[llvm-objdump] enhance test case for mach-o -private-headers

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220120 91177308-0d34-0410-b5e6-96231b3b80d8
[llvm-objdump] don't test timestamp dump as that is time zone dependent

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220123 91177308-0d34-0410-b5e6-96231b3b80d8
Remove a test that was ported from the old llvm-gcc frontend test suite.

This test is pretty awesome. It is claiming to test devirtualization.
However, the code in question is not in fact devirtualized by LLVM. If
you take the original C++ test case and run it through Clang at -O3 we
fail to devirtualize it completely. It also isn't a sufficiently focused
test case.

The *reason* we fail to devirtualize it isn't because of any missing
instcombine though. Instead, it is because we fail to emit an available
externally vtable and thus the vtable is just an external and completely
opaque. If I cause the vtable to be emitted, we successfully
devirtualize things.

Anyways, I'm just removing it because it is providing negative value at
this point: it isn't representative of the output of Clang really, LLVM
isn't doing the transform it claims to be testing, LLVM's failure to do
the transform isn't actually an LLVM bug at all and we shouldn't be
testing for it here, and finally the test is written in such a way that
it will trivially pass even when the point of the test is failing.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220137 91177308-0d34-0410-b5e6-96231b3b80d8
[InstCombine] Do an about-face on how LLVM canonicalizes (cast (load
...)) and (load (cast ...)): canonicalize toward the former.

Historically, we've tried to load using the type of the *pointer*, and
tried to match that type as closely as possible removing as many pointer
casts as we could and trading them for bitcasts of the loaded value.
This is deeply and fundamentally wrong.

Repeat after me: memory does not have a type! This was a hard lesson for
me to learn working on SROA.

There is only one thing that should actually drive the type used for
a pointer, and that is the type which we need to use to load from that
pointer. Matching up pointer types to the loaded value types is very
useful because it minimizes the physical size of the IR required for
no-op casts. Similarly, the only thing that should drive the type used
for a loaded value is *how that value is used*! Again, this minimizes
casts. And in fact, the *only* thing motivating types in any part of
LLVM's IR are the types used by the operations in the IR. We should
match them as closely as possible.

I've ended up removing some tests here as they were testing bugs or
behavior that is no longer present. Mostly though, this is just cleanup
to let the tests continue to function as intended.

The only fallout I've found so far from this change was SROA and I have
fixed it to not be impeded by the different type of load. If you find
more places where this change causes optimizations not to fire, those
too are likely bugs where we are assuming that the type of pointers is
"significant" for optimization purposes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220138 91177308-0d34-0410-b5e6-96231b3b80d8
Preserve AA metadata when combining (cast (load (...))) -> (load (cast
(...))).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220141 91177308-0d34-0410-b5e6-96231b3b80d8
[PBQP] Replace the interference-constraints algorithm with a faster version
loosely based on linear scan.

On x86-64 this is good for a ~2% drop in compile time on the nightly test suite.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220143 91177308-0d34-0410-b5e6-96231b3b80d8
[PBQP] Move register-allocation specific PBQP code into RegAllocPBQP.h.

Just clean-up - no functional change.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220145 91177308-0d34-0410-b5e6-96231b3b80d8
Clean up the formatting and trailing whitespace of a routine before
editting it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220146 91177308-0d34-0410-b5e6-96231b3b80d8
Clean up doxygen syntax and reword comments to flow better, have a brief
section, and not have unfinished sentence fragments.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220147 91177308-0d34-0410-b5e6-96231b3b80d8
More formatting cleanup brought to you by clang-format.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220149 91177308-0d34-0410-b5e6-96231b3b80d8
Fix the other comment to use modern doxygen style and be a bit more
direct. Notably, comment on the fact that the loaded type is significant
in that it determines how wide of an access must be safe.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220150 91177308-0d34-0410-b5e6-96231b3b80d8
Rename 'TD' to 'DL' in this function as the argument is now a DataLayout
argument.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220151 91177308-0d34-0410-b5e6-96231b3b80d8
Use triple predicate functions instead of checking values directly. NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220155 91177308-0d34-0410-b5e6-96231b3b80d8
Switch how the datalayout availability test is handled in this code to
make much more sense and in theory be more correct.

If you trace the code alllll the way back to when it was first
introduced, the comments make it slightly more clear what was going on
here. At that time, the only way Base != V was if DL (then TD) was
non-null. As a consequence, if DL *was* null, that meant we were loading
directly from the alloca or global found above the test. After
refactoring, this has become at least terribly subtle and potentially
incorrect. There are many forms of pointer manipulation that can be
traversed without DataLayout, and some of them would in fact change the
size of object being loaded vs. allocated.

Rather than this subtlety, I've hoisted the actual 'return true' bits
into the code which actually found an alloca or global and based them on
the loaded pointer being that alloca or global. This is both more clear
and safer. I've also added comments about exactly why this set of
predicates is used.

I've also corrected a misleading comment about globals -- if overridden
they may not just have a different size, they may be null and completely
unsafe to load from!

Hopefully this confuses the next reader a bit less. I don't have any
test cases or anything, the patch is motivated strictly to improve the
readability of the code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220156 91177308-0d34-0410-b5e6-96231b3b80d8
Fix a long-standing miscompile in the load analysis that was uncovered
by my refactoring of this code.

The method isSafeToLoadUnconditionally assumes that the load will
proceed with the preferred type alignment. Given that, it has to ensure
that the alloca or global is at least that aligned. It has always done
this historically when a datalayout is present, but has never checked it
when the datalayout is absent. When I refactored the code in r220156,
I exposed this path when datalayout was present and that turned the
latent bug into a patent bug.

This fixes the issue by just removing the special case which allows
folding things without datalayout. This isn't worth the complexity of
trying to tease apart when it is or isn't safe without actually knowing
the preferred alignment.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220161 91177308-0d34-0410-b5e6-96231b3b80d8
InstCombine: Optimize icmp eq/ne (shl Const2, A), Const1

The following implements the optimization for sequences of the form:
icmp eq/ne (shl Const2, A), Const1

Such sequences can be transformed to:
icmp eq/ne A, (TrailingZeros(Const1) - TrailingZeros(Const2))

This handles only the equality operators for now. Other operators need
to be handled.

Patch by Ankur Garg!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220162 91177308-0d34-0410-b5e6-96231b3b80d8
InstCombine: (sub (or A B) (xor A B)) --> (and A B)

The following implements the transformation:
(sub (or A B) (xor A B)) --> (and A B).

Patch by Ankur Garg!

Differential Revision: http://reviews.llvm.org/D5719

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220163 91177308-0d34-0410-b5e6-96231b3b80d8
Move previously dead code to handle computing the known bits of an alias
up to where it actually works as intended. The problem is that
a GlobalAlias isa GlobalValue and so the prior block handled all of the
cases.

This allows us to constant fold based on the actual constant expression
in the global alias. As an example, see the last function in the newly
added test case which explicitly aligns an unaligned pointer using
constant expression math. Without this change, we fail to see that and
fold an alignment test to zero.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220164 91177308-0d34-0410-b5e6-96231b3b80d8
Do a better and more complete job of preserving metadata when combining
loads.

This handles many more cases than just the AA metadata, some of them
suggested by Hal in his review of the AA metadata handling patch. I've
tried to test this behavior where tractable to do so.

I'll point out that I have specifically *not* included a test for
debuginfo because it was going to require 2 or 3 times as much work to
craft some input which would survive the "helpful" stripping of debug
info metadata that doesn't match the desired schema. This is another
good example of why the current state of write-ability for our debug
info metadata is unacceptable. I spent over 30 minutes trying to conjure
some test case that would survive, even copying from other debug info
tests, but it always failed to survive with no explanation of why or how
I might fix it. =[

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220165 91177308-0d34-0410-b5e6-96231b3b80d8