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Rollup merge of #122287 - RalfJung:simd-static-assert, r=pnkfelix

add test ensuring simd codegen checks don't run when a static assertion failed

stdarch relies on this to ensure that SIMD indices are in bounds.

I would love to know why this works, but I can't figure out where codegen decides to not codegen a function if a required-const does not evaluate. `@oli-obk` `@bjorn3` do you have any idea?
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Matthias Krüger 2024-03-14 15:44:33 +01:00 committed by GitHub
commit 6a4dd19ade
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7 changed files with 56 additions and 8 deletions

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@ -818,13 +818,16 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirUsedCollector<'a, 'tcx> {
self.super_rvalue(rvalue, location);
}
/// This does not walk the constant, as it has been handled entirely here and trying
/// to walk it would attempt to evaluate the `ty::Const` inside, which doesn't necessarily
/// work, as some constants cannot be represented in the type system.
/// This does not walk the MIR of the constant as that is not needed for codegen, all we need is
/// to ensure that the constant evaluates successfully and walk the result.
#[instrument(skip(self), level = "debug")]
fn visit_constant(&mut self, constant: &mir::ConstOperand<'tcx>, location: Location) {
let const_ = self.monomorphize(constant.const_);
let param_env = ty::ParamEnv::reveal_all();
// Evaluate the constant. This makes const eval failure a collection-time error (rather than
// a codegen-time error). rustc stops after collection if there was an error, so this
// ensures codegen never has to worry about failing consts.
// (codegen relies on this and ICEs will happen if this is violated.)
let val = match const_.eval(self.tcx, param_env, None) {
Ok(v) => v,
Err(ErrorHandled::Reported(..)) => return,