This adds LIBC_CONF_PRINTF_MODULAR, which causes floating point support
(later, others) to be weakly linked into the implementation.
__printf_modular becomes the main entry point of the implementaiton, an
printf itself wraps __printf_modular. printf it also contains a
BFD_RELOC_NONE relocation to bring in the float aspect.
See issue #146159 for context.
There are three flavors of WriteBuffer currently, all of which could be
passed into `printf_core::Writer` class. It's a tricky class, since it
chooses a flavor-specific logic either based on runtime dispatch (to
save code size and prevent generating three versions of the entirety of
printf_core), or based on template arguments (to avoid dealing with
function pointers in codegen for `FILL_BUFF_AND_DROP_OVERFLOW` path).
Refactor this somewhat convoluted logic to have three concrete
subclasses inheriting from the templated base class, and use static
polymorphism with `reinterpret_cast` to implement dispatching above. Now
we can actually have flavor-specific fields, constructors, and methods
(e.g. `flush_to_stream` is now a method of `FlushingBuffer`), and the
code on the user side is cleaner: the complexity of enabling/disabling
runtime-dispatch and using proper template arguments is now localized in
`writer.h`.
This code will need to be further templatized to support buffers of type
`wchar_t` to implement `swprintf()` and friends. This change would make
it (ever so slightly) easier.
Summary:
Currently we dispatch the writing mode off of a runtime enum passed in
by the constructor. This causes very unfortunate codegen for the GPU
targets where we get worst-case codegen because of the unused function
pointer for `sprintf`. Instead, this patch moves all of this to a
template so it can be masked out. This results in no dynamic stack and
uses 60 VGPRs instead of 117. It also compiles about 5x as fast.
The new printf writer design focuses on optimizing the fast path. It
inlines any write to a buffer or string, and by handling buffering
itself can more effectively work with both internal and external file
implementations. The overflow hook should allow for expansion to
asprintf with minimal extra code.
Reviewed By: sivachandra
Differential Revision: https://reviews.llvm.org/D153999
The FormatSection and the writer functions both previously took a char*
and a length to represent a string. Now they use the StringView class to
represent that more succinctly. This change also required fixing
everywhere these were used, so it touches a lot of files.
Reviewed By: sivachandra
Differential Revision: https://reviews.llvm.org/D131994
After adding sprintf, snprintf is simple. The functions are very
similar. The tests only cover the behavior of the max length since the
sprintf tests should cover the other behavior.
Reviewed By: lntue
Differential Revision: https://reviews.llvm.org/D125826
