* add x86 encodings for shift-immediate instructions
implements encodings for ishl_imm, sshr_imm, and ushr_imm. uses 8-bit immediates.
added tests for the encodings to intel/binary64.cton. Canonical versions
come from llvm-mc.
* translate test to use shift-immediates
* shift immediate encodings: use enc_i32_i64
and note why the regular shift encodings cant use it above
* add additional encoding tests for shift immediates
this covers 32 bit mode, and 64 bit operations in 64 bit mode.
Changes:
* Adds a new generic instruction, SELECTIF, that does value selection (a la
conditional move) similarly to existing SELECT, except that it is
controlled by condition code input and flags-register inputs.
* Adds a new Intel x86_64 variant, 'baseline', that supports SSE2 and
nothing else.
* Adds new Intel x86_64 instructions BSR and BSF.
* Implements generic CLZ, CTZ and POPCOUNT on x86_64 'baseline' targets
using the new BSR, BSF and SELECTIF instructions.
* Implements SELECTIF on x86_64 targets using conditional-moves.
* new test filetests/isa/intel/baseline_clz_ctz_popcount.cton
(for legalization)
* new test filetests/isa/intel/baseline_clz_ctz_popcount_encoding.cton
(for encoding)
* Allow lib/cretonne/meta/gen_legalizer.py to generate non-snake-caseified
Rust without rustc complaining.
Fixes#238.
