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remove struct_gep, use manual layout calculations for va_arg

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This commit is contained in:
Erik Desjardins 2024-02-24 01:46:30 -05:00
parent 123015e722
commit beed25be9a
6 changed files with 71 additions and 111 deletions
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94
compiler/rustc_codegen_llvm/src/va_arg.rs
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@ -89,11 +89,35 @@ fn emit_aapcs_va_arg<'ll, 'tcx>(
list: OperandRef<'tcx, &'ll Value>,
target_ty: Ty<'tcx>,
) -> &'ll Value {
let dl = bx.cx.data_layout();
// Implementation of the AAPCS64 calling convention for va_args see
// https://github.com/ARM-software/abi-aa/blob/master/aapcs64/aapcs64.rst
//
// typedef struct va_list {
// void * stack; // next stack param
// void * gr_top; // end of GP arg reg save area
// void * vr_top; // end of FP/SIMD arg reg save area
// int gr_offs; // offset from gr_top to next GP register arg
// int vr_offs; // offset from vr_top to next FP/SIMD register arg
// } va_list;
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);
// There is no padding between fields since `void*` is size=8 align=8, `int` is size=4 align=4.
// See https://github.com/ARM-software/abi-aa/blob/master/aapcs64/aapcs64.rst
// Table 1, Byte size and byte alignment of fundamental data types
// Table 3, Mapping of C & C++ built-in data types
let ptr_offset = 8;
let i32_offset = 4;
let gr_top = bx.inbounds_gep(bx.type_i8(), va_list_addr, &[bx.cx.const_usize(ptr_offset)]);
let vr_top = bx.inbounds_gep(bx.type_i8(), va_list_addr, &[bx.cx.const_usize(2 * ptr_offset)]);
let gr_offs = bx.inbounds_gep(bx.type_i8(), va_list_addr, &[bx.cx.const_usize(3 * ptr_offset)]);
let vr_offs = bx.inbounds_gep(
bx.type_i8(),
va_list_addr,
&[bx.cx.const_usize(3 * ptr_offset + i32_offset)],
);
let layout = bx.cx.layout_of(target_ty);
let maybe_reg = bx.append_sibling_block("va_arg.maybe_reg");
@ -104,16 +128,12 @@ fn emit_aapcs_va_arg<'ll, 'tcx>(
let offset_align = Align::from_bytes(4).unwrap();
let gr_type = target_ty.is_any_ptr() || target_ty.is_integral();
let (reg_off, reg_top_index, slot_size) = if gr_type {
let gr_offs =
bx.struct_gep(va_list_ty, va_list_addr, va_list_layout.llvm_field_index(bx.cx, 3));
let (reg_off, reg_top, slot_size) = if gr_type {
let nreg = (layout.size.bytes() + 7) / 8;
(gr_offs, va_list_layout.llvm_field_index(bx.cx, 1), nreg * 8)
(gr_offs, gr_top, nreg * 8)
} else {
let vr_off =
bx.struct_gep(va_list_ty, va_list_addr, va_list_layout.llvm_field_index(bx.cx, 4));
let nreg = (layout.size.bytes() + 15) / 16;
(vr_off, va_list_layout.llvm_field_index(bx.cx, 2), nreg * 16)
(vr_offs, vr_top, nreg * 16)
};
// if the offset >= 0 then the value will be on the stack
@ -141,8 +161,7 @@ fn emit_aapcs_va_arg<'ll, 'tcx>(
bx.switch_to_block(in_reg);
let top_type = bx.type_ptr();
let top = bx.struct_gep(va_list_ty, va_list_addr, reg_top_index);
let top = bx.load(top_type, top, bx.tcx().data_layout.pointer_align.abi);
let top = bx.load(top_type, reg_top, dl.pointer_align.abi);
// reg_value = *(@top + reg_off_v);
let mut reg_addr = bx.gep(bx.type_i8(), top, &[reg_off_v]);
@ -173,11 +192,33 @@ fn emit_s390x_va_arg<'ll, 'tcx>(
list: OperandRef<'tcx, &'ll Value>,
target_ty: Ty<'tcx>,
) -> &'ll Value {
let dl = bx.cx.data_layout();
// Implementation of the s390x ELF ABI calling convention for va_args see
// https://github.com/IBM/s390x-abi (chapter 1.2.4)
//
// typedef struct __va_list_tag {
// long __gpr;
// long __fpr;
// void *__overflow_arg_area;
// void *__reg_save_area;
// } va_list[1];
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);
// There is no padding between fields since `long` and `void*` both have size=8 align=8.
// https://github.com/IBM/s390x-abi (Table 1.1.: Scalar types)
let i64_offset = 8;
let ptr_offset = 8;
let gpr = va_list_addr;
let fpr = bx.inbounds_gep(bx.type_i8(), va_list_addr, &[bx.cx.const_usize(i64_offset)]);
let overflow_arg_area =
bx.inbounds_gep(bx.type_i8(), va_list_addr, &[bx.cx.const_usize(2 * i64_offset)]);
let reg_save_area = bx.inbounds_gep(
bx.type_i8(),
va_list_addr,
&[bx.cx.const_usize(2 * i64_offset + ptr_offset)],
);
let layout = bx.cx.layout_of(target_ty);
let in_reg = bx.append_sibling_block("va_arg.in_reg");
@ -192,15 +233,10 @@ fn emit_s390x_va_arg<'ll, 'tcx>(
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) };
let (max_regs, reg_count, reg_save_index, reg_padding) =
if gpr_type { (5, gpr, 2, padding) } else { (4, fpr, 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);
@ -209,9 +245,7 @@ fn emit_s390x_va_arg<'ll, 'tcx>(
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_ptr(), reg_ptr, bx.tcx().data_layout.pointer_align.abi);
let reg_ptr_v = bx.load(bx.type_ptr(), reg_save_area, dl.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]);
@ -225,27 +259,23 @@ fn emit_s390x_va_arg<'ll, 'tcx>(
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_ptr(), arg_ptr, bx.tcx().data_layout.pointer_align.abi);
let arg_ptr_v =
bx.load(bx.type_ptr(), overflow_arg_area, 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.store(new_arg_ptr_v, overflow_arg_area, dl.pointer_align.abi);
bx.br(end);
// Return the appropriate result.
bx.switch_to_block(end);
let val_addr = bx.phi(bx.type_ptr(), &[reg_addr, mem_addr], &[in_reg, in_mem]);
let val_type = layout.llvm_type(bx);
let val_addr = if indirect {
bx.load(bx.cx.type_ptr(), val_addr, bx.tcx().data_layout.pointer_align.abi)
} else {
val_addr
};
let val_addr =
if indirect { bx.load(bx.cx.type_ptr(), val_addr, dl.pointer_align.abi) } else { val_addr };
bx.load(val_type, val_addr, layout.align.abi)
}