On 06/25/14 21:38, Kito Cheng wrote:
For example in arm-elf-eabi, movmem need word align, otherwise it will
expand a libcall:
And gcc configure with "--target=arm-elf-eabi --disable-nls
--disable-shared --enable-languages=c,c++ --enable-threads=single
--enable-lto --with-newlib"
test.c:
extern bar(unsigned char p[3][2]);
void foo(int i)
{
unsigned char data[3][2] = {{1,1}, {1,0}, {1,1}};
bar(data);
}
First, note, I'm not an ARM expert. However, the first question I have
is are we sure the initializer is always going to be suitably aligned?
What guarantees this initializer is going to have 32 bit alignment
like you want? I can see how that *section* gets its alignment, but I
don't offhand see what in the ARM backend ensures that a CONSTRUCTOR
tree has larger than normal known alignment.
I think that needs to be settled first, then we need to verify that the
trees are correctly carrying that alignment requirement around and that
the code uses it appropriately (and I have my doubts because EXP is a
CONSTRUCTOR element and those seem to be largely ignored in the code
we're looking to change).
I would also strongly recommend turning your testcase into something we
can add to the testsuite.
If you look in gcc/testsuite/gcc.target/arm you'll see several examples.
I think you just want to compile this down to assembly code with the
optimizer enabled, then verify there is no call to memcpy in the
resulting output. 20030909-1.c would seem to be a reasonable example of
a test that does something similar.
Jeff
