x86: lib: Implement standalone __udivdi3 etc instead of libgcc ones

This patch removes the inclusion of the libgcc math functions and
replaces them by functions coded in C, taken from the coreboot
project. This makes U-Boot building more independent from the toolchain
installed / available on the build system.

The code taken from coreboot is authored from Vadim Bendebury
<vbendeb@chromium.org> on 2014-11-28 and committed with commit
ID e63990ef [libpayload: provide basic 64bit division implementation]
(coreboot git repository located here [1]).

I modified the code so that its checkpatch clean without any
functional changes.

[1] git://github.com/coreboot/coreboot.git

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Simon Glass <sjg@chromium.org>
Cc: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/config.mk

@@ -34,9 +34,6 @@ PLATFORM_RELFLAGS += -ffunction-sections -fvisibility=hidden
 PLATFORM_LDFLAGS += -Bsymbolic -Bsymbolic-functions
 PLATFORM_LDFLAGS += -m $(if $(IS_32BIT),elf_i386,elf_x86_64)
 
-LDFLAGS_FINAL += --wrap=__divdi3 --wrap=__udivdi3
-LDFLAGS_FINAL += --wrap=__moddi3 --wrap=__umoddi3
-
 # This is used in the top-level Makefile which does not include
 # PLATFORM_LDFLAGS
 LDFLAGS_EFI_PAYLOAD := -Bsymbolic -Bsymbolic-functions -shared --no-undefined

arch/x86/lib/Makefile

@@ -18,7 +18,6 @@ obj-$(CONFIG_SEABIOS) += coreboot_table.o
 obj-y	+= early_cmos.o
 obj-$(CONFIG_EFI) += efi/
 obj-y	+= e820.o
-obj-y	+= gcc.o
 obj-y	+= init_helpers.o
 obj-y	+= interrupts.o
 obj-y	+= lpc-uclass.o
@@ -49,12 +48,7 @@ endif
 obj-$(CONFIG_HAVE_FSP) += fsp/
 obj-$(CONFIG_SPL_BUILD) += spl.o
 
-extra-$(CONFIG_USE_PRIVATE_LIBGCC) += lib.a
-
-NORMAL_LIBGCC = $(shell $(CC) $(PLATFORM_CPPFLAGS) -print-libgcc-file-name)
-OBJCOPYFLAGS := --prefix-symbols=__normal_
-$(obj)/lib.a: $(NORMAL_LIBGCC) FORCE
-	$(call if_changed,objcopy)
+lib-$(CONFIG_USE_PRIVATE_LIBGCC) += div64.o
 
 ifeq ($(CONFIG_$(SPL_)X86_64),)
 obj-$(CONFIG_EFI_APP) += crt0_ia32_efi.o reloc_ia32_efi.o

arch/x86/lib/div64.c

@@ -0,0 +1,113 @@
+/*
+ * This file is copied from the coreboot repository as part of
+ * the libpayload project:
+ *
+ * Copyright 2014 Google Inc.
+ *
+ * SPDX-License-Identifier:     BSD-3-Clause
+ */
+
+#include <common.h>
+
+union overlay64 {
+	u64 longw;
+	struct {
+		u32 lower;
+		u32 higher;
+	} words;
+};
+
+u64 __ashldi3(u64 num, unsigned int shift)
+{
+	union overlay64 output;
+
+	output.longw = num;
+	if (shift >= 32) {
+		output.words.higher = output.words.lower << (shift - 32);
+		output.words.lower = 0;
+	} else {
+		if (!shift)
+			return num;
+		output.words.higher = (output.words.higher << shift) |
+			(output.words.lower >> (32 - shift));
+		output.words.lower = output.words.lower << shift;
+	}
+	return output.longw;
+}
+
+u64 __lshrdi3(u64 num, unsigned int shift)
+{
+	union overlay64 output;
+
+	output.longw = num;
+	if (shift >= 32) {
+		output.words.lower = output.words.higher >> (shift - 32);
+		output.words.higher = 0;
+	} else {
+		if (!shift)
+			return num;
+		output.words.lower = output.words.lower >> shift |
+			(output.words.higher << (32 - shift));
+		output.words.higher = output.words.higher >> shift;
+	}
+	return output.longw;
+}
+
+#define MAX_32BIT_UINT ((((u64)1) << 32) - 1)
+
+static u64 _64bit_divide(u64 dividend, u64 divider, u64 *rem_p)
+{
+	u64 result = 0;
+
+	/*
+	 * If divider is zero - let the rest of the system care about the
+	 * exception.
+	 */
+	if (!divider)
+		return 1 / (u32)divider;
+
+	/* As an optimization, let's not use 64 bit division unless we must. */
+	if (dividend <= MAX_32BIT_UINT) {
+		if (divider > MAX_32BIT_UINT) {
+			result = 0;
+			if (rem_p)
+				*rem_p = divider;
+		} else {
+			result = (u32)dividend / (u32)divider;
+			if (rem_p)
+				*rem_p = (u32)dividend % (u32)divider;
+		}
+		return result;
+	}
+
+	while (divider <= dividend) {
+		u64 locald = divider;
+		u64 limit = __lshrdi3(dividend, 1);
+		int shifts = 0;
+
+		while (locald <= limit) {
+			shifts++;
+			locald = locald + locald;
+		}
+		result |= __ashldi3(1, shifts);
+		dividend -= locald;
+	}
+
+	if (rem_p)
+		*rem_p = dividend;
+
+	return result;
+}
+
+u64 __udivdi3(u64 num, u64 den)
+{
+	return _64bit_divide(num, den, NULL);
+}
+
+u64 __umoddi3(u64 num, u64 den)
+{
+	u64 v = 0;
+
+	_64bit_divide(num, den, &v);
+	return v;
+}

arch/x86/lib/gcc.c

@@ -1,29 +0,0 @@
-/*
- * This file is part of the coreboot project.
- *
- * Copyright (C) 2009 coresystems GmbH
- *
- * SPDX-License-Identifier:	GPL-2.0
- */
-
-#ifdef __GNUC__
-
-/*
- * GCC's libgcc handling is quite broken. While the libgcc functions
- * are always regparm(0) the code that calls them uses whatever the
- * compiler call specifies. Therefore we need a wrapper around those
- * functions. See gcc bug PR41055 for more information.
- */
-#define WRAP_LIBGCC_CALL(type, name) \
-	type __normal_##name(type a, type b) __attribute__((regparm(0))); \
-	type __wrap_##name(type a, type b); \
-	type __attribute__((no_instrument_function)) \
-		__wrap_##name(type a, type b) \
-		 { return __normal_##name(a, b); }
-
-WRAP_LIBGCC_CALL(long long, __divdi3)
-WRAP_LIBGCC_CALL(unsigned long long, __udivdi3)
-WRAP_LIBGCC_CALL(long long, __moddi3)
-WRAP_LIBGCC_CALL(unsigned long long, __umoddi3)
-
-#endif