Commit Graph

8 Commits

Author SHA1 Message Date
Andrea Di Biagio 386d566395 [X86] Teach the backend how to lower vector shift left into multiply rather than scalarizing it.
Instead of expanding a packed shift into a sequence of scalar shifts,
the backend now tries (when possible) to convert the vector shift into a
vector multiply.

Before this change, a shift of a MVT::v8i16 vector by a
build_vector of constants was always scalarized into a long sequence of "vector
extracts + scalar shifts + vector insert".
With this change, if there is SSE2 support, we emit a single vector multiply.

This change also affects SSE4.1, AVX, AVX2 shifts:
 - A shift of a MVT::v4i32 vector by a build_vector of non uniform constants
is now lowered when possible into a single SSE4.1 vector multiply.
 - Packed v16i16 shift left by constant build_vector are now expanded when
possible into a single AVX2 vpmullw.
This change also improves the lowering of AVX512f vector shifts.

Added test CodeGen/X86/vec_shift6.ll with some code examples that are affected
by this change.

llvm-svn: 201271
2014-02-12 23:42:28 +00:00
Elena Demikhovsky 6769c50d9e Optimized integer vector multiplication operation by replacing it with shift/xor/sub when it is possible. Fixed a bug in SDIV, where the const operand is not a splat constant vector.
llvm-svn: 184931
2013-06-26 10:55:03 +00:00
Benjamin Kramer 2c3d0df8ee X86: Fold EXTRACT_SUBVECTORs of a BUILD_VECTOR into a smaller BUILD_VECTOR.
That can usually be lowered efficiently and is common in sandybridge code.
It would be nice to do this in DAGCombiner but we can't insert arbitrary
BUILD_VECTORs this late.

Fixes PR15462.

llvm-svn: 176634
2013-03-07 18:48:40 +00:00
Benjamin Kramer 2c9da989c2 X86: Open up some opportunities for constant folding by postponing shift lowering.
Fixes PR15141.

llvm-svn: 174327
2013-02-04 15:19:33 +00:00
Craig Topper a065238c6e Make LowerSIGN_EXTEND_INREG split 256-bit vectors when AVX1 is enabled and use AVX2 shifts when AVX2 is enabled.
llvm-svn: 145022
2011-11-21 01:12:36 +00:00
Craig Topper 3dc75f9e3b Add more AVX2 shift lowering support. Move AVX2 variable shift to use patterns instead of custom lowering code.
llvm-svn: 144457
2011-11-12 09:58:49 +00:00
Bruno Cardoso Lopes 1a87fcb9ba Fix PR10688. Add support for spliting 256-bit vector shifts when the
shift amount is variable

llvm-svn: 137885
2011-08-17 22:12:20 +00:00
Bruno Cardoso Lopes c96953c12a Add support for several vector shifts operations while in AVX mode. Fix PR10581
llvm-svn: 137067
2011-08-08 21:31:08 +00:00