[Bug tree-optimization/36844] New: Vectorizer doesn't support INT<->FP conversions with different size

["hjl dot tools at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

Intel AVX has variable vector lengths of 128bit and 256bit.
There are 128bit INT and 256bit FP vector arithmetic operations
as well as asymmetric vector conversion operations:

256bit vector (V4DF/V4DI) <-> 256bit vector (D4SI/V4SF)
256bit vector (V8SI) <-> 256bit vecor (V8SF)

The current vectorizer only supports different vector
size based on scalar type. But it doesn't support asymmetric
vector conversion nor different vector size based on
operation. The current AVX branch limits vector size
to 128bit for vectorizer:

/* ??? No autovectorization into MMX or 3DNOW until we can reliably
   place emms and femms instructions.
   FIXME: AVX has 32byte floating point vector operations and 16byte
   integer vector operations.  But vectorizer doesn't support
   different sizes for integer and floating point vectors.  We limit
   vector size to 16byte.  */
#define UNITS_PER_SIMD_WORD(MODE)                                       \
  (TARGET_AVX ? (((MODE) == DFmode || (MODE) == SFmode) ? 16 : 16)      \
              : (TARGET_SSE ? 16 : UNITS_PER_WORD))


-- 
           Summary: Vectorizer doesn't support  INT<->FP conversions with
                    different size
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: hjl dot tools at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36844