As pointed out in r226501, the distinction between `MDNode` and
`UniquableMDNode` is confusing. When we need subclasses of `MDNode`
that don't use all its functionality it might make sense to break it
apart again, but until then this makes the code clearer.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226520 91177308-0d34-0410-b5e6-96231b3b80d8
Now that we can create much more exhaustive X86 memory folding tests, this patch adds the missing AVX1/F16C floating point instruction stack foldings we can easily test for including the scalar intrinsics (add, div, max, min, mul, sub), conversions float/int to double, half precision conversions, rounding, dot product and bit test. The patch also adds a couple of obviously missing SSE instructions (more to follow once we have full SSE testing).
Now that scalar folding is working it broke a very old test (2006-10-07-ScalarSSEMiscompile.ll) - this test appears to make no sense as its trying to ensure that a scalar subtraction isn't folded as it 'would zero the top elts of the loaded vector' - this test just appears to be wrong to me.
Differential Revision: http://reviews.llvm.org/D7055
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226513 91177308-0d34-0410-b5e6-96231b3b80d8
Take advantage of the new ability of temporary nodes to mutate to
distinct and uniqued nodes to greatly simplify the `MapMetadata()`
helper functions.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226511 91177308-0d34-0410-b5e6-96231b3b80d8
Add `MDNode::replaceWithUniqued()` and `MDNode::replaceWithDistinct()`,
which mutate temporary nodes to become uniqued or distinct. On uniquing
collisions, the unique version is returned and the node is deleted.
This takes advantage of temporary nodes being folded back in, and should
let me clean up some awkward logic in `MapMetadata()`.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226510 91177308-0d34-0410-b5e6-96231b3b80d8
Change `MDTuple::getTemporary()` and `MDLocation::getTemporary()` to
return (effectively) `std::unique_ptr<T, MDNode::deleteTemporary>`, and
clean up call sites. (For now, `DIBuilder` call sites just call
`release()` immediately.)
There's an accompanying change in each of clang and polly to use the new
API.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226504 91177308-0d34-0410-b5e6-96231b3b80d8
The fixes are to note that AArch64 has additional restrictions on when local
relocations can be used. In particular, ld64 requires that relocations to
cstring/cfstrings use linker visible symbols.
Original message:
In an assembly expression like
bar:
.long L0 + 1
the intended semantics is that bar will contain a pointer one byte past L0.
In sections that are merged by content (strings, 4 byte constants, etc), a
single position in the section doesn't give the linker enough information.
For example, it would not be able to tell a relocation must point to the
end of a string, since that would look just like the start of the next.
The solution used in ELF to use relocation with symbols if there is a non-zero
addend.
In MachO before this patch we would just keep all symbols in some sections.
This would miss some cases (only cstrings on x86_64 were implemented) and was
inefficient since most relocations have an addend of 0 and can be represented
without the symbol.
This patch implements the non-zero addend logic for MachO too.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226503 91177308-0d34-0410-b5e6-96231b3b80d8
Remove `MDNodeFwdDecl` (as promised in r226481). Aside from API
changes, there's no real functionality change here.
`MDNode::getTemporary()` now forwards to `MDTuple::getTemporary()`,
which returns a tuple with `isTemporary()` equal to true.
The main point is that we can now add temporaries of other `MDNode`
subclasses, needed for PR22235 (I introduced `MDNodeFwdDecl` in the
first place because I didn't recognize this need, and thought they were
only needed to handle forward references).
A few things left out of (or highlighted by) this commit:
- I've had to remove the (few) uses of `std::unique_ptr<>` to deal
with temporaries, since the destructor is no longer public.
`getTemporary()` should probably return the equivalent of
`std::unique_ptr<T, MDNode::deleteTemporary>`.
- `MDLocation::getTemporary()` doesn't exist yet (worse, it actually
does exist, but does the wrong thing: `MDNode::getTemporary()` is
inherited and returns an `MDTuple`).
- `MDNode` now only has one subclass, `UniquableMDNode`, and the
distinction between them is actually somewhat confusing.
I'll fix those up next.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226501 91177308-0d34-0410-b5e6-96231b3b80d8
Merge `getDistinct()`'s implementation with those of `get()` and
`getIfExists()` for both `MDTuple` and `MDLocation`. This will make it
easier to scale to supporting temporaries.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226497 91177308-0d34-0410-b5e6-96231b3b80d8
Use `isUniqued()` instead of `isStoredDistinctInContext()`, and remove
an assertion that won't be valid once temporaries are merged back in.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226491 91177308-0d34-0410-b5e6-96231b3b80d8
Add an assertion in `UniquableMDNode::resolve()` to prevent temporaries
from being resolved (once they're merged back in). Needed to shuffle
order of `resolve()` and `storeDistinctInContext()` to prevent it from
firing.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226489 91177308-0d34-0410-b5e6-96231b3b80d8
Unify the definitions of `MDNode::isResolved()` and
`UniquableMDNode::isResolved()`. Previously, `UniquableMDNode` could
answer this question more efficiently, but now that RAUW support has
been unified with `MDNodeFwdDecl`, `MDNode` doesn't need any casts to
figure out the answer.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226485 91177308-0d34-0410-b5e6-96231b3b80d8
Add an `LLVMContext &` to `ReplaceableMetadataImpl`, create a class that
either holds a reference to an `LLVMContext` or owns a
`ReplaceableMetadataImpl`, and use the new class in `MDNode`.
- This saves a pointer in `UniquableMDNode` at the cost of a pointer
in `ValueAsMetadata` (which didn't used to store the `LLVMContext`).
There are far more of the former.
- Unifies RAUW support between `MDNodeFwdDecl` (which is going away,
see r226481) and `UniquableMDNode`.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226484 91177308-0d34-0410-b5e6-96231b3b80d8
Change `MDNode::isDistinct()` to only apply to 'distinct' nodes (not
temporaries), and introduce `MDNode::isUniqued()` and
`MDNode::isTemporary()` for the other two possibilities.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226482 91177308-0d34-0410-b5e6-96231b3b80d8
More clearly describe the type of storage used for `Metadata`.
- `Uniqued`: uniqued, stored in the context.
- `Distinct`: distinct, stored in the context.
- `Temporary`: not owned by anyone.
This is the first in a series of commits to fix a design problem with
`MDNodeFwdDecl` that I need to solve for PR22235. While `MDNodeFwdDecl`
works well as a forward declaration, we use `MDNode::getTemporary()` for
more than forward declarations -- we also need to create early versions
of nodes (with fields not filled in) that we'll fill out later (see
`DIBuilder::finalize()` and `CGDebugInfo::finalize()` for examples).
This was a blind spot I had when I introduced `MDNodeFwdDecl` (which
David Blaikie (indirectly) highlighted in an unrelated review [1]).
[1]: http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20150112/252381.html
In general, we need `MDTuple::getTemporary()` to give a temporary tuple
(like `MDNodeFwdDecl`), `MDLocation::getTemporary()` to give a temporary
location, and (the problem at hand) `GenericDebugMDNode::getTemporary()`
to give a temporary generic debug node.
So I need to fold the idea of "temporary" nodes back into
`UniquableMDNode`. (More commits to follow as I refactor.)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226481 91177308-0d34-0410-b5e6-96231b3b80d8
frontends to use a DIExpression with a DW_OP_deref instead.
This is not only a much more natural place for this informationl; there
is also a technical reason: The FlagIndirectVariable is used to mark a
variable that is turned into a reference by virtue of the calling
convention; this happens for example to aggregate return values.
The inliner, for example, may actually need to undo this indirection to
correctly represent the value in its new context. This is impossible to
implement because the DIVariable can't be safely modified. We can however
safely construct a new DIExpression on the fly.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226476 91177308-0d34-0410-b5e6-96231b3b80d8
An assignment will produce a symbol with a given section and offset. There is
no way to represent something like "1 byte after a common symbol".
This matches the behavior of GNU as.
Part of PR22217.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226470 91177308-0d34-0410-b5e6-96231b3b80d8
No change in this commit, but clang was changed to also produce trivial comdats when
needed.
Original message:
Don't create new comdats in CodeGen.
This patch stops the implicit creation of comdats during codegen.
Clang now sets the comdat explicitly when it is required. With this patch clang and gcc
now produce the same result in pr19848.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226467 91177308-0d34-0410-b5e6-96231b3b80d8
and updated.
This may appear to remove handling for things like alias analysis when
splitting critical edges here, but in fact no callers of SplitEdge
relied on this. Similarly, all of them wanted to preserve LCSSA if there
was any update of the loop info. That makes the interface much simpler.
With this, all of BasicBlockUtils.h is free of Pass arguments and
prepared for the new pass manager. This is tho majority of utilities
that relied on pass arguments.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226459 91177308-0d34-0410-b5e6-96231b3b80d8
while refactoring this API for the new pass manager.
No functionality changed here, the code didn't actually support this
option.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226457 91177308-0d34-0410-b5e6-96231b3b80d8
APIs and replace it and numerous booleans with an option struct.
The critical edge splitting API has a really large surface of flags and
so it seems worth burning a small option struct / builder. This struct
can be constructed with the various preserved analyses and then flags
can be flipped in a builder style.
The various users are now responsible for directly passing along their
analysis information. This should be enough for the critical edge
splitting to work cleanly with the new pass manager as well.
This API is still pretty crufty and could be cleaned up a lot, but I've
focused on this change just threading an option struct rather than
a pass through the API.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226456 91177308-0d34-0410-b5e6-96231b3b80d8
we can while splitting critical edges.
The only code which called this and didn't require simplified loops to
be preserved is polly, and the code behaves correctly there anyways.
Without this change, it becomes really hard to share this code with the
new pass manager where things like preserving loop simplify form don't
make any sense.
If anyone discovers this code behaving incorrectly, what it *should* be
testing for is whether the loops it needs to be in simplified form are
in fact in that form. It should always be trying to preserve that form
when it exists.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226443 91177308-0d34-0410-b5e6-96231b3b80d8
In case of blocks with many memory-accessing instructions, alias checking can take lot of time
(because calculating the memory dependencies has quadratic complexity).
I chose a limit which resulted in no changes when running the benchmarks.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226439 91177308-0d34-0410-b5e6-96231b3b80d8
We don't need to exclude patchpoints from the implicit r2 dependence in
FastISel because it is added as an implicit operand and, thus, should not
confuse that StackMap code.
By inspection / no test case.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226434 91177308-0d34-0410-b5e6-96231b3b80d8
Our PPC64 ELF V2 call lowering logic added r2 as an operand to all direct call
instructions in order to represent the dependency on the TOC base pointer
value. Restricting this to ELF V2, however, does not seem to make sense: calls
under ELF V1 have the same dependence, and indirect calls have an r2 dependence
just as direct ones. Make sure the dependence is noted for all calls under both
ELF V1 and ELF V2.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226432 91177308-0d34-0410-b5e6-96231b3b80d8
SplitLandingPadPredecessors and remove the Pass argument from its
interface.
Another step to the utilities being usable with both old and new pass
managers.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226426 91177308-0d34-0410-b5e6-96231b3b80d8
Instructions that have high-order TOC relocations always carry R2 as their base
register, so it does not matter whether we take the register from the
instruction or just hard-code it in PPCAsmPrinter. In the future, however, we
might want to apply these relocations to instructions using a different
register, so taking the register from the instruction is a better thing to do.
No change in functionality here, however.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226403 91177308-0d34-0410-b5e6-96231b3b80d8
So we don't forget, once we support FPR <-> GPR moves on the P8, we'll likely
want to re-visit this part of the calling convention.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226401 91177308-0d34-0410-b5e6-96231b3b80d8
The default calling convention specified by the PPC64 ELF (V1 and V2) ABI is
designed to work with both prototyped and non-prototyped/varargs functions. As
a result, GPRs and stack space are allocated for every argument, even those
that are passed in floating-point or vector registers.
GlobalOpt::OptimizeFunctions will transform local non-varargs functions (that
do not have their address taken) to use the 'fast' calling convention.
When functions are using the 'fast' calling convention, don't allocate GPRs for
arguments passed in other types of registers, and don't allocate stack space for
arguments passed in registers. Other changes for the fast calling convention
may be added in the future.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226399 91177308-0d34-0410-b5e6-96231b3b80d8
rather than relying on the pass object.
This one is a bit annoying, but will pay off. First, supporting this one
will make the next one much easier, and for utilities like LoopSimplify,
this is moving them (slowly) closer to not having to pass the pass
object around throughout their APIs.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226396 91177308-0d34-0410-b5e6-96231b3b80d8
interface, removing Pass from its interface.
This also makes those analyses optional so that passes which don't even
preserve these (or use them) can skip the logic entirely.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226394 91177308-0d34-0410-b5e6-96231b3b80d8
optionally updated by MergeBlockIntoPredecessors.
No functionality changed, just refactoring to clear the way for the new
pass manager.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226392 91177308-0d34-0410-b5e6-96231b3b80d8
Instead of querying the pass every where we need to, do that once and
cache a pointer in the pass object. This is both simpler and I'm about
to add yet another place where we need to dig out that pointer.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226391 91177308-0d34-0410-b5e6-96231b3b80d8
accepting a Pass and querying it for analyses.
This is necessary to allow the utilities to work both with the old and
new pass managers, and I also think this makes the interface much more
clear and helps the reader know what analyses the utility can actually
handle. I plan to repeat this process iteratively to clean up all the
pass utilities.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226386 91177308-0d34-0410-b5e6-96231b3b80d8
cleaner to derive from the generic base.
Thise removes a ton of boiler plate code and somewhat strange and
pointless indirections. It also remove a bunch of the previously needed
friend declarations. To fully remove these, I also lifted the verify
logic into the generic LoopInfoBase, which seems good anyways -- it is
generic and useful logic even for the machine side.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226385 91177308-0d34-0410-b5e6-96231b3b80d8
unused variables in a no-asserts build.
I've fixed this by putting the entire loop behind an #ifndef as it
contains nothing other than asserts.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226377 91177308-0d34-0410-b5e6-96231b3b80d8
This was dead even before I refactored how we initialized it, but my
refactoring made it trivially dead and it is now caught by a Clang
warning. This fixes the warning and should clean up the -Werror bot
failures (sorry!).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226376 91177308-0d34-0410-b5e6-96231b3b80d8
a LoopInfoWrapperPass to wire the object up to the legacy pass manager.
This switches all the clients of LoopInfo over and paves the way to port
LoopInfo to the new pass manager. No functionality change is intended
with this iteration.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226373 91177308-0d34-0410-b5e6-96231b3b80d8
R11's status is the same under both the PPC64 ELF V1 and V2 ABIs: it is
reserved for use as an "environment pointer" for compilation models that
require such a thing. We don't, we also don't need a second scratch register,
and because we support only "local" patchpoint call targets, we might as well
let R11 be used for anyregcc patchpoints.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226369 91177308-0d34-0410-b5e6-96231b3b80d8
Loading 2 2x32-bit float vectors into the bottom half of a 256-bit vector
produced suboptimal code in AVX2 mode with certain IR combinations.
In particular, the IR optimizer folded 2f32 + 2f32 -> 4f32, 4f32 + 4f32
(undef) -> 8f32 into a 2f32 + 2f32 -> 8f32, which seems more canonical,
but then mysteriously generated rather bad code; the movq/movhpd combination
didn't match.
The problem lay in the BUILD_VECTOR optimization path. The 2f32 inputs
would get promoted to 4f32 by the type legalizer, eventually resulting
in a BUILD_VECTOR on two 4f32 into an 8f32. The BUILD_VECTOR then, recognizing
these were both half the output size, concatted them and then produced
a shuffle. However, the resulting concat + shuffle was more complex than
it should be; in the case where the upper half of the output is undef, we
probably want to generate shuffle + concat instead.
This enhancement causes the vector_shuffle combine step to recognize this
suboptimal pattern and correct it. I included it there instead of in BUILD_VECTOR
in case the same suboptimal pattern occurs for other reasons.
This results in the optimizer correctly producing the optimal movq + movhpd
sequence for all three variations on this IR, even with AVX2.
I've included a test case.
Radar link: rdar://problem/19287012
Fix for PR 21943.
From: Fiona Glaser <fglaser@apple.com>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226360 91177308-0d34-0410-b5e6-96231b3b80d8
- Consistenly put comments above the function declaration, not the
definition. To achieve this some duplicate comments got merged and
some comment parts describing implementation details got moved into their
functions.
- Consistently use doxygen comments above functions.
- Do not use doxygen comments inside functions.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226351 91177308-0d34-0410-b5e6-96231b3b80d8
RuntimeDyld symbol info previously consisted of just a Section/Offset pair. This
patch replaces that pair type with a SymbolInfo class that also tracks symbol
visibility. A new method, RuntimeDyld::getExportedSymbolLoadAddress, is
introduced which only returns a non-zero result for exported symbols. For
non-exported or non-existant symbols this method will return zero. The
RuntimeDyld::getSymbolAddress method retains its current behavior, returning
non-zero results for all symbols regardless of visibility.
No in-tree clients of RuntimeDyld are changed. The newly introduced
functionality will be used by the Orc APIs.
No test case: Since this patch doesn't modify the behavior for any in-tree
clients we don't have a good tool to test this with yet. Once Orc is in we can
use it to write regression tests that test these changes.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226341 91177308-0d34-0410-b5e6-96231b3b80d8
Note: This change ended up being slightly more controversial than expected. Chandler has tentatively okayed this for the moment, but I may be revisiting this in the near future after we settle some high level questions.
Rather than have the GCStrategy object owned by the GCModuleInfo - which is an immutable analysis pass used mainly by gc.root - have it be owned by the LLVMContext. This simplifies the ownership logic (i.e. can you have two instances of the same strategy at once?), but more importantly, allows us to access the GCStrategy in the middle end optimizer. To this end, I add an accessor through Function which becomes the canonical way to get at a GCStrategy instance.
In the near future, this will allows me to move some of the checks from http://reviews.llvm.org/D6808 into the Verifier itself, and to introduce optimization legality predicates for some of the recent additions to InstCombine. (These will follow as separate changes.)
Differential Revision: http://reviews.llvm.org/D6811
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226311 91177308-0d34-0410-b5e6-96231b3b80d8
Searching all of the existing gc.root implementations I'm aware of (all three of them), there was exactly one use of this mechanism, and that was to implement a performance improvement that should have been applied to the default lowering.
Having this function is requiring a dependency on a CodeGen class (MachineFunction), in a class which is otherwise completely independent of CodeGen. I could solve this differently, but given that I see absolutely no value in preserving this mechanism, I going to just get rid of it.
Note: Tis is the first time I'm intentionally breaking previously supported gc.root functionality. Given 3.6 has branched, I believe this is a good time to do this.
Differential Revision: http://reviews.llvm.org/D7004
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226305 91177308-0d34-0410-b5e6-96231b3b80d8
Similar to the unaligned cases.
Test was generated with update_llc_test_checks.py.
Part of <rdar://problem/17688758>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226296 91177308-0d34-0410-b5e6-96231b3b80d8
This patch disables target specific combine on X86ISD::INSERTPS dag nodes
if optlevel is CodeGenOpt::None.
The backend currently implements a target specific combine rule that converts
a vector load used by an INSERTPS dag node into a scalar load plus a
scalar_to_vector. This allows ISel to select a single INSERTPSrm instead of
two instructions (i.e. a vector load plus INSERTPSrr).
However, the existing target combine rule on INSERTPS nodes only works under
the assumption that ISel will always be able to match an INSERTPSrm. This is
not true in general at -O0, since the backend only allows folding a load into
the memory operand of an instruction if the optimization level is not
CodeGenOpt::None.
In the example below:
//
__m128 test(__m128 a, __m128 *b) {
__m128 c = _mm_insert_ps(a, *b, 1 << 6);
return c;
}
//
Before this patch, at -O0, the backend would have canonicalized the load to 'b'
into a scalar load plus scalar_to_vector. Later on, ISel would have selected an
INSERTPSrr leaving the insertps mask in an inconsistent state:
movss 4(%rdi), %xmm1
insertps $64, %xmm1, %xmm0 # xmm0 = xmm1[1],xmm0[1,2,3].
With this patch, the backend avoids folding the vector load into the operand of
the INSERTPS. The new codegen at -O0 is:
movaps (%rdi), %xmm1
insertps $64, %xmm1, %xmm0 # %xmm1[1],xmm0[1,2,3].
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226277 91177308-0d34-0410-b5e6-96231b3b80d8
Bill Schmidt pointed out that some adjustments would be needed to properly
support powerpc64le (using the ELF V2 ABI). For one thing, R11 is not available
as a scratch register, so we need to use R12. R12 is also available under ELF
V1, so to maintain consistency, I flipped the order to make R12 the first
scratch register in the array under both ABIs.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226247 91177308-0d34-0410-b5e6-96231b3b80d8
This reverts commit r226173, adding r226038 back.
No change in this commit, but clang was changed to also produce trivial comdats for
costructors, destructors and vtables when needed.
Original message:
Don't create new comdats in CodeGen.
This patch stops the implicit creation of comdats during codegen.
Clang now sets the comdat explicitly when it is required. With this patch clang and gcc
now produce the same result in pr19848.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226242 91177308-0d34-0410-b5e6-96231b3b80d8
IRCE eliminates range checks of the form
0 <= A * I + B < Length
by splitting a loop's iteration space into three segments in a way
that the check is completely redundant in the middle segment. As an
example, IRCE will convert
len = < known positive >
for (i = 0; i < n; i++) {
if (0 <= i && i < len) {
do_something();
} else {
throw_out_of_bounds();
}
}
to
len = < known positive >
limit = smin(n, len)
// no first segment
for (i = 0; i < limit; i++) {
if (0 <= i && i < len) { // this check is fully redundant
do_something();
} else {
throw_out_of_bounds();
}
}
for (i = limit; i < n; i++) {
if (0 <= i && i < len) {
do_something();
} else {
throw_out_of_bounds();
}
}
IRCE can deal with multiple range checks in the same loop (it takes
the intersection of the ranges that will make each of them redundant
individually).
Currently IRCE does not do any profitability analysis. That is a
TODO.
Please note that the status of this pass is *experimental*, and it is
not part of any default pass pipeline. Having said that, I will love
to get feedback and general input from people interested in trying
this out.
This pass was originally r226201. It was reverted because it used C++
features not supported by MSVC 2012.
Differential Revision: http://reviews.llvm.org/D6693
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226238 91177308-0d34-0410-b5e6-96231b3b80d8
