#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

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;
	}*/
}