[U-Boot] [PATCH v2] x86: lib: Implement standalone __udivdi3 etc instead of libgcc ones

[Stefan Roese]

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 at 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 at denx.de>
Cc: Simon Glass <sjg at chromium.org>
Cc: Bin Meng <bmeng.cn at gmail.com>
---
v2:
- Added coreboot git repository link to commit message

 arch/x86/config.mk    |   3 --
 arch/x86/lib/Makefile |   2 +-
 arch/x86/lib/div64.c  | 113 ++++++++++++++++++++++++++++++++++++++++++++++++++
 arch/x86/lib/gcc.c    |  29 -------------
 4 files changed, 114 insertions(+), 33 deletions(-)
 create mode 100644 arch/x86/lib/div64.c
 delete mode 100644 arch/x86/lib/gcc.c

diff --git a/arch/x86/config.mk b/arch/x86/config.mk
index 8835dcf36f..472ada5490 100644
--- a/arch/x86/config.mk
+++ b/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
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index fe00d7573f..d9b23f5cc4 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -18,7 +18,7 @@ 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	+= div64.o
 obj-y	+= init_helpers.o
 obj-y	+= interrupts.o
 obj-y	+= lpc-uclass.o
diff --git a/arch/x86/lib/div64.c b/arch/x86/lib/div64.c
new file mode 100644
index 0000000000..4efed74037
--- /dev/null
+++ b/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;
+}
diff --git a/arch/x86/lib/gcc.c b/arch/x86/lib/gcc.c
deleted file mode 100644
index 3c70d790d4..0000000000
--- a/arch/x86/lib/gcc.c
+++ /dev/null
@@ -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
-- 
2.15.0