as long as possible.
** Context **
Each time the dominance information is modified, the dominator tree analysis
switches in a slow query mode. After a few queries without any modification on
the dominator tree, it performs an expensive update of its internal structure to
provide fast queries again.
** Problem **
Prior to this patch, the MachineSink pass was splitting the critical edges on
demand while relying heavy on the dominator tree information. In some cases,
this leads to pathological behavior where:
- We end up in the slow query mode right after splitting an edge.
- We update the dominance information.
- We break the dominance information again, thus ending up in the slow query
mode and so on.
** Proposed Solution **
To mitigate this effect, this patch postpones all the splitting of the edges at
the end of each iteration of the main loop.
The benefits are:
- The dominance information is valid for the life time of an iteration.
- This simplifies the code as we do not have to special treat instructions that
are sunk on critical edges. Indeed, the related block will be available
through the next iteration.
The downside is that when edges splitting is required, this incurs an additional
iteration of the main loop compared to the previous scheme.
** Performance **
Thanks to this patch, the motivating example compiles in 6+ minutes instead of
10+ minutes. No test case added as the motivating example as nothing special but
being huge!
I have measured only noise for both the compile time and the runtime on the llvm
test-suite + SPECs with Os and O3.
Note: The current implementation of MachineBasicBlock::SplitCriticalEdge also
uses the dominance information and therefore, hits this problem. A subsequent
patch will address that.
<rdar://problem/17894619>
llvm-svn: 215410
What follows bellow is a correctness proof of the transform using CVC3.
$ < t.cvc
A, B : BITVECTOR(32);
QUERY BVPLUS(32, A & B, A | B) = BVPLUS(32, A, B);
$ cvc3 < t.cvc
Valid.
llvm-svn: 215400
There are no variable values like registers encoded in the low 32 bits of MUBUF
instructions, so it is relatively easy to check these bits, and it will
help prevent us from introducing encoding bugs.
llvm-svn: 215397
This bit was left uninitialized, which was causing some random failures
of piglit tests.
NOTE: This is a candidate for the 3.5 branch.
llvm-svn: 215396
This patch adds a new property: isRegSequence and the related target hooks:
TargetIntrInfo::getRegSequenceInputs and
TargetInstrInfo::getRegSequenceLikeInputs to specify that a target specific
instruction is a (kind of) REG_SEQUENCE.
<rdar://problem/12702965>
llvm-svn: 215394
buildLocationLists easier to read.
The previous implementation conflated the merging of individual pieces
and the merging of entire DebugLocEntries.
By splitting this functionality into two separate functions the intention
of the code should be clearer.
llvm-svn: 215383
For many Thumb-1 register register instructions, setting the CPSR is not
permitted inside an IT block. We would not correctly flag those instructions.
The previous change to identify this scenario was insufficient as it did not
actually catch all the instances. The current list is formed by manual
inspection of the ARMv6M ARM.
The change to the Thumb2 IT block test is due to the fact that the new more
stringent checking of the MIs results in the If Conversion pass being prevented
from executing (since not all the instructions in the BB are predicable). This
results in code gen changes.
Thanks to Tim Northover for pointing out that the previous patch was
insufficient and hinting that the use of the v6M ARM would be much easier to use
than the v7 or v8!
llvm-svn: 215382
The timestamp meant these files changed with each invocation of
relocs.py, confusing matters when we add relocations and need to
update the tests.
llvm-svn: 215350
By default, LLVM uses the "C" calling convention for all runtime
library functions. The half-precision FP conversion functions use the
soft-float calling convention, and are needed for some targets which
use the hard-float convention by default, so must have their calling
convention explicitly set.
llvm-svn: 215348
be propagated to all its users, and this propagation could increase the
probability of finding common subexpressions. If the COPY has only one user,
the COPY itself can be removed.
llvm-svn: 215344
and the lattice will be updated to be a state other than "undefined". This
limiation could miss some opportunities of lowering "overdefined" to be an
even accurate value. So this patch ask the algorithm to try to lower the
lattice value again even if the value has been lowered to be "overdefined".
llvm-svn: 215343
That broke the build:
/data/buildslave/clang-amd64-freebsd/src-llvm/lib/CodeGen/PeepholeOptimizer.cpp:729:46: error: non-const lvalue reference to type 'SmallPtrSet<[...], 8>' cannot bind to a value of unrelated type 'SmallPtrSet<[...], 16>'
Changed |= optimizeExtInstr(MI, MBB, LocalMIs);
^~~~~~~~
/data/buildslave/clang-amd64-freebsd/src-llvm/lib/CodeGen/PeepholeOptimizer.cpp:265:49: note: passing argument to parameter 'LocalMIs' here
SmallPtrSet<MachineInstr*, 8> &LocalMIs) {
^
llvm-svn: 215341
