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cpu/vexriscv: Redo csr instruction fix 

Instead of enabling the zicsr extension in crt0.S, change -march to
specify that VexRISCV implements version 2.0 of I, rather than the
latest (2.1).  In 2.0 the csr instructions were still part of I.
This approach has two advantages:

* It is compatible with older versions of binutils, since they do not
  need to know about the new zicsr extension

* By modifying the -march in CFLAGS, csr instructions can be used in any
  code (for example by the inline functions in irq.h), not just in crt0.S.
This commit is contained in:
Marcus Comstedt 2022-06-04 13:36:08 +02:00
parent 3f8cafeb58
commit 91d79ae1da
4 changed files with 25 additions and 29 deletions
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48
litex/soc/cores/cpu/vexriscv/core.py
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@ -46,30 +46,30 @@ CPU_VARIANTS = {
# GCC Flags ---------------------------------------------------------------------------------------- # GCC Flags ----------------------------------------------------------------------------------------
GCC_FLAGS = { GCC_FLAGS = {
# /-------- Base ISA # /---------- Base ISA
# |/------- Hardware Multiply + Divide # | /----- Hardware Multiply + Divide
# ||/----- Atomics # | |/---- Atomics
# |||/---- Compressed ISA # | ||/--- Compressed ISA
# ||||/--- Single-Precision Floating-Point # | |||/-- Single-Precision Floating-Point
# |||||/-- Double-Precision Floating-Point # | ||||/- Double-Precision Floating-Point
# imacfd # i macfd
"minimal": "-march=rv32i -mabi=ilp32", "minimal": "-march=rv32i2p0 -mabi=ilp32",
"minimal+debug": "-march=rv32i -mabi=ilp32", "minimal+debug": "-march=rv32i2p0 -mabi=ilp32",
"lite": "-march=rv32im -mabi=ilp32", "lite": "-march=rv32i2p0_m -mabi=ilp32",
"lite+debug": "-march=rv32im -mabi=ilp32", "lite+debug": "-march=rv32i2p0_m -mabi=ilp32",
"standard": "-march=rv32im -mabi=ilp32", "standard": "-march=rv32i2p0_m -mabi=ilp32",
"standard+debug": "-march=rv32im -mabi=ilp32", "standard+debug": "-march=rv32i2p0_m -mabi=ilp32",
"imac": "-march=rv32imac -mabi=ilp32", "imac": "-march=rv32i2p0_mac -mabi=ilp32",
"imac+debug": "-march=rv32imac -mabi=ilp32", "imac+debug": "-march=rv32i2p0_mac -mabi=ilp32",
"full": "-march=rv32im -mabi=ilp32", "full": "-march=rv32i2p0_m -mabi=ilp32",
"full+cfu": "-march=rv32im -mabi=ilp32", "full+cfu": "-march=rv32i2p0_m -mabi=ilp32",
"full+debug": "-march=rv32im -mabi=ilp32", "full+debug": "-march=rv32i2p0_m -mabi=ilp32",
"full+cfu+debug": "-march=rv32im -mabi=ilp32", "full+cfu+debug": "-march=rv32i2p0_m -mabi=ilp32",
"linux": "-march=rv32ima -mabi=ilp32", "linux": "-march=rv32i2p0_ma -mabi=ilp32",
"linux+debug": "-march=rv32ima -mabi=ilp32", "linux+debug": "-march=rv32i2p0_ma -mabi=ilp32",
"linux+no-dsp": "-march=rv32ima -mabi=ilp32", "linux+no-dsp": "-march=rv32i2p0_ma -mabi=ilp32",
"secure": "-march=rv32ima -mabi=ilp32", "secure": "-march=rv32i2p0_ma -mabi=ilp32",
"secure+debug": "-march=rv32ima -mabi=ilp32", "secure+debug": "-march=rv32i2p0_ma -mabi=ilp32",
} }
# VexRiscv Timer ----------------------------------------------------------------------------------- # VexRiscv Timer -----------------------------------------------------------------------------------

2
litex/soc/cores/cpu/vexriscv/crt0.S
View File

@ -2,8 +2,6 @@
.global isr .global isr
.global _start .global _start
.option arch,+zicsr
_start: _start:
j crt_init j crt_init
nop nop

2
litex/soc/cores/cpu/vexriscv_smp/core.py
View File

@ -120,7 +120,7 @@ class VexRiscvSMP(CPU):
# Arch. # Arch.
@staticmethod @staticmethod
def get_arch(): def get_arch():
arch = "rv32ima" arch = "rv32i2p0_ma"
if VexRiscvSMP.with_fpu: if VexRiscvSMP.with_fpu:
arch += "fd" arch += "fd"
if VexRiscvSMP.with_rvc: if VexRiscvSMP.with_rvc:

2
litex/soc/cores/cpu/vexriscv_smp/crt0.S
View File

@ -7,8 +7,6 @@
.global smp_lottery_args .global smp_lottery_args
.global smp_slave .global smp_slave
.option arch,+zicsr
_start: _start:
j crt_init j crt_init
nop nop