MULX has somewhat improved register allocation constraints compared to the legacy MUL instruction. Both output registers are encoded instead of fixed to EAX/EDX, but EDX is used as input. It also doesn't touch flags. Unfortunately, the encoding is longer.
Prefering it whenever BMI2 is enabled is probably not optimal. Choosing it should somehow be a function of register allocation constraints like converting adds to three address. gcc and icc definitely don't pick MULX by default. Not sure what if any rules they have for using it.
Differential Revision: https://reviews.llvm.org/D55565
llvm-svn: 348975
I had to tweak the i32 tests so we check both reg-reg and reg-mem cases.
I also added i64 load tests.
Part of ongoing work to ensure we test all intrinsic style tests on 32 and 64 bit targets where possible.
llvm-svn: 333827
Craig Topper