PCC [AArch64]: load_constant64_full generates incorrect fact range for 32-bit MOVN

[feilongjiang]

Hi team, find another PCC fact range issue on AArch64.
When the top 32 bits of the value are zero and the upper_halfword of the lower 32 bits is u16::MAX, load_constant64_full will emit a single movn instruction. In that case, add_range_fact only adds lower_halfword as the fact range, which misses the upper halfword value. We should add the hole 32-bit value as the fact range.

Here is a simple test to reproduce the issue:

;; test_const.wat
(module
  (func (export "test_constant") (result i64) (i64.const 0xfffffff7))
)

Step to reproduce:

Compile the test with PCC on:

target/debug/wasmtime compile -C pcc=y test_const.wat

the output will be:

Error: Compilation error: Proof-carrying-code validation error: UnsupportedFact

[feilongjiang]

Hi @fitzgen, would you please take a look?

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[fitzgen]

Thanks!