Initial commit

src/optims.c

@@ -0,0 +1,93 @@
+#include"optims.h"
+
+#include<assert.h>
+
+// Currently performs only copy propagation.
+// But CP is NECESSARY, otherwise it creates too many variables
+// that are unable to be coalesced by the regallocator
+
+static void recalc_lifespan(VarTableEntry *vte) {
+	assert(vte->kind == VARTABLEENTRY_VAR);
+	
+	size_t start = 0xFFFFFFFF, end = 0;
+	
+	UseDef *ud = vte->data.var.usedefFirst;
+	while(ud) {
+		if(ud->t < start) start = ud->t;
+		
+		if(ud->t > end) end = ud->t;
+		
+		ud = ud->next;
+	}
+	
+	vte->data.var.start = start;
+	vte->data.var.end = end;
+}
+
+void optim_chunk(ASTChunk *chu) {
+	AST *s = chu->statementFirst, *sPrev = NULL;
+	while(s) {
+		if(s->nodeKind == AST_STMT_ASSIGN && s->stmtAssign.what->nodeKind == AST_EXPR_VAR && s->stmtAssign.to->nodeKind == AST_EXPR_VAR) {
+			VarTableEntry *dst = ((AST*) s->stmtAssign.what)->exprVar.thing;
+			VarTableEntry *src = ((AST*) s->stmtAssign.to)->exprVar.thing;
+			
+			if(dst->kind == VARTABLEENTRY_VAR && src->kind == VARTABLEENTRY_VAR) {
+				// Find reaching source definition
+				
+				UseDef *srcUD = src->data.var.usedefFirst;
+				while(srcUD && srcUD->use != s->stmtAssign.to) {
+					srcUD = srcUD->next;
+				}
+				
+				if(!srcUD) {
+					goto copypropfail;
+				}
+				
+				// Find first use of this def
+				
+				UseDef *dstUDPrev = NULL;
+				UseDef *dstUD = dst->data.var.usedefFirst;
+				while(dstUD->def != s) {
+					dstUDPrev = dstUD;
+					dstUD = dstUD->next;
+				}
+				
+				// Update all definitions
+				
+				while(dstUD && dstUD->def == s) {
+					((AST*) dstUD->use)->exprVar.thing = src;
+					
+					UseDef *next = dstUD->next;
+					
+					dstUD->def = srcUD->def;
+					dstUD->next = srcUD->next;
+					srcUD->next = dstUD;
+					
+					dstUD = next;
+					
+					if(dstUDPrev) {
+						dstUDPrev->next = dstUD;
+					} else {
+						dst->data.var.usedefFirst = dstUD;
+					}
+				}
+				
+				if(!dstUD) {
+					// dst was never used again -> DELETE ASSIGNMENT COMPLETELY
+					
+					if(sPrev) {
+						sPrev->statement.next = s->statement.next;
+						// TODO: free
+					}
+				}
+				
+				recalc_lifespan(dst);
+				recalc_lifespan(src);
+			}
+		}
+		
+copypropfail:
+		sPrev = s;
+		s = s->statement.next;
+	}
+}