Mips16/32 floating point interoperability.
When Mips16 code calls external functions that would normally have some
of its parameters or return values passed in floating point registers,
it needs (Mips32) helper functions to do this because while in Mips16 mode
there is no ability to access the floating point registers.
In Pic mode, this is done with a set of predefined functions in libc.
This case is already handled in llvm for Mips16.
In static relocation mode, for efficiency reasons, the compiler generates
stubs that the linker will use if it turns out that the external function
is a Mips32 function. (If it's Mips16, then it does not need the helper
stubs).
These stubs are identically named and the linker knows about these tricks
and will not create multiple copies and will delete them if they are not
needed.
llvm-svn: 181753
mips16/mips32 floating point interoperability.
This patch fixes returns from mips16 functions so that if the function
was in fact called by a mips32 hard float routine, then values
that would have been returned in floating point registers are so returned.
Mips16 mode has no floating point instructions so there is no way to
load values into floating point registers.
This is needed when returning float, double, single complex, double complex
in the Mips ABI.
Helper functions in libc for mips16 are available to do this.
For efficiency purposes, these helper functions have a different calling
convention from normal Mips calls.
Registers v0,v1,a0,a1 are used to pass parameters instead of
a0,a1,a2,a3.
This is because v0,v1,a0,a1 are the natural registers used to return
floating point values in soft float. These values can then be moved
to the appropriate floating point registers with no extra cost.
The only register that is modified is ra in this call.
The helper functions make sure that the return values are in the floating
point registers that they would be in if soft float was not in effect
(which it is for mips16, though the soft float is implemented using a mips32
library that uses hard float).
llvm-svn: 181641
Reed Kotler