Previously, __internal_syscall() compiled into asm-code that unconditionally
sets the syscall argument registers a0 to a5.
For example, the instruction sequence for a exit syscall looked like
this:
li a0, 1 # in ther caller of exit()
# ... # in newlib:
li a1, 0 # unused arguments
li a2, 0
li a3, 0
li a4, 0
li a5, 0
li a7, 93 # exit syscall number
(i.e. the binary contains then 5 superfluous instructions for this
one argument syscall)
This commit changes the RISC-V syscall code such that only the required
syscall argument registers are set.
GCC detects that argc is known at compile time and thus evaluates all the
if-statements where argc is used at compile time (tested with -O2 and -Os).
bfin - Analog Devices Blackfin processor.
sparc - Fujitsu Sparclite board. Works on the ex930, ex931, ex933
hp74x - Hewlett Packard HP742 board. Also some support for the hp743.
m68hc11 - Motorola 68HC11 or 68HC12 support.
m68k - Motorola MVME135 and IDP board. For CPU32 systems.
mep - Toshiba Media Processor.
pa - WinBond and Oki boards with a PA.
mips - R3000 support. Array Tech LSI33k based RAID disk controller.
lm32 - Lattice Mico32 simulator.
epiphany - Adapteva Epiphany multicore processor.
or1k - OpenRISC 1000 processor.
9b51beeb2a