Enable 'C'-compressed ISA extension.

This was disabled recently due to lack of support in KDB disassembler
and DTrace FBT provider. Support for 'C'-extension to both of these was
added, so we can now enable 'C'-extension.

This reduces size of the kernel important for low-end embedded devices,
and saves cache footprint for high perfomance machines.

Approved by:	re (kib)
Sponsored by:	DARPA, AFRL

share/mk/bsd.cpu.mk

@@ -367,9 +367,9 @@ CFLAGS += -mcpu=8540 -Wa,-me500 -mspe=yes -mabi=spe -mfloat-gprs=double
 
 .if ${MACHINE_CPUARCH} == "riscv"
 .if ${MACHINE_ARCH:Mriscv*sf}
-CFLAGS += -march=rv64ima -mabi=lp64
+CFLAGS += -march=rv64imac -mabi=lp64
 .else
-CFLAGS += -march=rv64imafd -mabi=lp64d
+CFLAGS += -march=rv64imafdc -mabi=lp64d
 .endif
 .endif
 

stand/defs.mk

@@ -108,7 +108,7 @@ CFLAGS+=	-ffreestanding ${CFLAGS_NO_SIMD}
 .if ${MACHINE_CPUARCH} == "aarch64"
 CFLAGS+=	-mgeneral-regs-only -fPIC
 .elif ${MACHINE_CPUARCH} == "riscv"
-CFLAGS+=	-march=rv64ima -mabi=lp64
+CFLAGS+=	-march=rv64imac -mabi=lp64
 .else
 CFLAGS+=	-msoft-float
 .endif

sys/conf/kern.mk

@@ -131,7 +131,7 @@ INLINE_LIMIT?=	8000
 .endif
 
 .if ${MACHINE_CPUARCH} == "riscv"
-CFLAGS.gcc+=	-mcmodel=medany -march=rv64imafd -mabi=lp64
+CFLAGS.gcc+=	-mcmodel=medany -march=rv64imafdc -mabi=lp64
 INLINE_LIMIT?=	8000
 .endif