On Aug 8, 2018, Segher Boessenkool <seg...@kernel.crashing.org> wrote:
> Then you get sdata2 used (via srodata in generic code), and it is accessed
> via GPR2 (via the sda21 reloc and linker magic). It is hard to trace down :-)
Aah, it didn't occur to me that the r2 uses could be introduced by the
linker. I was cutting corners and looking at the asm output, after
building only gcc, without binutils. Thanks for the explanation. Mind
if I add a comment about that next to... hmm... how about the
SMALL_DATA_* macros?
for gcc/ChangeLog
* config/rs6000/rs6000.c (SMALL_DATA_RELOC, SMALL_DATA_REG): Add
a comment about how uses of r2 for .sdata2 come about.
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index ddc61bdaffe7..bbc564de41ae 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -21240,6 +21240,9 @@ rs6000_output_function_entry (FILE *file, const char
*fname)
/* Print an operand. Recognize special options, documented below. */
#if TARGET_ELF
+/* Access to .sdata2 through r2 (see -msdata=eabi in invoke.texi) is
+ only introduced by the linker, when applying the sda21
+ relocation. */
#define SMALL_DATA_RELOC ((rs6000_sdata == SDATA_EABI) ? "sda21" : "sdarel")
#define SMALL_DATA_REG ((rs6000_sdata == SDATA_EABI) ? 0 : 13)
#else
--
Alexandre Oliva, freedom fighter https://FSFLA.org/blogs/lxo
Be the change, be Free! FSF Latin America board member
GNU Toolchain Engineer Free Software Evangelist
