transmit return value to caller via a register

This avoids the awkward top swapping after coming back from a call. This will
get worse once we we start plaing call args on the caller's side of the call
stack boundary.

3 files changed, 22 insertions, 24 deletions

diff --git a/src/bytecode.c b/src/bytecode.c
index 1bed2e5b..c2b0cb6c 100644
--- a/src/bytecode.c
+++ b/src/bytecode.c
@@ -1743,15 +1743,6 @@ again:
 			vm_push_value( val );
 			break;
 		}
-		case IN_TOP_SWAP: {
-			debug( prg, REALM_BYTECODE, "IN_TOP_SWAP\n" );
-
-			Tree *v1 = vm_pop_tree();
-			Tree *v2 = vm_pop_tree();
-			vm_push_tree( v1 );
-			vm_push_tree( v2 );
-			break;
-		}
 		case IN_DUP_VAL: {
 			debug( prg, REALM_BYTECODE, "IN_DUP_VAL\n" );
 
@@ -2277,6 +2268,12 @@ again:
 			break;
 		}
 
+		case IN_LOAD_RETVAL: {
+			debug( prg, REALM_BYTECODE, "IN_LOAD_RETVAL\n" );
+			vm_push_tree( exec->retVal );
+			break;
+		}
+
 		case IN_PCR_RET: {
 			debug( prg, REALM_BYTECODE, "IN_PCR_RET\n" );
 
@@ -3299,8 +3296,8 @@ again:
 			userIterDestroy( prg, &sp, uiter );
 			break;
 		}
-		case IN_RET: {
 
+		case IN_RET: {
 			FrameInfo *fi = &prg->rtd->frameInfo[exec->frameId];
 			downref_local_trees( prg, sp, exec->framePtr, fi->locals, fi->localsLen );
 			vm_popn( fi->frameSize );
@@ -3308,9 +3305,8 @@ again:
 			exec->frameId = vm_pop_type(long);
 			exec->framePtr = vm_pop_type(Tree**);
 			instr = vm_pop_type(Code*);
-			Tree *retVal = vm_pop_tree();
+			exec->retVal = vm_pop_tree();
 			vm_popn( fi->argSize );
-			vm_push_tree( retVal );
 
 			fi = &prg->rtd->frameInfo[exec->frameId];
 			debug( prg, REALM_BYTECODE, "IN_RET %s\n", fi->name );
@@ -3991,9 +3987,6 @@ again:
 				prg->exitStatus = vm_pop_type(long);
 				prg->induceExit = 1;
 
-				/* The callArgs push for exit. */
-				vm_pop_value();
-
 				while ( true ) {
 					FrameInfo *fi = &prg->rtd->frameInfo[exec->frameId];
 					int frameId = exec->frameId;
@@ -4021,7 +4014,6 @@ again:
 					Tree *retVal = vm_pop_tree();
 					vm_popn( fi->argSize );
 
-
 					/* The CONTIGUOS PUSH. */
 					vm_pop_tree();
 
diff --git a/src/bytecode.h b/src/bytecode.h
index c24913bb..8cc4ae25 100644
--- a/src/bytecode.h
+++ b/src/bytecode.h
@@ -78,6 +78,9 @@ typedef unsigned long colm_value_t;
 // 0xeb
 // 0xec
 // 0xd4
+// 0x20
+
+#define IN_LOAD_RETVAL           0xd4
 
 #define IN_PREP_ARGS             0xe8
 #define IN_CLEAR_ARGS            0xe9
@@ -107,7 +110,6 @@ typedef unsigned long colm_value_t;
 #define IN_POP_VAL               0xbe
 #define IN_DUP_VAL               0x1f
 #define IN_DUP_TREE              0xf2
-#define IN_TOP_SWAP              0x20
 
 #define IN_REJECT                0x21
 #define IN_MATCH                 0x22
@@ -590,6 +592,7 @@ typedef struct colm_execution
 	Parser *parser;
 	long steps;
 	long pcr;
+	Tree *retVal;
 } Execution;
 
 long stringLength( Head *str );
diff --git a/src/synthesis.cc b/src/synthesis.cc
index 92afd5c8..442ac8c0 100644
--- a/src/synthesis.cc
+++ b/src/synthesis.cc
@@ -1085,10 +1085,8 @@ void Compiler::endContiguous( CodeVect &code, bool resetContiguous )
 
 void Compiler::clearContiguous( CodeVect &code, bool resetContiguous )
 {
-	if ( resetContiguous ) {
-		code.append( IN_TOP_SWAP );
+	if ( resetContiguous )
 		code.append( IN_POP );
-	}
 }
 
 UniqueType *LangVarRef::evaluateCall( Compiler *pd, CodeVect &code, CallArgVect *args ) 
@@ -1096,11 +1094,13 @@ UniqueType *LangVarRef::evaluateCall( Compiler *pd, CodeVect &code, CallArgVect
 	/* Evaluate the object. */
 	VarRefLookup lookup = lookupMethod( pd );
 
+	Function *func = lookup.objMethod->func;
+
 	/* Prepare the contiguous call args space. */
-	code.append( IN_PREP_ARGS );
+	if ( func != 0 )
+		code.append( IN_PREP_ARGS );
 
 	bool resetContiguous = false;
-	Function *func = lookup.objMethod->func;
 	if ( func != 0 ) {
 		long stretch = func->paramListSize + 5 + func->localFrame->size();
 		resetContiguous = pd->beginContiguous( code, stretch );
@@ -1121,8 +1121,11 @@ UniqueType *LangVarRef::evaluateCall( Compiler *pd, CodeVect &code, CallArgVect
 	pd->endContiguous( code, resetContiguous );
 	pd->clearContiguous( code, resetContiguous );
 
-	code.append( IN_TOP_SWAP );
-	code.append( IN_CLEAR_ARGS );
+	if ( func != 0 )
+		code.append( IN_CLEAR_ARGS );
+
+	if ( func != 0 )
+		code.append( IN_LOAD_RETVAL );
 
 	/* Return the type to the expression. */
 	return lookup.uniqueType;