parsing,
the operand types can be removed in favor of simply using
s16imm.
This completes the patch series to decouple lo/hi operand part
processing from the particular instruction whose operand it is.
No change in code generation expected from this patch.
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- move AsmWriter.h from public headers into lib
- marked all AssemblyWriter functions as non-virtual; no need to override them
- DebugIR now "plugs into" AssemblyWriter with an AssemblyAnnotationWriter helper
- exposed flags to control hiding of a) debug metadata b) debug intrinsic calls
C/R: Paul Redmond
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When targeting the Darwin assembler, we need to generate markers ha16() and
lo16() to designate the high and low parts of a (symbolic) immediate. This
is necessary not just for plain symbols, but also for certain symbolic
expression, typically along the lines of ha16(A - B). The latter doesn't
work when simply using VariantKind flags on the symbol reference.
This is why the current back-end uses hacks (explicitly called out as such
via multiple FIXMEs) in the symbolLo/symbolHi print methods.
This patch uses target-defined MCExpr codes to represent the Darwin
ha16/lo16 constructs, following along the lines of the equivalent solution
used by the ARM back end to handle their :upper16: / :lower16: markers.
This allows us to get rid of special handling both in the symbolLo/symbolHi
print method and in the common code MCExpr::print routine. Instead, the
ha16 / lo16 markers are printed simply in a custom print routine for the
target MCExpr types. (As a result, the symbolLo/symbolHi print methods
can now replaced by a single printS16ImmOperand routine that also handles
symbolic operands.)
The patch also provides a EvaluateAsRelocatableImpl routine to handle
ha16/lo16 constructs. This is not actually used at the moment by any
in-tree code, but is provided as it makes merging into David Fang's
out-of-tree Mach-O object writer simpler.
Since there is no longer any need to treat VK_PPC_GAS_HA16 and
VK_PPC_DARWIN_HA16 differently, they are merged into a single
VK_PPC_ADDR16_HA (and likewise for the _LO16 types).
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Move the processing of the command line options to right before we create the
TargetMachine instead of after.
<rdar://problem/13468287>
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This implements the @llvm.readcyclecounter intrinsic as the specific
MRC instruction specified in the ARM manuals for CPUs with the Power
Management extensions.
Older CPUs had slightly different methods which may also have to be
implemented eventually, but this should cover all v7 cases.
rdar://problem/13939186
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Performance monitors, including a basic cycle counter, are an official
extension in the ARMv7 specification. This adds support for enabling and
disabling them, orthogonally from CPU selection.
rdar://problem/13939186
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Now that the LiveDebugVariables pass is running *after* register
coalescing, the ConnectedVNInfoEqClasses class needs to deal with
DBG_VALUE instructions.
This only comes up when rematerialization during coalescing causes the
remaining live range of a virtual register to separate into two
connected components.
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The error was:
error: non-constant-expression cannot be narrowed from type 'long long' to 'long' in initializer list [-Wc++11-narrowing]
MI.getOperand(6).getImm() & 0x1F,
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API with my 176880 revision. If a bad Triple is passed in it can also assert.
In this case too it should just return 0 to indicate failure to create the
disassembler.
rdar://13955214
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There were bits & pieces of code lying around that may've given the
impression that debug info metadata supported the possibility that a
subprogram's type could be specified by a non-subroutine type describing
the return type of a void function. This support was incomplete &
unnecessary. Asserts & API have been changed to make the desired usage
more clear.
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Currently the fast-isel table generator recognizes registers, register
classes, and immediates for source pattern operands. ValueType
operands are not recognized. This is not a problem for existing
targets with fast-isel support, but will not work for targets like
PowerPC and SPARC that use types in source patterns.
The proposed patch allows ValueType operands and treats them in the
same manner as register classes. There is no convenient way to map
from a ValueType to a register class, but there's no need to do so.
The table generator already requires that all types in the source
pattern be identical, and we know the register class of the output
operand already. So we just assign that register class to any
ValueType operands we encounter.
No functional effect on existing targets. Testing deferred until the
PowerPC target implements fast-isel.
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Using PatLeaf rather than ImmLeaf when defining immediate predicates
prevents simple patterns using those predicates from being recognized
for fast instruction selection. This patch replaces the immSExt16
PatLeaf predicate with two ImmLeaf predicates, imm32SExt16 and
imm64SExt16, allowing a few more patterns to be recognized (ADDI,
ADDIC, MULLI, ADDI8, and ADDIC8). Using the new predicates does not
help for LI, LI8, SUBFIC, and SUBFIC8 because these are rejected for
other reasons, but I see no reason to retain the PatLeaf predicate.
No functional change intended, and thus no test cases yet. This is
preliminary work for enabling fast-isel support for PowerPC. When
that support is ready, we'll be able to test this function.
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We are not working on a DAG and I ran into a number of problems when I enabled the vectorizations of 'diamond-trees' (trees that share leafs).
* Imroved the numbering API.
* Changed the placement of new instructions to the last root.
* Fixed a bug with external tree users with non-zero lane.
* Fixed a bug in the placement of in-tree users.
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The earlier change list introduced the following inst combines:
B * (uitofp i1 C) —> select C, B, 0
A * (1 - uitofp i1 C) —> select C, 0, A
select C, 0, B + select C, A, 0 —> select C, A, B
Together these 3 changes would simplify :
A * (1 - uitofp i1 C) + B * uitofp i1 C
down to :
select C, B, A
In practice we found that the first two substitutions can have a
negative effect on performance, because they reduce opportunities to
use FMA contractions; between the two options FMAs are often the
better choice. This change list amends the previous one to enable
just these inst combines:
select C, B, 0 + select C, 0, A —> select C, B, A
A * (1 - uitofp i1 C) + B * uitofp i1 C —> select C, B, A
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The Value pointers we store in the induction variable list can be RAUW'ed by a
call to SCEVExpander::expandCodeFor, use a TrackingVH instead. Do the same thing
in some other places where we store pointers that could potentially be RAUW'ed.
Fixes PR16073.
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Addresses a review comment from Ulrich Weigand. No functional change intended.
I'm not sure whether the old TODO that this patch touches still holds,
but that's something we'd get to when adding a targetted scheduling
description.
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The original version of the pass could underestimate the length of a backward
branch in cases like:
alignment to N bytes or more
...
relaxable branch A
...
foo: (aligned to M<N bytes)
...
bar: (aligned to N bytes)
...
relaxable branch B to foo
We don't add any misalignment gap for "bar" because N bytes of alignment
had already been reached earlier in the function. In this case, assuming
that A is relaxed can push "foo" closer to "bar", and make B appear to be
in range. Similar problems can occur for forward branches.
I don't think it's possible to create blocks with mixed alignments as
things stand, not least because we haven't yet defined getPrefLoopAlignment()
for SystemZ (that would need benchmarking). So I don't think we can test
this yet.
Thanks to Rafael Espíndola for spotting the bug.
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