targets: let specific targets inherit more general targets

This avoids a ton of duplication and makes it easier to change a generic
target (for example, the "cortex-m" target) for all boards that use it.

Also, by making it possible to inherit properties from a parent target
specification, it is easier to support out-of-tree boards that don't
have to be updated so often. A target specification for a
special-purpose board can simply inherit the specification of a
supported chip and override the properites it needs to override (like
the programming interface).

9 files changed, 89 insertions, 71 deletions

diff --git a/targets/bluepill.json b/targets/bluepill.json
index cded74dbc..3c086ec69 100644
--- a/targets/bluepill.json
+++ b/targets/bluepill.json
@@ -1,9 +1,18 @@
 {
+	"inherits": ["cortex-m"],
 	"llvm-target": "armv7m-none-eabi",
-	"build-tags": ["bluepill", "stm32f103xx", "stm32", "tinygo.arm", "js", "wasm"],
-	"linker": "arm-none-eabi-gcc",
-	"rtlib": "compiler-rt",
-	"pre-link-args": ["-nostdlib", "-nostartfiles", "-mcpu=cortex-m3", "-mthumb", "-T", "targets/stm32.ld", "-Wl,--gc-sections", "-fno-exceptions", "-fno-unwind-tables", "-ffunction-sections", "-fdata-sections", "-Os", "src/device/stm32/stm32f103xx.s"],
-	"objcopy": "arm-none-eabi-objcopy",
+	"build-tags": ["bluepill", "stm32f103xx", "stm32"],
+	"pre-link-args": [
+		"-nostdlib",
+		"-nostartfiles",
+		"-mcpu=cortex-m3",
+		"-mthumb",
+		"-T", "targets/stm32.ld",
+		"-Wl,--gc-sections",
+		"-fno-exceptions", "-fno-unwind-tables",
+		"-ffunction-sections", "-fdata-sections",
+		"-Os",
+		"src/device/stm32/stm32f103xx.s"
+	],
 	"flash": "openocd -f interface/stlink-v2.cfg -f target/stm32f1x.cfg -c 'program {hex} reset exit'"
 }
diff --git a/targets/cortex-m.json b/targets/cortex-m.json
new file mode 100644
index 000000000..71d354f45
--- /dev/null
+++ b/targets/cortex-m.json
@@ -0,0 +1,7 @@
+{
+	"build-tags": ["tinygo.arm", "js", "wasm"],
+	"linker": "arm-none-eabi-gcc",
+	"rtlib": "compiler-rt",
+	"objcopy": "arm-none-eabi-objcopy",
+	"gdb": "arm-none-eabi-gdb"
+}
diff --git a/targets/microbit.json b/targets/microbit.json
index e9e5ec9b3..d2cd698dc 100644
--- a/targets/microbit.json
+++ b/targets/microbit.json
@@ -1,26 +1,7 @@
 {
-	"llvm-target": "armv6m-none-eabi",
-	"build-tags": ["microbit", "nrf51822", "nrf51", "nrf", "tinygo.arm", "js", "wasm"],
-	"linker": "arm-none-eabi-gcc",
-	"rtlib": "compiler-rt",
-	"pre-link-args": [
-		"-nostdlib",
-		"-nostartfiles",
-		"-mcpu=cortex-m0",
-		"-mthumb",
-		"-T", "targets/nrf51.ld",
-		"-Wl,--gc-sections",
-		"-fno-exceptions", "-fno-unwind-tables",
-		"-ffunction-sections", "-fdata-sections",
-		"-Os",
-		"-DNRF51",
-		"-Ilib/CMSIS/CMSIS/Include",
-		"lib/nrfx/mdk/system_nrf51.c",
-		"src/device/nrf/nrf51.s"
-	],
-	"objcopy": "arm-none-eabi-objcopy",
+	"inherits": ["nrf51"],
+	"build-tags": ["microbit"],
 	"flash": "openocd -f interface/cmsis-dap.cfg -f target/nrf51.cfg -c 'program {hex} reset exit'",
 	"ocd-daemon": ["openocd", "-f", "interface/cmsis-dap.cfg", "-f", "target/nrf51.cfg"],
-	"gdb": "arm-none-eabi-gdb",
 	"gdb-initial-cmds": ["target remote :3333", "monitor halt", "load", "monitor reset", "c"]
 }
diff --git a/targets/nrf51.json b/targets/nrf51.json
new file mode 100644
index 000000000..68c6b14f3
--- /dev/null
+++ b/targets/nrf51.json
@@ -0,0 +1,20 @@
+{
+	"inherits": ["cortex-m"],
+	"llvm-target": "armv6m-none-eabi",
+	"build-tags": ["nrf51822", "nrf51", "nrf"],
+	"pre-link-args": [
+		"-nostdlib",
+		"-nostartfiles",
+		"-mcpu=cortex-m0",
+		"-mthumb",
+		"-T", "targets/nrf51.ld",
+		"-Wl,--gc-sections",
+		"-fno-exceptions", "-fno-unwind-tables",
+		"-ffunction-sections", "-fdata-sections",
+		"-Os",
+		"-DNRF51",
+		"-Ilib/CMSIS/CMSIS/Include",
+		"lib/nrfx/mdk/system_nrf51.c",
+		"src/device/nrf/nrf51.s"
+	]
+}
diff --git a/targets/nrf52.json b/targets/nrf52.json
new file mode 100644
index 000000000..53ff2a47e
--- /dev/null
+++ b/targets/nrf52.json
@@ -0,0 +1,20 @@
+{
+	"inherits": ["cortex-m"],
+	"llvm-target": "armv7em-none-eabi",
+	"build-tags": ["nrf52", "nrf"],
+	"pre-link-args": [
+		"-nostdlib",
+		"-nostartfiles",
+		"-mcpu=cortex-m4",
+		"-mthumb",
+		"-T", "targets/nrf52.ld",
+		"-Wl,--gc-sections",
+		"-fno-exceptions", "-fno-unwind-tables",
+		"-ffunction-sections", "-fdata-sections",
+		"-Os",
+		"-DNRF52832_XXAA",
+		"-Ilib/CMSIS/CMSIS/Include",
+		"lib/nrfx/mdk/system_nrf52.c",
+		"src/device/nrf/nrf52.s"
+	]
+}
diff --git a/targets/nrf52840-mdk.json b/targets/nrf52840-mdk.json
index 7be436422..388c325b1 100644
--- a/targets/nrf52840-mdk.json
+++ b/targets/nrf52840-mdk.json
@@ -1,25 +1,7 @@
 {
-	"llvm-target": "armv7em-none-eabi",
-	"build-tags": ["nrf52840_mdk", "nrf52840", "nrf", "tinygo.arm", "js", "wasm"],
-	"linker": "arm-none-eabi-gcc",
-	"pre-link-args": [
-		"-nostdlib",
-		"-nostartfiles",
-		"-mcpu=cortex-m4",
-		"-mthumb",
-		"-T", "targets/nrf52840.ld",
-		"-Wl,--gc-sections",
-		"-fno-exceptions", "-fno-unwind-tables",
-		"-ffunction-sections", "-fdata-sections",
-		"-Os",
-		"-DNRF52840_XXAA",
-		"-Ilib/CMSIS/CMSIS/Include",
-		"lib/nrfx/mdk/system_nrf52840.c",
-		"src/device/nrf/nrf52840.s"
-	],
-	"objcopy": "arm-none-eabi-objcopy",
+	"inherits": ["nrf52840"],
+	"build-tags": ["nrf52840_mdk"],
 	"flash": "openocd -f interface/cmsis-dap.cfg -f target/nrf51.cfg -c 'program {hex} reset exit'",
 	"ocd-daemon": ["openocd", "-f", "interface/cmsis-dap.cfg", "-f", "target/nrf51.cfg"],
-	"gdb": "arm-none-eabi-gdb",
 	"gdb-initial-cmds": ["target remote :3333", "monitor halt", "load", "monitor reset", "c"]
 }
diff --git a/targets/nrf52840.json b/targets/nrf52840.json
new file mode 100644
index 000000000..8346735c2
--- /dev/null
+++ b/targets/nrf52840.json
@@ -0,0 +1,20 @@
+{
+	"inherits": ["cortex-m"],
+	"llvm-target": "armv7em-none-eabi",
+	"build-tags": ["nrf52840", "nrf"],
+	"pre-link-args": [
+		"-nostdlib",
+		"-nostartfiles",
+		"-mcpu=cortex-m4",
+		"-mthumb",
+		"-T", "targets/nrf52840.ld",
+		"-Wl,--gc-sections",
+		"-fno-exceptions", "-fno-unwind-tables",
+		"-ffunction-sections", "-fdata-sections",
+		"-Os",
+		"-DNRF52840_XXAA",
+		"-Ilib/CMSIS/CMSIS/Include",
+		"lib/nrfx/mdk/system_nrf52840.c",
+		"src/device/nrf/nrf52840.s"
+	]
+}
diff --git a/targets/pca10040.json b/targets/pca10040.json
index 0a3cbb4e9..1bff6e8cc 100644
--- a/targets/pca10040.json
+++ b/targets/pca10040.json
@@ -1,26 +1,7 @@
 {
-	"llvm-target": "armv7em-none-eabi",
-	"build-tags": ["pca10040", "nrf52832", "nrf52", "nrf", "tinygo.arm", "js", "wasm"],
-	"linker": "arm-none-eabi-gcc",
-	"rtlib": "compiler-rt",
-	"pre-link-args": [
-		"-nostdlib",
-		"-nostartfiles",
-		"-mcpu=cortex-m4",
-		"-mthumb",
-		"-T", "targets/nrf52.ld",
-		"-Wl,--gc-sections",
-		"-fno-exceptions", "-fno-unwind-tables",
-		"-ffunction-sections", "-fdata-sections",
-		"-Os",
-		"-DNRF52832_XXAA",
-		"-Ilib/CMSIS/CMSIS/Include",
-		"lib/nrfx/mdk/system_nrf52.c",
-		"src/device/nrf/nrf52.s"
-	],
-	"objcopy": "arm-none-eabi-objcopy",
+	"inherits": ["nrf52"],
+	"build-tags": ["pca10040"],
 	"flash": "nrfjprog -f nrf52 --sectorerase --program {hex} --reset",
 	"ocd-daemon": ["openocd", "-f", "interface/jlink.cfg", "-c", "transport select swd", "-f", "target/nrf51.cfg"],
-	"gdb": "arm-none-eabi-gdb",
 	"gdb-initial-cmds": ["target remote :3333", "monitor halt", "load", "monitor reset", "c"]
 }
diff --git a/targets/qemu.json b/targets/qemu.json
index cd0ecaf59..7cc23da8f 100644
--- a/targets/qemu.json
+++ b/targets/qemu.json
@@ -1,8 +1,7 @@
 {
+	"inherits": ["cortex-m"],
 	"llvm-target": "armv7m-none-eabi",
-	"build-tags": ["qemu", "lm3s6965", "tinygo.arm", "js", "wasm"],
-	"linker": "arm-none-eabi-gcc",
-	"rtlib": "compiler-rt",
+	"build-tags": ["qemu", "lm3s6965"],
 	"pre-link-args": [
 		"-nostdlib",
 		"-nostartfiles",
@@ -15,6 +14,5 @@
 		"-Os",
 		"targets/cortex-m.s"
 	],
-	"objcopy": "arm-none-eabi-objcopy",
 	"emulator": ["qemu-system-arm", "-machine", "lm3s6965evb", "-semihosting", "-nographic", "-kernel"]
 }