Commit Graph

8 Commits

Author SHA1 Message Date
Reid Kleckner 85ba5f637a Rename TTI::getIntImmCost for instructions and intrinsics
Soon Intrinsic::ID will be a plain integer, so this overload will not be
possible.

Rename both overloads to ensure that downstream targets observe this as
a build failure instead of a runtime failure.

Split off from D71320

Reviewers: efriedma

Differential Revision: https://reviews.llvm.org/D71381
2019-12-11 18:00:20 -08:00
Bill Wendling cc2bebe039 Ignore indirect branches from callbr.
Summary:
We can't speculate around indirect branches: indirectbr and invoke. The
callbr instruction needs to be included here.

Reviewers: nickdesaulniers, manojgupta, chandlerc

Reviewed By: chandlerc

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66200

llvm-svn: 368873
2019-08-14 16:44:07 +00:00
Matt Arsenault 36e7254441 SpeculateAroundPHIs: Respect convergent
llvm-svn: 361957
2019-05-29 13:14:39 +00:00
Chandler Carruth 2946cd7010 Update the file headers across all of the LLVM projects in the monorepo
to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351636
2019-01-19 08:50:56 +00:00
Nico Weber e75fd1b184 fix comment typo
llvm-svn: 340744
2018-08-27 14:25:22 +00:00
Hiroshi Inoue f209649dfc [NFC] fix trivial typos in comments
llvm-svn: 334687
2018-06-14 05:41:49 +00:00
Nicola Zaghen d34e60ca85 Rename DEBUG macro to LLVM_DEBUG.
The DEBUG() macro is very generic so it might clash with other projects.
The renaming was done as follows:
- git grep -l 'DEBUG' | xargs sed -i 's/\bDEBUG\s\?(/LLVM_DEBUG(/g'
- git diff -U0 master | ../clang/tools/clang-format/clang-format-diff.py -i -p1 -style LLVM
- Manual change to APInt
- Manually chage DOCS as regex doesn't match it.

In the transition period the DEBUG() macro is still present and aliased
to the LLVM_DEBUG() one.

Differential Revision: https://reviews.llvm.org/D43624

llvm-svn: 332240
2018-05-14 12:53:11 +00:00
Chandler Carruth c34f789e38 Add a new pass to speculate around PHI nodes with constant (integer) operands when profitable.
The core idea is to (re-)introduce some redundancies where their cost is
hidden by the cost of materializing immediates for constant operands of
PHI nodes. When the cost of the redundancies is covered by this,
avoiding materializing the immediate has numerous benefits:
1) Less register pressure
2) Potential for further folding / combining
3) Potential for more efficient instructions due to immediate operand

As a motivating example, consider the remarkably different cost on x86
of a SHL instruction with an immediate operand versus a register
operand.

This pattern turns up surprisingly frequently, but is somewhat rarely
obvious as a significant performance problem.

The pass is entirely target independent, but it does rely on the target
cost model in TTI to decide when to speculate things around the PHI
node. I've included x86-focused tests, but any target that sets up its
immediate cost model should benefit from this pass.

There is probably more that can be done in this space, but the pass
as-is is enough to get some important performance on our internal
benchmarks, and should be generally performance neutral, but help with
more extensive benchmarking is always welcome.

One awkward part is that this pass has to be scheduled after
*everything* that can eliminate these kinds of redundancies. This
includes SimplifyCFG, GVN, etc. I'm open to suggestions about better
places to put this. We could in theory make it part of the codegen pass
pipeline, but there doesn't really seem to be a good reason for that --
it isn't "lowering" in any sense and only relies on pretty standard cost
model based TTI queries, so it seems to fit well with the "optimization"
pipeline model. Still, further thoughts on the pipeline position are
welcome.

I've also only implemented this in the new pass manager. If folks are
very interested, I can try to add it to the old PM as well, but I didn't
really see much point (my use case is already switched over to the new
PM).

I've tested this pretty heavily without issue. A wide range of
benchmarks internally show no change outside the noise, and I don't see
any significant changes in SPEC either. However, the size class
computation in tcmalloc is substantially improved by this, which turns
into a 2% to 4% win on the hottest path through tcmalloc for us, so
there are definitely important cases where this is going to make
a substantial difference.

Differential revision: https://reviews.llvm.org/D37467

llvm-svn: 319164
2017-11-28 11:32:31 +00:00