From efa1b2615064395d6862a972314bd2f0b749b35f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Emmanuel=20Beno=C3=AEt?= <tseeker@nocternity.net>
Date: Tue, 12 Dec 2017 18:30:41 +0100
Subject: [PATCH] Optimizer - Constant propagation for variables
* It doesn't work for function arguments at this point, but shouldn't be
too hard to implement that.
* Can't use it to its full potential mostly because I need to get rid of
the node-specific shit in the AST.
---
c-opast.cc | 34 +++++++++++++++++-
c-opast.hh | 12 +++++++
c-opopt.cc | 97 +++++++++++++++++++++++++++++++++++++++++++++++++-
test/build.srd | 4 ++-
4 files changed, 144 insertions(+), 3 deletions(-)
diff --git a/c-opast.cc b/c-opast.cc
index f16b332..ceb1b17 100644
--- a/c-opast.cc
+++ b/c-opast.cc
@@ -32,6 +32,15 @@ T_RootNode& A_Node::root( ) const noexcept
const_cast< A_Node* >( node ) );
}
+void A_Node::replaceChild(
+ A_Node const& /*child*/ ,
+ T_OwnPtr< A_Node > /*replacement*/
+ ) noexcept
+{
+ fprintf( stderr , "replaceChild called on invalid node\n" );
+ std::terminate( );
+}
+
/*----------------------------------------------------------------------------*/
A_Node* opast::ASTVisitorBrowser(
@@ -492,6 +501,19 @@ T_BinaryOperatorNode::T_BinaryOperatorNode(
})( ) , parent ) , op_( op )
{ }
+void T_BinaryOperatorNode::replaceChild(
+ A_Node const& child ,
+ T_OwnPtr< A_Node > replacement
+ ) noexcept
+{
+ if ( right_.get( ) == &child ) {
+ right_ = std::move( replacement );
+ } else {
+ assert( left_.get( ) == &child );
+ left_ = std::move( replacement );
+ }
+}
+
/*= T_FramebufferInstrNode ===================================================*/
@@ -629,7 +651,17 @@ T_Optional< T_SRDLocation > T_LocalsInstrNode::addVariable(
}
-/*= T_CondInstrNode ============================================================*/
+/*= T_CondInstrNode ==========================================================*/
+
+void T_CondInstrNode::T_Expression::replaceChild(
+ A_Node const& child ,
+ T_OwnPtr< A_Node > replacement ) noexcept
+{
+ assert( expression_.get( ) == &child );
+ expression_ = std::move( replacement );
+}
+
+/*----------------------------------------------------------------------------*/
void T_CondInstrNode::setExpression(
P_ExpressionNode expression ) noexcept
diff --git a/c-opast.hh b/c-opast.hh
index 4a499e5..bb5eb19 100644
--- a/c-opast.hh
+++ b/c-opast.hh
@@ -94,6 +94,10 @@ class A_Node
{ assert( parent_ ); return *parent_; }
T_RootNode& root( ) const noexcept;
+
+ virtual void replaceChild(
+ A_Node const& child ,
+ T_OwnPtr< A_Node > replacement ) noexcept;
};
// Browser function to be used with T_Visitor
@@ -460,6 +464,10 @@ class T_CondInstrNode : public A_InstructionNode
void expression( P_ExpressionNode expr ) noexcept
{ assert( expr ); expression_ = std::move( expr ); }
+
+ void replaceChild(
+ A_Node const& child ,
+ T_OwnPtr< A_Node > replacement ) noexcept override;
};
class T_ValuedCase : public A_Node
@@ -1362,6 +1370,10 @@ class T_BinaryOperatorNode : public A_ExpressionNode
{ return *right_; }
A_ExpressionNode& right( ) noexcept
{ return *right_; }
+
+ void replaceChild(
+ A_Node const& child ,
+ T_OwnPtr< A_Node > replacement ) noexcept override;
};
diff --git a/c-opopt.cc b/c-opopt.cc
index d23323c..5ed3864 100644
--- a/c-opopt.cc
+++ b/c-opopt.cc
@@ -1441,6 +1441,41 @@ bool opopt::FoldConstants(
/*= CONSTANT PROPAGATION =====================================================*/
+namespace {
+
+void CPReplaceWithConstant_(
+ A_InstructionNode& instruction ,
+ T_OptData::T_VarId const& var ,
+ const double value ,
+ T_OptData& oData
+ ) noexcept
+{
+ oData.visitor.visit( instruction , [&]( A_Node& node , const bool exit ) {
+ if ( !exit || node.type( ) != A_Node::EXPR_ID ) {
+ return node.type( ) != A_Node::ILIST;
+ }
+
+ auto& eid{ (T_IdentifierExprNode&) node };
+ if ( eid.id( ) != var.name ) {
+ return true;
+ }
+
+ auto& p{ eid.parent( ) };
+ auto replacement{ NewOwned< T_ConstantExprNode >( p , value ) };
+ replacement->location( ) = eid.location( );
+ p.replaceChild( eid , std::move( replacement ) );
+ oData.logger( [&]() {
+ T_StringBuilder sb;
+ sb << "Propagated constant from " << var.name
+ << " at " << instruction.location( )
+ << " (value " << value << ")";
+ return sb;
+ } , LL2 );
+ return true;
+ } );
+}
+
+} // namespace <anon>
bool opopt::PropagateConstants(
T_OpsParserOutput& program ,
@@ -1463,7 +1498,67 @@ bool opopt::PropagateConstants(
oData.buildUseDefineChains( program );
M_LOGSTR_( "... Propagating constants" , 2 );
- return false;
+ T_Set< uint32_t > cDefs{ UseTag< ArrayBacked< 16 > >( ) };
+ T_AutoArray< double , 16 > cValues;
+ bool changesMade{ false };
+ for ( auto const& udc : oData.varUDChains.values( ) ) {
+ cDefs.clear( );
+ cValues.clear( );
+
+ // Find all constant definitions
+ const auto nDefs{ udc.defines.size( ) };
+ for ( auto i = 0u ; i < nDefs ; i ++ ) {
+ auto const& def{ udc.defines[ i ] };
+ auto const* const ri{ oData.instructions[ def.node ].node };
+ if ( ri->type( ) == A_Node::OP_SET ) {
+ auto const* const si{
+ dynamic_cast< T_SetInstrNode const* >( ri ) };
+ if ( si->expression( ).type( ) == A_Node::EXPR_CONST ) {
+ cDefs.add( i );
+ cValues.add( ( (T_ConstantExprNode&) si->expression( ) ).floatValue( ) );
+ }
+ } else {
+ // Instruction is not supported, exit
+ assert( cDefs.size( ) == 0 );
+ break;
+ }
+ }
+ assert( cValues.size( ) == cDefs.size( ) );
+ if ( cValues.empty( ) ) {
+ continue;
+ }
+
+ const auto nUses{ udc.uses.size( ) };
+ for ( auto i = 0u ; i < nUses ; i ++ ) {
+ auto const& use{ udc.uses[ i ] };
+ const auto nRefs{ use.refs.size( ) };
+ T_Optional< double > repVal{ };
+ for ( auto j = 0u ; j < nRefs ; j ++ ) {
+ const auto dIdx{ cDefs.indexOf( use.refs[ j ] ) };
+ if ( dIdx == -1 ) {
+ repVal.clear( );
+ break;
+ }
+ if ( !repVal ) {
+ repVal = cValues[ dIdx ];
+ } else if ( *repVal != cValues[ dIdx ] ) {
+ repVal.clear( );
+ break;
+ }
+ }
+ if ( !repVal ) {
+ continue;
+ }
+
+ printf( "Could replace use at %d with constant %f\n" ,
+ use.node , *repVal );
+ CPReplaceWithConstant_( *oData.instructions[ use.node ].node ,
+ udc.var , *repVal , oData );
+ changesMade = true;
+ }
+ }
+
+ return changesMade;
}
diff --git a/test/build.srd b/test/build.srd
index 139ec1d..bd62872 100644
--- a/test/build.srd
+++ b/test/build.srd
@@ -4,7 +4,9 @@
(1920 1080)
)
(optimizer on
- (constant-folding on)
+ (constant-folding on
+ # (fixed-resolution on)
+ )
(constant-propagation on)
)
)