Update CmpResult to use a pointer-sized return type
#920
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As seen at [1], LLVM uses `long long` on LLP64 (to get a 64-bit integer matching pointer size) and `long` on everything else, with exceptions for AArch64 and AVR. Our current logic always uses an `i32`. This happens to work because LLVM uses 32-bit instructions to check the output on x86-64, but the GCC checks the full 64-bit register so garbage in the upper half leads to incorrect results. Update our return type to be `isize`, with exceptions for AArch64 and AVR. Fixes: rust-lang#919 [1]: https://github.com/llvm/llvm-project/blob/0cf3c437c18ed27d9663d87804a9a15ff6874af2/compiler-rt/lib/builtins/fp_compare_impl.inc#L11-L27
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As seen at 1, LLVM uses
long longon LLP64 (to get a 64-bit integer matching pointer size) andlongon everything else, with exceptions for AArch64 and AVR. Our current logic always uses ani32. This happens to work because LLVM uses 32-bit instructions to check the output on x86-64, but the GCC checks the full 64-bit register so garbage in the upper half leads to incorrect results.Update our return type to be
isize, with exceptions for AArch64 and AVR.Fixes: #919