[x86] add fake scalar FP logic instructions to ReplaceableInstrs to save some bytes

We can replace "scalar" FP-bitwise-logic with other forms of bitwise-logic instructions. 
Scalar SSE/AVX FP-logic instructions only exist in your imagination and/or the bowels of 
compilers, but logically equivalent int, float, and double variants of bitwise-logic 
instructions are reality in x86, and the float variant may be a shorter instruction 
depending on which flavor (SSE or AVX) of vector ISA you have...so just prefer float all 
the time.

This is a preliminary step towards solving PR6137:
https://llvm.org/bugs/show_bug.cgi?id=6137

Differential Revision:
https://reviews.llvm.org/D26712

llvm-svn: 287122
diff --git a/llvm/test/CodeGen/X86/fp-logic.ll b/llvm/test/CodeGen/X86/fp-logic.ll
index 40bab00..2c6698f 100644
--- a/llvm/test/CodeGen/X86/fp-logic.ll
+++ b/llvm/test/CodeGen/X86/fp-logic.ll
@@ -223,7 +223,7 @@
 define double @doubles(double %x, double %y) {
 ; CHECK-LABEL: doubles:
 ; CHECK:       # BB#0:
-; CHECK-NEXT:    andpd %xmm1, %xmm0
+; CHECK-NEXT:    andps %xmm1, %xmm0
 ; CHECK-NEXT:    retq
 ;
   %bc1 = bitcast double %x to i64