This is purely a plumbing patch. No functional changes intended.
The ultimate goal is to allow targets other than PowerPC (certainly X86 and Aarch64) to turn this:
z = y / sqrt(x)
into:
z = y * rsqrte(x)
using whatever HW magic they can use. See http://llvm.org/bugs/show_bug.cgi?id=20900 .
The first step is to add a target hook for RSQRTE, take the already target-independent code selfishly hoarded by PPC, and put it into DAGCombiner.
Next steps:
The code in DAGCombiner::BuildRSQRTE() should be refactored further; tests that exercise that logic need to be added.
Logic in PPCTargetLowering::BuildRSQRTE() should be hoisted into DAGCombiner.
X86 and AArch64 overrides for TargetLowering.BuildRSQRTE() should be added.
Differential Revision: http://reviews.llvm.org/D5425
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the new vector shuffle lowering no longer needs to check both symmetric
forms of UNPCK patterns for v4f64.
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lowering when it can use a symmetric SHUFPS across both 128-bit lanes.
This required making the SHUFPS lowering tolerant of other vector types,
and adjusting our canonicalization to canonicalize harder.
This is the last of the clever uses of symmetry I've thought of for
v8f32. The rest of the tricks I'm aware of here are to work around
assymetry in the mask.
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a generic vector shuffle mask into a helper that isn't specific to the
other things that influence which choice is made or the specific types
used with the instruction.
No functionality changed.
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of a single element into a zero vector for v4f64 and v4i64 in AVX.
Ironically, there is less to see here because xor+blend is so crazy fast
that we can't really beat that to zero the high 128-bit lane.
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UNPCKHPS with AVX vectors by recognizing those patterns when they are
repeated for both 128-bit lanes.
With this, we now generate the exact same (really nice) code for
Quentin's avx_test_case.ll which was the most significant regression
reported for the new shuffle lowering. In fact, I'm out of specific test
cases for AVX lowering, the rest were AVX2 I think. However, there are
a bunch of pretty obvious remaining things to improve with AVX...
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important bits of cleverness: to detect and lower repeated shuffle
patterns between the two 128-bit lanes with a single instruction.
This patch just teaches it how to lower single-input shuffles that fit
this model using VPERMILPS. =] There is more that needs to happen here.
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generating the test cases to format things more consistently and
actually catch all the operand sequences that should be elided in favor
of the asm comments. No actual changes here.
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v8f32 shuffles in the new vector shuffle lowering code.
This is very cheap to do and makes it much more clear that anything more
expensive but overlapping with this lowering should be selected
afterward (for example using AVX2's VPERMPS). However, no functionality
changed here as without this code we would fall through to create no-op
shuffles of each input and a blend. =]
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VBLENDPD over using VSHUFPD. While the 256-bit variant of VBLENDPD slows
down to the same speed as VSHUFPD on Sandy Bridge CPUs, it has twice the
reciprocal throughput on Ivy Bridge CPUs much like it does everywhere
for 128-bits. There isn't a downside, so just eagerly use this
instruction when it suffices.
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This expands the integer cases to cover the fact that AVX2 moves their
lane-crossing shuffles into the integer domain. It also adds proper
support for AVX2 run lines and the "ALL" group when it doesn't matter.
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awkward conditions. The readability improvement of this will be even
more important as I generalize it to handle more types.
No functionality changed.
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128-bit lane crossings, not 'half' crossings. This came up in code
review ages ago, but I hadn't really addresesd it. Also added some
documentation for the helper.
No functionality changed.
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actual support for complex AVX shuffling tricks. We can do independent
blends of the low and high 128-bit lanes of an avx vector, so shuffle
the inputs into place and then do the blend at 256 bits. This will in
many cases remove one blend instruction.
The next step is to permute the low and high halves in-place rather than
extracting them and re-inserting them.
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link.exe:
Fuzz testing has shown that COMMON symbols with size > 32 will always
have an alignment of at least 32 and all symbols with size < 32 will
have an alignment of at least the largest power of 2 less than the size
of the symbol.
binutils:
The BFD linker essentially work like the link.exe behavior but with
alignment 4 instead of 32. The BFD linker also supports an extension to
COFF which adds an -aligncomm argument to the .drectve section which
permits specifying a precise alignment for a variable but MC currently
doesn't support editing .drectve in this way.
With all of this in mind, we decide to play a little trick: we can
ensure that the alignment will be respected by bumping the size of the
global to it's alignment.
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under AVX.
This really just documents the current state of the world. I'm going to
try to flesh it out to cover any test cases I plan to improve prior to
improving them so that the delta made by changes is actually visible to
code reviewers.
This is made easier by the fact that I now have a script to automate the
process of producing test cases including the check lines. =]
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single-input shuffles with doubles. This allows them to fold memory
operands into the shuffle, etc. This is just the analog to the v4f32
case in my prior commit.
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instruction for single-vector floating point shuffles. This in turn
allows the shuffles to fold a load into the instruction which is one of
the common regressions hit with the new shuffle lowering.
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We had a few bugs:
- We were considering the GVKind instead of just looking at the section
characteristics
- We would never print out 'y' when a section was meant to be unreadable
- We would never print out 's' when a section was meant to be shared
- We translated IMAGE_SCN_MEM_DISCARDABLE to 'n' when it should've meant
IMAGE_SCN_LNK_REMOVE
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duplication of check lines. The idea is to have broad sets of
compilation modes that will frequently diverge without having to always
and immediately explode to the precise ISA feature set.
While this already helps due to VEX encoded differences, it will help
much more as I teach the new shuffle lowering about more of the new VEX
encoded instructions which can still be used to implement 128-bit
shuffles.
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This patch modifies RTDyldMemoryManager::getSymbolAddress(Name)'s behavior to
make it consistent with how clients are using it: Name should be mangled, and
getSymbolAddress should demangle it on the caller's behalf before looking the
name up in the process. This patch also fixes the one client
(MCJIT::getPointerToFunction) that had been passing unmangled names (by having
it pass mangled names instead).
Background:
RTDyldMemoryManager::getSymbolAddress(Name) has always used a re-try mechanism
when looking up symbol names in the current process. Prior to this patch
getSymbolAddress first tried to look up 'Name' exactly as the user passed it in
and then, if that failed, tried to demangle 'Name' and re-try the look up. The
implication of this behavior is that getSymbolAddress expected to be called with
unmangled names, and that handling mangled names was a fallback for convenience.
This is inconsistent with how clients (particularly the RuntimeDyldImpl
subclasses, but also MCJIT) usually use this API. Most clients pass in mangled
names, and succeed only because of the fallback case. For clients passing in
mangled names, getSymbolAddress's old behavior was actually dangerous, as it
could cause unmangled names in the process to shadow mangled names being looked
up.
For example, consider:
foo.c:
int _x = 7;
int x() { return _x; }
foo.o:
000000000000000c D __x
0000000000000000 T _x
If foo.c becomes part of the process (E.g. via dlopen("libfoo.dylib")) it will
add symbols 'x' (the function) and '_x' (the variable) to the process. However
jit clients looking for the function 'x' will be using the mangled function name
'_x' (note how function 'x' appears in foo.o). When getSymbolAddress goes
looking for '_x' it will find the variable instead, and return its address and
in place of the function, leading to JIT'd code calling the variable and
crashing (if we're lucky).
By requiring that getSymbolAddress be called with mangled names, and demangling
only when we're about to do a lookup in the process, the new behavior
implemented in this patch should eliminate any chance of names being shadowed
during lookup.
There's no good way to test this at the moment: This issue only arrises when
looking up process symbols (not JIT'd symbols). Any test case would have to
generate a platform-appropriate dylib to pass to llvm-rtdyld, and I'm not
aware of any in-tree tool for doing this in a portable way.
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This splits the logic for actually looking up coverage information
from the logic that displays it. These were tangled rather thoroughly
so this change is a bit large, but it mostly consists of moving things
around. The coverage lookup logic itself now lives in the library,
rather than being spread between the library and the tool.
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This debug output is really for testing CoverageMappingReader, not the
llvm-cov tool. Move it to where it can be more useful.
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A problem with our old behavior becomes observable under x86-64 COFF
when we need a read-only GV which has an initializer which is referenced
using a relocation: we would mark the section as writable. Marking the
section as writable interferes with section merging.
This fixes PR21009.
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tricky case of single-element insertion into the zero lane of a zero
vector.
We can't just use the same pattern here as we do in every other vector
type because the general insertion logic can handle insertion into the
non-zero lane of the vector. However, in SSE4.1 with v4f32 vectors we
have INSERTPS that is a much better choice than the generic one for such
lowerings. But INSERTPS can do lots of other lowerings as well so
factoring its logic into the general insertion logic doesn't work very
well. We also can't just extract the core common part of the general
insertion logic that is faster (forming VZEXT_MOVL synthetic nodes that
lower to MOVSS when they can) because VZEXT_MOVL is often *faster* than
a blend while INSERTPS is slower! So instead we do a restrictive
condition on attempting to use the generic insertion logic to narrow it
to those cases where VZEXT_MOVL won't need a shuffle afterward and thus
will do better than INSERTPS. Then we try blending. Then we go back to
INSERTPS.
This still doesn't generate perfect code for some silly reasons that can
be fixed by tweaking the td files for lowering VZEXT_MOVL to use
XORPS+BLENDPS when available rather than XORPS+MOVSS when the input ends
up in a register rather than a load from memory -- BLENDPSrr has twice
the reciprocal throughput of MOVSSrr. Don't you love this ISA?
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analysis used elsewhere. This removes the last duplicate of this logic.
Also simplify the code here quite a bit. No functionality changed.
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floating point types and use it for both v2f64 and v2i64 single-element
insertion lowering.
This fixes the last non-AVX performance regression test case I've gotten
of for the new vector shuffle lowering. There is obvious analogous
lowering for v4f32 that I'll add in a follow-up patch (because with
INSERTPS, v4f32 requires special treatment). After that, its AVX stuff.
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vector lanes can be modeled as zero with a call to the new function that
computes a bit-vector representing that information.
No functionality changed here, but will allow doing more clever things
with the zero-test.
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I just tried reproducing some of the optimization failures in README.txt in the
X86 backend, and many of them could not be reproduced. In general the entire
file appears quite bit-rotted, whatever interesting parts remain should be
moved to bugzilla, and the rest deleted. I did not spend the time to do that,
so I just deleted the few I tried reproducing which are obsolete, to save some
time to whoever will find the courage to do it.
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