[arm-gnu] BLX instruction generated for Cortex-M3 with 2009q3

[James Snyder <jbsnyder@xxxxxxxxxxxxxx>]

Hi -

I've been attempting to track down a hard fault that I've been getting  
when compiling eLua (http://eluaproject.net) with the 2009q3 G++ Lite  
release.  I compiled my own toolchain with the following options (from  
my Makefile):

cross-binutils:
	mkdir -p build/binutils && cd build/binutils && \
	(./config.status || ../../binutils-*/configure --prefix=$(PREFIX) -- 
target=$(TARGET) --disable-nls --disable-werror) && \
	$(MAKE) -j$(PROCS)&& \
	$(MAKE) install

cross-gcc: cross-binutils
	mkdir -p build/gcc && cd build/gcc && \
	(./config.status || ../../gcc-*/configure --prefix=$(PREFIX) --target= 
$(TARGET) --enable-languages="c" --with-gnu-ld --with-gnu-as --with- 
newlib --disable-nls --disable-libssp --with-newlib --without-headers  
--disable-shared --disable-threads --disable-libmudflap --disable- 
libgomp --disable-libstdcxx-pch --disable-libunwind-exceptions -- 
disable-libffi) && \
	$(MAKE) && \
	$(MAKE) install

cross-g++: cross-binutils cross-gcc cross-newlib
	mkdir -p build/g++ && cd build/g++ && \
	(./config.status || ../../gcc-*/configure --prefix=$(PREFIX) --target= 
$(TARGET) --enable-languages="c++" --with-gnu-ld --with-gnu-as --with- 
newlib --disable-nls --disable-libssp --with-newlib --without-headers  
--disable-shared --disable-threads --disable-libmudflap --disable- 
libgomp --disable-libstdcxx-pch --disable-libunwind-exceptions -- 
disable-libffi) && \
	$(MAKE) && \
	$(MAKE) install

cross-newlib: cross-binutils cross-gcc
	mkdir -p build/newlib && cd build/newlib && \
	(./config.status || ../../newlib-*/configure --prefix=$(PREFIX) -- 
target=$(TARGET) --disable-newlib-supplied-syscalls  --disable- 
libgloss --disable-nls --disable-shared) && \
	$(MAKE) -j$(PROCS) CFLAGS_FOR_TARGET="-ffunction-sections -fdata- 
sections -DPREFER_SIZE_OVER_SPEED -D__OPTIMIZE_SIZE__ -Os -fomit-frame- 
pointer -D__BUFSIZ__=256" && \
	$(MAKE) install

What's strange is that I seem to be getting blx instructions generated  
where with the previous G++ Lite (2009Q1) used bl, generating no hard  
fault.  The compilation options for both versions are the same, though  
they differ from the CodeSourcery build options used for release (at  
least what's in the shell script included with the sources).  Of note,  
the precompiled CodeSourcery binaries for 2009Q3 on Linux use bl in  
the same function rather than blx.

Compilation options used in both cases:
Compiler Flags: -mcpu=cortex-m3 -mthumb -mlittle-endian $_CPPINCFLAGS - 
ffunction-sections -fdata-sections -fno-strict-aliasing %s -Wall -c  
$SOURCE -o $TARGET"
Linker Flags:  -mcpu=cortex-m3 -mthumb -Wl,-T -Xlinker -u _start -Wl,- 
e,Reset_Handler -Wl,-static -Wl,--gc-sections -nostartfiles -nostdlib - 
Wl,--allow-multiple-definition -o $TARGET $SOURCES -lc -lgcc -lm

Any ideas?

Example assembler generated from C:

2009Q1
08000ce0 <platform_timer_get_diff_us>:
 8000ce0:       b570            push    {r4, r5, r6, lr}
 8000ce2:       460d            mov     r5, r1
 8000ce4:       4614            mov     r4, r2
 8000ce6:       2103            movs    r1, #3
 8000ce8:       2200            movs    r2, #0
 8000cea:       f7ff fff5       bl      8000cd8 <platform_timer_op>
 8000cee:       42ac            cmp     r4, r5
 8000cf0:       4602            mov     r2, r0
 8000cf2:       d202            bcs.n   8000cfa  
<platform_timer_get_diff_us+0x1a>
 8000cf4:       4623            mov     r3, r4
 8000cf6:       462c            mov     r4, r5
 8000cf8:       461d            mov     r5, r3
 8000cfa:       4805            ldr     r0, [pc, #20]   (8000d10  
<platform_timer_get_diff_us+0x30>)
 8000cfc:       1b63            subs    r3, r4, r5
 8000cfe:       fba3 0100       umull   r0, r1, r3, r0
 8000d02:       4612            mov     r2, r2
 8000d04:       f04f 0300       mov.w   r3, #0  ; 0x0
 8000d08:       f01f fc08       bl      802051c <__aeabi_uldivmod>
 8000d0c:       bd70            pop     {r4, r5, r6, pc}
 8000d0e:       bf00            nop
 8000d10:       000f4240        .word   0x000f4240

2009Q3:
08000cd0 <platform_timer_get_diff_us>:
 8000cd0:       b538            push    {r3, r4, r5, lr}
 8000cd2:       460c            mov     r4, r1
 8000cd4:       4615            mov     r5, r2
 8000cd6:       2103            movs    r1, #3
 8000cd8:       2200            movs    r2, #0
 8000cda:       f7ff fff5       bl      8000cc8 <platform_timer_op>
 8000cde:       42a5            cmp     r5, r4
 8000ce0:       4602            mov     r2, r0
 8000ce2:       d202            bcs.n   8000cea  
<platform_timer_get_diff_us+0x1a>
 8000ce4:       4623            mov     r3, r4
 8000ce6:       462c            mov     r4, r5
 8000ce8:       461d            mov     r5, r3
 8000cea:       4b04            ldr     r3, [pc, #16]   (8000cfc  
<platform_timer_get_diff_us+0x2c>)
 8000cec:       1b2c            subs    r4, r5, r4
 8000cee:       fba4 0103       umull   r0, r1, r4, r3
 8000cf2:       2300            movs    r3, #0
 8000cf4:       f01f ecf6       blx     80206e4 <__aeabi_uldivmod>  
<--- this causes the hard fault
 8000cf8:       bd38            pop     {r3, r4, r5, pc}
 8000cfa:       bf00            nop
 8000cfc:       000f4240        .word   0x000f4240



--
James Snyder
Biomedical Engineering
Northwestern University
jbsnyder@xxxxxxxxxxxxxx
http://fanplastic.org/key.txt
ph: 847.448.0386

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