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carbon-lang/toolchain/lower/handle_call.cpp
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Richard Smith 246ec785df Add support for converting between integer types (#4753) 
Add a builtin `"int.convert"` supporting unchecked conversions between
different integer types. This performs a truncation, zero-extension, or
sign-extension, depending on the widths of the operands and the
signedness of the source type. Add explicit `As` support to the prelude.
No implicit conversions are supported yet as we don't have a way to
express the constraint that we can only implicitly convert to wider
types.
2025-01-08 08:25:20 +00:00

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// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "llvm/IR/Type.h"
#include "llvm/IR/Value.h"
#include "toolchain/lower/function_context.h"
#include "toolchain/sem_ir/builtin_function_kind.h"
#include "toolchain/sem_ir/ids.h"
#include "toolchain/sem_ir/typed_insts.h"
namespace Carbon::Lower {
// Get the predicate to use for an `icmp` instruction generated for the
// specified builtin.
static auto GetBuiltinICmpPredicate(SemIR::BuiltinFunctionKind builtin_kind,
bool is_signed)
-> llvm::CmpInst::Predicate {
switch (builtin_kind) {
case SemIR::BuiltinFunctionKind::IntEq:
case SemIR::BuiltinFunctionKind::BoolEq:
return llvm::CmpInst::ICMP_EQ;
case SemIR::BuiltinFunctionKind::IntNeq:
case SemIR::BuiltinFunctionKind::BoolNeq:
return llvm::CmpInst::ICMP_NE;
case SemIR::BuiltinFunctionKind::IntLess:
return is_signed ? llvm::CmpInst::ICMP_SLT : llvm::CmpInst::ICMP_ULT;
case SemIR::BuiltinFunctionKind::IntLessEq:
return is_signed ? llvm::CmpInst::ICMP_SLE : llvm::CmpInst::ICMP_ULE;
case SemIR::BuiltinFunctionKind::IntGreater:
return is_signed ? llvm::CmpInst::ICMP_SGT : llvm::CmpInst::ICMP_UGT;
case SemIR::BuiltinFunctionKind::IntGreaterEq:
return is_signed ? llvm::CmpInst::ICMP_SGE : llvm::CmpInst::ICMP_UGE;
default:
CARBON_FATAL("Unexpected builtin kind {0}", builtin_kind);
}
}
// Get the predicate to use for an `fcmp` instruction generated for the
// specified builtin.
static auto GetBuiltinFCmpPredicate(SemIR::BuiltinFunctionKind builtin_kind)
-> llvm::CmpInst::Predicate {
switch (builtin_kind) {
case SemIR::BuiltinFunctionKind::FloatEq:
return llvm::CmpInst::FCMP_OEQ;
case SemIR::BuiltinFunctionKind::FloatNeq:
return llvm::CmpInst::FCMP_ONE;
case SemIR::BuiltinFunctionKind::FloatLess:
return llvm::CmpInst::FCMP_OLT;
case SemIR::BuiltinFunctionKind::FloatLessEq:
return llvm::CmpInst::FCMP_OLE;
case SemIR::BuiltinFunctionKind::FloatGreater:
return llvm::CmpInst::FCMP_OGT;
case SemIR::BuiltinFunctionKind::FloatGreaterEq:
return llvm::CmpInst::FCMP_OGE;
default:
CARBON_FATAL("Unexpected builtin kind {0}", builtin_kind);
}
}
// Returns whether the specified instruction has a signed integer type.
static auto IsSignedInt(FunctionContext& context, SemIR::InstId int_id)
-> bool {
return context.sem_ir().types().IsSignedInt(
context.sem_ir().insts().Get(int_id).type_id());
}
// Creates a zext or sext instruction depending on the signedness of the
// operand.
static auto CreateExt(FunctionContext& context, llvm::Value* value,
llvm::Type* type, bool is_signed,
const llvm::Twine& name = "") -> llvm::Value* {
return is_signed ? context.builder().CreateSExt(value, type, name)
: context.builder().CreateZExt(value, type, name);
}
// Creates a zext, sext, or trunc instruction depending on the signedness of the
// operand.
static auto CreateExtOrTrunc(FunctionContext& context, llvm::Value* value,
llvm::Type* type, bool is_signed,
const llvm::Twine& name = "") -> llvm::Value* {
return is_signed ? context.builder().CreateSExtOrTrunc(value, type, name)
: context.builder().CreateZExtOrTrunc(value, type, name);
}
// Handles a call to a builtin integer bit shift operator.
static auto HandleIntShift(FunctionContext& context, SemIR::InstId inst_id,
llvm::Instruction::BinaryOps bin_op,
SemIR::InstId lhs_id, SemIR::InstId rhs_id) -> void {
llvm::Value* lhs = context.GetValue(lhs_id);
llvm::Value* rhs = context.GetValue(rhs_id);
// Weirdly, LLVM requires the operands of bit shift operators to be of the
// same type. We can always use the width of the LHS, because if the RHS
// doesn't fit in that then the cast is out of range anyway. Zero-extending is
// always fine because it's an error for the RHS to be negative.
//
// TODO: In a development build we should trap if the RHS is signed and
// negative or greater than or equal to the number of bits in the left-hand
// type.
rhs = context.builder().CreateZExtOrTrunc(rhs, lhs->getType(), "rhs");
context.SetLocal(inst_id, context.builder().CreateBinOp(bin_op, lhs, rhs));
}
// Handles a call to a builtin integer comparison operator.
static auto HandleIntComparison(FunctionContext& context, SemIR::InstId inst_id,
SemIR::BuiltinFunctionKind builtin_kind,
SemIR::InstId lhs_id, SemIR::InstId rhs_id)
-> void {
llvm::Value* lhs = context.GetValue(lhs_id);
llvm::Value* rhs = context.GetValue(rhs_id);
const auto* lhs_type = cast<llvm::IntegerType>(lhs->getType());
const auto* rhs_type = cast<llvm::IntegerType>(rhs->getType());
// We perform a signed comparison if either operand is signed.
bool lhs_signed = IsSignedInt(context, lhs_id);
bool rhs_signed = IsSignedInt(context, rhs_id);
bool cmp_signed = lhs_signed || rhs_signed;
// Compute the width for the comparison. This is the smallest width that
// fits both types, after widening them to include a sign bit if
// necessary.
auto width_for_cmp = [&](const llvm::IntegerType* type, bool is_signed) {
unsigned width = type->getBitWidth();
if (!is_signed && cmp_signed) {
// We're performing a signed comparison but this input is unsigned.
// Widen it by at least one bit to provide a sign bit.
++width;
}
return width;
};
// TODO: This might be an awkward size, such as 33 or 65 bits, for a
// signed/unsigned comparison. Would it be better to round this up to a
// "nicer" bit width?
unsigned cmp_width = std::max(width_for_cmp(lhs_type, lhs_signed),
width_for_cmp(rhs_type, rhs_signed));
auto* cmp_type = llvm::IntegerType::get(context.llvm_context(), cmp_width);
// Widen the operands as needed.
lhs = CreateExt(context, lhs, cmp_type, lhs_signed, "lhs");
rhs = CreateExt(context, rhs, cmp_type, rhs_signed, "rhs");
context.SetLocal(
inst_id,
context.builder().CreateICmp(
GetBuiltinICmpPredicate(builtin_kind, cmp_signed), lhs, rhs));
}
// Handles a call to a builtin function.
static auto HandleBuiltinCall(FunctionContext& context, SemIR::InstId inst_id,
SemIR::BuiltinFunctionKind builtin_kind,
llvm::ArrayRef<SemIR::InstId> arg_ids) -> void {
// TODO: Consider setting this to true in the performance build mode if the
// result type is a signed integer type.
constexpr bool SignedOverflowIsUB = false;
// TODO: Move the instruction names here into InstNamer.
switch (builtin_kind) {
case SemIR::BuiltinFunctionKind::None:
CARBON_FATAL("No callee in function call.");
case SemIR::BuiltinFunctionKind::PrintChar: {
auto* i32_type = llvm::IntegerType::getInt32Ty(context.llvm_context());
llvm::Value* arg_value = context.builder().CreateSExtOrTrunc(
context.GetValue(arg_ids[0]), i32_type);
auto putchar = context.llvm_module().getOrInsertFunction(
"putchar", i32_type, i32_type);
auto* result = context.builder().CreateCall(putchar, {arg_value});
context.SetLocal(
inst_id,
context.builder().CreateSExtOrTrunc(
result, context.GetType(
context.sem_ir().insts().Get(inst_id).type_id())));
return;
}
case SemIR::BuiltinFunctionKind::PrintInt: {
auto* i32_type = llvm::IntegerType::getInt32Ty(context.llvm_context());
auto* ptr_type = llvm::PointerType::get(context.llvm_context(), 0);
auto* printf_type = llvm::FunctionType::get(i32_type, {ptr_type},
/*isVarArg=*/true);
llvm::FunctionCallee printf =
context.llvm_module().getOrInsertFunction("printf", printf_type);
llvm::Value* format_string =
context.builder().CreateGlobalString("%d\n", "printf.int.format");
llvm::Value* arg_value = context.builder().CreateSExtOrTrunc(
context.GetValue(arg_ids[0]), i32_type);
context.SetLocal(inst_id, context.builder().CreateCall(
printf, {format_string, arg_value}));
return;
}
case SemIR::BuiltinFunctionKind::ReadChar: {
auto* i32_type = llvm::IntegerType::getInt32Ty(context.llvm_context());
auto getchar =
context.llvm_module().getOrInsertFunction("getchar", i32_type);
auto* result = context.builder().CreateCall(getchar, {});
context.SetLocal(
inst_id,
context.builder().CreateSExtOrTrunc(
result, context.GetType(
context.sem_ir().insts().Get(inst_id).type_id())));
return;
}
case SemIR::BuiltinFunctionKind::BoolMakeType:
case SemIR::BuiltinFunctionKind::FloatMakeType:
case SemIR::BuiltinFunctionKind::IntLiteralMakeType:
case SemIR::BuiltinFunctionKind::IntMakeTypeSigned:
case SemIR::BuiltinFunctionKind::IntMakeTypeUnsigned:
context.SetLocal(inst_id, context.GetTypeAsValue());
return;
case SemIR::BuiltinFunctionKind::IntConvert: {
context.SetLocal(
inst_id,
CreateExtOrTrunc(
context, context.GetValue(arg_ids[0]),
context.GetType(context.sem_ir().insts().Get(inst_id).type_id()),
IsSignedInt(context, arg_ids[0])));
return;
}
case SemIR::BuiltinFunctionKind::IntSNegate: {
// Lower `-x` as `0 - x`.
auto* operand = context.GetValue(arg_ids[0]);
context.SetLocal(
inst_id,
context.builder().CreateSub(
llvm::ConstantInt::getNullValue(operand->getType()), operand, "",
/*HasNUW=*/false,
/*HasNSW=*/SignedOverflowIsUB));
return;
}
case SemIR::BuiltinFunctionKind::IntUNegate: {
// Lower `-x` as `0 - x`.
auto* operand = context.GetValue(arg_ids[0]);
context.SetLocal(
inst_id,
context.builder().CreateSub(
llvm::ConstantInt::getNullValue(operand->getType()), operand));
return;
}
case SemIR::BuiltinFunctionKind::IntComplement: {
// Lower `^x` as `-1 ^ x`.
auto* operand = context.GetValue(arg_ids[0]);
context.SetLocal(
inst_id,
context.builder().CreateXor(
llvm::ConstantInt::getSigned(operand->getType(), -1), operand));
return;
}
case SemIR::BuiltinFunctionKind::IntSAdd: {
context.SetLocal(
inst_id, context.builder().CreateAdd(context.GetValue(arg_ids[0]),
context.GetValue(arg_ids[1]), "",
/*HasNUW=*/false,
/*HasNSW=*/SignedOverflowIsUB));
return;
}
case SemIR::BuiltinFunctionKind::IntSSub: {
context.SetLocal(
inst_id, context.builder().CreateSub(context.GetValue(arg_ids[0]),
context.GetValue(arg_ids[1]), "",
/*HasNUW=*/false,
/*HasNSW=*/SignedOverflowIsUB));
return;
}
case SemIR::BuiltinFunctionKind::IntSMul: {
context.SetLocal(
inst_id, context.builder().CreateMul(context.GetValue(arg_ids[0]),
context.GetValue(arg_ids[1]), "",
/*HasNUW=*/false,
/*HasNSW=*/SignedOverflowIsUB));
return;
}
case SemIR::BuiltinFunctionKind::IntSDiv: {
context.SetLocal(
inst_id, context.builder().CreateSDiv(context.GetValue(arg_ids[0]),
context.GetValue(arg_ids[1])));
return;
}
case SemIR::BuiltinFunctionKind::IntSMod: {
context.SetLocal(
inst_id, context.builder().CreateSRem(context.GetValue(arg_ids[0]),
context.GetValue(arg_ids[1])));
return;
}
case SemIR::BuiltinFunctionKind::IntUAdd: {
context.SetLocal(
inst_id, context.builder().CreateAdd(context.GetValue(arg_ids[0]),
context.GetValue(arg_ids[1])));
return;
}
case SemIR::BuiltinFunctionKind::IntUSub: {
context.SetLocal(
inst_id, context.builder().CreateSub(context.GetValue(arg_ids[0]),
context.GetValue(arg_ids[1])));
return;
}
case SemIR::BuiltinFunctionKind::IntUMul: {
context.SetLocal(
inst_id, context.builder().CreateMul(context.GetValue(arg_ids[0]),
context.GetValue(arg_ids[1])));
return;
}
case SemIR::BuiltinFunctionKind::IntUDiv: {
context.SetLocal(
inst_id, context.builder().CreateUDiv(context.GetValue(arg_ids[0]),
context.GetValue(arg_ids[1])));
return;
}
case SemIR::BuiltinFunctionKind::IntUMod: {
context.SetLocal(
inst_id, context.builder().CreateURem(context.GetValue(arg_ids[0]),
context.GetValue(arg_ids[1])));
return;
}
case SemIR::BuiltinFunctionKind::IntAnd: {
context.SetLocal(
inst_id, context.builder().CreateAnd(context.GetValue(arg_ids[0]),
context.GetValue(arg_ids[1])));
return;
}
case SemIR::BuiltinFunctionKind::IntOr: {
context.SetLocal(
inst_id, context.builder().CreateOr(context.GetValue(arg_ids[0]),
context.GetValue(arg_ids[1])));
return;
}
case SemIR::BuiltinFunctionKind::IntXor: {
context.SetLocal(
inst_id, context.builder().CreateXor(context.GetValue(arg_ids[0]),
context.GetValue(arg_ids[1])));
return;
}
case SemIR::BuiltinFunctionKind::IntLeftShift: {
HandleIntShift(context, inst_id, llvm::Instruction::Shl, arg_ids[0],
arg_ids[1]);
return;
}
case SemIR::BuiltinFunctionKind::IntRightShift: {
HandleIntShift(context, inst_id,
IsSignedInt(context, inst_id) ? llvm::Instruction::AShr
: llvm::Instruction::LShr,
arg_ids[0], arg_ids[1]);
return;
}
case SemIR::BuiltinFunctionKind::IntEq:
case SemIR::BuiltinFunctionKind::IntNeq:
case SemIR::BuiltinFunctionKind::IntLess:
case SemIR::BuiltinFunctionKind::IntLessEq:
case SemIR::BuiltinFunctionKind::IntGreater:
case SemIR::BuiltinFunctionKind::IntGreaterEq:
case SemIR::BuiltinFunctionKind::BoolEq:
case SemIR::BuiltinFunctionKind::BoolNeq: {
HandleIntComparison(context, inst_id, builtin_kind, arg_ids[0],
arg_ids[1]);
return;
}
case SemIR::BuiltinFunctionKind::FloatNegate: {
context.SetLocal(
inst_id, context.builder().CreateFNeg(context.GetValue(arg_ids[0])));
return;
}
case SemIR::BuiltinFunctionKind::FloatAdd: {
context.SetLocal(
inst_id, context.builder().CreateFAdd(context.GetValue(arg_ids[0]),
context.GetValue(arg_ids[1])));
return;
}
case SemIR::BuiltinFunctionKind::FloatSub: {
context.SetLocal(
inst_id, context.builder().CreateFSub(context.GetValue(arg_ids[0]),
context.GetValue(arg_ids[1])));
return;
}
case SemIR::BuiltinFunctionKind::FloatMul: {
context.SetLocal(
inst_id, context.builder().CreateFMul(context.GetValue(arg_ids[0]),
context.GetValue(arg_ids[1])));
return;
}
case SemIR::BuiltinFunctionKind::FloatDiv: {
context.SetLocal(
inst_id, context.builder().CreateFDiv(context.GetValue(arg_ids[0]),
context.GetValue(arg_ids[1])));
return;
}
case SemIR::BuiltinFunctionKind::FloatEq:
case SemIR::BuiltinFunctionKind::FloatNeq:
case SemIR::BuiltinFunctionKind::FloatLess:
case SemIR::BuiltinFunctionKind::FloatLessEq:
case SemIR::BuiltinFunctionKind::FloatGreater:
case SemIR::BuiltinFunctionKind::FloatGreaterEq: {
context.SetLocal(inst_id, context.builder().CreateFCmp(
GetBuiltinFCmpPredicate(builtin_kind),
context.GetValue(arg_ids[0]),
context.GetValue(arg_ids[1])));
return;
}
case SemIR::BuiltinFunctionKind::IntConvertChecked: {
// TODO: Check this statically.
CARBON_CHECK(builtin_kind.IsCompTimeOnly(
context.sem_ir(), arg_ids,
context.sem_ir().insts().Get(inst_id).type_id()));
CARBON_FATAL("Missing constant value for call to comptime-only function");
}
}
CARBON_FATAL("Unsupported builtin call.");
}
auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
SemIR::Call inst) -> void {
llvm::ArrayRef<SemIR::InstId> arg_ids =
context.sem_ir().inst_blocks().Get(inst.args_id);
auto callee_function =
SemIR::GetCalleeFunction(context.sem_ir(), inst.callee_id);
CARBON_CHECK(callee_function.function_id.is_valid());
if (auto builtin_kind = context.sem_ir()
.functions()
.Get(callee_function.function_id)
.builtin_function_kind;
builtin_kind != SemIR::BuiltinFunctionKind::None) {
HandleBuiltinCall(context, inst_id, builtin_kind, arg_ids);
return;
}
auto* callee = context.GetOrCreateFunction(
callee_function.function_id, callee_function.resolved_specific_id);
std::vector<llvm::Value*> args;
if (SemIR::ReturnTypeInfo::ForType(context.sem_ir(), inst.type_id)
.has_return_slot()) {
args.push_back(context.GetValue(arg_ids.back()));
arg_ids = arg_ids.drop_back();
}
for (auto arg_id : arg_ids) {
auto arg_type_id = context.sem_ir().insts().Get(arg_id).type_id();
if (SemIR::ValueRepr::ForType(context.sem_ir(), arg_type_id).kind !=
SemIR::ValueRepr::None) {
args.push_back(context.GetValue(arg_id));
}
}
context.SetLocal(inst_id, context.builder().CreateCall(callee, args));
}
} // namespace Carbon::Lower
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