If a local_unnamed_addr attribute is attached to a global, the address
is known to be insignificant within the module. It is distinct from the
existing unnamed_addr attribute in that it only describes a local property
of the module rather than a global property of the symbol.
This attribute is intended to be used by the code generator and LTO to allow
the linker to decide whether the global needs to be in the symbol table. It is
possible to exclude a global from the symbol table if three things are true:
- This attribute is present on every instance of the global (which means that
the normal rule that the global must have a unique address can be broken without
being observable by the program by performing comparisons against the global's
address)
- The global has linkonce_odr linkage (which means that each linkage unit must have
its own copy of the global if it requires one, and the copy in each linkage unit
must be the same)
- It is a constant or a function (which means that the program cannot observe that
the unique-address rule has been broken by writing to the global)
Although this attribute could in principle be computed from the module
contents, LTO clients (i.e. linkers) will normally need to be able to compute
this property as part of symbol resolution, and it would be inefficient to
materialize every module just to compute it.
See:
http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160509/356401.htmlhttp://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160516/356738.html
for earlier discussion.
Part of the fix for PR27553.
Differential Revision: http://reviews.llvm.org/D20348
llvm-svn: 272709
Summary:
Iterates all (except the first and the last) operands within each GEP
instruction for instrumentation.
Adds test struct_field_gep.ll.
Reviewers: aizatsky
Subscribers: vitalybuka, zhaoqin, kcc, eugenis, bruening, llvm-commits
Differential Revision: http://reviews.llvm.org/D21242
llvm-svn: 272442
Summary:
Adds ClInstrumentFastpath option to control fastpath instrumentation.
Avoids the load/store instrumentation for the cache fragmentation tool.
Renames cache_frag_basic.ll to working_set_slow.ll for slowpath
instrumentation test.
Adds the __esan_init check in struct_field_count_basic.ll.
Reviewers: aizatsky
Subscribers: llvm-commits, bruening, eugenis, kcc, zhaoqin, vitalybuka
Differential Revision: http://reviews.llvm.org/D21079
llvm-svn: 272355
Summary:
Adds an option -esan-assume-intra-cache-line which causes esan to assume
that a single memory access touches just one cache line, even if it is not
aligned, for better performance at a potential accuracy cost. Experiments
show that the performance difference can be 2x or more, and accuracy loss
is typically negligible, so we turn this on by default. This currently
applies just to the working set tool.
Reviewers: aizatsky
Subscribers: vitalybuka, zhaoqin, kcc, eugenis, llvm-commits
Differential Revision: http://reviews.llvm.org/D20978
llvm-svn: 271743
Summary:
Adds a global variable to specify the tool, to support handling early
interceptors that invoke instrumented code and require shadow memory to be
initialized prior to __esan_init() being invoked.
Reviewers: aizatsky
Subscribers: vitalybuka, zhaoqin, kcc, eugenis, llvm-commits
Differential Revision: http://reviews.llvm.org/D20973
llvm-svn: 271715
Summary:
Instrument GEP instruction for counting the number of struct field
address calculation to approximate the number of struct field accesses.
Adds test struct_field_count_basic.ll to test the struct field
instrumentation.
Reviewers: bruening, aizatsky
Subscribers: junbuml, zhaoqin, llvm-commits, eugenis, vitalybuka, kcc, bruening
Differential Revision: http://reviews.llvm.org/D20892
llvm-svn: 271619
Summary:
Creates a global variable containing preliminary information
for the cache-fragmentation tool runtime.
Passes a pointer to the variable (null if no variable is created) to the
compilation unit init and exit routines in the runtime.
Reviewers: aizatsky, bruening
Subscribers: filcab, kubabrecka, bruening, kcc, vitalybuka, eugenis, llvm-commits, zhaoqin
Differential Revision: http://reviews.llvm.org/D20541
llvm-svn: 271298
Summary:
Adds fastpath instrumentation for esan's working set tool. The
instrumentation for an intra-cache-line load or store consists of an
inlined write to shadow memory bits for the corresponding cache line.
Adds a basic test for this instrumentation.
Reviewers: aizatsky
Subscribers: vitalybuka, zhaoqin, kcc, eugenis, llvm-commits
Differential Revision: http://reviews.llvm.org/D20483
llvm-svn: 270640
Summary:
Adds createEsanInitToolGV for creating a tool-specific variable passed
to the runtime library.
Adds dtor "esan.module_dtor" and inserts calls from the dtor to
"__esan_exit" in the runtime library.
Updates the EfficiencySanitizer test.
Patch by Qin Zhao.
Reviewers: aizatsky
Subscribers: bruening, kcc, vitalybuka, eugenis, llvm-commits
Differential Revision: http://reviews.llvm.org/D20488
llvm-svn: 270627
Summary:
Uses ModulePass instead of FunctionPass for EfficiencySanitizerPass to
better support global variable creation for a forthcoming struct field
counter tool.
Patch by Qin Zhao.
Reviewers: aizatsky
Subscribers: llvm-commits, eugenis, vitalybuka, bruening, kcc
Differential Revision: http://reviews.llvm.org/D20458
llvm-svn: 270263
Summary:
Adds an instrumentation pass for the new EfficiencySanitizer ("esan")
performance tuning family of tools. Multiple tools will be supported
within the same framework. Preliminary support for a cache fragmentation
tool is included here.
The shared instrumentation includes:
+ Turn mem{set,cpy,move} instrinsics into library calls.
+ Slowpath instrumentation of loads and stores via callouts to
the runtime library.
+ Fastpath instrumentation will be per-tool.
+ Which memory accesses to ignore will be per-tool.
Reviewers: eugenis, vitalybuka, aizatsky, filcab
Subscribers: filcab, vkalintiris, pcc, silvas, llvm-commits, zhaoqin, kcc
Differential Revision: http://reviews.llvm.org/D19167
llvm-svn: 267058
Peter Collingbourne