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stmt.cpp
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/*
Copyright (c) 2010-2014, Intel Corporation
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
* Neither the name of Intel Corporation nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/** @file stmt.cpp
@brief File with definitions classes related to statements in the language
*/
#include "stmt.h"
#include "ctx.h"
#include "util.h"
#include "expr.h"
#include "type.h"
#include "func.h"
#include "sym.h"
#include "module.h"
#include "llvmutil.h"
#include <stdio.h>
#include <map>
#if ISPC_LLVM_VERSION == ISPC_LLVM_3_2
#include <llvm/Module.h>
#include <llvm/Type.h>
#include <llvm/Instructions.h>
#include <llvm/Function.h>
#include <llvm/DerivedTypes.h>
#include <llvm/LLVMContext.h>
#include <llvm/Metadata.h>
#include <llvm/CallingConv.h>
#else
#include <llvm/IR/Module.h>
#include <llvm/IR/Type.h>
#include <llvm/IR/Instructions.h>
#include <llvm/IR/Function.h>
#include <llvm/IR/DerivedTypes.h>
#include <llvm/IR/LLVMContext.h>
#include <llvm/IR/Metadata.h>
#include <llvm/IR/CallingConv.h>
#endif
#include <llvm/Support/raw_ostream.h>
///////////////////////////////////////////////////////////////////////////
// Stmt
Stmt *
Stmt::Optimize() {
return this;
}
///////////////////////////////////////////////////////////////////////////
// ExprStmt
ExprStmt::ExprStmt(Expr *e, SourcePos p)
: Stmt(p, ExprStmtID) {
expr = e;
}
void
ExprStmt::EmitCode(FunctionEmitContext *ctx) const {
if (!ctx->GetCurrentBasicBlock())
return;
ctx->SetDebugPos(pos);
if (expr)
expr->GetValue(ctx);
}
Stmt *
ExprStmt::TypeCheck() {
return this;
}
void
ExprStmt::Print(int indent) const {
if (!expr)
return;
printf("%*c", indent, ' ');
printf("Expr stmt: ");
pos.Print();
expr->Print();
printf("\n");
}
int
ExprStmt::EstimateCost() const {
return 0;
}
///////////////////////////////////////////////////////////////////////////
// DeclStmt
DeclStmt::DeclStmt(const std::vector<VariableDeclaration> &v, SourcePos p)
: Stmt(p, DeclStmtID), vars(v) {
}
static bool
lHasUnsizedArrays(const Type *type) {
const ArrayType *at = CastType<ArrayType>(type);
if (at == NULL)
return false;
if (at->GetElementCount() == 0)
return true;
else
return lHasUnsizedArrays(at->GetElementType());
}
#ifdef ISPC_NVPTX_ENABLED
static llvm::Value* lConvertToGenericPtr(FunctionEmitContext *ctx, llvm::Value *value, const SourcePos ¤tPos, const bool variable = false)
{
if (!value->getType()->isPointerTy() || g->target->getISA() != Target::NVPTX)
return value;
llvm::PointerType *pt = llvm::dyn_cast<llvm::PointerType>(value->getType());
const int addressSpace = pt->getAddressSpace();
if (addressSpace != 3 && addressSpace != 4)
return value;
llvm::Type *elTy = pt->getElementType();
/* convert elTy addrspace(3)* to i64* addrspace(3)* */
llvm::PointerType *Int64Ptr3 = llvm::PointerType::get(LLVMTypes::Int64Type, addressSpace);
value = ctx->BitCastInst(value, Int64Ptr3, "gep2gen_cast1");
/* convert i64* addrspace(3) to i64* */
llvm::Function *__cvt2gen = m->module->getFunction(
addressSpace == 3 ? (variable ? "__cvt_loc2gen_var" : "__cvt_loc2gen") : "__cvt_const2gen");
std::vector<llvm::Value *> __cvt2gen_args;
__cvt2gen_args.push_back(value);
value = llvm::CallInst::Create(__cvt2gen, __cvt2gen_args, variable ? "gep2gen_cvt_var" : "gep2gen_cvt", ctx->GetCurrentBasicBlock());
/* compute offset */
if (addressSpace == 3)
{
assert(elTy->isArrayTy());
const int numElTot = elTy->getArrayNumElements();
const int numEl = numElTot/4;
#if 0
fprintf(stderr, " --- detected addrspace(3) sz= %d --- \n", numEl);
#endif
llvm::ArrayType *arrTy = llvm::dyn_cast<llvm::ArrayType>(pt->getArrayElementType());
assert(arrTy != NULL);
llvm::Type *arrElTy = arrTy->getElementType();
#if 0
if (arrElTy->isArrayTy())
Error(currentPos, "Currently \"nvptx\" target doesn't support array-of-array");
#endif
/* convert i64* to errElTy* */
llvm::PointerType *arrElTyPt0 = llvm::PointerType::get(arrElTy, 0);
value = ctx->BitCastInst(value, arrElTyPt0, "gep2gen_cast2");
llvm::Function *func_warp_index = m->module->getFunction("__warp_index");
llvm::Value *warpId = ctx->CallInst(func_warp_index, NULL, std::vector<llvm::Value*>(), "gep2gen_warp_index");
llvm::Value *offset = ctx->BinaryOperator(llvm::Instruction::Mul, warpId, LLVMInt32(numEl), "gep2gen_offset");
#if ISPC_LLVM_VERSION <= ISPC_LLVM_3_6
value = llvm::GetElementPtrInst::Create(value, offset, "gep2gen_offset", ctx->GetCurrentBasicBlock());
#else
value = llvm::GetElementPtrInst::Create(NULL, value, offset, "gep2gen_offset", ctx->GetCurrentBasicBlock());
#endif
}
/* convert arrElTy* to elTy* */
llvm::PointerType *elTyPt0 = llvm::PointerType::get(elTy, 0);
value = ctx->BitCastInst(value, elTyPt0, "gep2gen_cast3");
return value;
}
#endif /* ISPC_NVPTX_ENABLED */
void
DeclStmt::EmitCode(FunctionEmitContext *ctx) const {
if (!ctx->GetCurrentBasicBlock())
return;
for (unsigned int i = 0; i < vars.size(); ++i) {
Symbol *sym = vars[i].sym;
AssertPos(pos, sym != NULL);
if (sym->type == NULL)
continue;
Expr *initExpr = vars[i].init;
// Now that we're in the thick of emitting code, it's easy for us
// to find out the level of nesting of varying control flow we're
// in at this declaration. So we can finally set that
// Symbol::varyingCFDepth variable.
// @todo It's disgusting to be doing this here.
sym->varyingCFDepth = ctx->VaryingCFDepth();
ctx->SetDebugPos(sym->pos);
// If it's an array that was declared without a size but has an
// initializer list, then use the number of elements in the
// initializer list to finally set the array's size.
sym->type = ArrayType::SizeUnsizedArrays(sym->type, initExpr);
if (sym->type == NULL)
continue;
if (lHasUnsizedArrays(sym->type)) {
Error(pos, "Illegal to declare an unsized array variable without "
"providing an initializer expression to set its size.");
continue;
}
// References must have initializer expressions as well.
if (IsReferenceType(sym->type) == true) {
if (initExpr == NULL) {
Error(sym->pos, "Must provide initializer for reference-type "
"variable \"%s\".", sym->name.c_str());
continue;
}
if (IsReferenceType(initExpr->GetType()) == false) {
const Type *initLVType = initExpr->GetLValueType();
if (initLVType == NULL) {
Error(initExpr->pos, "Initializer for reference-type variable "
"\"%s\" must have an lvalue type.", sym->name.c_str());
continue;
}
if (initLVType->IsUniformType() == false) {
Error(initExpr->pos, "Initializer for reference-type variable "
"\"%s\" must have a uniform lvalue type.", sym->name.c_str());
continue;
}
}
}
llvm::Type *llvmType = sym->type->LLVMType(g->ctx);
if (llvmType == NULL) {
AssertPos(pos, m->errorCount > 0);
return;
}
if (sym->storageClass == SC_STATIC) {
#ifdef ISPC_NVPTX_ENABLED
if (g->target->getISA() == Target::NVPTX && !sym->type->IsConstType())
{
Error(sym->pos,
"Non-constant static variable ""\"%s\" is not supported with ""\"nvptx\" target.",
sym->name.c_str());
return;
}
if (g->target->getISA() == Target::NVPTX && sym->type->IsVaryingType())
PerformanceWarning(sym->pos,
"\"const static varying\" variable ""\"%s\" is stored in __global address space with ""\"nvptx\" target.",
sym->name.c_str());
if (g->target->getISA() == Target::NVPTX && sym->type->IsUniformType())
PerformanceWarning(sym->pos,
"\"const static uniform\" variable ""\"%s\" is stored in __constant address space with ""\"nvptx\" target.",
sym->name.c_str());
#endif /* ISPC_NVPTX_ENABLED */
// For static variables, we need a compile-time constant value
// for its initializer; if there's no initializer, we use a
// zero value.
llvm::Constant *cinit = NULL;
if (initExpr != NULL) {
if (PossiblyResolveFunctionOverloads(initExpr, sym->type) == false)
continue;
// FIXME: we only need this for function pointers; it was
// already done for atomic types and enums in
// DeclStmt::TypeCheck()...
if (llvm::dyn_cast<ExprList>(initExpr) == NULL) {
initExpr = TypeConvertExpr(initExpr, sym->type,
"initializer");
// FIXME: and this is only needed to re-establish
// constant-ness so that GetConstant below works for
// constant artithmetic expressions...
initExpr = ::Optimize(initExpr);
}
cinit = initExpr->GetConstant(sym->type);
if (cinit == NULL)
Error(initExpr->pos, "Initializer for static variable "
"\"%s\" must be a constant.", sym->name.c_str());
}
if (cinit == NULL)
cinit = llvm::Constant::getNullValue(llvmType);
// Allocate space for the static variable in global scope, so
// that it persists across function calls
#ifdef ISPC_NVPTX_ENABLED
int addressSpace = 0;
if (g->target->getISA() == Target::NVPTX &&
sym->type->IsConstType() &&
sym->type->IsUniformType())
addressSpace = 4;
sym->storagePtr =
new llvm::GlobalVariable(*m->module, llvmType,
sym->type->IsConstType(),
llvm::GlobalValue::InternalLinkage, cinit,
llvm::Twine("static.") +
llvm::Twine(sym->pos.first_line) +
llvm::Twine(".") + sym->name.c_str(),
NULL,
llvm::GlobalVariable::NotThreadLocal,
addressSpace);
sym->storagePtr = lConvertToGenericPtr(ctx, sym->storagePtr, sym->pos);
#else /* ISPC_NVPTX_ENABLED */
sym->storagePtr =
new llvm::GlobalVariable(*m->module, llvmType,
sym->type->IsConstType(),
llvm::GlobalValue::InternalLinkage, cinit,
llvm::Twine("static.") +
llvm::Twine(sym->pos.first_line) +
llvm::Twine(".") + sym->name.c_str());
#endif /* ISPC_NVPTX_ENABLED */
// Tell the FunctionEmitContext about the variable
ctx->EmitVariableDebugInfo(sym);
}
#ifdef ISPC_NVPTX_ENABLED
else if ((sym->type->IsUniformType() || sym->type->IsSOAType()) &&
/* NVPTX:
* only non-constant uniform data types are stored in shared memory
* constant uniform are automatically promoted to varying
*/
!sym->type->IsConstType() &&
#if 1
sym->type->IsArrayType() &&
#endif
g->target->getISA() == Target::NVPTX)
{
PerformanceWarning(sym->pos,
"Non-constant \"uniform\" data types might be slow with \"nvptx\" target. "
"Unless data sharing between program instances is desired, try \"const [static] uniform\", \"varying\" or \"uniform new uniform \"+\"delete\" if possible.");
/* with __shared__ memory everything must be an array */
int nel = 4;
ArrayType *nat;
bool variable = true;
if (sym->type->IsArrayType())
{
const ArrayType *at = CastType<ArrayType>(sym->type);
/* we must scale # elements by 4, because a thread-block will run 4 warps
* or 128 threads.
* ***note-to-me***:please define these value (128threads/4warps)
* in nvptx-target definition
* instead of compile-time constants
*/
nel *= at->GetElementCount();
if (sym->type->IsSOAType())
nel *= sym->type->GetSOAWidth();
nat = new ArrayType(at->GetElementType(), nel);
variable = false;
}
else
nat = new ArrayType(sym->type, nel);
llvm::Type *llvmTypeUn = nat->LLVMType(g->ctx);
llvm::Constant *cinit = llvm::UndefValue::get(llvmTypeUn);
sym->storagePtr =
new llvm::GlobalVariable(*m->module, llvmTypeUn,
sym->type->IsConstType(),
llvm::GlobalValue::InternalLinkage,
cinit,
llvm::Twine("local_") +
llvm::Twine(sym->pos.first_line) +
llvm::Twine("_") + sym->name.c_str(),
NULL,
llvm::GlobalVariable::NotThreadLocal,
/*AddressSpace=*/3);
sym->storagePtr = lConvertToGenericPtr(ctx, sym->storagePtr, sym->pos, variable);
llvm::PointerType *ptrTy = llvm::PointerType::get(sym->type->LLVMType(g->ctx),0);
sym->storagePtr = ctx->BitCastInst(sym->storagePtr, ptrTy, "uniform_decl");
// Tell the FunctionEmitContext about the variable; must do
// this before the initializer stuff.
ctx->EmitVariableDebugInfo(sym);
if (initExpr == 0 && sym->type->IsConstType())
Error(sym->pos, "Missing initializer for const variable "
"\"%s\".", sym->name.c_str());
// And then get it initialized...
sym->parentFunction = ctx->GetFunction();
InitSymbol(sym->storagePtr, sym->type, initExpr, ctx, sym->pos);
}
#endif /* ISPC_NVPTX_ENABLED */
else
{
// For non-static variables, allocate storage on the stack
sym->storagePtr = ctx->AllocaInst(llvmType, sym->name.c_str());
// Tell the FunctionEmitContext about the variable; must do
// this before the initializer stuff.
ctx->EmitVariableDebugInfo(sym);
if (initExpr == 0 && sym->type->IsConstType())
Error(sym->pos, "Missing initializer for const variable "
"\"%s\".", sym->name.c_str());
// And then get it initialized...
sym->parentFunction = ctx->GetFunction();
InitSymbol(sym->storagePtr, sym->type, initExpr, ctx, sym->pos);
}
}
}
Stmt *
DeclStmt::Optimize() {
for (unsigned int i = 0; i < vars.size(); ++i) {
Expr *init = vars[i].init;
if (init != NULL && llvm::dyn_cast<ExprList>(init) == NULL) {
// If the variable is const-qualified, after we've optimized
// the initializer expression, see if we have a ConstExpr. If
// so, save it in Symbol::constValue where it can be used in
// optimizing later expressions that have this symbol in them.
// Note that there are cases where the expression may be
// constant but where we don't have a ConstExpr; an example is
// const arrays--the ConstExpr implementation just can't
// represent an array of values.
//
// All this is fine in terms of the code that's generated in
// the end (LLVM's constant folding stuff is good), but it
// means that the ispc compiler's ability to reason about what
// is definitely a compile-time constant for things like
// computing array sizes from non-trivial expressions is
// consequently limited.
Symbol *sym = vars[i].sym;
if (sym->type && sym->type->IsConstType() &&
Type::Equal(init->GetType(), sym->type))
sym->constValue = llvm::dyn_cast<ConstExpr>(init);
}
}
return this;
}
// Do type conversion if needed and check for not initializing array with
// another array (array assignment is not allowed).
// Do that recursively to handle brace initialization, which may contain
// another brace initialization.
static
bool checkInit(const Type *type, Expr *init) {
bool encounteredError = false;
// get the right type for stuff like const float foo = 2; so that
// the int->float type conversion is in there and we don't return
// an int as the constValue later...
if (CastType<AtomicType>(type) != NULL ||
CastType<EnumType>(type) != NULL) {
// If it's an expr list with an atomic type, we'll later issue
// an error. Need to leave vars[i].init as is in that case so
// it is in fact caught later, though.
if (llvm::dyn_cast<ExprList>(init) == NULL) {
init = TypeConvertExpr(init, type, "initializer");
if (init == NULL)
encounteredError = true;
}
} else if (CastType<ArrayType>(type) != NULL &&
llvm::dyn_cast<ExprList>(init) == NULL) {
encounteredError = true;
Error(init->pos, "Array initializer must be an initializer list");
} else if (CastType<StructType>(type) != NULL &&
llvm::dyn_cast<ExprList>(init) != NULL) {
const StructType *st = CastType<StructType>(type);
ExprList *el = llvm::dyn_cast<ExprList>(init);
int elt_count = st->GetElementCount() < el->exprs.size() ?
st->GetElementCount() : el->exprs.size();
for (int i=0; i < elt_count; i++) {
encounteredError |= checkInit(st->GetElementType(i), el->exprs[i]);
}
}
return encounteredError;
}
Stmt *
DeclStmt::TypeCheck() {
bool encounteredError = false;
for (unsigned int i = 0; i < vars.size(); ++i) {
if (vars[i].sym == NULL) {
encounteredError = true;
continue;
}
if (vars[i].init == NULL)
continue;
// Check an init.
encounteredError |= checkInit(vars[i].sym->type, vars[i].init);
}
return encounteredError ? NULL : this;
}
void
DeclStmt::Print(int indent) const {
printf("%*cDecl Stmt:", indent, ' ');
pos.Print();
for (unsigned int i = 0; i < vars.size(); ++i) {
printf("%*cVariable %s (%s)", indent+4, ' ',
vars[i].sym->name.c_str(),
vars[i].sym->type->GetString().c_str());
if (vars[i].init != NULL) {
printf(" = ");
vars[i].init->Print();
}
printf("\n");
}
printf("\n");
}
int
DeclStmt::EstimateCost() const {
return 0;
}
///////////////////////////////////////////////////////////////////////////
// IfStmt
IfStmt::IfStmt(Expr *t, Stmt *ts, Stmt *fs, bool checkCoherence, SourcePos p)
: Stmt(p, IfStmtID), test(t), trueStmts(ts), falseStmts(fs),
doAllCheck(checkCoherence &&
!g->opt.disableCoherentControlFlow) {
}
static void
lEmitIfStatements(FunctionEmitContext *ctx, Stmt *stmts, const char *trueOrFalse) {
if (!stmts)
return;
if (llvm::dyn_cast<StmtList>(stmts) == NULL)
ctx->StartScope();
ctx->AddInstrumentationPoint(trueOrFalse);
stmts->EmitCode(ctx);
if (llvm::dyn_cast<const StmtList>(stmts) == NULL)
ctx->EndScope();
}
/** Returns true if the "true" block for the if statement consists of a
single 'break' statement, and the "false" block is empty. */
/*
static bool
lCanApplyBreakOptimization(Stmt *trueStmts, Stmt *falseStmts) {
if (falseStmts != NULL) {
if (StmtList *sl = llvm::dyn_cast<StmtList>(falseStmts)) {
return (sl->stmts.size() == 0);
}
else
return false;
}
if (llvm::dyn_cast<BreakStmt>(trueStmts))
return true;
else if (StmtList *sl = llvm::dyn_cast<StmtList>(trueStmts))
return (sl->stmts.size() == 1 &&
llvm::dyn_cast<BreakStmt>(sl->stmts[0]) != NULL);
else
return false;
}
*/
void
IfStmt::EmitCode(FunctionEmitContext *ctx) const {
// First check all of the things that might happen due to errors
// earlier in compilation and bail out if needed so that we don't
// dereference NULL pointers in the below...
if (!ctx->GetCurrentBasicBlock())
return;
if (!test)
return;
const Type *testType = test->GetType();
if (!testType)
return;
ctx->SetDebugPos(pos);
bool isUniform = testType->IsUniformType();
llvm::Value *testValue = test->GetValue(ctx);
if (testValue == NULL)
return;
#ifdef ISPC_NVPTX_ENABLED
#if 0
if (!isUniform && g->target->getISA() == Target::NVPTX)
{
/* With "nvptx" target, SIMT hardware takes care of non-uniform
* control flow. We trick ISPC to generate uniform control flow.
*/
testValue = ctx->ExtractInst(testValue, 0);
isUniform = true;
}
#endif
#endif /* ISPC_NVPTX_ENABLED */
if (isUniform) {
ctx->StartUniformIf();
if (doAllCheck)
Warning(test->pos, "Uniform condition supplied to \"cif\" statement.");
// 'If' statements with uniform conditions are relatively
// straightforward. We evaluate the condition and then jump to
// either the 'then' or 'else' clause depending on its value.
llvm::BasicBlock *bthen = ctx->CreateBasicBlock("if_then");
llvm::BasicBlock *belse = ctx->CreateBasicBlock("if_else");
llvm::BasicBlock *bexit = ctx->CreateBasicBlock("if_exit");
// Jump to the appropriate basic block based on the value of
// the 'if' test
ctx->BranchInst(bthen, belse, testValue);
// Emit code for the 'true' case
ctx->SetCurrentBasicBlock(bthen);
lEmitIfStatements(ctx, trueStmts, "true");
if (ctx->GetCurrentBasicBlock())
ctx->BranchInst(bexit);
// Emit code for the 'false' case
ctx->SetCurrentBasicBlock(belse);
lEmitIfStatements(ctx, falseStmts, "false");
if (ctx->GetCurrentBasicBlock())
ctx->BranchInst(bexit);
// Set the active basic block to the newly-created exit block
// so that subsequent emitted code starts there.
ctx->SetCurrentBasicBlock(bexit);
ctx->EndIf();
}
/*
// Disabled for performance reasons. Change to an optional compile-time opt switch.
else if (lCanApplyBreakOptimization(trueStmts, falseStmts)) {
// If we have a simple break statement inside the 'if' and are
// under varying control flow, just update the execution mask
// directly and don't emit code for the statements. This leads to
// better code for this case--this is surprising and should be
// root-caused further, but for now this gives us performance
// benefit in this case.
ctx->SetInternalMaskAndNot(ctx->GetInternalMask(), testValue);
}
*/
else
emitVaryingIf(ctx, testValue);
}
Stmt *
IfStmt::TypeCheck() {
if (test != NULL) {
const Type *testType = test->GetType();
if (testType != NULL) {
bool isUniform = (testType->IsUniformType() &&
!g->opt.disableUniformControlFlow);
test = TypeConvertExpr(test, isUniform ? AtomicType::UniformBool :
AtomicType::VaryingBool,
"\"if\" statement test");
if (test == NULL)
return NULL;
}
}
return this;
}
int
IfStmt::EstimateCost() const {
const Type *type;
if (test == NULL || (type = test->GetType()) == NULL)
return 0;
return type->IsUniformType() ? COST_UNIFORM_IF : COST_VARYING_IF;
}
void
IfStmt::Print(int indent) const {
printf("%*cIf Stmt %s", indent, ' ', doAllCheck ? "DO ALL CHECK" : "");
pos.Print();
printf("\n%*cTest: ", indent+4, ' ');
test->Print();
printf("\n");
if (trueStmts) {
printf("%*cTrue:\n", indent+4, ' ');
trueStmts->Print(indent+8);
}
if (falseStmts) {
printf("%*cFalse:\n", indent+4, ' ');
falseStmts->Print(indent+8);
}
}
/** Emit code to run both the true and false statements for the if test,
with the mask set appropriately before running each one.
*/
void
IfStmt::emitMaskedTrueAndFalse(FunctionEmitContext *ctx, llvm::Value *oldMask,
llvm::Value *test) const {
if (trueStmts) {
ctx->SetInternalMaskAnd(oldMask, test);
lEmitIfStatements(ctx, trueStmts, "if: expr mixed, true statements");
// under varying control flow,, returns can't stop instruction
// emission, so this better be non-NULL...
AssertPos(ctx->GetDebugPos(), ctx->GetCurrentBasicBlock());
}
if (falseStmts) {
ctx->SetInternalMaskAndNot(oldMask, test);
lEmitIfStatements(ctx, falseStmts, "if: expr mixed, false statements");
AssertPos(ctx->GetDebugPos(), ctx->GetCurrentBasicBlock());
}
}
/** Emit code for an if test that checks the mask and the test values and
tries to be smart about jumping over code that doesn't need to be run.
*/
void
IfStmt::emitVaryingIf(FunctionEmitContext *ctx, llvm::Value *ltest) const {
llvm::Value *oldMask = ctx->GetInternalMask();
if (doAllCheck) {
// We can't tell if the mask going into the if is all on at the
// compile time. Emit code to check for this and then either run
// the code for the 'all on' or the 'mixed' case depending on the
// mask's value at runtime.
llvm::BasicBlock *bAllOn = ctx->CreateBasicBlock("cif_mask_all");
llvm::BasicBlock *bMixedOn = ctx->CreateBasicBlock("cif_mask_mixed");
llvm::BasicBlock *bDone = ctx->CreateBasicBlock("cif_done");
// Jump to either bAllOn or bMixedOn, depending on the mask's value
llvm::Value *maskAllQ = ctx->All(ctx->GetFullMask());
ctx->BranchInst(bAllOn, bMixedOn, maskAllQ);
// Emit code for the 'mask all on' case
ctx->SetCurrentBasicBlock(bAllOn);
emitMaskAllOn(ctx, ltest, bDone);
// And emit code for the mixed mask case
ctx->SetCurrentBasicBlock(bMixedOn);
emitMaskMixed(ctx, oldMask, ltest, bDone);
// When done, set the current basic block to the block that the two
// paths above jump to when they're done.
ctx->SetCurrentBasicBlock(bDone);
}
else if (trueStmts != NULL || falseStmts != NULL) {
// If there is nothing that is potentially unsafe to run with all
// lanes off in the true and false statements and if the total
// complexity of those two is relatively simple, then we'll go
// ahead and emit straightline code that runs both sides, updating
// the mask accordingly. This is useful for efficiently compiling
// things like:
//
// if (foo) x = 0;
// else ++x;
//
// Where the overhead of checking if any of the program instances wants
// to run one side or the other is more than the actual computation.
// SafeToRunWithMaskAllOff() checks to make sure that we don't do this
// for potentially dangerous code like:
//
// if (index < count) array[index] = 0;
//
// where our use of blend for conditional assignments doesn't check
// for the 'all lanes' off case.
int trueFalseCost = (::EstimateCost(trueStmts) +
::EstimateCost(falseStmts));
bool costIsAcceptable = (trueFalseCost <
PREDICATE_SAFE_IF_STATEMENT_COST);
bool safeToRunWithAllLanesOff = (SafeToRunWithMaskAllOff(trueStmts) &&
SafeToRunWithMaskAllOff(falseStmts));
Debug(pos, "If statement: true cost %d (safe %d), false cost %d (safe %d).",
::EstimateCost(trueStmts), (int)SafeToRunWithMaskAllOff(trueStmts),
::EstimateCost(falseStmts), (int)SafeToRunWithMaskAllOff(falseStmts));
if (safeToRunWithAllLanesOff &&
(costIsAcceptable || g->opt.disableCoherentControlFlow)) {
ctx->StartVaryingIf(oldMask);
emitMaskedTrueAndFalse(ctx, oldMask, ltest);
AssertPos(pos, ctx->GetCurrentBasicBlock());
ctx->EndIf();
}
else {
llvm::BasicBlock *bDone = ctx->CreateBasicBlock("if_done");
emitMaskMixed(ctx, oldMask, ltest, bDone);
ctx->SetCurrentBasicBlock(bDone);
}
}
}
/** Emits code for 'if' tests under the case where we know that the program
mask is all on going into the 'if'.
*/
void
IfStmt::emitMaskAllOn(FunctionEmitContext *ctx, llvm::Value *ltest,
llvm::BasicBlock *bDone) const {
// We start by explicitly storing "all on" into the mask mask. Note
// that this doesn't change its actual value, but doing so lets the
// compiler see what's going on so that subsequent optimizations for
// code emitted here can operate with the knowledge that the mask is
// definitely all on (until it modifies the mask itself).
AssertPos(pos, !g->opt.disableCoherentControlFlow);
if (!g->opt.disableMaskAllOnOptimizations)
ctx->SetInternalMask(LLVMMaskAllOn);
llvm::Value *oldFunctionMask = ctx->GetFunctionMask();
if (!g->opt.disableMaskAllOnOptimizations)
ctx->SetFunctionMask(LLVMMaskAllOn);
// First, check the value of the test. If it's all on, then we jump to
// a basic block that will only have code for the true case.
llvm::BasicBlock *bTestAll = ctx->CreateBasicBlock("cif_test_all");
llvm::BasicBlock *bTestNoneCheck = ctx->CreateBasicBlock("cif_test_none_check");
llvm::Value *testAllQ = ctx->All(ltest);
ctx->BranchInst(bTestAll, bTestNoneCheck, testAllQ);
// Emit code for the 'test is all true' case
ctx->SetCurrentBasicBlock(bTestAll);
ctx->StartVaryingIf(LLVMMaskAllOn);
lEmitIfStatements(ctx, trueStmts, "if: all on mask, expr all true");
ctx->EndIf();
if (ctx->GetCurrentBasicBlock() != NULL)
// bblock may legitimately be NULL since if there's a return stmt
// or break or continue we can actually jump and end emission since
// we know all of the lanes are following this path...
ctx->BranchInst(bDone);
// The test isn't all true. Now emit code to determine if it's all
// false, or has mixed values.
ctx->SetCurrentBasicBlock(bTestNoneCheck);
llvm::BasicBlock *bTestNone = ctx->CreateBasicBlock("cif_test_none");
llvm::BasicBlock *bTestMixed = ctx->CreateBasicBlock("cif_test_mixed");
llvm::Value *testMixedQ = ctx->Any(ltest);
ctx->BranchInst(bTestMixed, bTestNone, testMixedQ);
// Emit code for the 'test is all false' case
ctx->SetCurrentBasicBlock(bTestNone);
ctx->StartVaryingIf(LLVMMaskAllOn);
lEmitIfStatements(ctx, falseStmts, "if: all on mask, expr all false");
ctx->EndIf();
if (ctx->GetCurrentBasicBlock())
// bblock may be NULL since if there's a return stmt or break or
// continue we can actually jump or whatever and end emission...
ctx->BranchInst(bDone);
// Finally emit code for the 'mixed true/false' case. We unavoidably
// need to run both the true and the false statements.
ctx->SetCurrentBasicBlock(bTestMixed);
ctx->StartVaryingIf(LLVMMaskAllOn);
emitMaskedTrueAndFalse(ctx, LLVMMaskAllOn, ltest);
// In this case, return/break/continue isn't allowed to jump and end
// emission.
AssertPos(pos, ctx->GetCurrentBasicBlock());
ctx->EndIf();
ctx->BranchInst(bDone);
ctx->SetCurrentBasicBlock(bDone);
ctx->SetFunctionMask(oldFunctionMask);
}
/** Emit code for an 'if' test where the lane mask is known to be mixed
on/off going into it.
*/
void
IfStmt::emitMaskMixed(FunctionEmitContext *ctx, llvm::Value *oldMask,
llvm::Value *ltest, llvm::BasicBlock *bDone) const {
ctx->StartVaryingIf(oldMask);
llvm::BasicBlock *bNext = ctx->CreateBasicBlock("safe_if_after_true");
llvm::BasicBlock *bRunTrue = ctx->CreateBasicBlock("safe_if_run_true");
ctx->SetInternalMaskAnd(oldMask, ltest);
// Do any of the program instances want to run the 'true'
// block? If not, jump ahead to bNext.
#ifdef ISPC_NVPTX_ENABLED
#if 0
llvm::Value *maskAnyTrueQ = ctx->ExtractInst(ctx->GetFullMask(),0);
#else
llvm::Value *maskAnyTrueQ = ctx->Any(ctx->GetFullMask());
#endif
#else /* ISPC_NVPTX_ENABLED */
llvm::Value *maskAnyTrueQ = ctx->Any(ctx->GetFullMask());
#endif /* ISPC_NVPTX_ENABLED */
ctx->BranchInst(bRunTrue, bNext, maskAnyTrueQ);
// Emit statements for true
ctx->SetCurrentBasicBlock(bRunTrue);
if (trueStmts != NULL)
lEmitIfStatements(ctx, trueStmts, "if: expr mixed, true statements");
AssertPos(pos, ctx->GetCurrentBasicBlock());
ctx->BranchInst(bNext);
ctx->SetCurrentBasicBlock(bNext);
// False...
llvm::BasicBlock *bRunFalse = ctx->CreateBasicBlock("safe_if_run_false");
ctx->SetInternalMaskAndNot(oldMask, ltest);
// Similarly, check to see if any of the instances want to
// run the 'false' block...
#ifdef ISPC_NVPTX_ENABLED
#if 0
llvm::Value *maskAnyFalseQ = ctx->ExtractInst(ctx->GetFullMask(),0);
#else
llvm::Value *maskAnyFalseQ = ctx->Any(ctx->GetFullMask());
#endif
#else /* ISPC_NVPTX_ENABLED */
llvm::Value *maskAnyFalseQ = ctx->Any(ctx->GetFullMask());
#endif /* ISPC_NVPTX_ENABLED */
ctx->BranchInst(bRunFalse, bDone, maskAnyFalseQ);
// Emit code for false
ctx->SetCurrentBasicBlock(bRunFalse);
if (falseStmts)
lEmitIfStatements(ctx, falseStmts, "if: expr mixed, false statements");
AssertPos(pos, ctx->GetCurrentBasicBlock());
ctx->BranchInst(bDone);
ctx->SetCurrentBasicBlock(bDone);
ctx->EndIf();
}
///////////////////////////////////////////////////////////////////////////
// DoStmt
struct VaryingBCCheckInfo {
VaryingBCCheckInfo() {
varyingControlFlowDepth = 0;
foundVaryingBreakOrContinue = false;
}
int varyingControlFlowDepth;
bool foundVaryingBreakOrContinue;
};
/** Returns true if the given node is an 'if' statement where the test
condition has varying type. */
static bool
lIsVaryingFor(ASTNode *node) {
IfStmt *ifStmt;
if ((ifStmt = llvm::dyn_cast<IfStmt>(node)) != NULL &&
ifStmt->test != NULL) {
const Type *type = ifStmt->test->GetType();
return (type != NULL && type->IsVaryingType());
}
else
return false;
}
/** Preorder callback function for checking for varying breaks or
continues. */
static bool
lVaryingBCPreFunc(ASTNode *node, void *d) {
VaryingBCCheckInfo *info = (VaryingBCCheckInfo *)d;
// We found a break or continue statement; if we're under varying
// control flow, then bingo.
if ((llvm::dyn_cast<BreakStmt>(node) != NULL ||
llvm::dyn_cast<ContinueStmt>(node) != NULL) &&
info->varyingControlFlowDepth > 0) {
info->foundVaryingBreakOrContinue = true;
return false;
}