In some cases its more efficient to combine TRUNC( BINOP( X, Y ) ) --> BINOP( TRUNC( X ), TRUNC( Y ) ) if the binop is legal for the truncated types.
This is true for vector integer multiplication (especially vXi64), as well as ADD/AND/XOR/OR in cases where we only need to truncate one of the inputs at runtime (e.g. a duplicated input or an one use constant we can fold).
Further work could be done here - scalar cases (especially i64) could often benefit (if we avoid partial registers etc.), other opcodes, and better analysis of when truncating the inputs reduces costs.
I have considered implementing this for all targets within the DAGCombiner but wasn't sure we could devise a suitable cost model system that would give us the range we need.
Differential Revision: https://reviews.llvm.org/D28219
llvm-svn: 290947
This is a tiny patch with a big pile of test changes.
This partially fixes PR27885:
https://llvm.org/bugs/show_bug.cgi?id=27885
My motivating case looks like this:
- vpshufd {{.*#+}} xmm1 = xmm1[0,1,0,2]
- vpshufd {{.*#+}} xmm0 = xmm0[0,2,2,3]
- vpblendw {{.*#+}} xmm0 = xmm0[0,1,2,3],xmm1[4,5,6,7]
+ vshufps {{.*#+}} xmm0 = xmm0[0,2],xmm1[0,2]
And this happens several times in the diffs. For chips with domain-crossing penalties,
the instruction count and size reduction should usually overcome any potential
domain-crossing penalty due to using an FP op in a sequence of int ops. For chips such
as recent Intel big cores and Atom, there is no domain-crossing penalty for shufps, so
using shufps is a pure win.
So the test case diffs all appear to be improvements except one test in
vector-shuffle-combining.ll where we miss an opportunity to use a shift to generate
zero elements and one test in combine-sra.ll where multiple uses prevent the expected
shuffle combining.
Differential Revision: https://reviews.llvm.org/D27692
llvm-svn: 289837
With D24253 we can now use SelectionDAG::SignBitIsZero with vector operations.
This patch uses SelectionDAG::SignBitIsZero to recognise that a zero sign bit means that we can use a sitofp instead of a uitofp (which is not directly support on pre-AVX512 hardware).
While AVX512 does provide support for uitofp, the conversion to sitofp should not cause any regressions.
Differential Revision: https://reviews.llvm.org/D24343
llvm-svn: 281852
Until AVX512DQ we only support i64/vXi64 sitofp conversion as scalars.
This patch sees if the sign bit extends far enough that we can truncate to a i32 type and then perform sitofp without loss of precision.
Differential Revision: https://reviews.llvm.org/D24345
llvm-svn: 281502
Simon Pilgrim