Avoid possible spill conflict (one of the problem that caused phpGH-16821) (php#16947)

Author: dstogov

ext/opcache/jit/zend_jit_ir.c

@@ -1306,6 +1306,13 @@ static bool zend_jit_spilling_may_cause_conflict(zend_jit_ctx *jit, int var, ir_
 		 && (jit->ssa->cfg.blocks[jit->ssa->vars[jit->ssa->ops[jit->ssa->vars[var].definition].op1_use].definition_phi->block].flags & ZEND_BB_LOOP_HEADER)) {
 			/* Avoid moving spill store out of loop */
 			return 1;
+		} else if (jit->ssa->vars[var].definition >= 0
+		 && jit->ssa->ops[jit->ssa->vars[var].definition].op1_def == var
+		 && jit->ssa->ops[jit->ssa->vars[var].definition].op1_use >= 0
+		 && jit->ssa->ops[jit->ssa->vars[var].definition].op2_use >= 0
+		 && jit->ra[jit->ssa->ops[jit->ssa->vars[var].definition].op2_use].ref == val) {
+			/* Avoid spill conflict between of ASSIGN.op1_def and ASSIGN.op1_use */
+			return 1;
 		}
 		return 0;
 	}