Fix argument extension on riscv64 for Wasmtime builtins #10069
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This commit fixes a crash found in the CI of bytecodealliance#10040. That PR itself isn't the fault per-se but rather uncovered a preexisting issue on riscv64. According to riscv64's ABI docs it looks like arguments are all expected to be sign-extended, whereas currently in Wasmtime all host signatures are zero-extended on all platforms. This commit applies two changes to fix this: * A new `TargetIsa::default_argument_extension` method was added which is now used instead of unconditionally using `uext` to apply to all arguments/results. * While I was here I went ahead and split apart things where the wasm signature of a builtin doesn't use `uext` or `sext`. The host signature still does, however, which means that any extension necessary happens in the trampoline we generate per-libcall as opposed to at all callsites. I'm not certain that all platforms require `uext` but I've left the `TargetIsa` implementation as `uext` for now with a comment explaining why. Currently the only non-`uext` platforms are riscv64, which is `sext` to fix the issue from bytecodealliance#10040, and Pulley which is "none" as things work differently there.
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This commit fixes a crash found in the CI of #10040. That PR itself isn't the fault per-se but rather uncovered a preexisting issue on riscv64. According to riscv64's ABI docs it looks like arguments are all expected to be sign-extended, whereas currently in Wasmtime all host signatures are zero-extended on all platforms. This commit applies two changes to fix this:
A new
TargetIsa::default_argument_extensionmethod was added which is now used instead of unconditionally usinguextto apply to all arguments/results.While I was here I went ahead and split apart things where the wasm signature of a builtin doesn't use
uextorsext. The host signature still does, however, which means that any extension necessary happens in the trampoline we generate per-libcall as opposed to at all callsites.I'm not certain that all platforms require
uextbut I've left theTargetIsaimplementation asuextfor now with a comment explaining why. Currently the only non-uextplatforms are riscv64, which issextto fix the issue from #10040, and Pulley which is "none" as things work differently there.