Files
sx/examples/86-callconv-c-fnptr-large-aggregate.sx
agra 63565e41ff abi: pass >16B aggregates by ptr-in-next-reg (Apple ARM64 ABI) + Path B for fn-ptr casts
Three stacked compiler bugs were causing iOS-sim chess to crash inside
[MTLTexture replaceRegion:...]. Fixing them lets every replaceRegion call
site succeed (1×1 RGBA8, 1MB R8 atlas, 440×440 chess pieces).

Path B for callconv(.c) fn-pointer casts:
- FunctionInfo now carries call_conv: CallConv (TypeInfo.CallConv) so
  function-type interning distinguishes sx-CC from C-CC. Inst.zig's
  Function.CallingConvention aliases the same enum.
- Parser accepts an optional `callconv(.c)` suffix on fn-pointer type
  spellings (factored into parseOptionalCallConv() shared with parseFnDecl
  and parseLambda).
- resolveFunctionType passes the parsed CC through functionTypeCC().
- .call_indirect reads fp.call_conv == .c and applies the C-ABI
  alloca+materialize for >16B aggregate args (Path A's behaviour at .call).

Apple ARM64 ABI (drop LLVM byval):
- Side-by-side asm diff vs clang's emission for the equivalent C call site
  showed LLVM's `byval` attribute lowers Apple-arm64 byval on the stack,
  while clang passes the struct via a pointer in the next int register
  (x2 for replaceRegion:). The runtime objc_msgSend dispatch path expects
  clang's convention.
- Dropped the byval attribute from the function-signature emission and
  from both call sites (.call and .call_indirect). The materialize-into-
  alloca + pass-plain-ptr pattern stays — the call site now matches
  clang's `mov x2, sp` exactly.
- Path A's sx-to-sx case continues to work since both ends use plain ptr
  (caller does alloca+store+pass, callee loads from the ptr in prologue).

Protocol dispatch (emitProtocolDispatch):
- Untargeted `null` lowers as const_null with type .void (per
  target_type orelse .void). The "wrap-value-in-alloca-pass-pointer"
  branch alloca'd a void slot, which LLVM's IRBuilder asserts on —
  EXC_BREAKPOINT in getTypeSizeInBits, manifesting as exit 133 / SIGTRAP
  when building the chess game. Fixed by re-emitting as
  constNull(void_ptr) when arg_ty == .void && expected_ty == void_ptr.
- is_pointer_ty only recognized .pointer, so [*]T (many_pointer) was
  alloca-wrapped — the heap pixels pointer from stbi_load was stored
  into a stack slot and the slot's address was passed as the *void arg.
  Fixed by extending the check to `.pointer or .many_pointer`.

metal.sx call sites + lifecycle guards:
- msg_replace (replaceRegion:, MTLRegion = 48B) and the two setScissorRect:
  sites (MTLScissorRect = 32B) now spell their fn-pointer types with
  by-value params + callconv(.c) — the *MTLRegion/@local workaround is
  gone.
- metal_begin_frame_ios bails before nextDrawable when pixel_w/h are 0
  (drawableSize 0×0 makes nextDrawable abort via XPC).
- metal_init_ios only sets drawableSize when dims are positive.
- begin_frame's encoder/cmd_buffer failure paths now clear self.drawable
  so a partial failure doesn't leak a drawable back into the pool.

Examples + tests:
- examples/86-callconv-c-fnptr-large-aggregate.sx — new, covers Path B
  with C-CC fn-ptr cast.
- examples/87-fnptr-cast-large-aggregate.sx — renamed from issue-0025.sx,
  covers Path B with default sx-CC (the negative case).
- examples/85-cc-c-large-aggregate.sx — from Session 60, covers Path A.
- examples/issue-0014.sx, issue-0024.sx, issue-0025.sx — removed
  (resolved earlier this work).

71 regression tests pass, 0 failed. Chess game builds clean for iOS sim
and reaches its frame loop without aborting. Runtime: chess UI still
doesn't render — remaining issue is in the UIKit lifecycle / CAMetalLayer
setup (legacy-app vs scene-API hybrid), not a compiler bug. See
current/CHECKPOINT.md "Next step" for the diagnosis + options.
2026-05-18 00:11:23 +03:00

38 lines
1.2 KiB
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// Regression test for issue-0025 path B.
//
// When a fn-pointer's type is spelled with `callconv(.c)`, the indirect
// call must apply the same C-ABI byval coercion that direct C-ABI calls
// do at the call site (path A): >16-byte non-HFA aggregates are passed
// as `ptr byval(<T>)`. Without the fix, the indirect call site builds
// an LLVM function type whose param slot is the raw struct, which the
// AArch64/x86_64 backend tries to lay out across registers + stack in
// ways that don't match the byval-attributed callee signature — the
// callee then reads garbage out of the wrong machine-state slots.
//
// The opt-in is the `callconv(.c)` on the fn-pointer type spelling.
// Pure-sx fn-pointer casts (no callconv suffix) keep their default
// calling convention — verified by examples/87-fnptr-cast-large-aggregate.sx.
#import "modules/std.sx";
Wide :: struct {
a: s64;
b: s64;
c: s64;
d: s64;
}
accept_c :: (w: Wide) -> s64 callconv(.c) {
w.a + w.b + w.c + w.d;
}
main :: () -> s32 {
w := Wide.{ a = 1, b = 10, c = 100, d = 1000 };
if accept_c(w) != 1111 { return 1; }
fn_ptr : (Wide) -> s64 callconv(.c) = xx accept_c;
if fn_ptr(w) != 1111 { return 2; }
0;
}