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stage1: Follow the C ABI for return types

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The current implementation of the target C ABI rules is hopelessly bad,
let's tack some more rules on top in order to prevent some
miscompilations.

Truth to be told the same rule should be applied also to parameters, but
I really can't stand stage1.
This commit is contained in:
LemonBoy 2021-03-05 12:37:49 +01:00
parent 9f722f43ac
commit 7813068e21
1 changed files with 47 additions and 0 deletions
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47
src/stage1/codegen.cpp
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@ -487,6 +487,53 @@ static LLVMValueRef make_fn_llvm_value(CodeGen *g, ZigFn *fn) {
addLLVMFnAttr(llvm_fn, "noreturn");
}
if (!calling_convention_allows_zig_types(cc)) {
// A simplistic and desperate attempt at making the compiler respect the
// target ABI for return types.
// This is just enough to avoid miscompiling the test suite, it will be
// better in stage2.
ZigType *int_type = return_type->id == ZigTypeIdInt ? return_type :
return_type->id == ZigTypeIdEnum ? return_type->data.enumeration.tag_int_type :
nullptr;
if (int_type != nullptr) {
const bool is_signed = int_type->data.integral.is_signed;
const uint32_t bit_width = int_type->data.integral.bit_count;
bool should_extend = false;
// Rough equivalent of Clang's isPromotableIntegerType.
switch (bit_width) {
case 1: // bool
case 8: // {un,}signed char
case 16: // {un,}signed short
should_extend = true;
break;
default:
break;
}
switch (g->zig_target->arch) {
case ZigLLVM_sparcv9:
case ZigLLVM_riscv64:
case ZigLLVM_ppc64:
case ZigLLVM_ppc64le:
// Always extend to the register width.
should_extend = bit_width < 64;
break;
default:
break;
}
// {zero,sign}-extend the result.
if (should_extend) {
if (is_signed)
addLLVMAttr(llvm_fn, 0, "signext");
else
addLLVMAttr(llvm_fn, 0, "zeroext");
}
}
}
if (fn->body_node != nullptr) {
maybe_export_dll(g, llvm_fn, linkage);