[U-Boot] [PATCH] powerpc: Minimal private libgcc to build on Debian

[Kyle Moffett]

Standard Debian powerpc and powerpcspe systems only include hard-float
libgcc in their native compilers, which causes scary build warnings when
building U-Boot.

While U-Boot does not use floating point at all, it is perfectly legal
for a hard-float libgcc to use features of the floating point unit to
implement 64-bit divides and shifts.  Since U-Boot does not set up the
floating point unit or initialize the registers, that could cause
crashes or other misbehavior.

In particular, on e500 systems with SPE extensions, a "hard-float"
libgcc might use the top half of the "extended" 64-bit registers for
various 64-bit shifts and other operations, which is probably unsafe.

To avoid a dependency on "nof" (IE: soft-float) libgcc provided by the
system toolchain, U-Boot should be able to provide its own copies of the
necessary routines just like the Linux kernel does.  In particular, this
resolves build failures on native Debian PowerPC systems which no longer
provide any soft-float libraries in the system toolchain.

This patch provides an implementation of USE_PRIVATE_LIBGCC=yes from the
Linux Kernel that matches what the ARM architecture implements in
assembly files in arch/arm/lib/*.S

Specifically, the routines are: _ashldi3(), _ashrdi3(), and _lshrdi3().
They were borrowed from arch/powerpc/kernel/misc_32.S as of v2.6.38-rc5,
commit 85e2efbb1db9a18d218006706d6e4fbeb0216213, and are GPLv2+.

The Makefile framework was copied from the U-Boot ARM port.

Signed-off-by: Kyle Moffett <Kyle.D.Moffett at boeing.com>
Cc: Wolfgang Denk <wd at denx.de>
Cc: Kim Phillips <kim.phillips at freescale.com>
Cc: Andy Fleming <afleming at gmail.com>
Cc: Kumar Gala <kumar.gala at freescale.com>
Cc: Stefan Roese <sr at denx.de>

---

I believe I have addressed all of the previous questions regarding
this patch with an updated commit message.  Can this be merged?

Cheers,
Kyle Moffett

--
Curious about my work on the Debian powerpcspe port?
I'm keeping a blog here: http://pureperl.blogspot.com/
---
 arch/powerpc/lib/Makefile   |   23 ++++++++++++++++++++-
 arch/powerpc/lib/_ashldi3.S |   45 +++++++++++++++++++++++++++++++++++++++++
 arch/powerpc/lib/_ashrdi3.S |   47 +++++++++++++++++++++++++++++++++++++++++++
 arch/powerpc/lib/_lshrdi3.S |   45 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 159 insertions(+), 1 deletions(-)
 create mode 100644 arch/powerpc/lib/_ashldi3.S
 create mode 100644 arch/powerpc/lib/_ashrdi3.S
 create mode 100644 arch/powerpc/lib/_lshrdi3.S

diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
index 724d8ee..cdd62a2 100644
--- a/arch/powerpc/lib/Makefile
+++ b/arch/powerpc/lib/Makefile
@@ -23,6 +23,19 @@
 
 include $(TOPDIR)/config.mk
 
+## Build a couple of necessary functions into a private libgcc
+LIBGCC	= $(obj)libgcc.o
+GLSOBJS	+= _ashldi3.o
+GLSOBJS	+= _ashrdi3.o
+GLSOBJS	+= _lshrdi3.o
+LGOBJS	:= $(addprefix $(obj),$(GLSOBJS)) \
+	   $(addprefix $(obj),$(GLCOBJS))
+
+## But only build it if the user asked for it
+ifdef USE_PRIVATE_LIBGCC
+TARGETS	+= $(LIBGCC)
+endif
+
 LIB	= $(obj)lib$(ARCH).o
 
 SOBJS-y	+= ppccache.o
@@ -53,9 +66,14 @@ endif
 
 COBJS	+= $(sort $(COBJS-y))
 
-SRCS	:= $(SOBJS-y:.o=.S) $(COBJS-y:.o=.c)
+SRCS	:= $(GLSOBJS:.o=.S) $(GLCOBJS:.o=.c) \
+	   $(SOBJS-y:.o=.S) $(COBJS-y:.o=.c)
 OBJS	:= $(addprefix $(obj),$(SOBJS-y) $(COBJS-y))
 
+TARGETS += $(LIB)
+
+all: $(TARGETS)
+
 $(LIB):	$(obj).depend $(OBJS)
 	@if ! $(CROSS_COMPILE)readelf -S $(OBJS) | grep -q '\.fixup.*PROGBITS';\
 	then \
@@ -65,6 +83,9 @@ $(LIB):	$(obj).depend $(OBJS)
 	fi;
 	$(call cmd_link_o_target, $(OBJS))
 
+$(LIBGCC): $(obj).depend $(LGOBJS)
+	$(call cmd_link_o_target, $(LGOBJS))
+
 #########################################################################
 
 # defines $(obj).depend target
diff --git a/arch/powerpc/lib/_ashldi3.S b/arch/powerpc/lib/_ashldi3.S
new file mode 100644
index 0000000..e452f56
--- /dev/null
+++ b/arch/powerpc/lib/_ashldi3.S
@@ -0,0 +1,45 @@
+/*
+ * This code was copied from arch/powerpc/kernel/misc_32.S in the Linux
+ * kernel sources (commit 85e2efbb1db9a18d218006706d6e4fbeb0216213, also
+ * known as 2.6.38-rc5).  The source file copyrights are as follows:
+ *
+ * (C) Copyright 1995-1996 Gary Thomas (gdt at linuxppc.org)
+ *
+ * Largely rewritten by Cort Dougan (cort at cs.nmt.edu)
+ * and Paul Mackerras.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ */
+
+#include <ppc_asm.tmpl>
+#include <ppc_defs.h>
+#include <config.h>
+
+/*
+ * Extended precision shifts.
+ *
+ * Updated to be valid for shift counts from 0 to 63 inclusive.
+ * -- Gabriel
+ *
+ * R3/R4 has 64 bit value
+ * R5    has shift count
+ * result in R3/R4
+ *
+ *  ashrdi3: arithmetic right shift (sign propagation)
+ *  lshrdi3: logical right shift
+ *  ashldi3: left shift
+ */
+	.globl __ashldi3
+__ashldi3:
+	subfic	r6,r5,32
+	slw	r3,r3,r5	# MSW = count > 31 ? 0 : MSW << count
+	addi	r7,r5,32	# could be xori, or addi with -32
+	srw	r6,r4,r6	# t1 = count > 31 ? 0 : LSW >> (32-count)
+	slw	r7,r4,r7	# t2 = count < 32 ? 0 : LSW << (count-32)
+	or	r3,r3,r6	# MSW |= t1
+	slw	r4,r4,r5	# LSW = LSW << count
+	or	r3,r3,r7	# MSW |= t2
+	blr
diff --git a/arch/powerpc/lib/_ashrdi3.S b/arch/powerpc/lib/_ashrdi3.S
new file mode 100644
index 0000000..f28ab49
--- /dev/null
+++ b/arch/powerpc/lib/_ashrdi3.S
@@ -0,0 +1,47 @@
+/*
+ * This code was copied from arch/powerpc/kernel/misc_32.S in the Linux
+ * kernel sources (commit 85e2efbb1db9a18d218006706d6e4fbeb0216213, also
+ * known as 2.6.38-rc5).  The source file copyrights are as follows:
+ *
+ * (C) Copyright 1995-1996 Gary Thomas (gdt at linuxppc.org)
+ *
+ * Largely rewritten by Cort Dougan (cort at cs.nmt.edu)
+ * and Paul Mackerras.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ */
+
+#include <ppc_asm.tmpl>
+#include <ppc_defs.h>
+#include <config.h>
+
+/*
+ * Extended precision shifts.
+ *
+ * Updated to be valid for shift counts from 0 to 63 inclusive.
+ * -- Gabriel
+ *
+ * R3/R4 has 64 bit value
+ * R5    has shift count
+ * result in R3/R4
+ *
+ *  ashrdi3: arithmetic right shift (sign propagation)
+ *  lshrdi3: logical right shift
+ *  ashldi3: left shift
+ */
+	.globl __ashrdi3
+__ashrdi3:
+	subfic	r6,r5,32
+	srw	r4,r4,r5	# LSW = count > 31 ? 0 : LSW >> count
+	addi	r7,r5,32	# could be xori, or addi with -32
+	slw	r6,r3,r6	# t1 = count > 31 ? 0 : MSW << (32-count)
+	rlwinm	r8,r7,0,32	# t3 = (count < 32) ? 32 : 0
+	sraw	r7,r3,r7	# t2 = MSW >> (count-32)
+	or	r4,r4,r6	# LSW |= t1
+	slw	r7,r7,r8	# t2 = (count < 32) ? 0 : t2
+	sraw	r3,r3,r5	# MSW = MSW >> count
+	or	r4,r4,r7	# LSW |= t2
+	blr
diff --git a/arch/powerpc/lib/_lshrdi3.S b/arch/powerpc/lib/_lshrdi3.S
new file mode 100644
index 0000000..c1bbe7b
--- /dev/null
+++ b/arch/powerpc/lib/_lshrdi3.S
@@ -0,0 +1,45 @@
+/*
+ * This code was copied from arch/powerpc/kernel/misc_32.S in the Linux
+ * kernel sources (commit 85e2efbb1db9a18d218006706d6e4fbeb0216213, also
+ * known as 2.6.38-rc5).  The source file copyrights are as follows:
+ *
+ * (C) Copyright 1995-1996 Gary Thomas (gdt at linuxppc.org)
+ *
+ * Largely rewritten by Cort Dougan (cort at cs.nmt.edu)
+ * and Paul Mackerras.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ */
+
+#include <ppc_asm.tmpl>
+#include <ppc_defs.h>
+#include <config.h>
+
+/*
+ * Extended precision shifts.
+ *
+ * Updated to be valid for shift counts from 0 to 63 inclusive.
+ * -- Gabriel
+ *
+ * R3/R4 has 64 bit value
+ * R5    has shift count
+ * result in R3/R4
+ *
+ *  ashrdi3: arithmetic right shift (sign propagation)
+ *  lshrdi3: logical right shift
+ *  ashldi3: left shift
+ */
+	.globl __lshrdi3
+__lshrdi3:
+	subfic	r6,r5,32
+	srw	r4,r4,r5	# LSW = count > 31 ? 0 : LSW >> count
+	addi	r7,r5,32	# could be xori, or addi with -32
+	slw	r6,r3,r6	# t1 = count > 31 ? 0 : MSW << (32-count)
+	srw	r7,r3,r7	# t2 = count < 32 ? 0 : MSW >> (count-32)
+	or	r4,r4,r6	# LSW |= t1
+	srw	r3,r3,r5	# MSW = MSW >> count
+	or	r4,r4,r7	# LSW |= t2
+	blr
-- 
1.7.2.5