================
@@ -4619,6 +4619,31 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl
GD, unsigned BuiltinID,
// Buffer is a void**.
Address Buf = EmitPointerWithAlignment(E->getArg(0));
+ if (getTarget().getTriple().getArch() == llvm::Triple::systemz) {
+ // Call LLVM's EH setjmp, which is lightweight.
+ // We're not filling any fields of the jmp_buf here and leave
+ // it all to the back-end.
+ // Current LLVM implementation and documentation of the builtin is
+ // somewhat inconsistent with itself. The documentation starts out with:
+ // The buffer format and the overall functioning of this intrinsic is
+ // compatible with the GCC __builtin_setjmp implementation allowing code
+ // built with the clang and GCC to interoperate.
+ // But in GCC the format of the buffer is completely target-dependent,
+ // while LLVM attempts to impose some constraints on certain fields.
+ // 1. LLVM documentation continues with - The front end places the frame
+ // pointer in the first word - What clang puts into the first word,
+ // however, is the result of the frameaddress intrinsic - this value
+ // matches the frame pointer register contents on some but not all
+ // targets. On SystemZ these values differ, which would cause
+ // incompatibilties with GCC.
+ // 2. Clang front-end also writes the stack pointer into the third
+ // slot. Not only is this not even mentioned in the docs, it also does
+ // not match GCC behavior on all targets. On SystemZ we use the fourth
+ // slot.
----------------
efriedma-quic wrote:
I think we should specifically call out which targets are which, for reference.
No point in being overly generic. Otherwise I guess that's fine.
It's worth pointing out that if the backend completely fills the buffer, it
doesn't really matter if the frontend stores to the buffer before calling
setjmp.
https://github.com/llvm/llvm-project/pull/116642
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