[X86] Add ISel patterns to select SSE3/AVX ADDSUB instructions.
This patch adds ISel patterns to select SSE3/AVX ADDSUB instructions
from a sequence of "vadd + vsub + blend".
Example:
///
typedef float float4 __attribute__((ext_vector_type(4)));
float4 foo(float4 A, float4 B) {
float4 X = A - B;
float4 Y = A + B;
return (float4){X[0], Y[1], X[2], Y[3]};
}
///
Before this patch, (with flag -mcpu=corei7) llc produced the following
assembly sequence:
movaps %xmm0, %xmm2
addps %xmm1, %xmm2
subps %xmm1, %xmm0
blendps $10, %xmm2, %xmm0
With this patch, we now get a single
addsubps %xmm1, %xmm0
llvm-svn: 211427