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Auto merge of rust-lang#105381 - uweigand:s390x-ffi-vaarg, r=nikic
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Implement va_list and va_arg for s390x FFI

Following the s390x ELF ABI and based on the clang implementation, provide appropriate definitions of va_list in library/core/src/ffi/mod.rs and va_arg handling in compiler/rustc_codegen_llvm/src/va_arg.rs.

Fixes the following test cases on s390x:
src/test/run-make-fulldeps/c-link-to-rust-va-list-fn src/test/ui/abi/variadic-ffi.rs

Fixes rust-lang#84628.
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bors committed Dec 20, 2022
2 parents 65bd2a6 + eb22d70 commit d6da428
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Showing 2 changed files with 134 additions and 5 deletions.
84 changes: 84 additions & 0 deletions compiler/rustc_codegen_llvm/src/va_arg.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -175,6 +175,89 @@ fn emit_aapcs_va_arg<'ll, 'tcx>(
val
}

fn emit_s390x_va_arg<'ll, 'tcx>(
bx: &mut Builder<'_, 'll, 'tcx>,
list: OperandRef<'tcx, &'ll Value>,
target_ty: Ty<'tcx>,
) -> &'ll Value {
// Implementation of the s390x ELF ABI calling convention for va_args see
// https://github.com/IBM/s390x-abi (chapter 1.2.4)
let va_list_addr = list.immediate();
let va_list_layout = list.deref(bx.cx).layout;
let va_list_ty = va_list_layout.llvm_type(bx);
let layout = bx.cx.layout_of(target_ty);

let in_reg = bx.append_sibling_block("va_arg.in_reg");
let in_mem = bx.append_sibling_block("va_arg.in_mem");
let end = bx.append_sibling_block("va_arg.end");

// FIXME: vector ABI not yet supported.
let target_ty_size = bx.cx.size_of(target_ty).bytes();
let indirect: bool = target_ty_size > 8 || !target_ty_size.is_power_of_two();
let unpadded_size = if indirect { 8 } else { target_ty_size };
let padded_size = 8;
let padding = padded_size - unpadded_size;

let gpr_type = indirect || !layout.is_single_fp_element(bx.cx);
let (max_regs, reg_count_field, reg_save_index, reg_padding) =
if gpr_type { (5, 0, 2, padding) } else { (4, 1, 16, 0) };

// Check whether the value was passed in a register or in memory.
let reg_count = bx.struct_gep(
va_list_ty,
va_list_addr,
va_list_layout.llvm_field_index(bx.cx, reg_count_field),
);
let reg_count_v = bx.load(bx.type_i64(), reg_count, Align::from_bytes(8).unwrap());
let use_regs = bx.icmp(IntPredicate::IntULT, reg_count_v, bx.const_u64(max_regs));
bx.cond_br(use_regs, in_reg, in_mem);

// Emit code to load the value if it was passed in a register.
bx.switch_to_block(in_reg);

// Work out the address of the value in the register save area.
let reg_ptr =
bx.struct_gep(va_list_ty, va_list_addr, va_list_layout.llvm_field_index(bx.cx, 3));
let reg_ptr_v = bx.load(bx.type_i8p(), reg_ptr, bx.tcx().data_layout.pointer_align.abi);
let scaled_reg_count = bx.mul(reg_count_v, bx.const_u64(8));
let reg_off = bx.add(scaled_reg_count, bx.const_u64(reg_save_index * 8 + reg_padding));
let reg_addr = bx.gep(bx.type_i8(), reg_ptr_v, &[reg_off]);

// Update the register count.
let new_reg_count_v = bx.add(reg_count_v, bx.const_u64(1));
bx.store(new_reg_count_v, reg_count, Align::from_bytes(8).unwrap());
bx.br(end);

// Emit code to load the value if it was passed in memory.
bx.switch_to_block(in_mem);

// Work out the address of the value in the argument overflow area.
let arg_ptr =
bx.struct_gep(va_list_ty, va_list_addr, va_list_layout.llvm_field_index(bx.cx, 2));
let arg_ptr_v = bx.load(bx.type_i8p(), arg_ptr, bx.tcx().data_layout.pointer_align.abi);
let arg_off = bx.const_u64(padding);
let mem_addr = bx.gep(bx.type_i8(), arg_ptr_v, &[arg_off]);

// Update the argument overflow area pointer.
let arg_size = bx.cx().const_u64(padded_size);
let new_arg_ptr_v = bx.inbounds_gep(bx.type_i8(), arg_ptr_v, &[arg_size]);
bx.store(new_arg_ptr_v, arg_ptr, bx.tcx().data_layout.pointer_align.abi);
bx.br(end);

// Return the appropriate result.
bx.switch_to_block(end);
let val_addr = bx.phi(bx.type_i8p(), &[reg_addr, mem_addr], &[in_reg, in_mem]);
let val_type = layout.llvm_type(bx);
let val_addr = if indirect {
let ptr_type = bx.cx.type_ptr_to(val_type);
let ptr_addr = bx.bitcast(val_addr, bx.cx.type_ptr_to(ptr_type));
bx.load(ptr_type, ptr_addr, bx.tcx().data_layout.pointer_align.abi)
} else {
bx.bitcast(val_addr, bx.cx.type_ptr_to(val_type))
};
bx.load(val_type, val_addr, layout.align.abi)
}

pub(super) fn emit_va_arg<'ll, 'tcx>(
bx: &mut Builder<'_, 'll, 'tcx>,
addr: OperandRef<'tcx, &'ll Value>,
Expand All @@ -200,6 +283,7 @@ pub(super) fn emit_va_arg<'ll, 'tcx>(
emit_ptr_va_arg(bx, addr, target_ty, false, Align::from_bytes(8).unwrap(), true)
}
"aarch64" => emit_aapcs_va_arg(bx, addr, target_ty),
"s390x" => emit_s390x_va_arg(bx, addr, target_ty),
// Windows x86_64
"x86_64" if target.is_like_windows => {
let target_ty_size = bx.cx.size_of(target_ty).bytes();
Expand Down
55 changes: 50 additions & 5 deletions library/core/src/ffi/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -227,7 +227,12 @@ impl fmt::Debug for c_void {
/// Basic implementation of a `va_list`.
// The name is WIP, using `VaListImpl` for now.
#[cfg(any(
all(not(target_arch = "aarch64"), not(target_arch = "powerpc"), not(target_arch = "x86_64")),
all(
not(target_arch = "aarch64"),
not(target_arch = "powerpc"),
not(target_arch = "s390x"),
not(target_arch = "x86_64")
),
all(target_arch = "aarch64", any(target_os = "macos", target_os = "ios")),
target_family = "wasm",
target_arch = "asmjs",
Expand All @@ -251,7 +256,12 @@ pub struct VaListImpl<'f> {
}

#[cfg(any(
all(not(target_arch = "aarch64"), not(target_arch = "powerpc"), not(target_arch = "x86_64")),
all(
not(target_arch = "aarch64"),
not(target_arch = "powerpc"),
not(target_arch = "s390x"),
not(target_arch = "x86_64")
),
all(target_arch = "aarch64", any(target_os = "macos", target_os = "ios")),
target_family = "wasm",
target_arch = "asmjs",
Expand Down Expand Up @@ -319,6 +329,25 @@ pub struct VaListImpl<'f> {
_marker: PhantomData<&'f mut &'f c_void>,
}

/// s390x ABI implementation of a `va_list`.
#[cfg(target_arch = "s390x")]
#[repr(C)]
#[derive(Debug)]
#[unstable(
feature = "c_variadic",
reason = "the `c_variadic` feature has not been properly tested on \
all supported platforms",
issue = "44930"
)]
#[lang = "va_list"]
pub struct VaListImpl<'f> {
gpr: i64,
fpr: i64,
overflow_arg_area: *mut c_void,
reg_save_area: *mut c_void,
_marker: PhantomData<&'f mut &'f c_void>,
}

/// x86_64 ABI implementation of a `va_list`.
#[cfg(all(target_arch = "x86_64", not(target_os = "uefi"), not(windows)))]
#[repr(C)]
Expand Down Expand Up @@ -352,6 +381,7 @@ pub struct VaList<'a, 'f: 'a> {
all(
not(target_arch = "aarch64"),
not(target_arch = "powerpc"),
not(target_arch = "s390x"),
not(target_arch = "x86_64")
),
all(target_arch = "aarch64", any(target_os = "macos", target_os = "ios")),
Expand All @@ -363,7 +393,12 @@ pub struct VaList<'a, 'f: 'a> {
inner: VaListImpl<'f>,

#[cfg(all(
any(target_arch = "aarch64", target_arch = "powerpc", target_arch = "x86_64"),
any(
target_arch = "aarch64",
target_arch = "powerpc",
target_arch = "s390x",
target_arch = "x86_64"
),
any(not(target_arch = "aarch64"), not(any(target_os = "macos", target_os = "ios"))),
not(target_family = "wasm"),
not(target_arch = "asmjs"),
Expand All @@ -376,7 +411,12 @@ pub struct VaList<'a, 'f: 'a> {
}

#[cfg(any(
all(not(target_arch = "aarch64"), not(target_arch = "powerpc"), not(target_arch = "x86_64")),
all(
not(target_arch = "aarch64"),
not(target_arch = "powerpc"),
not(target_arch = "s390x"),
not(target_arch = "x86_64")
),
all(target_arch = "aarch64", any(target_os = "macos", target_os = "ios")),
target_family = "wasm",
target_arch = "asmjs",
Expand All @@ -398,7 +438,12 @@ impl<'f> VaListImpl<'f> {
}

#[cfg(all(
any(target_arch = "aarch64", target_arch = "powerpc", target_arch = "x86_64"),
any(
target_arch = "aarch64",
target_arch = "powerpc",
target_arch = "s390x",
target_arch = "x86_64"
),
any(not(target_arch = "aarch64"), not(any(target_os = "macos", target_os = "ios"))),
not(target_family = "wasm"),
not(target_arch = "asmjs"),
Expand Down

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