Another ss-fannkuch problem. There's a bunch of LValueToInt32 instructions caused by suboptimal phi specialization in some edge cases.
Created attachment 631391 [details] [diff] [review] Patch GuessPhiType tries to guess the type of the phi based on the operand types. If all operands are phis we still have to visit, GuessPhiType returns MIRType_None. The patch ensures we never propagate MIRType_None to other phis. We have to wait until we know one of the operand types and then we can propagate the type. This + bug 762887 should make ss-fannkuch a bit faster, but especially x86 needs more work.