[X86][FastIsel] Avoid introducing legacy SSE instructions if the target has AVX.
This patch teaches X86FastISel how to select AVX instructions for scalar
float/double convert operations.
Before this patch, X86FastISel always selected legacy SSE instructions
for FPExt (from float to double) and FPTrunc (from double to float).
For example:
\code
define double @foo(float %f) {
%conv = fpext float %f to double
ret double %conv
}
\end code
Before (with -mattr=+avx -fast-isel) X86FastIsel selected a CVTSS2SDrr which is
legacy SSE:
cvtss2sd %xmm0, %xmm0
With this patch, X86FastIsel selects a VCVTSS2SDrr instead:
vcvtss2sd %xmm0, %xmm0, %xmm0
Added test fast-isel-fptrunc-fpext.ll to check both the register-register and
the register-memory float/double conversion variants.
Differential Revision: http://reviews.llvm.org/D7438
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228682
91177308-0d34-0410-b5e6-
96231b3b80d8