libflash: Provide an internal parity implementation, to remove libgcc dependency

In commit 8f5b8616, we introduced a dependency on libgcc, for the
__builtin_parityl() function in commit 6cfaa3ba.

However, if we're building with a biarch compiler, we may not have a
libgcc available.

This commit removes the __builtin_parityl() call, and replaces with the
equivalent instructions, and removes the dependency on libgcc.

Although this is untested, I have confirmed that the __builtin_parityl()
functions emits the same instructions (on power7 and power8, with
gcc-4.9) as we're using in the parity() function.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
[stewart@linux.vnet.ibm.com: only use inline asm for skiboot build]
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>

2 files changed, 19 insertions, 4 deletions

diff --git a/Makefile.main b/Makefile.main
index 71bce5d..78bab2d 100644
--- a/Makefile.main
+++ b/Makefile.main
@@ -158,7 +158,6 @@ OBJS += $(LIBPORE)
 endif
 OBJS += $(LIBC) $(CCAN) $(DEVSRC_OBJ)
 OBJS_NO_VER = $(OBJS)
-EXTRA_LIBS = -Wl,-lgcc
 ALL_OBJS = $(OBJS) version.o
 
 ALL_OBJS_1 = $(ALL_OBJS) asm/dummy_map.o
@@ -168,12 +167,12 @@ $(TARGET).lid: $(TARGET).elf
 	$(call Q,OBJCOPY, $(OBJCOPY) -O binary -S $^ $@, $@)
 
 $(TARGET).tmp.elf: $(ALL_OBJS_1) $(TARGET).lds $(KERNEL)
-	$(call Q,LD, $(CC) $(LDFLAGS) -T $(TARGET).lds $(ALL_OBJS_1) $(EXTRA_LIBS) -o $@, $@)
+	$(call Q,LD, $(CC) $(LDFLAGS) -T $(TARGET).lds $(ALL_OBJS_1) -o $@, $@)
 
 asm/real_map.o : $(TARGET).tmp.map
 
 $(TARGET).elf: $(ALL_OBJS_2) $(TARGET).lds $(KERNEL)
-	$(call Q,LD, $(CC) $(LDFLAGS) -T $(TARGET).lds $(ALL_OBJS_2) $(EXTRA_LIBS) -o $@, $@)
+	$(call Q,LD, $(CC) $(LDFLAGS) -T $(TARGET).lds $(ALL_OBJS_2) -o $@, $@)
 
 $(SUBDIRS):
 	$(call Q,MKDIR,mkdir $@, $@)
diff --git a/libflash/ecc.c b/libflash/ecc.c
index 05c0e14..9cd6ad2 100644
--- a/libflash/ecc.c
+++ b/libflash/ecc.c
@@ -108,6 +108,22 @@ static enum eccbitfields syndromematrix[] = {
         UE, UE, UE, UE,  4, UE, UE, UE, UE, UE, UE, UE, UE, UE, UE, UE,
 };
 
+static uint8_t parity(uint64_t data)
+{
+#ifdef __SKIBOOT__
+	uint8_t p;
+
+	asm volatile(
+		"popcntb %1,%0\n"
+		"prtyd   %1,%1\n"
+		: "=r"(p) : "r"(data));
+
+	return p;
+#else
+	return __builtin_parityl(data);
+#endif
+}
+
 /**
  * Create the ECC field corresponding to a 8-byte data field
  *
@@ -120,7 +136,7 @@ static uint8_t eccgenerate(uint64_t data)
 	uint8_t result = 0;
 
 	for (i = 0; i < 8; i++)
-		result |= __builtin_parityl(eccmatrix[i] & data) << i;
+		result |= parity(eccmatrix[i] & data) << i;
 
 	return result;
 }