all: add HiFive1 rev B board with RISC-V architecture

This page has been a big help in adding support for this new chip:
https://wiki.osdev.org/HiFive-1_Bare_Bones

.circleci/config.yml

@@ -67,7 +67,7 @@ commands:
       - run: go install .
       - run: go test -v
       - run: make gen-device -j4
-      - run: make smoketest
+      - run: make smoketest RISCV=0
       - save_cache:
           key: go-cache-{{ checksum "Gopkg.lock" }}-{{ .Environment.CIRCLE_BUILD_NUM }}
           paths:
@@ -100,7 +100,7 @@ commands:
       - llvm-source-linux
       - restore_cache:
           keys:
-            - llvm-build-8-linux-v6
+            - llvm-build-8-linux-v7
       - run:
           name: "Build LLVM"
           command: |
@@ -118,7 +118,7 @@ commands:
               make llvm-build
             fi
       - save_cache:
-          key: llvm-build-8-linux-v6
+          key: llvm-build-8-linux-v7
           paths:
             llvm-build
       - run:
@@ -149,6 +149,11 @@ commands:
             tar -C ~/lib -xf /tmp/tinygo.linux-amd64.tar.gz
             ln -s ~/lib/tinygo/bin/tinygo /go/bin/tinygo
             tinygo version
+      - run:
+          name: "Download SiFive GNU toolchain"
+          command: |
+            curl -O https://static.dev.sifive.com/dev-tools/riscv64-unknown-elf-gcc-8.2.0-2019.05.3-x86_64-linux-ubuntu14.tar.gz
+            sudo tar -C /usr/local --strip-components=1 -xf riscv64-unknown-elf-gcc-8.2.0-2019.05.3-x86_64-linux-ubuntu14.tar.gz
       - run: make smoketest
   build-macos:
     steps:
@@ -173,7 +178,7 @@ commands:
             - llvm-project
       - restore_cache:
           keys:
-            - llvm-build-8-macos-v5
+            - llvm-build-8-macos-v6
       - run:
           name: "Build LLVM"
           command: |
@@ -185,7 +190,7 @@ commands:
               make llvm-build
             fi
       - save_cache:
-          key: llvm-build-8-macos-v5
+          key: llvm-build-8-macos-v6
           paths:
             llvm-build
       - run:
@@ -209,6 +214,11 @@ commands:
             tar -C /usr/local/opt -xf /tmp/tinygo.darwin-amd64.tar.gz
             ln -s /usr/local/opt/tinygo/bin/tinygo /usr/local/bin/tinygo
             tinygo version
+      - run:
+          name: "Download SiFive GNU toolchain"
+          command: |
+            curl -O https://static.dev.sifive.com/dev-tools/riscv64-unknown-elf-gcc-8.2.0-2019.05.3-x86_64-apple-darwin.tar.gz
+            sudo tar -C /usr/local --strip-components=1 -xf riscv64-unknown-elf-gcc-8.2.0-2019.05.3-x86_64-apple-darwin.tar.gz
       - run: make smoketest AVR=0
 
 

.gitignore

@@ -5,10 +5,12 @@ src/device/avr/*.ld
 src/device/avr/*.s
 src/device/nrf/*.go
 src/device/nrf/*.s
-src/device/stm32/*.go
-src/device/stm32/*.s
 src/device/sam/*.go
 src/device/sam/*.s
+src/device/sifive/*.go
+src/device/sifive/*.s
+src/device/stm32/*.go
+src/device/stm32/*.s
 vendor
 llvm
 llvm-build

.gitmodules

@@ -9,7 +9,7 @@
 	url = https://github.com/avr-rust/avr-mcu.git
 [submodule "lib/cmsis-svd"]
 	path = lib/cmsis-svd
-	url = https://github.com/posborne/cmsis-svd
+	url = https://github.com/tinygo-org/cmsis-svd
 [submodule "lib/compiler-rt"]
 	path = lib/compiler-rt
 	url = https://github.com/llvm-mirror/compiler-rt.git

Makefile

@@ -41,7 +41,7 @@ fmt-check:
 	@unformatted=$$(gofmt -l $(FMT_PATHS)); [ -z "$$unformatted" ] && exit 0; echo "Unformatted:"; for fn in $$unformatted; do echo "  $$fn"; done; exit 1
 
 
-gen-device: gen-device-avr gen-device-nrf gen-device-sam gen-device-stm32
+gen-device: gen-device-avr gen-device-nrf gen-device-sam gen-device-sifive gen-device-stm32
 
 gen-device-avr:
 	./tools/gen-device-avr.py lib/avr/packs/atmega src/device/avr/
@@ -56,6 +56,10 @@ gen-device-sam:
 	./tools/gen-device-svd.py lib/cmsis-svd/data/Atmel/ src/device/sam/ --source=https://github.com/posborne/cmsis-svd/tree/master/data/Atmel
 	go fmt ./src/device/sam
 
+gen-device-sifive:
+	./tools/gen-device-svd.py lib/cmsis-svd/data/SiFive-Community/ src/device/sifive/ --source=https://github.com/AdaCore/svd2ada/tree/master/CMSIS-SVD/SiFive-Community
+	go fmt ./src/device/sifive
+
 gen-device-stm32:
 	./tools/gen-device-svd.py lib/cmsis-svd/data/STMicro/ src/device/stm32/ --source=https://github.com/posborne/cmsis-svd/tree/master/data/STMicro
 	go fmt ./src/device/stm32
@@ -69,7 +73,7 @@ llvm-source: llvm-project/README.md
 # Configure LLVM.
 TINYGO_SOURCE_DIR=$(shell pwd)
 $(LLVM_BUILDDIR)/build.ninja: llvm-source
-	mkdir -p $(LLVM_BUILDDIR); cd $(LLVM_BUILDDIR); cmake -G Ninja $(TINYGO_SOURCE_DIR)/llvm-project/llvm "-DLLVM_TARGETS_TO_BUILD=X86;ARM;AArch64;WebAssembly" "-DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD=AVR" -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_ASSERTIONS=OFF -DLIBCLANG_BUILD_STATIC=ON -DLLVM_ENABLE_TERMINFO=OFF -DLLVM_ENABLE_ZLIB=OFF -DLLVM_ENABLE_PROJECTS="clang;lld" -DLLVM_TOOL_CLANG_TOOLS_EXTRA_BUILD=OFF
+	mkdir -p $(LLVM_BUILDDIR); cd $(LLVM_BUILDDIR); cmake -G Ninja $(TINYGO_SOURCE_DIR)/llvm-project/llvm "-DLLVM_TARGETS_TO_BUILD=X86;ARM;AArch64;WebAssembly" "-DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD=AVR;RISCV" -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_ASSERTIONS=OFF -DLIBCLANG_BUILD_STATIC=ON -DLLVM_ENABLE_TERMINFO=OFF -DLLVM_ENABLE_ZLIB=OFF -DLLVM_ENABLE_PROJECTS="clang;lld" -DLLVM_TOOL_CLANG_TOOLS_EXTRA_BUILD=OFF
 
 # Build LLVM.
 $(LLVM_BUILDDIR): $(LLVM_BUILDDIR)/build.ninja
@@ -123,6 +127,9 @@ smoketest:
 ifneq ($(AVR), 0)
 	tinygo build -size short -o test.elf -target=arduino             examples/blinky1
 	tinygo build -size short -o test.elf -target=digispark           examples/blinky1
+endif
+ifneq ($(RISCV), 0)
+	tinygo build -size short -o test.elf -target=hifive1b            examples/blinky1
 endif
 	tinygo build             -o wasm.wasm -target=wasm               examples/wasm/export
 	tinygo build             -o wasm.wasm -target=wasm               examples/wasm/main

compiler/compiler.go

@@ -226,7 +226,7 @@ func (c *Compiler) Compile(mainPath string) []error {
 					return path
 				} else if path == "syscall" {
 					for _, tag := range c.BuildTags {
-						if tag == "avr" || tag == "cortexm" || tag == "darwin" {
+						if tag == "avr" || tag == "cortexm" || tag == "darwin" || tag == "riscv" {
 							return path
 						}
 					}
@@ -1304,11 +1304,11 @@ func (c *Compiler) parseCall(frame *Frame, instr *ssa.CallCommon) (llvm.Value, e
 	if fn := instr.StaticCallee(); fn != nil {
 		name := fn.RelString(nil)
 		switch {
-		case name == "device/arm.ReadRegister":
+		case name == "device/arm.ReadRegister" || name == "device/riscv.ReadRegister":
-			return c.emitReadRegister(instr.Args)
+			return c.emitReadRegister(name, instr.Args)
-		case name == "device/arm.Asm" || name == "device/avr.Asm":
+		case name == "device/arm.Asm" || name == "device/avr.Asm" || name == "device/riscv.Asm":
 			return c.emitAsm(instr.Args)
-		case name == "device/arm.AsmFull" || name == "device/avr.AsmFull":
+		case name == "device/arm.AsmFull" || name == "device/avr.AsmFull" || name == "device/riscv.AsmFull":
 			return c.emitAsmFull(frame, instr)
 		case strings.HasPrefix(name, "device/arm.SVCall"):
 			return c.emitSVCall(frame, instr.Args)

compiler/gc.go

@@ -18,7 +18,7 @@ func (c *Compiler) needsStackObjects() bool {
 		return false
 	}
 	for _, tag := range c.BuildTags {
-		if tag == "cortexm" {
+		if tag == "cortexm" || tag == "tinygo.riscv" {
 			return false
 		}
 	}

compiler/inlineasm.go

@@ -18,10 +18,19 @@ import (
 //     func ReadRegister(name string) uintptr
 //
 // The register name must be a constant, for example "sp".
-func (c *Compiler) emitReadRegister(args []ssa.Value) (llvm.Value, error) {
+func (c *Compiler) emitReadRegister(name string, args []ssa.Value) (llvm.Value, error) {
 	fnType := llvm.FunctionType(c.uintptrType, []llvm.Type{}, false)
 	regname := constant.StringVal(args[0].(*ssa.Const).Value)
-	target := llvm.InlineAsm(fnType, "mov $0, "+regname, "=r", false, false, 0)
+	var asm string
+	switch name {
+	case "device/arm.ReadRegister":
+		asm = "mov $0, " + regname
+	case "device/riscv.ReadRegister":
+		asm = "mv $0, " + regname
+	default:
+		panic("unknown architecture")
+	}
+	target := llvm.InlineAsm(fnType, asm, "=r", false, false, 0)
 	return c.builder.CreateCall(target, nil, ""), nil
 }
 

lib/cmsis-svd

@@ -1 +1 @@
-Subproject commit b6f0a65ac37760f52d6ade23dd3205424d6c91fa
+Subproject commit 5910f3d115a53ead55c8158da24a8fa8bda1eb50

src/device/riscv/riscv.go

@@ -0,0 +1,10 @@
+package riscv
+
+// Run the given assembly code. The code will be marked as having side effects,
+// as it doesn't produce output and thus would normally be eliminated by the
+// optimizer.
+func Asm(asm string)
+
+// ReadRegister returns the contents of the specified register. The register
+// must be a processor register, reachable with the "mov" instruction.
+func ReadRegister(name string) uintptr

src/device/riscv/start.S

@@ -0,0 +1,13 @@
+.section .init
+.global _start
+.type _start,@function
+
+_start:
+    // Workaround for missing support of the la pseudo-instruction in Clang 8:
+    // https://reviews.llvm.org/D55325
+    lui sp,      %hi(_stack_top)
+    addi sp, sp, %lo(_stack_top)
+    // see https://gnu-mcu-eclipse.github.io/arch/riscv/programmer/#the-gp-global-pointer-register
+    lui gp,      %hi(__global_pointer$)
+    addi gp, gp, %lo(__global_pointer$)
+    call main

src/machine/board_fe310.go

@@ -0,0 +1,38 @@
+// +build hifive1b
+
+package machine
+
+const (
+	P00 Pin = 0
+	P01 Pin = 1
+	P02 Pin = 2
+	P03 Pin = 3
+	P04 Pin = 4
+	P05 Pin = 5
+	P06 Pin = 6
+	P07 Pin = 7
+	P08 Pin = 8
+	P09 Pin = 9
+	P10 Pin = 10
+	P11 Pin = 11
+	P12 Pin = 12
+	P13 Pin = 13
+	P14 Pin = 14
+	P15 Pin = 15
+	P16 Pin = 16
+	P17 Pin = 17
+	P18 Pin = 18
+	P19 Pin = 19
+	P20 Pin = 20
+	P21 Pin = 21
+	P22 Pin = 22
+	P23 Pin = 23
+	P24 Pin = 24
+	P25 Pin = 25
+	P26 Pin = 26
+	P27 Pin = 27
+	P28 Pin = 28
+	P29 Pin = 29
+	P30 Pin = 30
+	P31 Pin = 31
+)

src/machine/board_hifive1b.go

@@ -0,0 +1,19 @@
+// +build hifive1b
+
+package machine
+
+const (
+	LED       = LED1
+	LED1      = LED_RED
+	LED2      = LED_GREEN
+	LED3      = LED_BLUE
+	LED_RED   = P22
+	LED_GREEN = P19
+	LED_BLUE  = P21
+)
+
+const (
+	// TODO: figure out the pin numbers for these.
+	UART_TX_PIN = NoPin
+	UART_RX_PIN = NoPin
+)

src/machine/i2c.go

@@ -1,4 +1,4 @@
-// +build !stm32f4disco
+// +build !stm32f4disco,!hifive1b
 
 package machine
 

src/machine/machine_fe310.go

@@ -0,0 +1,54 @@
+// +build fe310
+
+package machine
+
+import (
+	"device/sifive"
+)
+
+type PinMode uint8
+
+const (
+	PinInput PinMode = iota
+	PinOutput
+)
+
+// Configure this pin with the given configuration.
+func (p Pin) Configure(config PinConfig) {
+	sifive.GPIO0.INPUT_EN.SetBits(1 << uint8(p))
+	if config.Mode == PinOutput {
+		sifive.GPIO0.OUTPUT_EN.SetBits(1 << uint8(p))
+	}
+}
+
+// Set the pin to high or low.
+func (p Pin) Set(high bool) {
+	if high {
+		sifive.GPIO0.PORT.SetBits(1 << uint8(p))
+	} else {
+		sifive.GPIO0.PORT.ClearBits(1 << uint8(p))
+	}
+}
+
+type UART struct {
+	Bus    *sifive.UART_Type
+	Buffer *RingBuffer
+}
+
+var (
+	UART0 = UART{Bus: sifive.UART0, Buffer: NewRingBuffer()}
+)
+
+func (uart UART) Configure(config UARTConfig) {
+	// Assuming a 16Mhz Crystal (which is Y1 on the HiFive1), the divisor for a
+	// 115200 baud rate is 138.
+	sifive.UART0.DIV.Set(138)
+	sifive.UART0.TXCTRL.Set(sifive.UART_TXCTRL_ENABLE)
+}
+
+func (uart UART) WriteByte(c byte) {
+	for sifive.UART0.TXDATA.Get()&sifive.UART_TXDATA_FULL != 0 {
+	}
+
+	sifive.UART0.TXDATA.Set(uint32(c))
+}

src/machine/machine_generic.go

@@ -1,4 +1,4 @@
-// +build !avr,!nrf,!sam,!stm32
+// +build !avr,!nrf,!sam,!sifive,!stm32
 
 package machine
 

src/machine/spi.go

@@ -1,4 +1,4 @@
-// +build !stm32f407,!avr
+// +build !stm32f407,!avr,!hifive1b
 
 package machine
 

src/machine/uart.go

@@ -1,4 +1,4 @@
-// +build avr nrf sam stm32
+// +build avr nrf sam sifive stm32
 
 package machine
 

src/os/file_other.go

@@ -1,4 +1,4 @@
-// +build avr cortexm wasm
+// +build avr cortexm tinygo.riscv wasm
 
 package os
 

src/os/file_unix.go

@@ -1,4 +1,4 @@
-// +build darwin linux,!avr,!cortexm
+// +build darwin linux,!avr,!cortexm,!tinygo.riscv
 
 package os
 

src/runtime/arch_arm.go

@@ -1,4 +1,4 @@
-// +build arm,!avr,!cortexm
+// +build arm,!avr,!cortexm,!tinygo.riscv
 
 package runtime
 

src/runtime/arch_avr.go

@@ -2,26 +2,11 @@
 
 package runtime
 
-import (
+const GOARCH = "arm" // avr pretends to be arm
-	"unsafe"
-)
-
-const GOARCH = "avr"
 
 // The bitness of the CPU (e.g. 8, 32, 64).
 const TargetBits = 8
 
-//go:extern _heap_start
-var heapStartSymbol unsafe.Pointer
-
-//go:extern _heap_end
-var heapEndSymbol unsafe.Pointer
-
-var (
-	heapStart = uintptr(unsafe.Pointer(&heapStartSymbol))
-	heapEnd   = uintptr(unsafe.Pointer(&heapEndSymbol))
-)
-
 // Align on a word boundary.
 func align(ptr uintptr) uintptr {
 	// No alignment necessary on the AVR.

src/runtime/arch_cortexm.go

@@ -3,8 +3,6 @@
 package runtime
 
 import (
-	"unsafe"
-
 	"device/arm"
 )
 
@@ -13,29 +11,6 @@ const GOARCH = "arm"
 // The bitness of the CPU (e.g. 8, 32, 64).
 const TargetBits = 32
 
-//go:extern _heap_start
-var heapStartSymbol unsafe.Pointer
-
-//go:extern _heap_end
-var heapEndSymbol unsafe.Pointer
-
-//go:extern _globals_start
-var globalsStartSymbol unsafe.Pointer
-
-//go:extern _globals_end
-var globalsEndSymbol unsafe.Pointer
-
-//go:extern _stack_top
-var stackTopSymbol unsafe.Pointer
-
-var (
-	heapStart    = uintptr(unsafe.Pointer(&heapStartSymbol))
-	heapEnd      = uintptr(unsafe.Pointer(&heapEndSymbol))
-	globalsStart = uintptr(unsafe.Pointer(&globalsStartSymbol))
-	globalsEnd   = uintptr(unsafe.Pointer(&globalsEndSymbol))
-	stackTop     = uintptr(unsafe.Pointer(&stackTopSymbol))
-)
-
 // Align on word boundary.
 func align(ptr uintptr) uintptr {
 	return (ptr + 3) &^ 3

src/runtime/arch_tinygoriscv.go

@@ -0,0 +1,19 @@
+// +build tinygo.riscv
+
+package runtime
+
+import "device/riscv"
+
+const GOARCH = "arm" // riscv pretends to be arm
+
+// The bitness of the CPU (e.g. 8, 32, 64).
+const TargetBits = 32
+
+// Align on word boundary.
+func align(ptr uintptr) uintptr {
+	return (ptr + 3) &^ 3
+}
+
+func getCurrentStackPointer() uintptr {
+	return riscv.ReadRegister("sp")
+}

src/runtime/baremetal.go

@@ -0,0 +1,30 @@
+// +build avr cortexm tinygo.riscv
+
+package runtime
+
+import (
+	"unsafe"
+)
+
+//go:extern _heap_start
+var heapStartSymbol unsafe.Pointer
+
+//go:extern _heap_end
+var heapEndSymbol unsafe.Pointer
+
+//go:extern _globals_start
+var globalsStartSymbol unsafe.Pointer
+
+//go:extern _globals_end
+var globalsEndSymbol unsafe.Pointer
+
+//go:extern _stack_top
+var stackTopSymbol unsafe.Pointer
+
+var (
+	heapStart    = uintptr(unsafe.Pointer(&heapStartSymbol))
+	heapEnd      = uintptr(unsafe.Pointer(&heapEndSymbol))
+	globalsStart = uintptr(unsafe.Pointer(&globalsStartSymbol))
+	globalsEnd   = uintptr(unsafe.Pointer(&globalsEndSymbol))
+	stackTop     = uintptr(unsafe.Pointer(&stackTopSymbol))
+)

src/runtime/gc_globals_conservative.go

@@ -1,5 +1,5 @@
 // +build gc.conservative
-// +build cortexm
+// +build cortexm tinygo.riscv
 
 package runtime
 

src/runtime/gc_globals_precise.go

@@ -1,5 +1,5 @@
 // +build gc.conservative
-// +build !cortexm
+// +build !cortexm,!tinygo.riscv
 
 package runtime
 

src/runtime/gc_stack_portable.go

@@ -1,5 +1,5 @@
 // +build gc.conservative
-// +build !cortexm
+// +build !cortexm,!tinygo.riscv
 
 package runtime
 

src/runtime/gc_stack_raw.go

@@ -1,5 +1,5 @@
 // +build gc.conservative
-// +build cortexm
+// +build cortexm tinygo.riscv
 
 package runtime
 

src/runtime/runtime_fe310.go

@@ -0,0 +1,115 @@
+// +build fe310
+
+// This file implements target-specific things for the FE310 chip as used in the
+// HiFive1.
+
+package runtime
+
+import (
+	"machine"
+	"unsafe"
+
+	"device/riscv"
+	"device/sifive"
+)
+
+type timeUnit int64
+
+const tickMicros = 32768 // RTC runs at 32.768kHz
+
+//go:extern _sbss
+var _sbss unsafe.Pointer
+
+//go:extern _ebss
+var _ebss unsafe.Pointer
+
+//go:extern _sdata
+var _sdata unsafe.Pointer
+
+//go:extern _sidata
+var _sidata unsafe.Pointer
+
+//go:extern _edata
+var _edata unsafe.Pointer
+
+//go:export main
+func main() {
+	preinit()
+	initAll()
+	callMain()
+	abort()
+}
+
+func init() {
+	pric_init()
+	machine.UART0.Configure(machine.UARTConfig{})
+}
+
+func pric_init() {
+	// Make sure the HFROSC is on
+	sifive.PRIC.HFROSCCFG.SetBits(sifive.PRIC_HFROSCCFG_ENABLE)
+
+	// Run off 16 MHz Crystal for accuracy.
+	sifive.PRIC.PLLCFG.SetBits(sifive.PRIC_PLLCFG_REFSEL | sifive.PRIC_PLLCFG_BYPASS)
+	sifive.PRIC.PLLCFG.SetBits(sifive.PRIC_PLLCFG_SEL)
+
+	// Turn off HFROSC to save power
+	sifive.PRIC.HFROSCCFG.ClearBits(sifive.PRIC_HFROSCCFG_ENABLE)
+
+	// Enable the RTC.
+	sifive.RTC.CONFIG.Set(sifive.RTC_CONFIG_ENALWAYS)
+}
+
+func preinit() {
+	// Initialize .bss: zero-initialized global variables.
+	ptr := uintptr(unsafe.Pointer(&_sbss))
+	for ptr != uintptr(unsafe.Pointer(&_ebss)) {
+		*(*uint32)(unsafe.Pointer(ptr)) = 0
+		ptr += 4
+	}
+
+	// Initialize .data: global variables initialized from flash.
+	src := uintptr(unsafe.Pointer(&_sidata))
+	dst := uintptr(unsafe.Pointer(&_sdata))
+	for dst != uintptr(unsafe.Pointer(&_edata)) {
+		*(*uint32)(unsafe.Pointer(dst)) = *(*uint32)(unsafe.Pointer(src))
+		dst += 4
+		src += 4
+	}
+}
+
+func putchar(c byte) {
+	machine.UART0.WriteByte(c)
+}
+
+func ticks() timeUnit {
+	// Combining the low bits and the high bits yields a time span of over 270
+	// years without counter rollover.
+	highBits := sifive.RTC.HI.Get()
+	for {
+		lowBits := sifive.RTC.LO.Get()
+		newHighBits := sifive.RTC.HI.Get()
+		if newHighBits == highBits {
+			// High bits stayed the same.
+			return timeUnit(lowBits) | (timeUnit(highBits) << 32)
+		}
+		// Retry, because there was a rollover in the low bits (happening every
+		// 1.5 days).
+		highBits = newHighBits
+	}
+}
+
+const asyncScheduler = false
+
+func sleepTicks(d timeUnit) {
+	target := ticks() + d
+	for ticks() < target {
+	}
+}
+
+func abort() {
+	// lock up forever
+	for {
+		riscv.Asm("wfi")
+	}
+}

src/runtime/runtime_tinygoriscv.go

@@ -0,0 +1,19 @@
+// +build tinygo.riscv
+
+package runtime
+
+import "unsafe"
+
+// Implement memset for LLVM.
+//go:export memset
+func libc_memset(ptr unsafe.Pointer, c byte, size uintptr) {
+	for i := uintptr(0); i < size; i++ {
+		*(*byte)(unsafe.Pointer(uintptr(ptr) + i)) = c
+	}
+}
+
+// Implement memmove for LLVM.
+//go:export memmove
+func libc_memmove(dst, src unsafe.Pointer, size uintptr) {
+	memmove(dst, src, size)
+}

src/runtime/runtime_unix.go

@@ -1,4 +1,4 @@
-// +build darwin linux,!avr,!cortexm
+// +build darwin linux,!avr,!cortexm,!tinygo.riscv
 
 package runtime
 

targets/fe310.json

@@ -0,0 +1,5 @@
+{
+	"inherits": ["riscv"],
+	"features": ["+a", "+c", "+m"],
+	"build-tags": ["fe310", "sifive"]
+}

targets/hifive1b.json

@@ -0,0 +1,7 @@
+{
+	"inherits": ["fe310"],
+	"build-tags": ["hifive1b"],
+	"ldflags": [
+		"-T", "targets/hifive1b.ld"
+	]
+}

targets/hifive1b.ld

@@ -0,0 +1,10 @@
+
+MEMORY
+{
+    FLASH_TEXT (rw) : ORIGIN = 0x20010000, LENGTH = 0x6a120
+    RAM (xrw)       : ORIGIN = 0x80000000, LENGTH = 0x4000
+}
+
+_stack_size = 2K;
+
+INCLUDE "targets/riscv.ld"

targets/riscv.json

@@ -0,0 +1,25 @@
+{
+	"llvm-target": "riscv32--none",
+	"goos": "linux",
+	"goarch": "arm",
+	"build-tags": ["tinygo.riscv", "linux", "arm"],
+	"gc": "conservative",
+	"compiler": "riscv64-unknown-elf-gcc",
+	"linker": "riscv64-unknown-elf-ld",
+	"cflags": [
+		"-march=rv32imac",
+		"-mabi=ilp32",
+		"-Os",
+		"-Werror",
+		"-nostdinc",
+		"-fno-exceptions", "-fno-unwind-tables",
+		"-ffunction-sections", "-fdata-sections"
+	],
+	"ldflags": [
+		"-melf32lriscv",
+		"--gc-sections"
+	],
+	"extra-files": [
+		"src/device/riscv/start.S"
+	]
+}

targets/riscv.ld

@@ -0,0 +1,56 @@
+SECTIONS
+{
+    .text :
+    {
+        KEEP(*(.init))
+        *(.text)
+        *(.text.*)
+        *(.rodata)
+        *(.rodata.*)
+        . = ALIGN(4);
+    } >FLASH_TEXT
+
+    /* Put the stack at the bottom of RAM, so that the application will
+     * crash on stack overflow instead of silently corrupting memory.
+     * See: http://blog.japaric.io/stack-overflow-protection/ */
+    .stack :
+    {
+        . = ALIGN(4);
+        . += _stack_size;
+        _stack_top = .;
+    } >RAM
+
+    /* Start address (in flash) of .data, used by startup code. */
+    _sidata = LOADADDR(.data);
+
+    /* Globals with initial value */
+    .data :
+    {
+        . = ALIGN(4);
+        /* see https://gnu-mcu-eclipse.github.io/arch/riscv/programmer/#the-gp-global-pointer-register */
+        PROVIDE( __global_pointer$ = . + (4K / 2) );
+        _sdata = .;        /* used by startup code */
+        *(.data)
+        *(.data*)
+        . = ALIGN(4);
+        _edata = .;        /* used by startup code */
+    } >RAM AT>FLASH_TEXT
+
+    /* Zero-initialized globals  */
+    .bss :
+    {
+        . = ALIGN(4);
+        _sbss = .;         /* used by startup code */
+        *(.bss)
+        *(.bss*)
+        *(COMMON)
+        . = ALIGN(4);
+        _ebss = .;         /* used by startup code */
+    } >RAM
+}
+
+/* For the memory allocator. */
+_heap_start = _ebss;
+_heap_end = ORIGIN(RAM) + LENGTH(RAM);
+_globals_start = _sdata;
+_globals_end = _ebss;

tools/gen-device-svd.py

@@ -151,7 +151,10 @@ def readSVD(path, sourceURL):
                     dimIncrement = None
                 else:
                     dim = int(getText(cluster.find('dim')))
-                    dimIncrement = int(getText(cluster.find('dimIncrement')), 0)
+                    if dim == 1:
+                        dimIncrement = None
+                    else:
+                        dimIncrement = int(getText(cluster.find('dimIncrement')), 0)
                 clusterRegisters = []
                 for regEl in cluster.findall('register'):
                     clusterRegisters.extend(parseRegister(groupName or name, regEl, baseAddress + clusterOffset, clusterPrefix))
@@ -241,7 +244,7 @@ def parseBitfields(groupName, regName, fieldsEls, bitfieldPrefix=''):
                 })
             for enumEl in fieldEl.findall('enumeratedValues/enumeratedValue'):
                 enumName = getText(enumEl.find('name'))
-                enumDescription = getText(enumEl.find('description'))
+                enumDescription = getText(enumEl.find('description')).replace('\n', ' ')
                 enumValue = int(getText(enumEl.find('value')), 0)
                 fields.append({
                     'name':        '{}_{}{}_{}_{}'.format(groupName, bitfieldPrefix, regName, fieldName, enumName),