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optimization of scripting idioms - min/max, has-elements

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Vern Paxson 2024-04-08 18:16:15 -04:00 • committed by Tim Wojtulewicz
parent e38053ee3c
commit 5445e8c7ff
5 changed files with 194 additions and 8 deletions
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85
src/script_opt/Stmt.cc
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@ -166,7 +166,7 @@ void IfStmt::Inline(Inliner* inl) {
}
bool IfStmt::IsReduced(Reducer* c) const {
if ( e->IsConst() || ! e->IsReducedConditional(c) )
if ( e->IsConst() || ! e->IsReducedConditional(c) || IsMinMaxConstruct() )
return NonReduced(e.get());
return s1->IsReduced(c) && s2->IsReduced(c);
@ -179,11 +179,11 @@ StmtPtr IfStmt::DoReduce(Reducer* c) {
e = e->ReduceToConditional(c, red_e_stmt);
// First, assess some fundamental transformations.
if ( e->Tag() == EXPR_NOT ) { // Change "if ( ! x ) s1 else s2" to "if ( x ) s2 else s1".
auto s1_orig = s1;
s1 = s2;
s2 = s1_orig;
if ( IsMinMaxConstruct() )
return ConvertToMinMaxConstruct()->Reduce(c);
if ( e->Tag() == EXPR_NOT ) { // Change "if ( ! x ) s1 else s2" to "if ( x ) s2 else s1".
std::swap(s1, s2);
e = e->GetOp1();
}
@ -274,6 +274,81 @@ bool IfStmt::CouldReturn(bool ignore_break) const {
return (s1 && s1->CouldReturn(ignore_break)) || (s2 && s2->CouldReturn(ignore_break));
}
bool IfStmt::IsMinMaxConstruct() const {
if ( ! s1 || ! s2 )
// not an if-else construct
return false;
if ( s1->Tag() != STMT_EXPR || s2->Tag() != STMT_EXPR )
// definitely not if-else assignments
return false;
auto es1 = s1->AsExprStmt()->StmtExpr();
auto es2 = s2->AsExprStmt()->StmtExpr();
if ( es1->Tag() != EXPR_ASSIGN || es2->Tag() != EXPR_ASSIGN )
return false;
switch ( e->Tag() ) {
case EXPR_LT:
case EXPR_LE:
case EXPR_GE:
case EXPR_GT: break;
default:
// Not an apt conditional.
return false;
}
auto a1 = es1->AsAssignExpr();
auto a2 = es2->AsAssignExpr();
auto a1_lhs = a1->GetOp1();
auto a2_lhs = a2->GetOp1();
if ( ! same_expr(a1_lhs, a2_lhs) )
// if-else assignments are not to the same variable
return false;
auto a1_rhs = a1->GetOp2();
auto a2_rhs = a2->GetOp2();
auto op1 = e->GetOp1();
auto op2 = e->GetOp2();
if ( ! same_expr(op1, a1_rhs) && ! same_expr(op1, a2_rhs) )
// Operand does not appear in the assignment RHS.
return false;
if ( ! same_expr(op2, a1_rhs) && ! same_expr(op2, a2_rhs) )
// Operand does not appear in the assignment RHS.
return false;
if ( same_expr(op1, op2) )
// This is degenerate and should be found by other reductions.
return false;
return true;
}
StmtPtr IfStmt::ConvertToMinMaxConstruct() {
auto relop1 = e->GetOp1();
auto relop2 = e->GetOp2();
auto is_min = (e->Tag() == EXPR_LT || e->Tag() == EXPR_LE);
auto assign2 = s2->AsExprStmt()->StmtExpr();
auto lhs2 = assign2->GetOp1();
auto rhs2 = assign2->GetOp2();
if ( same_expr(relop1, rhs2) )
is_min = ! is_min;
auto built_in = is_min ? ScriptOptBuiltinExpr::MINIMUM : ScriptOptBuiltinExpr::MAXIMUM;
auto bi = with_location_of(make_intrusive<ScriptOptBuiltinExpr>(built_in, relop1, relop2), this);
auto new_assign = with_location_of(make_intrusive<AssignExpr>(lhs2, bi, false), this);
return with_location_of(make_intrusive<ExprStmt>(new_assign), this);
}
IntrusivePtr<Case> Case::Duplicate() {
if ( expr_cases ) {
auto new_exprs = expr_cases->Duplicate()->AsListExprPtr();