Summary:
Now that the DataLayout is a mandatory part of the module, let's start
cleaning the codebase. This patch is a first attempt at doing that.
This patch is not exactly NFC as for instance some places were passing
a nullptr instead of the DataLayout, possibly just because there was a
default value on the DataLayout argument to many functions in the API.
Even though it is not purely NFC, there is no change in the
validation.
I turned as many pointer to DataLayout to references, this helped
figuring out all the places where a nullptr could come up.
I had initially a local version of this patch broken into over 30
independant, commits but some later commit were cleaning the API and
touching part of the code modified in the previous commits, so it
seemed cleaner without the intermediate state.
Test Plan:
Reviewers: echristo
Subscribers: llvm-commits
From: Mehdi Amini <mehdi.amini@apple.com>
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Selection conditions may be vectors or scalars. Make sure InstCombine
doesn't indiscriminately assume that a select which is value dependent
on another select have identical select condition types.
This fixes PR22773.
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This case is interesting because ScalarEvolutionExpander lowers min(a,
b) as ~max(~a,~b). I think the profitability heuristics can be made
more clever/aggressive, but this is a start.
Differential Revision: http://reviews.llvm.org/D7821
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This patch fixes a problem I accidentally introduced in an instruction combine
on select instructions added at r227197. That revision taught the instruction
combiner how to fold a cttz/ctlz followed by a icmp plus select into a single
cttz/ctlz with flag 'is_zero_undef' cleared.
However, the new rule added at r227197 would have produced wrong results in the
case where a cttz/ctlz with flag 'is_zero_undef' cleared was follwed by a
zero-extend or truncate. In that case, the folded instruction would have
been inserted in a wrong location thus leaving the CFG in an inconsistent
state.
This patch fixes the problem and add two reproducible test cases to
existing test 'InstCombine/select-cmp-cttz-ctlz.ll'.
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Normalize
select(C0, select(C1, a, b), b) -> select((C0 & C1), a, b)
select(C0, a, select(C1, a, b)) -> select((C0 | C1), a, b)
This normal form may enable further combines on the And/Or and shortens
paths for the values. Many targets prefer the other but can go back
easily in CodeGen.
Differential Revision: http://reviews.llvm.org/D7399
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This patch teaches the Instruction Combiner how to fold a cttz/ctlz followed by
a icmp plus select into a single cttz/ctlz with flag 'is_zero_undef' cleared.
Added test InstCombine/select-cmp-cttz-ctlz.ll.
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creating a non-internal header file for the InstCombine pass.
I thought about calling this InstCombiner.h or in some way more clearly
associating it with the InstCombiner clas that it is primarily defining,
but there are several other utility interfaces defined within this for
InstCombine. If, in the course of refactoring, those end up moving
elsewhere or going away, it might make more sense to make this the
combiner's header alone.
Naturally, this is a bikeshed to a certain degree, so feel free to lobby
for a different shade of paint if this name just doesn't suit you.
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a cache of assumptions for a single function, and an immutable pass that
manages those caches.
The motivation for this change is two fold. Immutable analyses are
really hacks around the current pass manager design and don't exist in
the new design. This is usually OK, but it requires that the core logic
of an immutable pass be reasonably partitioned off from the pass logic.
This change does precisely that. As a consequence it also paves the way
for the *many* utility functions that deal in the assumptions to live in
both pass manager worlds by creating an separate non-pass object with
its own independent API that they all rely on. Now, the only bits of the
system that deal with the actual pass mechanics are those that actually
need to deal with the pass mechanics.
Once this separation is made, several simplifications become pretty
obvious in the assumption cache itself. Rather than using a set and
callback value handles, it can just be a vector of weak value handles.
The callers can easily skip the handles that are null, and eventually we
can wrap all of this up behind a filter iterator.
For now, this adds boiler plate to the various passes, but this kind of
boiler plate will end up making it possible to port these passes to the
new pass manager, and so it will end up factored away pretty reasonably.
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(X & INT_MIN) == 0 ? X ^ INT_MIN : X into X | INT_MIN
(X & INT_MIN) != 0 ? X ^ INT_MIN : X into X & INT_MAX
This fixes PR21993.
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This restores our ability to optimize:
(X & C) == 0 ? X ^ C : X into X | C
(X & C) != 0 ? X ^ C : X into X & ~C
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This reverts commit r210006, it miscompiled libapr which is used in who
knows how many projects.
A test has been added to ensure that we don't regress again.
I'll work on a rewrite of what the optimization was trying to do later.
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This change, which allows @llvm.assume to be used from within computeKnownBits
(and other associated functions in ValueTracking), adds some (optional)
parameters to computeKnownBits and friends. These functions now (optionally)
take a "context" instruction pointer, an AssumptionTracker pointer, and also a
DomTree pointer, and most of the changes are just to pass this new information
when it is easily available from InstSimplify, InstCombine, etc.
As explained below, the significant conceptual change is that known properties
of a value might depend on the control-flow location of the use (because we
care that the @llvm.assume dominates the use because assumptions have
control-flow dependencies). This means that, when we ask if bits are known in a
value, we might get different answers for different uses.
The significant changes are all in ValueTracking. Two main changes: First, as
with the rest of the code, new parameters need to be passed around. To make
this easier, I grouped them into a structure, and I made internal static
versions of the relevant functions that take this structure as a parameter. The
new code does as you might expect, it looks for @llvm.assume calls that make
use of the value we're trying to learn something about (often indirectly),
attempts to pattern match that expression, and uses the result if successful.
By making use of the AssumptionTracker, the process of finding @llvm.assume
calls is not expensive.
Part of the structure being passed around inside ValueTracking is a set of
already-considered @llvm.assume calls. This is to prevent a query using, for
example, the assume(a == b), to recurse on itself. The context and DT params
are used to find applicable assumptions. An assumption needs to dominate the
context instruction, or come after it deterministically. In this latter case we
only handle the specific case where both the assumption and the context
instruction are in the same block, and we need to exclude assumptions from
being used to simplify their own ephemeral values (those which contribute only
to the assumption) because otherwise the assumption would prove its feeding
comparison trivial and would be removed.
This commit adds the plumbing and the logic for a simple masked-bit propagation
(just enough to write a regression test). Future commits add more patterns
(and, correspondingly, more regression tests).
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if ((x & C) == 0) x |= C becomes x |= C
if ((x & C) != 0) x ^= C becomes x &= ~C
if ((x & C) == 0) x ^= C becomes x |= C
if ((x & C) != 0) x &= ~C becomes x &= ~C
if ((x & C) == 0) x &= ~C becomes nothing
Differential Revision: http://reviews.llvm.org/D3777
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if ((x & C) == 0) x |= C becomes x |= C
if ((x & C) != 0) x ^= C becomes x &= ~C
if ((x & C) == 0) x ^= C becomes x |= C
if ((x & C) != 0) x &= ~C becomes x &= ~C
if ((x & C) == 0) x &= ~C becomes nothing
Z3 Verifications code for above transform
http://rise4fun.com/Z3/Pmsh
Differential Revision: http://reviews.llvm.org/D3717
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definition below all of the header #include lines, lib/Transforms/...
edition.
This one is tricky for two reasons. We again have a couple of passes
that define something else before the includes as well. I've sunk their
name macros with the DEBUG_TYPE.
Also, InstCombine contains headers that need DEBUG_TYPE, so now those
headers #define and #undef DEBUG_TYPE around their code, leaving them
well formed modular headers. Fixing these headers was a large motivation
for all of these changes, as "leaky" macros of this form are hard on the
modules implementation.
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header files and into the cpp files.
These files will require more touches as the header files actually use
DEBUG(). Eventually, I'll have to introduce a matched #define and #undef
of DEBUG_TYPE for the header files, but that comes as step N of many to
clean all of this up.
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I am really sorry for the noise, but the current state where some parts of the
code use TD (from the old name: TargetData) and other parts use DL makes it
hard to write a patch that changes where those variables come from and how
they are passed along.
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Currently foldSelectICmpAndOr asserts if the "or" involves a vector
containing several of the same power of two. We can easily avoid this by
only performing the fold on integer types, like foldSelectICmpAnd does.
Fixes <rdar://problem/15012516>
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Inserting a zext or trunc is sufficient. This pattern is somewhat common in
LLVM's pointer mangling code.
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Differences in bitwidth between X and Y could exist even if C1 and C2 have
the same Log2 representation.
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This fixes the optimization introduced in r179748 and reverted in r179750.
While the optimization was sound, it did not properly respect differences in
bit-width.
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Sooooo many of these had incorrect or strange main module includes.
I have manually inspected all of these, and fixed the main module
include to be the nearest plausible thing I could find. If you own or
care about any of these source files, I encourage you to take some time
and check that these edits were sensible. I can't have broken anything
(I strictly added headers, and reordered them, never removed), but they
may not be the headers you'd really like to identify as containing the
API being implemented.
Many forward declarations and missing includes were added to a header
files to allow them to parse cleanly when included first. The main
module rule does in fact have its merits. =]
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This can happen as long as the instruction is not reachable. Instcombine does generate these unreachable malformed selects when doing RAUW
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The test case feeds the following into InstCombine's visitSelect:
%tobool8 = icmp ne i32 0, 0
%phitmp = select i1 %tobool8, i32 3, i32 0
Then instcombine replaces the right side of the switch with 0, doesn't notice
that nothing changes and tries again indefinitely.
This fixes PR12897.
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