efe3930215
There has been occasional confusion with the representation that we use for bool-typed values in registers, at least when these are wider than one bit. Does a `b8` store `true` as 1, or as all-ones (`0xff`)? We've settled on the latter because of some use-cases where the wide bool becomes a mask -- see #2058 for more on this. This is fine, and transparent, to most operations within CLIF, because the bool-typed value still has only two semantically-visible states, namely `true` and `false`. However, we have to be careful with bool-to-int conversions. `bint` on aarch64 correctly masked the all-ones value down to 0 or 1, as required by the instruction specification, but on x64 it did not. This PR fixes that bug and makes x64 consistent with aarch64. While staring at this code I realized that `bextend` was also not consistent with the all-ones invariant: it should do a sign-extend, not a zero-extend as it previously did. This is also rectified and tested. (Aarch64 also already had this case implemented correctly.) Fixes #3003.
17 lines
292 B
Plaintext
17 lines
292 B
Plaintext
test compile
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target x86_64 machinst
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function %f0(b8) -> b64 {
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block0(v0: b8):
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v1 = bextend.b64 v0
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return v1
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}
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; check: pushq %rbp
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; nextln: movq %rsp, %rbp
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; nextln: movsbq %dil, %rsi
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; nextln: movq %rsi, %rax
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; nextln: movq %rbp, %rsp
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; nextln: popq %rbp
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; nextln: ret
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