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[Codegen_LLVM] Radically simplify visit(const Reinterpret *op) #6865

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Jul 21, 2022
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[Codegen_LLVM] Radically simplify visit(const Reinterpret *op) #6865

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56 changes: 6 additions & 50 deletions src/CodeGen_LLVM.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1478,58 +1478,14 @@ void CodeGen_LLVM::visit(const Cast *op) {

void CodeGen_LLVM::visit(const Reinterpret *op) {
Type dst = op->type;
Type src = op->value.type();
llvm::Type *llvm_dst = llvm_type_of(dst);
value = codegen(op->value);
if (src.is_handle() && !dst.is_handle()) {
internal_assert(dst.is_uint() && dst.bits() == 64);

// Handle -> UInt64
llvm::DataLayout d(module.get());
if (d.getPointerSize() == 4) {
llvm::Type *intermediate = llvm_type_of(UInt(32, dst.lanes()));
value = builder->CreatePtrToInt(value, intermediate);
value = builder->CreateZExt(value, llvm_dst);
} else if (d.getPointerSize() == 8) {
value = builder->CreatePtrToInt(value, llvm_dst);
} else {
internal_error << "Pointer size is neither 4 nor 8 bytes\n";
}

} else if (dst.is_handle() && !src.is_handle()) {
internal_assert(src.is_uint() && src.bits() == 64);

// UInt64 -> Handle
llvm::DataLayout d(module.get());
if (d.getPointerSize() == 4) {
llvm::Type *intermediate = llvm_type_of(UInt(32, src.lanes()));
value = builder->CreateTrunc(value, intermediate);
value = builder->CreateIntToPtr(value, llvm_dst);
} else if (d.getPointerSize() == 8) {
value = builder->CreateIntToPtr(value, llvm_dst);
} else {
internal_error << "Pointer size is neither 4 nor 8 bytes\n";
}

} else {
if (src.is_scalar() && dst.is_vector()) {
// If the source type is a scalar, we promote it to an
// equivalent vector of width one before doing the
// bitcast, because llvm's bitcast operator doesn't
// want to convert between scalars and vectors.
value = create_broadcast(value, 1);
}
if (src.is_vector() && dst.is_scalar()) {
// Similarly, if we're converting from a vector to a
// scalar, convert to a vector of width 1 first, and
// then extract the first lane.
llvm_dst = get_vector_type(llvm_dst, 1);
}
value = builder->CreateBitCast(value, llvm_dst);
if (src.is_vector() && dst.is_scalar()) {
value = builder->CreateExtractElement(value, (uint64_t)0);
}
}
// Our `Reinterpret` expr directly maps to LLVM IR bitcast/ptrtoint/inttoptr
// instructions with no additional handling required:
// * bitcast between vectors and scalars is well-formed.
// * ptrtoint/inttoptr implicitly truncates/zero-extends the integer
// to match the pointer size.
value = builder->CreateBitOrPointerCast(value, llvm_dst);
}

void CodeGen_LLVM::visit(const Variable *op) {
Expand Down