[DFSan] Remove -dfsan-args-abi support in favor of TLS.

ArgsABI was originally added in https://reviews.llvm.org/D965

Current benchmarking does not show a significant difference.
There is no need t

[DFSan] Remove -dfsan-args-abi support in favor of TLS.

ArgsABI was originally added in https://reviews.llvm.org/D965

Current benchmarking does not show a significant difference.
There is no need to maintain both ABIs.

Reviewed By: pcc

Differential Revision: https://reviews.llvm.org/D111097

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[dfsan] Replace dfs$ prefix with .dfsan suffix

The current naming scheme adds the `dfs$` prefix to all
DFSan-instrumented functions. This breaks mangling and prevents stack
trace printers and other

[dfsan] Replace dfs$ prefix with .dfsan suffix

The current naming scheme adds the `dfs$` prefix to all
DFSan-instrumented functions. This breaks mangling and prevents stack
trace printers and other tools from automatically demangling function
names.

This new naming scheme is mangling-compatible, with the `.dfsan`
suffix being a vendor-specific suffix:
https://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangling-structure

With this fix, demangling utils would work out-of-the-box.

Reviewed By: stephan.yichao.zhao

Differential Revision: https://reviews.llvm.org/D104494

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[dfsan] Add full fast8 support

Complete support for fast8:
- amend shadow size and mapping in runtime
- remove fast16 mode and -dfsan-fast-16-labels flag
- remove legacy mode and make fast8 mode the

[dfsan] Add full fast8 support

Complete support for fast8:
- amend shadow size and mapping in runtime
- remove fast16 mode and -dfsan-fast-16-labels flag
- remove legacy mode and make fast8 mode the default
- remove dfsan-fast-8-labels flag
- remove functions in dfsan interface only applicable to legacy
- remove legacy-related instrumentation code and tests
- update documentation.

Reviewed By: stephan.yichao.zhao, browneee

Differential Revision: https://reviews.llvm.org/D103745

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[dfsan] Add -dfsan-fast-8-labels flag

This is only adding support to the dfsan instrumentation pass but not
to the runtime.

Added more RUN lines for testing: for each instrumentation test that
had

[dfsan] Add -dfsan-fast-8-labels flag

This is only adding support to the dfsan instrumentation pass but not
to the runtime.

Added more RUN lines for testing: for each instrumentation test that
had a -dfsan-fast-16-labels invocation, a new invocation was added
using fast8.

Reviewed By: stephan.yichao.zhao

Differential Revision: https://reviews.llvm.org/D98734

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[dfsan] Increase coverage of vector and select tests

Add more expectations in vector.ll and select.ll based on command-line option combinations.
Also, remove hard-coded shadow width references to en

[dfsan] Increase coverage of vector and select tests

Add more expectations in vector.ll and select.ll based on command-line option combinations.
Also, remove hard-coded shadow width references to enable fast8 transition.

Reviewed By: stephan.yichao.zhao

Differential Revision: https://reviews.llvm.org/D97903

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[dfsan] Track field/index-level shadow values in variables

*************
* The problem
*************
See motivation examples in compiler-rt/test/dfsan/pair.cpp. The current
DFSan always uses a 16bit

[dfsan] Track field/index-level shadow values in variables

*************
* The problem
*************
See motivation examples in compiler-rt/test/dfsan/pair.cpp. The current
DFSan always uses a 16bit shadow value for a variable with any type by
combining all shadow values of all bytes of the variable. So it cannot
distinguish two fields of a struct: each field's shadow value equals the
combined shadow value of all fields. This introduces an overtaint issue.

Consider a parsing function

std::pair<char*, int> get_token(char* p);

where p points to a buffer to parse, the returned pair includes the next
token and the pointer to the position in the buffer after the token.

If the token is tainted, then both the returned pointer and int ar
tainted. If the parser keeps on using get_token for the rest parsing,
all the following outputs are tainted because of the tainted pointer.

The CL is the first change to address the issue.

**************************
* The proposed improvement
**************************
Eventually all fields and indices have their own shadow values in
variables and memory.

For example, variables with type {i1, i3}, [2 x i1], {[2 x i4], i8},
[2 x {i1, i1}] have shadow values with type {i16, i16}, [2 x i16],
{[2 x i16], i16}, [2 x {i16, i16}] correspondingly; variables with
primary type still have shadow values i16.

***************************
* An potential implementation plan
***************************

The idea is to adopt the change incrementially.

1) This CL
Support field-level accuracy at variables/args/ret in TLS mode,
load/store/alloca still use combined shadow values.

After the alloca promotion and SSA construction phases (>=-O1), we
assume alloca and memory operations are reduced. So if struct
variables do not relate to memory, their tracking is accurate at
field level.

2) Support field-level accuracy at alloca
3) Support field-level accuracy at load/store

These two should make O0 and real memory access work.

4) Support vector if necessary.
5) Support Args mode if necessary.
6) Support passing more accurate shadow values via custom functions if
necessary.

***************
* About this CL.
***************
The CL did the following

1) extended TLS arg/ret to work with aggregate types. This is similar
to what MSan does.

2) implemented how to map between an original type/value/zero-const to
its shadow type/value/zero-const.

3) extended (insert|extract)value to use field/index-level progagation.

4) for other instructions, propagation rules are combining inputs by or.
The CL converts between aggragate and primary shadow values at the
cases.

5) Custom function interfaces also need such a conversion because
all existing custom functions use i16. It is unclear whether custome
functions need more accurate shadow propagation yet.

6) Added test cases for aggregate type related cases.

Reviewed-by: morehouse

Differential Revision: https://reviews.llvm.org/D92261

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