From a4fc6204ce27a4fcce071515ee9e5757818b4af5 Mon Sep 17 00:00:00 2001
From: George Hahn <George.Hahn.VHS@gmail.com>
Date: Sun, 29 May 2022 20:30:02 -0600
Subject: Parallelize alternate fw builds (#66)

---
 make.mk  | 26 ++++++++++++++++++++++++++
 rules.mk | 11 +++++++----
 2 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/make.mk b/make.mk
index ac5be775..d8e2bf8a 100644
--- a/make.mk
+++ b/make.mk
@@ -9,12 +9,38 @@ endif
 ##############################################################################
 .PHONY: all directory clean size
 
+# OS detection, adapted from https://gist.github.com/sighingnow/deee806603ec9274fd47
+DETECTED_OS :=
+ifeq ($(OS),Windows_NT)
+  DETECTED_OS = WINDOWS
+else
+  UNAME_S := $(shell uname -s)
+  ifeq ($(UNAME_S),Linux)
+    DETECTED_OS = LINUX
+  endif
+  ifeq ($(UNAME_S),Darwin)
+    DETECTED_OS = OSX
+  endif
+endif
+$(if ${VERBOSE},$(info OS detected: $(DETECTED_OS)))
+
 ifeq ($(OS), Windows_NT)
   MKDIR = gmkdir
 else
   MKDIR = mkdir
 endif
 
+ifeq ($(DETECTED_OS), LINUX)
+  MAKEFLAGS += -j `nproc`
+endif
+ifeq ($(DETECTED_OS), OSX)
+  NPROCS = $(shell sysctl hw.ncpu  | grep -o '[0-9]\+')
+  MAKEFLAGS += -j $(NPROCS)
+endif
+ifeq ($(DETECTED_OS), WINDOWS)
+  MAKEFLAGS += -j $(NUMBER_OF_PROCESSORS)
+endif
+
 ifndef EMSCRIPTEN
 CC = arm-none-eabi-gcc
 OBJCOPY = arm-none-eabi-objcopy
diff --git a/rules.mk b/rules.mk
index 2f2f3922..8de3fc1e 100644
--- a/rules.mk
+++ b/rules.mk
@@ -7,9 +7,9 @@ SUBMODULES = tinyusb
 COBRA = cobra -f
 
 ifndef EMSCRIPTEN
-all: directory $(SUBMODULES) $(BUILD)/$(BIN).elf $(BUILD)/$(BIN).hex $(BUILD)/$(BIN).bin $(BUILD)/$(BIN).uf2 size
+all: $(BUILD)/$(BIN).elf $(BUILD)/$(BIN).hex $(BUILD)/$(BIN).bin $(BUILD)/$(BIN).uf2 size
 else
-all: directory $(SUBMODULES) $(BUILD)/$(BIN).html
+all: $(BUILD)/$(BIN).html
 endif
 
 $(BUILD)/$(BIN).html: $(OBJS)
@@ -35,13 +35,14 @@ $(BUILD)/$(BIN).uf2: $(BUILD)/$(BIN).bin
 	@echo UF2CONV $@
 	@$(UF2) $^ -co $@
 
+.phony: $(SUBMODULES)
 $(SUBMODULES):
 	git submodule update --init
 
 install:
 	@$(UF2) -D $(BUILD)/$(BIN).uf2
 
-%.o:
+$(BUILD)/%.o: | $(SUBMODULES) directory
 	@echo CC $@
 	@$(CC) $(CFLAGS) $(filter %/$(subst .o,.c,$(notdir $@)), $(SRCS)) -c -o $@
 
@@ -59,4 +60,6 @@ clean:
 analyze:
 	@$(COBRA) basic $(INCLUDES) $(DEFINES) $(SRCS)
 
--include $(wildcard $(BUILD)/*.d)
+DEPFILES := $(SRCS:%.c=$(BUILD)/%.d)
+
+-include $(wildcard $(DEPFILES))
-- 
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