Hi all,
I encountered a wrong-code issue with my WIP store merging pass when it was
trying to encode HFmode constants.
I am using native_encode_real to write the constants to a byte array and it's
breaking on big-endian.
For a 2-byte constant it ended up writing bytes at offsets 3 and 2 rather than
1 and 0.
The fix in this patch makes the logic in native_encode_real match the logic in
native_interpret_real,
I just copied the logic across.
I don't have a testcase against clean trunk that demonstrates the issue but
with my store merging patch
the testcase gcc.target/aarch64/advsimd-intrinsics/vldX.c starts failing
without this patch because
adjacent 16-bit float constants are not being merged correctly.
Bootstrapped and tested on aarch64-none-linux-gnu.
As this patch only affects the big-endian code path I also tested it on
aarch64_be-none-elf.
Ok for trunk? Do you think this needs to be backported?
Thanks,
Kyrill
2016-10-05 Kyrylo Tkachov <kyrylo.tkac...@arm.com>
* fold-const.c (native_encode_real): Fix logic for selecting offset
to write to when BYTES_BIG_ENDIAN.
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 81671e9fec68a3281b744626db1b94f26d19aabc..564d086e9636743104d629cd6f5620ac2ee6a544 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -7142,7 +7142,16 @@ native_encode_real (const_tree expr, unsigned char *ptr, int len, int off)
offset += byte % UNITS_PER_WORD;
}
else
- offset = BYTES_BIG_ENDIAN ? 3 - byte : byte;
+ {
+ offset = byte;
+ if (BYTES_BIG_ENDIAN)
+ {
+ /* Reverse bytes within each long, or within the entire float
+ if it's smaller than a long (for HFmode). */
+ offset = MIN (3, total_bytes - 1) - offset;
+ gcc_assert (offset >= 0);
+ }
+ }
offset = offset + ((bitpos / BITS_PER_UNIT) & ~3);
if (offset >= off
&& offset - off < len)
