Reimplements MisExpect diagnostics from D66324 to reconstruct its
original checking methodology only using MD_prof branch_weights
metadata.
New checks rely on 2 invariants:
1) For frontend instrumentation, MD_prof branch_weights will always be
populated before llvm.expect intrinsics are lowered.
2) for IR and sample profiling, llvm.expect intrinsics will always be
lowered before branch_weights are populated from the IR profiles.
These invariants allow the checking to assume how the existing branch
weights are populated depending on the profiling method used, and emit
the correct diagnostics. If these invariants are ever invalidated, the
MisExpect related checks would need to be updated, potentially by
re-introducing MD_misexpect metadata, and ensuring it always will be
transformed the same way as branch_weights in other optimization passes.
Frontend based profiling is now enabled without using LLVM Args, by
introducing a new CodeGen option, and checking if the -Wmisexpect flag
has been passed on the command line.
Reviewed By: tejohnson
Differential Revision: https://reviews.llvm.org/D115907
Reimplements MisExpect diagnostics from D66324 to reconstruct its
original checking methodology only using MD_prof branch_weights
metadata.
New checks rely on 2 invariants:
1) For frontend instrumentation, MD_prof branch_weights will always be
populated before llvm.expect intrinsics are lowered.
2) for IR and sample profiling, llvm.expect intrinsics will always be
lowered before branch_weights are populated from the IR profiles.
These invariants allow the checking to assume how the existing branch
weights are populated depending on the profiling method used, and emit
the correct diagnostics. If these invariants are ever invalidated, the
MisExpect related checks would need to be updated, potentially by
re-introducing MD_misexpect metadata, and ensuring it always will be
transformed the same way as branch_weights in other optimization passes.
Frontend based profiling is now enabled without using LLVM Args, by
introducing a new CodeGen option, and checking if the -Wmisexpect flag
has been passed on the command line.
Reviewed By: tejohnson
Differential Revision: https://reviews.llvm.org/D115907
Reimplements MisExpect diagnostics from D66324 to reconstruct its
original checking methodology only using MD_prof branch_weights
metadata.
New checks rely on 2 invariants:
1) For frontend instrumentation, MD_prof branch_weights will always be
populated before llvm.expect intrinsics are lowered.
2) for IR and sample profiling, llvm.expect intrinsics will always be
lowered before branch_weights are populated from the IR profiles.
These invariants allow the checking to assume how the existing branch
weights are populated depending on the profiling method used, and emit
the correct diagnostics. If these invariants are ever invalidated, the
MisExpect related checks would need to be updated, potentially by
re-introducing MD_misexpect metadata, and ensuring it always will be
transformed the same way as branch_weights in other optimization passes.
Frontend based profiling is now enabled without using LLVM Args, by
introducing a new CodeGen option, and checking if the -Wmisexpect flag
has been passed on the command line.
Differential Revision: https://reviews.llvm.org/D115907
The `SplitIndirectBrCriticalEdges` function was originally designed for
`CodeGenPrepare` and skipped splitting of edges when the destination
block didn't contain any `PHI` instructions. This only makes sense when
reducing COPYs like `CodeGenPrepare`. In the case of
`PGOInstrumentation` or `GCOVProfiling` it would result in missed
counters and wrong result in functions with computed goto.
Differential Revision: https://reviews.llvm.org/D120096
The IRPGOFlag symbol (__llvm_profile_raw_version) is dropped when
identified as non-prevailing for either regular or thin LTO during
the mixed-LTO mode compilation. This happens in the module where
IRPGOFlag is marked as non-prevailing. This variable
is emitted in the final object from the prevailing module.
This is still problematic because we currently query this symbol
to coordinate some actions between PGOInstrumentation pass
and InstrProfiling lowering pass, like whether to do value
profiling, whether to do comdat renaming.
This problem is bought up by YolandaCY in
https://reviews.llvm.org/D107034
YolandCY reported unresolved symbol linker errors in
CSPGO instrumentation build for chromium.
This patch let LTO retain IRPGOFlag decl by adding it to
CompilerUsed list and relax the check in isIRPGOFlagSet() when
doing the InstrProfiling lowering.
The test case in the patch is from D107034
<https://reviews.llvm.org/D107034>.
Differential Revision: https://reviews.llvm.org/D108581
Hoisting and sinking instructions out of conditional blocks enables
additional vectorization by:
1. Executing memory accesses unconditionally.
2. Reducing the number of instructions that need predication.
After disabling early hoisting / sinking, we miss out on a few
vectorization opportunities. One of those is causing a ~10% performance
regression in one of the Geekbench benchmarks on AArch64.
This patch tires to recover the regression by running hoisting/sinking
as part of a SimplifyCFG run after LoopRotate and before LoopVectorize.
Note that in the legacy pass-manager, we run LoopRotate just before
vectorization again and there's no SimplifyCFG run in between, so the
sinking/hoisting may impact the later run on LoopRotate. But the impact
should be limited and the benefit of hosting/sinking at this stage
should outweigh the risk of not rotating.
Compile-time impact looks slightly positive for most cases.
http://llvm-compile-time-tracker.com/compare.php?from=2ea7fb7b1c045a7d60fcccf3df3ebb26aa3699e5&to=e58b4a763c691da651f25996aad619cb3d946faf&stat=instructions
NewPM-O3: geomean -0.19%
NewPM-ReleaseThinLTO: geoman -0.54%
NewPM-ReleaseLTO-g: geomean -0.03%
With a few benchmarks seeing a notable increase, but also some
improvements.
Alternative to D101290.
Reviewed By: lebedev.ri
Differential Revision: https://reviews.llvm.org/D101468
Under certain (currently unknown) conditions, llvm-profdata is outputting
profiles that have two consecutive entries in the MemOPSize section for the
value 0. This causes the PGOMemOPSizeOpt pass to output an invalid switch
instruction with two cases for 0. As mentioned, we’re not quite sure what’s
causing this to happen, but this patch prevents llvm-profdata from outputting a
profile that has this problem and gives an error with a request for a
reproducible.
Differential Revision: https://reviews.llvm.org/D92074
This patch emits "instr_prof_hash_mismatch" function annotation metadata if
there is a hash mismatch while applying instrumented profiles.
During the PGO optimized build using instrumented profiles, if the CFG of
the function has changed since generating the profile, a hash mismatch is
encountered. This patch emits this information as annotation metadata. We
plan to use this with Propeller which is done at the machine IR level.
Propeller is usually applied on top of PGO and a hash mismatch during
PGO could be used to detect source drift.
Differential Revision: https://reviews.llvm.org/D95495
Raw profile count values for each BB are not kept after profile
annotation. We record function entry count and branch weights
and use them to compute the count when needed. This mechanism
works well in a perfect world, but often breaks in real programs,
because of number prevision, inconsistent profile, or bugs in
BFI). This patch uses sum of profile count values to fix
function entry count to make the BFI count close to real profile
counts.
Differential Revision: https://reviews.llvm.org/D61540
This patch adds the functionality to compare BFI counts with real
profile
counts right after reading the profile. It will print remarks under
-Rpass-analysis=pgo, or the internal option -pass-remarks-analysis=pgo.
Differential Revision: https://reviews.llvm.org/D91813
See discussion in https://bugs.llvm.org/show_bug.cgi?id=45073 / https://reviews.llvm.org/D66324#2334485
the implementation is known-broken for certain inputs,
the bugreport was up for a significant amount of timer,
and there has been no activity to address it.
Therefore, just completely rip out all of misexpect handling.
I suspect, fixing it requires redesigning the internals of MD_misexpect.
Should anyone commit to fixing the implementation problem,
starting from clean slate may be better anyways.
This reverts commit 7bdad08429411e7d0ecd58cd696b1efe3cff309e,
and some of it's follow-ups, that don't stand on their own.
PGO profile is usually more precise than sample profile. However, PGO profile
needs to be collected from loadtest and loadtest may not be representative
enough to the production workload. Sample profile collected from production
can be used as a supplement -- for functions cold in loadtest but warm/hot
in production, we can scale up the related function in PGO profile if the
function is warm or hot in sample profile.
The implementation contains changes in compiler side and llvm-profdata side.
Given an instr profile and a sample profile, for a function cold in PGO
profile but warm/hot in sample profile, llvm-profdata will either mark
all the counters in the profile to be -1 or scale up the max count in the
function to be above hot threshold, depending on the zero counter ratio in
the profile. The assumption is if there are too many counters being zero
in the function profile, the profile is more likely to cause harm than good,
then llvm-profdata will mark all the counters to be -1 indicating the
function is hot but the profile is unaccountable. In compiler side, if a
function profile with all -1 counters is seen, the function entry count will
be set to be above hot threshold but its internal profile will be dropped.
In the long run, it may be useful to let compiler support using PGO profile
and sample profile at the same time, but that requires more careful design
and more substantial changes to make two profiles work seamlessly. The patch
here serves as a simple intermediate solution.
Differential Revision: https://reviews.llvm.org/D81981
Function entry count might be zero after the profile counts reset and
before reentry to the function.
Zero profile entry count is very bad as the profile count from BFI will
be wrong.
A simple fix is to set the profile entry count to 1 if there are
non-zero profile counts in this function.
Differential Revision: https://reviews.llvm.org/D84378
This patch includes the supporting code that enables always
instrumenting the function entry block by default.
This patch will NOT the default behavior.
It adds a variant bit in the profile version, adds new directives in
text profile format, and changes llvm-profdata tool accordingly.
This patch is a split of D83024 (https://reviews.llvm.org/D83024)
Many test changes from D83024 are also included.
Differential Revision: https://reviews.llvm.org/D84261
Summary: This adds support for memcmp/bcmp to the existing memcpy/memset value profiling.
Reviewers: davidxl
Subscribers: hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D79751
Summary:
The PGO counter reading will add cold and inlinehint (hot) attributes
to functions that are very cold or hot. This was using hardcoded
thresholds, instead of the profile summary cutoffs which are used in
other hot/cold detection and are more dynamic and adaptable. Switch
to using the summary-based cold/hot detection.
The hardcoded limits were causing some code that had a medium level of
hotness (per the summary) to be incorrectly marked with a cold
attribute, blocking inlining.
Reviewers: davidxl
Subscribers: llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D67673
llvm-svn: 372189
This patch contains the basic functionality for reporting potentially
incorrect usage of __builtin_expect() by comparing the developer's
annotation against a collected PGO profile. A more detailed proposal and
discussion appears on the CFE-dev mailing list
(http://lists.llvm.org/pipermail/cfe-dev/2019-July/062971.html) and a
prototype of the initial frontend changes appear here in D65300
We revised the work in D65300 by moving the misexpect check into the
LLVM backend, and adding support for IR and sampling based profiles, in
addition to frontend instrumentation.
We add new misexpect metadata tags to those instructions directly
influenced by the llvm.expect intrinsic (branch, switch, and select)
when lowering the intrinsics. The misexpect metadata contains
information about the expected target of the intrinsic so that we can
check against the correct PGO counter when emitting diagnostics, and the
compiler's values for the LikelyBranchWeight and UnlikelyBranchWeight.
We use these branch weight values to determine when to emit the
diagnostic to the user.
A future patch should address the comment at the top of
LowerExpectIntrisic.cpp to hoist the LikelyBranchWeight and
UnlikelyBranchWeight values into a shared space that can be accessed
outside of the LowerExpectIntrinsic pass. Once that is done, the
misexpect metadata can be updated to be smaller.
In the long term, it is possible to reconstruct portions of the
misexpect metadata from the existing profile data. However, we have
avoided this to keep the code simple, and because some kind of metadata
tag will be required to identify which branch/switch/select instructions
are influenced by the use of llvm.expect
Patch By: paulkirth
Differential Revision: https://reviews.llvm.org/D66324
llvm-svn: 371635
This reverts commit r371584. It introduced a dependency from compiler-rt
to llvm/include/ADT, which is problematic for multiple reasons.
One is that it is a novel dependency edge, which needs cross-compliation
machinery for llvm/include/ADT (yes, it is true that right now
compiler-rt included only header-only libraries, however, if we allow
compiler-rt to depend on anything from ADT, other libraries will
eventually get used).
Secondly, depending on ADT from compiler-rt exposes ADT symbols from
compiler-rt, which would cause ODR violations when Clang is built with
the profile library.
llvm-svn: 371598
This patch contains the basic functionality for reporting potentially
incorrect usage of __builtin_expect() by comparing the developer's
annotation against a collected PGO profile. A more detailed proposal and
discussion appears on the CFE-dev mailing list
(http://lists.llvm.org/pipermail/cfe-dev/2019-July/062971.html) and a
prototype of the initial frontend changes appear here in D65300
We revised the work in D65300 by moving the misexpect check into the
LLVM backend, and adding support for IR and sampling based profiles, in
addition to frontend instrumentation.
We add new misexpect metadata tags to those instructions directly
influenced by the llvm.expect intrinsic (branch, switch, and select)
when lowering the intrinsics. The misexpect metadata contains
information about the expected target of the intrinsic so that we can
check against the correct PGO counter when emitting diagnostics, and the
compiler's values for the LikelyBranchWeight and UnlikelyBranchWeight.
We use these branch weight values to determine when to emit the
diagnostic to the user.
A future patch should address the comment at the top of
LowerExpectIntrisic.cpp to hoist the LikelyBranchWeight and
UnlikelyBranchWeight values into a shared space that can be accessed
outside of the LowerExpectIntrinsic pass. Once that is done, the
misexpect metadata can be updated to be smaller.
In the long term, it is possible to reconstruct portions of the
misexpect metadata from the existing profile data. However, we have
avoided this to keep the code simple, and because some kind of metadata
tag will be required to identify which branch/switch/select instructions
are influenced by the use of llvm.expect
Patch By: paulkirth
Differential Revision: https://reviews.llvm.org/D66324
llvm-svn: 371584
This patch contains the basic functionality for reporting potentially
incorrect usage of __builtin_expect() by comparing the developer's
annotation against a collected PGO profile. A more detailed proposal and
discussion appears on the CFE-dev mailing list
(http://lists.llvm.org/pipermail/cfe-dev/2019-July/062971.html) and a
prototype of the initial frontend changes appear here in D65300
We revised the work in D65300 by moving the misexpect check into the
LLVM backend, and adding support for IR and sampling based profiles, in
addition to frontend instrumentation.
We add new misexpect metadata tags to those instructions directly
influenced by the llvm.expect intrinsic (branch, switch, and select)
when lowering the intrinsics. The misexpect metadata contains
information about the expected target of the intrinsic so that we can
check against the correct PGO counter when emitting diagnostics, and the
compiler's values for the LikelyBranchWeight and UnlikelyBranchWeight.
We use these branch weight values to determine when to emit the
diagnostic to the user.
A future patch should address the comment at the top of
LowerExpectIntrisic.cpp to hoist the LikelyBranchWeight and
UnlikelyBranchWeight values into a shared space that can be accessed
outside of the LowerExpectIntrinsic pass. Once that is done, the
misexpect metadata can be updated to be smaller.
In the long term, it is possible to reconstruct portions of the
misexpect metadata from the existing profile data. However, we have
avoided this to keep the code simple, and because some kind of metadata
tag will be required to identify which branch/switch/select instructions
are influenced by the use of llvm.expect
Patch By: paulkirth
Differential Revision: https://reviews.llvm.org/D66324
llvm-svn: 371484
As shown in PR41279, some basic blocks (such as catchswitch) cannot be
instrumented. This patch filters out these BBs in PGO instrumentation.
It also sets the profile count to the fail-to-instrument edge, so that we
can propagate the counts in the CFG.
Differential Revision: https://reviews.llvm.org/D62700
llvm-svn: 362995
As it's causing some bot failures (and per request from kbarton).
This reverts commit r358543/ab70da07286e618016e78247e4a24fcb84077fda.
llvm-svn: 358546
We currently assume profile hash conflicts will be caught by an upfront
check and we assert for the cases that escape the check. The assumption
is not always true as there are chances of conflict. This patch prints
a warning and skips annotating the function for the escaped cases,.
Differential Revision: https://reviews.llvm.org/D60154
llvm-svn: 358225
Part 4 of CSPGO changes:
(1) add support in cmake for cspgo build.
(2) fix an issue in big endian.
(3) test cases.
Differential Revision: https://reviews.llvm.org/D54175
llvm-svn: 355541
If all the edge counts for a function are zero, skip count population and
annotation, as nothing will happen. This can save some compile time.
Differential Revision: https://reviews.llvm.org/D54212
llvm-svn: 346370
This can be used to preserve profiling information across codebase
changes that have widespread impact on mangled names, but across which
most profiling data should still be usable. For example, when switching
from libstdc++ to libc++, or from the old libstdc++ ABI to the new ABI,
or even from a 32-bit to a 64-bit build.
The user can provide a remapping file specifying parts of mangled names
that should be treated as equivalent (eg, std::__1 should be treated as
equivalent to std::__cxx11), and profile data will be treated as
applying to a particular function if its name is equivalent to the name
of a function in the profile data under the provided equivalences. See
the documentation change for a description of how this is configured.
Remapping is supported for both sample-based profiling and instruction
profiling. We do not support remapping indirect branch target
information, but all other profile data should be remapped
appropriately.
Support is only added for the new pass manager. If someone wants to also
add support for this for the old pass manager, doing so should be
straightforward.
This is the LLVM side of Clang r344199.
Reviewers: davidxl, tejohnson, dlj, erik.pilkington
Subscribers: mehdi_amini, steven_wu, dexonsmith, llvm-commits
Differential Revision: https://reviews.llvm.org/D51249
llvm-svn: 344200
Fixed counter/weight overflow that leads to an assertion. Also fixed the help
string for pgo-emit-branch-prob option.
Differential Revision: https://reviews.llvm.org/D44809
llvm-svn: 328653
Summary:
The PGO gen/use passes currently fail with an assert failure if there's a
critical edge whose source is an IndirectBr instruction and that edge
needs to be instrumented.
To avoid this in certain cases, split IndirectBr critical edges in the PGO
gen/use passes. This works for blocks with single indirectbr predecessors,
but not for those with multiple indirectbr predecessors (splitting an
IndirectBr critical edge isn't always possible.)
Reviewers: davidxl, xur
Reviewed By: davidxl
Subscribers: efriedma, llvm-commits, mehdi_amini
Differential Revision: https://reviews.llvm.org/D40699
llvm-svn: 320511
Summary:
Currently the block frequency analysis is an approximation for irreducible
loops.
The new irreducible loop metadata is used to annotate the irreducible loop
headers with their header weights based on the PGO profile (currently this is
approximated to be evenly weighted) and to help improve the accuracy of the
block frequency analysis for irreducible loops.
This patch is a basic support for this.
Reviewers: davidxl
Reviewed By: davidxl
Subscribers: mehdi_amini, llvm-commits, eraman
Differential Revision: https://reviews.llvm.org/D39028
llvm-svn: 317278
Summary:
The fix for dead stripping analysis in the case of SamplePGO indirect
calls to local functions (r313151) introduced the possibility of an
infinite loop.
Make sure we check for the value being already live after we update it
for SamplePGO indirect call handling.
Reviewers: danielcdh
Subscribers: mehdi_amini, inglorion, llvm-commits, eraman
Differential Revision: https://reviews.llvm.org/D38086
llvm-svn: 313766
Summary:
SamplePGO indirect call profiles record the target as the original GUID
for statics. The importer had special handling to map to the normal GUID
in that case. The dead global analysis needs the same treatment or
inconsistencies arise, resulting in linker unsats due to some dead
symbols being exported and kept, leaving in references to other dead
symbols that are removed.
This can happen when a SamplePGO profile collected by one binary is used
for a different binary, so the indirect call profiles may not accurately
reflect live targets.
Reviewers: danielcdh
Subscribers: mehdi_amini, inglorion, llvm-commits, eraman
Differential Revision: https://reviews.llvm.org/D37783
llvm-svn: 313151
Current PGO only annotates the edge weight for branch and switch instructions
with profile counts. We should also annotate the indirectbr instruction as
all the information is there. This patch enables the annotating for indirectbr
instructions. Also uses this annotation in branch probability analysis.
Differential Revision: https://reviews.llvm.org/D37074
llvm-svn: 311604
