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Add --no-relative-cfuncs and related default optimization, bug1224.

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Signed-off-by: Wilson Snyder <[email protected]>
This commit is contained in:
John Coiner
2017-10-05 18:18:11 -04:00
committed by Wilson Snyder
parent 8281ee1520
commit ba270e09a4
8 changed files with 195 additions and 48 deletions
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src/V3Descope.cpp
+92 -43
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@@ -53,7 +53,8 @@ private:
// STATE
AstNodeModule* m_modp; // Current module
AstScope* m_scopep; // Current scope
bool m_needThis; // Add thisp to function
bool m_modSingleton; // m_modp is only instanced once
bool m_needThis; // Make function non-static
FuncMmap m_modFuncs; // Name of public functions added
// METHODS
@@ -63,41 +64,91 @@ private:
return level;
}
string descopedName(AstScope* scopep, bool& hierThisr, AstVar* varp=NULL) {
static bool modIsSingleton(AstNodeModule* modp) {
// True iff there's exactly one instance of this module in the design.
int instances = 0;
for (AstNode* stmtp = modp->stmtsp(); stmtp; stmtp=stmtp->nextp()) {
if (stmtp->castScope()) {
if (++instances > 1) { return false; }
}
}
return (instances == 1);
}
// Construct the best prefix to reference an object in 'scopep'
// from a CFunc in 'm_scopep'. Result may be relative
// ("this->[...]") or absolute ("vlTOPp->[...]").
//
// Using relative references allows V3Combine'ing
// code across multiple instances of the same module.
//
// Sets 'hierThisr' true if the object is local to this scope
// (and could be made into a function-local later in V3Localize),
// false if the object is in another scope.
string descopedName(const AstScope* scopep, bool& hierThisr,
const AstVar* varp=NULL) {
UASSERT(scopep, "Var/Func not scoped\n");
hierThisr = true;
hierThisr = (scopep == m_scopep);
// It's possible to disable relative references. This is a concession
// to older compilers (gcc < 4.5.x) that don't understand __restrict__
// well and emit extra ld/st to guard against pointer aliasing
// when this-> and vlTOPp-> are mixed in the same function.
//
// "vlTOPp" is declared "restrict" so better compilers understand
// that it won't alias with "this".
bool relativeRefOk = v3Global.opt.relativeCFuncs();
// Use absolute refs in top-scoped routines, keep them static.
// The DPI callback registration depends on representing top-level
// static routines as plain function pointers. That breaks if those
// become true OO routines.
//
// V3Combine wouldn't likely be able to combine top-level
// routines anyway, so there's no harm in keeping these static.
if (m_modp->isTop()) {
relativeRefOk = false;
}
// Use absolute refs if this scope is the only instance of the module.
// Saves a bit of overhead on passing the 'this' pointer, and there's no
// need to be nice to V3Combine when we have only a single instance.
// The risk that this prevents combining identical logic from differently-
// named but identical modules seems low.
if (m_modSingleton) {
relativeRefOk = false;
}
if (varp && varp->isFuncLocal()) {
hierThisr = true;
return ""; // Relative to function, not in this
} else if (scopep == m_scopep && m_modp->isTop()) {
//return ""; // Reference to scope we're in, no need to HIER-> it
return "vlTOPp->";
} else if (scopep == m_scopep && !m_modp->isTop()
&& 0) { // We no longer thisp-> as still get ambiguation problems
m_needThis = true;
return "thisp->"; // this-> but with restricted aliasing
} else if (scopep->aboveScopep() && scopep->aboveScopep()==m_scopep
&& 0 // DISABLED: GCC considers the pointers ambiguous, so goes ld/store crazy
) {
// Reference to scope of cell directly under this module, can just "cell->"
string name = scopep->name();
string::size_type pos;
if ((pos = name.rfind(".")) != string::npos) {
name.erase(0,pos+1);
}
hierThisr = false;
return name+"->";
} else {
// Reference to something else, use global variable
UINFO(8," Descope "<<scopep<<endl);
UINFO(8," to "<<scopep->name()<<endl);
UINFO(8," under "<<m_scopep->name()<<endl);
hierThisr = false;
if (!scopep->aboveScopep()) { // Top
return "vlTOPp->"; // == "vlSymsp->TOPp->", but GCC would suspect aliases
} else {
return scopep->nameVlSym()+".";
}
}
} else if (relativeRefOk && scopep == m_scopep) {
m_needThis = true;
return "this->";
} else if (relativeRefOk && scopep->aboveScopep()
&& scopep->aboveScopep()==m_scopep) {
// Reference to scope of cell directly under this module, can just "cell->"
string name = scopep->name();
string::size_type pos;
if ((pos = name.rfind(".")) != string::npos) {
name.erase(0,pos+1);
}
m_needThis = true;
return name+"->";
} else {
// Reference to something elsewhere, or relative refences
// are disabled. Use global variable
UINFO(8," Descope "<<scopep<<endl);
UINFO(8," to "<<scopep->name()<<endl);
UINFO(8," under "<<m_scopep->name()<<endl);
if (!scopep->aboveScopep()) { // Top
// We could also return "vlSymsp->TOPp->" here, but GCC would
// suspect aliases.
return "vlTOPp->";
} else {
return scopep->nameVlSym()+".";
}
}
}
void makePublicFuncWrappers() {
@@ -182,6 +233,7 @@ private:
virtual void visit(AstNodeModule* nodep) {
m_modp = nodep;
m_modFuncs.clear();
m_modSingleton = modIsSingleton(m_modp);
nodep->iterateChildren(*this);
makePublicFuncWrappers();
m_modp = NULL;
@@ -222,11 +274,7 @@ private:
nodep->iterateChildren(*this);
nodep->user1(true);
if (m_needThis) {
nodep->v3fatalSrc("old code");
// Really we should have more node types for backend optimization of this stuff
string text = v3Global.opt.modPrefix() + "_" + m_modp->name()
+"* thisp = &("+m_scopep->nameVlSym()+");\n";
nodep->addInitsp(new AstCStmt(nodep->fileline(), text));
nodep->isStatic(false);
}
// If it's under a scope, move it up to the top
if (m_scopep) {
@@ -248,11 +296,12 @@ private:
}
public:
// CONSTRUCTORS
explicit DescopeVisitor(AstNetlist* nodep) {
m_modp = NULL;
m_scopep = NULL;
m_needThis = false;
nodep->accept(*this);
explicit DescopeVisitor(AstNetlist* nodep)
: m_modp(NULL),
m_scopep(NULL),
m_modSingleton(false),
m_needThis(false) {
nodep->accept(*this);
}
virtual ~DescopeVisitor() {}
};