https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70963
Bug ID: 70963
Summary: vec_cts/vec_ctf intrinsics produce wrong results for
64-bit floating point
Product: gcc
Version: 5.3.1
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: markos at freevec dot org
Target Milestone: ---
Host: powerpc64le-linux-gnu
Target: powerpc64le-linux-gnu
Build: powerpc64le-linux-gnu
Created attachment 38420
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38420&action=edit
small test program to verify vec_cts/vec_ctf working on doubles
I've noticed some tests in Eigen failing for VSX 64-bit doubles code, when the
algorithm looked perfectly normal. Further investigation -and comparison with
direct output using same inputs from an SSE test program, showed that the
conversion to integer yielded 0 results in the case of VSX (vec_cts basically
returned 0 vectors). I've written a small test case that verifies this on both
big/little endian VSX-capable systems (compiled with -m64 -mvsx). When using
the intrinsic the result is wrong, when using the inline asm version, it works
as expected. I could not test it in a more recent gcc so it may well be fixed,
however it would be great if this would be backported to gcc 5.
Some asm output follows from test program (attached):
vec_cts:
1000066c: 60 67 00 f0 xvcvdpsxds vs0,vs12
10000670: 50 02 00 f0 xxswapd vs0,vs0
asm:
10000674: 51 02 00 f0 xxswapd vs32,vs0
10000678: 60 07 00 f0 xvcvdpsxds vs0,vs0
1000067c: 56 02 00 f0 xxswapd vs0,vs32
vec_ctf:
100006f8: 50 02 00 f0 xxswapd vs0,vs0
100006fc: e0 07 00 f0 xvcvsxddp vs0,vs0
10000700: 50 02 00 f0 xxswapd vs0,vs0
asm:
100006f8: 51 02 00 f0 xxswapd vs32,vs0
100006fc: e0 07 00 f0 xvcvsxddp vs0,vs0
10000700: 56 02 00 f0 xxswapd vs0,vs32
