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ZAM fixes for loops indexed with variables not used in the loop body

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Vern Paxson 2024-01-10 18:41:47 -08:00 • committed by Arne Welzel
parent e0736afe4c
commit d1dffd3e1b
1 changed files with 5 additions and 14 deletions
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19
src/script_opt/ZAM/Stmt.cc
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@ -681,13 +681,10 @@ const ZAMStmt ZAMCompiler::LoopOverTable(const ForStmt* f, const NameExpr* val)
auto value_var = f->ValueVar();
auto body = f->LoopBody();
// Check whether the loop variables are actually used in the body.
// This is motivated by an idiom where there's both loop_vars and
// a value_var, but the script only actually needs the value_var;
// and also some weird cases where the script is managing a
// separate iteration process manually.
ProfileFunc body_pf(body);
// We used to have more involved logic here to check whether the loop
// variables are actually used in the body. Now that we have '_'
// loop placeholder variables, this is no longer worth trying to
// optimize for, though we still optimize for those placeholders.
int num_unused = 0;
auto aux = new ZInstAux(0);
@ -695,7 +692,7 @@ const ZAMStmt ZAMCompiler::LoopOverTable(const ForStmt* f, const NameExpr* val)
for ( auto i = 0; i < loop_vars->length(); ++i ) {
auto id = (*loop_vars)[i];
if ( body_pf.Locals().count(id) == 0 || id->IsBlank() )
if ( id->IsBlank() )
++num_unused;
int slot = id->IsBlank() ? -1 : FrameSlot(id);
@ -707,12 +704,6 @@ const ZAMStmt ZAMCompiler::LoopOverTable(const ForStmt* f, const NameExpr* val)
bool no_loop_vars = (num_unused == loop_vars->length());
if ( value_var && body_pf.Locals().count(value_var.get()) == 0 )
// This is more clearly a coding botch - someone left in
// an unnecessary value_var variable. But might as
// well not do the work.
value_var = nullptr;
if ( value_var )
aux->value_var_type = value_var->GetType();