core: riscv: use configuration options for RISC-V extensions

RISC-V is a modular ISA, add config options to allow platforms
to customize their binaries with specific "-march" and "-mabi".

Also, enable RVC and FPU extension for QEMU virt machine.

Note that the RISC-V FPU for OP-TEE will be introduced later.
Enable FPU to temporarily bypass incompatible soft/hard-fp
linker errors.

Signed-off-by: Yu Chien Peter Lin <peterlin@andestech.com>
Reviewed-by: Alvin Chang <alvinga@andestech.com>
Acked-by: Jens Wiklander <jens.wiklander@linaro.org>

core/arch/riscv/plat-virt/conf.mk

@@ -1,5 +1,9 @@
 $(call force,CFG_RV64_core,y)
 
+# ISA extension flags
+$(call force,CFG_RISCV_ISA_C,y)
+$(call force,CFG_RISCV_FPU,y)
+
 $(call force,CFG_CORE_LARGE_PHYS_ADDR,y)
 $(call force,CFG_TEE_CORE_DEBUG,n)
 $(call force,CFG_CORE_RESERVED_SHM,n)
@@ -23,9 +27,6 @@ CFG_TEE_CORE_NB_CORE ?= 1
 CFG_NUM_THREADS ?= 1
 $(call force,CFG_BOOT_SYNC_CPU,y)
 
-# RISC-V-specific flags
-rv64-platform-isa ?= rv64imafdc_zicsr_zifencei
-
 $(call force,CFG_RISCV_M_MODE,n)
 $(call force,CFG_RISCV_S_MODE,y)
 $(call force,CFG_RISCV_PLIC,y)

core/arch/riscv/riscv.mk

@@ -88,19 +88,35 @@ core-platform-cppflags	+= -I$(arch-dir)/include
 core-platform-subdirs += \
 	$(addprefix $(arch-dir)/, kernel mm tee) $(platform-dir)
 
-# Default values for "-mcmodel", "-march", and "-abi" compiler flags.
-# Platform-specific overrides are in core/arch/riscv/plat-*/conf.mk.
+# Default values for "-mcmodel" compiler flag
 riscv-platform-mcmodel ?= medany
-rv64-platform-isa ?= rv64imafd
-rv64-platform-abi ?= lp64d
-rv32-platform-isa ?= rv32imafd
-rv32-platform-abi ?= ilp32d
+
+ifeq ($(CFG_RV64_core),y)
+ISA_BASE = rv64ima
+ABI_BASE = lp64
+else
+ISA_BASE = rv32ima
+ABI_BASE = ilp32
+endif
+ifeq ($(CFG_RISCV_FPU),y)
+ISA_D = fd
+ABI_D = d
+endif
+ifeq ($(CFG_RISCV_ISA_C),y)
+ISA_C = c
+endif
+ifeq ($(CFG_RISCV_ISA_ZBB),y)
+ISA_ZBB = _zbb
+endif
+
+riscv-isa = $(ISA_BASE)$(ISA_D)$(ISA_C)$(ISA_ZBB)_zicsr_zifencei
+riscv-abi = $(ABI_BASE)$(ABI_D)
 
 rv64-platform-cflags += -mcmodel=$(riscv-platform-mcmodel)
-rv64-platform-cflags += -march=$(rv64-platform-isa) -mabi=$(rv64-platform-abi)
+rv64-platform-cflags += -march=$(riscv-isa) -mabi=$(riscv-abi)
 rv64-platform-cflags += -Wno-missing-include-dirs
 rv32-platform-cflags += -mcmodel=$(riscv-platform-mcmodel)
-rv32-platform-cflags += -march=$(rv32-platform-isa) -mabi=$(rv32-platform-abi)
+rv32-platform-cflags += -march=$(riscv-isa) -mabi=$(riscv-abi)
 
 rv64-platform-cppflags += -DRV64=1 -D__LP64__=1
 rv32-platform-cppflags += -DRV32=1 -D__ILP32__=1