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/* TargetABI implementation for x86-64.
* Written for LDC by Frits van Bommel in 2009.
*
* extern(C) implements the C calling convention for x86-64, as found in
* http://www.x86-64.org/documentation/abi-0.99.pdf
*
* Note:
* Where a discrepancy was found between llvm-gcc and the ABI documentation,
* llvm-gcc behavior was used for compatibility (after it was verified that
* regular gcc has the same behavior).
*
* LLVM gets it right for most types, but complex numbers and structs need some
* help. To make sure it gets those right we essentially bitcast small structs
* to a type to which LLVM assigns the appropriate registers, and pass that
* instead. Structs that are required to be passed in memory are explicitly
* marked with the ByVal attribute to ensure no part of them ends up in
* registers when only a subset of the desired registers are available.
*
* We don't perform the same transformation for D-specific types that contain
* multiple parts, such as dynamic arrays and delegates. They're passed as if
* the parts were passed as separate parameters. This helps make things like
* printf("%.*s", o.toString()) work as expected; if we didn't do this that
* wouldn't work if there were 4 other integer/pointer arguments before the
* toString() call because the string got bumped to memory with one integer
* register still free. Keeping it untransformed puts the length in a register
* and the pointer in memory, as printf expects it.
*/
#include "mtype.h"
#include "declaration.h"
#include "aggregate.h"
#include "gen/irstate.h"
#include "gen/llvm.h"
#include "gen/tollvm.h"
#include "gen/logger.h"
#include "gen/dvalue.h"
#include "gen/llvmhelpers.h"
#include "gen/abi.h"
#include "gen/abi-x86-64.h"
#include "gen/abi-generic.h"
#include "ir/irfunction.h"
#include <cassert>
#include <map>
#include <string>
#include <utility>
// Implementation details for extern(C)
namespace {
/**
* This function helps filter out things that look like structs to C,
* but should be passed to C in separate arguments anyway.
*
* (e.g. dynamic arrays are passed as separate length and ptr. This
* is both less work and makes printf("%.*s", o.toString()) work)
*/
inline bool keepUnchanged(Type* t) {
switch (t->ty) {
case Tarray: // dynamic array
case Taarray: // assoc array
case Tdelegate:
return true;
default:
return false;
}
}
enum ArgClass {
Integer, Sse, SseUp, X87, X87Up, ComplexX87, NoClass, Memory
};
struct Classification {
bool isMemory;
ArgClass classes[2];
Classification() : isMemory(false) {
classes[0] = NoClass;
classes[1] = NoClass;
}
void addField(unsigned offset, ArgClass cl) {
if (isMemory)
return;
// Note that we don't need to bother checking if it crosses 8 bytes.
// We don't get here with unaligned fields, and anything that can be
// big enough to cross 8 bytes (cdoubles, reals, structs and arrays)
// is special-cased in classifyType()
int idx = (offset < 8 ? 0 : 1);
ArgClass nw = merge(classes[idx], cl);
if (nw != classes[idx]) {
classes[idx] = nw;
if (nw == Memory) {
classes[1-idx] = Memory;
isMemory = true;
}
}
}
private:
ArgClass merge(ArgClass accum, ArgClass cl) {
if (accum == cl)
return accum;
if (accum == NoClass)
return cl;
if (cl == NoClass)
return accum;
if (accum == Memory || cl == Memory)
return Memory;
if (accum == Integer || cl == Integer)
return Integer;
if (accum == X87 || accum == X87Up || accum == ComplexX87 ||
cl == X87 || cl == X87Up || cl == ComplexX87)
return Memory;
return Sse;
}
};
void classifyType(Classification& accum, Type* ty, d_uns64 offset) {
if (Logger::enabled())
Logger::cout() << "Classifying " << ty->toChars() << " @ " << offset << '\n';
ty = ty->toBasetype();
if (ty->isintegral() || ty->ty == Tpointer) {
accum.addField(offset, Integer);
} else if (ty->ty == Tfloat80 || ty->ty == Timaginary80) {
accum.addField(offset, X87);
accum.addField(offset+8, X87Up);
} else if (ty->ty == Tcomplex80) {
accum.addField(offset, ComplexX87);
// make sure other half knows about it too:
accum.addField(offset+16, ComplexX87);
} else if (ty->ty == Tcomplex64) {
accum.addField(offset, Sse);
accum.addField(offset+8, Sse);
} else if (ty->ty == Tcomplex32) {
accum.addField(offset, Sse);
accum.addField(offset+4, Sse);
} else if (ty->isfloating()) {
accum.addField(offset, Sse);
} else if (ty->size() > 16 || hasUnalignedFields(ty)) {
// This isn't creal, yet is > 16 bytes, so pass in memory.
// Must be after creal case but before arrays and structs,
// the other types that can get bigger than 16 bytes
accum.addField(offset, Memory);
} else if (ty->ty == Tsarray) {
Type* eltType = ty->nextOf();
d_uns64 eltsize = eltType->size();
if (eltsize > 0) {
d_uns64 dim = ty->size() / eltsize;
assert(dim <= 16
&& "Array of non-empty type <= 16 bytes but > 16 elements?");
for (d_uns64 i = 0; i < dim; i++) {
classifyType(accum, eltType, offset);
offset += eltsize;
}
}
} else if (ty->ty == Tstruct) {
Array* fields = &static_cast<TypeStruct*>(ty)->sym->fields;
for (size_t i = 0; i < fields->dim; i++) {
VarDeclaration* field = static_cast<VarDeclaration*>(fields->data[i]);
classifyType(accum, field->type, offset + field->offset);
}
} else {
if (Logger::enabled())
Logger::cout() << "x86-64 ABI: Implicitly handled type: "
<< ty->toChars() << '\n';
// arrays, delegates, etc. (pointer-sized fields, <= 16 bytes)
assert(offset == 0 || offset == 8
&& "must be aligned and doesn't fit otherwise");
assert(ty->size() % 8 == 0 && "Not a multiple of pointer size?");
accum.addField(offset, Integer);
if (ty->size() > 8)
accum.addField(offset+8, Integer);
}
}
Classification classify(Type* ty) {
typedef std::map<Type*, Classification> ClassMap;
static ClassMap cache;
ClassMap::iterator it = cache.find(ty);
if (it != cache.end()) {
return it->second;
} else {
Classification cl;
classifyType(cl, ty, 0);
cache[ty] = cl;
return cl;
}
}
/// Returns the type to pass as, or null if no transformation is needed.
LLType* getAbiType(Type* ty) {
ty = ty->toBasetype();
// First, check if there's any need of a transformation:
if (keepUnchanged(ty))
return 0;
if (ty->ty != Tcomplex32 && ty->ty != Tstruct)
return 0; // Nothing to do,
Classification cl = classify(ty);
assert(!cl.isMemory);
if (cl.classes[0] == NoClass) {
assert(cl.classes[1] == NoClass && "Non-empty struct with empty first half?");
return 0; // Empty structs should also be handled correctly by LLVM
}
// Okay, we may need to transform. Figure out a canonical type:
std::vector<LLType*> parts;
unsigned size = ty->size();
switch (cl.classes[0]) {
case Integer: {
unsigned bits = (size >= 8 ? 64 : (size * 8));
parts.push_back(LLIntegerType::get(gIR->context(), bits));
break;
}
case Sse:
parts.push_back(size <= 4 ? LLType::getFloatTy(gIR->context()) : LLType::getDoubleTy(gIR->context()));
break;
case X87:
assert(cl.classes[1] == X87Up && "Upper half of real not X87Up?");
/// The type only contains a single real/ireal field,
/// so just use that type.
return const_cast<LLType*>(LLType::getX86_FP80Ty(gIR->context()));
default:
assert(0 && "Unanticipated argument class");
}
switch(cl.classes[1]) {
case NoClass:
assert(parts.size() == 1);
// No need to use a single-element struct type.
// Just use the element type instead.
return const_cast<LLType*>(parts[0]);
break;
case Integer: {
assert(size > 8);
unsigned bits = (size - 8) * 8;
parts.push_back(LLIntegerType::get(gIR->context(), bits));
break;
}
case Sse:
parts.push_back(size <= 12 ? LLType::getFloatTy(gIR->context()) : LLType::getDoubleTy(gIR->context()));
break;
case X87Up:
if(cl.classes[0] == X87) {
// This won't happen: it was short-circuited while
// processing the first half.
} else {
// I can't find this anywhere in the ABI documentation,
// but this is what gcc does (both regular and llvm-gcc).
// (This triggers for types like union { real r; byte b; })
parts.push_back(LLType::getDoubleTy(gIR->context()));
}
break;
default:
assert(0 && "Unanticipated argument class for second half");
}
return LLStructType::get(gIR->context(), parts);
}
}
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
/// Just store to memory and it's readable as the other type.
struct X86_64_C_struct_rewrite : ABIRewrite {
// Get struct from ABI-mangled representation
LLValue* get(Type* dty, DValue* v)
{
LLValue* lval;
if (v->isLVal()) {
lval = v->getLVal();
} else {
// No memory location, create one.
LLValue* rval = v->getRVal();
lval = DtoRawAlloca(rval->getType(), 0);
DtoStore(rval, lval);
}
LLType* pTy = getPtrToType(DtoType(dty));
return DtoLoad(DtoBitCast(lval, pTy), "get-result");
}
// Get struct from ABI-mangled representation, and store in the provided location.
void getL(Type* dty, DValue* v, llvm::Value* lval) {
LLValue* rval = v->getRVal();
LLType* pTy = getPtrToType(rval->getType());
DtoStore(rval, DtoBitCast(lval, pTy));
}
// Turn a struct into an ABI-mangled representation
LLValue* put(Type* dty, DValue* v)
{
LLValue* lval;
if (v->isLVal()) {
lval = v->getLVal();
} else {
// No memory location, create one.
LLValue* rval = v->getRVal();
lval = DtoRawAlloca(rval->getType(), 0);
DtoStore(rval, lval);
}
LLType* abiTy = getAbiType(dty);
assert(abiTy && "Why are we rewriting a non-rewritten type?");
LLType* pTy = getPtrToType(abiTy);
return DtoLoad(DtoBitCast(lval, pTy), "put-result");
}
/// should return the transformed type for this rewrite
LLType* type(Type* dty, LLType* t)
{
return getAbiType(dty);
}
};
struct RegCount {
unsigned char int_regs, sse_regs;
};
struct X86_64TargetABI : TargetABI {
X86_64_C_struct_rewrite struct_rewrite;
X87_complex_swap swapComplex;
CompositeToInt compositeToInt;
void newFunctionType(TypeFunction* tf) {
funcTypeStack.push_back(FuncTypeData(tf->linkage));
}
bool returnInArg(TypeFunction* tf);
bool passByVal(Type* t);
void rewriteFunctionType(TypeFunction* tf);
void doneWithFunctionType() {
funcTypeStack.pop_back();
}
private:
struct FuncTypeData {
LINK linkage; // Linkage of the function type currently under construction
RegCount state; // bookkeeping for extern(C) parameter registers
FuncTypeData(LINK linkage_)
: linkage(linkage_)
{
state.int_regs = 6;
state.sse_regs = 8;
}
};
std::vector<FuncTypeData> funcTypeStack;
LINK linkage() {
assert(funcTypeStack.size() != 0);
return funcTypeStack.back().linkage;
}
RegCount& state() {
assert(funcTypeStack.size() != 0);
return funcTypeStack.back().state;
}
void fixup(IrFuncTyArg& arg);
};
// The public getter for abi.cpp
TargetABI* getX86_64TargetABI() {
return new X86_64TargetABI;
}
bool X86_64TargetABI::returnInArg(TypeFunction* tf) {
assert(linkage() == tf->linkage);
Type* rt = tf->next->toBasetype();
if (tf->linkage == LINKd) {
#if DMDV2
if (tf->isref)
return false;
#endif
// All non-structs can be returned in registers.
return (rt->ty == Tstruct);
} else {
if (rt == Type::tvoid || keepUnchanged(rt))
return false;
Classification cl = classify(rt);
if (cl.isMemory) {
assert(state().int_regs > 0
&& "No int registers available when determining sret-ness?");
// An sret parameter takes an integer register.
state().int_regs--;
return true;
}
return false;
}
}
bool X86_64TargetABI::passByVal(Type* t) {
t = t->toBasetype();
if (linkage() == LINKd) {
// static arrays are also passed byval
return t->ty == Tstruct || t->ty == Tsarray;
} else {
// This implements the C calling convention for x86-64.
// It might not be correct for other calling conventions.
Classification cl = classify(t);
if (cl.isMemory)
return true;
// Figure out how many registers we want for this arg:
RegCount wanted = { 0, 0 };
for (int i = 0 ; i < 2; i++) {
if (cl.classes[i] == Integer)
wanted.int_regs++;
else if (cl.classes[i] == Sse)
wanted.sse_regs++;
}
// See if they're available:
RegCount& state = this->state();
if (wanted.int_regs <= state.int_regs && wanted.sse_regs <= state.sse_regs) {
state.int_regs -= wanted.int_regs;
state.sse_regs -= wanted.sse_regs;
} else {
if (keepUnchanged(t)) {
// Not enough registers available, but this is passed as if it's
// multiple arguments. Just use the registers there are,
// automatically spilling the rest to memory.
if (wanted.int_regs > state.int_regs)
state.int_regs = 0;
else
state.int_regs -= wanted.int_regs;
if (wanted.sse_regs > state.sse_regs)
state.sse_regs = 0;
else
state.sse_regs -= wanted.sse_regs;
} else if (t->iscomplex() || t->ty == Tstruct) {
// Spill entirely to memory, even if some of the registers are
// available.
// FIXME: Don't do this if *none* of the wanted registers are available,
// (i.e. only when absolutely necessary for abi-compliance)
// so it gets alloca'd by the callee and -scalarrepl can
// more easily break it up?
// Note: this won't be necessary if the following LLVM bug gets fixed:
// http://llvm.org/bugs/show_bug.cgi?id=3741
return true;
} else {
assert(t == Type::tfloat80 || t == Type::timaginary80 || t->ty == Tsarray || t->size() <= 8
&& "What other big types are there?");
// In any case, they shouldn't be represented as structs in LLVM:
assert(!isaStruct(DtoType(t)));
}
}
// Everything else that's passed in memory is handled by LLVM.
return false;
}
}
// Helper function for rewriteFunctionType.
// Return type and parameters are passed here (unless they're already in memory)
// to get the rewrite applied (if necessary).
void X86_64TargetABI::fixup(IrFuncTyArg& arg) {
LLType* abiTy = getAbiType(arg.type);
if (abiTy && abiTy != arg.ltype) {
assert(arg.type == Type::tcomplex32 || arg.type->ty == Tstruct);
arg.ltype = abiTy;
arg.rewrite = &struct_rewrite;
}
}
void X86_64TargetABI::rewriteFunctionType(TypeFunction* tf) {
IrFuncTy& fty = tf->fty;
Type* rt = fty.ret->type->toBasetype();
if (tf->linkage == LINKd) {
// RETURN VALUE
// complex {re,im} -> {im,re}
if (rt->iscomplex())
{
Logger::println("Rewriting complex return value");
fty.ret->rewrite = &swapComplex;
}
// IMPLICIT PARAMETERS
int regcount = 6; // RDI,RSI,RDX,RCX,R8,R9
int xmmcount = 8; // XMM0..XMM7
// mark this/nested params inreg
if (fty.arg_this)
{
Logger::println("Putting 'this' in register");
fty.arg_this->attrs = llvm::Attribute::InReg;
--regcount;
}
else if (fty.arg_nest)
{
Logger::println("Putting context ptr in register");
fty.arg_nest->attrs = llvm::Attribute::InReg;
--regcount;
}
else if (IrFuncTyArg* sret = fty.arg_sret)
{
Logger::println("Putting sret ptr in register");
// sret and inreg are incompatible, but the ABI requires the
// sret parameter to be in RDI in this situation...
sret->attrs = (sret->attrs | llvm::Attribute::InReg)
& ~llvm::Attribute::StructRet;
--regcount;
}
Logger::println("x86-64 D ABI: Transforming arguments");
LOG_SCOPE;
for (IrFuncTy::ArgRIter I = fty.args.rbegin(), E = fty.args.rend(); I != E; ++I) {
IrFuncTyArg& arg = **I;
Type* ty = arg.type->toBasetype();
unsigned sz = ty->size();
if (ty->isfloating() && sz <= 8)
{
if (xmmcount > 0) {
Logger::println("Putting float parameter in register");
arg.attrs |= llvm::Attribute::InReg;
--xmmcount;
}
}
else if (regcount == 0)
{
continue;
}
else if (arg.byref && !arg.isByVal())
{
Logger::println("Putting byref parameter in register");
arg.attrs |= llvm::Attribute::InReg;
--regcount;
}
else if (ty->ty == Tpointer)
{
Logger::println("Putting pointer parameter in register");
arg.attrs |= llvm::Attribute::InReg;
--regcount;
}
else if (ty->isintegral() && sz <= 8)
{
Logger::println("Putting integral parameter in register");
arg.attrs |= llvm::Attribute::InReg;
--regcount;
}
else if ((ty->ty == Tstruct || ty->ty == Tsarray) &&
(sz == 1 || sz == 2 || sz == 4 || sz == 8))
{
Logger::println("Putting struct/sarray in register");
arg.rewrite = &compositeToInt;
arg.ltype = compositeToInt.type(arg.type, arg.ltype);
arg.byref = false;
arg.attrs = llvm::Attribute::InReg;
--regcount;
}
}
// EXPLICIT PARAMETERS
// reverse parameter order
// for non variadics
if (!fty.args.empty() && tf->varargs != 1)
{
fty.reverseParams = true;
}
} else {
// TODO: See if this is correct for more than just extern(C).
if (!fty.arg_sret) {
Logger::println("x86-64 ABI: Transforming return type");
Type* rt = fty.ret->type->toBasetype();
if (rt != Type::tvoid)
fixup(*fty.ret);
}
Logger::println("x86-64 ABI: Transforming arguments");
LOG_SCOPE;
for (IrFuncTy::ArgIter I = fty.args.begin(), E = fty.args.end(); I != E; ++I) {
IrFuncTyArg& arg = **I;
if (Logger::enabled())
Logger::cout() << "Arg: " << arg.type->toChars() << '\n';
// Arguments that are in memory are of no interest to us.
if (arg.byref)
continue;
fixup(arg);
if (Logger::enabled())
Logger::cout() << "New arg type: " << *arg.ltype << '\n';
}
}
}
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