[LLVMdev] X86TarIgetLowering::LowerToBT

[Chris Sears]

'Bug' may be too strong a word. Their emitted code is correct
else it would have failed one of their test suites.

They could use TESTL as well for bit 31.
So I'll be curious to see what Intel's guidelines are.
They don't mention this in their Optimization manual.

Right now, I'm convinced that TEST should be used when it's available.
But even with partial flag hazards, BT is not worth avoiding for 32-63.
For the -Oz case it's worth emitting for bits 8-63.
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