stage2: lower float negation explicitly + modify hash/eql logic for floats #11967
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Rather than lowering float negation as `0.0 - x`. * Add AIR instruction for float negation. * Add compiler-rt functions for f128, f80 negation closes #11853
Zig guarantees the memory layout of f16, f32, f64, f80, and f128 which means for generic function purposes, values of these types need to be compared on the basis of their bits in memory. This means nan-packing can be used with generic functions, for example. For comptime_float, the sign is observable, whether it is nan is observable, but not any more kinds of bit patterns are observable. This fixes the std.fmt tests that check printing "-nan".
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Stage1 (and LLVM) just directly generates an XOR with an appropriate constant, I think stage2 should too. |
Rather than a compiler-rt call in the case that LLVM does not support lowering the fneg instruction.
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Rather than lowering float negation as
0.0 - x, this commit makes Zig lower it with a negation AIR instruction. It also adds compiler-rt functions for f128 and f80 negation.This revealed a problem with the way generic functions work for floats:
Zig guarantees the memory layout of f16, f32, f64, f80, and f128 which
means for generic function purposes, values of these types need to be
compared on the basis of their bits in memory. This means nan-packing
can be used with generic functions, for example.
For comptime_float, the sign is observable, whether it is nan is
observable, but not any more kinds of bit patterns are observable.
This fixes the std.fmt tests that check printing "-nan".
closes #11853