Fixed FPU support.

Selecting proper FPU flags in build_rules and enabling FPU during startup.

3 files changed, 38 insertions, 10 deletions

diff --git a/build_rules b/build_rules
index 385fde1..a6d8899 100644
--- a/build_rules
+++ b/build_rules
@@ -14,17 +14,17 @@ def select_arm(env, family):
 		has_mcu = False
 	
 	env.Replace(
-		CC = '${TOOLCHAIN}gcc',
-		CXX = '${TOOLCHAIN}g++',
-		AS = '${TOOLCHAIN}gcc',
-		LINK = '${TOOLCHAIN}gcc',
-		AR = '${TOOLCHAIN}ar',
+		CC     = '${TOOLCHAIN}gcc',
+		CXX    = '${TOOLCHAIN}g++',
+		AS     = '${TOOLCHAIN}gcc',
+		LINK   = '${TOOLCHAIN}gcc',
+		AR     = '${TOOLCHAIN}ar',
 		RANLIB = '${TOOLCHAIN}ranlib',
 		
-		CCFLAGS = '-O2 -Wall -ggdb -mcpu=${CPU_FAMILY} -mthumb -ffunction-sections',
-		CXXFLAGS = '-std=c++11 -fno-exceptions -fno-rtti -Wno-pmf-conversions',
-		ASFLAGS = '-c -x assembler-with-cpp -mcpu=${CPU_FAMILY} -mthumb',
-		LINKFLAGS = '-Wall -mcpu=${CPU_FAMILY} -mthumb -mhard-float -nostartfiles -Wl,-T${LINK_SCRIPT} -Wl,--gc-sections',
+		CCFLAGS   = Split('-O2 -Wall -ggdb -mcpu=${CPU_FAMILY} -mthumb -ffunction-sections'),
+		CXXFLAGS  = Split('-std=c++11 -fno-exceptions -fno-rtti -Wno-pmf-conversions'),
+		ASFLAGS   = Split('-c -x assembler-with-cpp -mcpu=${CPU_FAMILY} -mthumb'),
+		LINKFLAGS = Split('-Wall -mcpu=${CPU_FAMILY} -mthumb -nostartfiles -Wl,-T${LINK_SCRIPT} -Wl,--gc-sections'),
 		
 		CPPPATH = [laks_dir],
 		LIBPATH = [ld_dir],
@@ -35,7 +35,9 @@ def select_arm(env, family):
 	)
 	
 	if has_mcu:
-		env.Append(CCFLAGS = ' -mhard-float')
+		env.Append(CCFLAGS = Split('-mfloat-abi=hard -mfpu=fpv4-sp-d16'))
+		env.Append(LINKFLAGS = Split('-mfloat-abi=hard -mfpu=fpv4-sp-d16'))
+		env.Append(CPPDEFINES = ['HAS_FPU'])
 
 def select_stm32(env, variant):
 	family = variant[5:9]
diff --git a/cortex_m/fpu.h b/cortex_m/fpu.h
new file mode 100644
index 0000000..e5d4872
--- /dev/null
+++ b/cortex_m/fpu.h
@@ -0,0 +1,20 @@
+#ifndef FPU_H
+#define FPU_H
+
+#include <stdint.h>
+
+struct COPROC_t {
+	volatile uint32_t CPAC;
+};
+
+static COPROC_t& COPROC = *(COPROC_t*)0xe000ed88;
+
+struct FPU_t {
+	volatile uint32_t FPCC;
+	volatile uint32_t FPCA;
+	volatile uint32_t FPDSC;
+};
+
+static FPU_t& FPU = *(FPU_t*)0xe000ef34;
+
+#endif
diff --git a/startup/entry.cpp b/startup/entry.cpp
index d7385f8..64aac37 100644
--- a/startup/entry.cpp
+++ b/startup/entry.cpp
@@ -1,5 +1,6 @@
 #include <stdint.h>
 #include <rcc/rcc.h>
+#include <cortex_m/fpu.h>
 
 int main();
 
@@ -35,6 +36,11 @@ void __attribute__((naked)) entry() {
 		*wp++ = 0;
 	}
 	
+	// Enable FPU before calling any functions that can invoke FPU instructions.
+	#ifdef HAS_FPU
+	COPROC.CPAC |= (3 << 22) | (3 << 20);
+	#endif
+	
 	// Call constructors.
 	funcp_t* fp = &_init_array_start;