trong added inline comments.
Herald added a project: LLVM.

Comment at: clang/lib/Driver/ToolChains/Arch/AArch64.cpp:318
+  if (Args.hasArg(options::OPT_ffixed_x0))
+    Features.push_back("+reserve-x0");
phosek wrote:
> trong wrote:
> > What happens (should happen) if we reserve x0 and compile a function with a 
> > return value?
> Clang throws `error: AArch64 doesn't support function calls if any of the 
> argument registers is reserved.` as for any other argument register.
Yes, if x0 is reserved, it can't be used to pass arguments. But what happens if 
x0 is used to return a value? For example:
int foo() {
    return 1;
It would be helpful if compiling `foo()` with x0 reserved threw an error.

  rG LLVM Github Monorepo


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