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Author SHA1 Message Date
Simon Pilgrim 6c21e6a54e [X86][SSE] Improve recognition of uitofp conversions that can be performed as sitofp 
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
 2016-09-18 12:45:23 +00:00
Simon Pilgrim a369219ce6 [X86][SSE] Improve recognition of i64 sitofp conversions that can be performed as i32 (PR29078) 
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
 2016-09-14 17:15:26 +00:00
Simon Pilgrim 6dd4b3526a [X86][SSE] Add test cases for PR29078 
'Failure to recognise i64 sitofp/uitofp conversions that can be performed as i32'

llvm-svn: 280671
 2016-09-05 18:11:17 +00:00