[clang] Fix codegen of consteval functions returning an empty class, and related issues (PR #93115)

[Eli Friedman via cfe-commits]

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@@ -46,9 +46,9 @@ int mane() {
     char1 f1{1};
     char1 f2{1};
 
-// CHECK: [[TMP:%.+]] = alloca i16
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efriedma-quic wrote:

The revised version of casting integers is a bit more aggressive; it's hard to make it precisely match the old code while still preserving the correct semantics.

https://github.com/llvm/llvm-project/pull/93115