From 2bece04b20fa99f034b7117451d80d8878179d6c Mon Sep 17 00:00:00 2001
From: Ved Shanbhogue <ved@rivosinc.com>
Date: Mon, 27 Nov 2023 20:21:39 -0600
Subject: [PATCH] ELP is violated if lpad not fetched when expected

---
 model/riscv_step.sail | 30 +++++++++++++++++++++---------
 1 file changed, 21 insertions(+), 9 deletions(-)

diff --git a/model/riscv_step.sail b/model/riscv_step.sail
index 550f11a4a..dcae569b1 100644
--- a/model/riscv_step.sail
+++ b/model/riscv_step.sail
@@ -115,14 +115,20 @@ function step(step_no : int) -> bool = {
             then {
               print_instr("[" ^ string_of_int(step_no) ^ "] [" ^ to_str(cur_privilege) ^ "]: " ^ BitStr(PC) ^ " (" ^ BitStr(h) ^ ") " ^ to_str(ast));
             };
-            /* check for RVC once here instead of every RVC execute clause. */
-            if haveRVC() then {
-              nextPC = PC + 2;
-              (execute(ast), true)
-             } else {
-              handle_illegal();
+            /* Zicfilp requires a landing pad (a base inst) if ELP is LP_EXPECTED */
+            if elp != ElpState_to_bits(LP_EXPECTED) then {
+              handle_sw_check_exception(LANDING_PAD_FAULT);
               (RETIRE_FAIL, true)
-             }
+            } else {
+              /* check for RVC once here instead of every RVC execute clause. */
+              if haveRVC() then {
+                nextPC = PC + 2;
+                (execute(ast), true)
+               } else {
+                handle_illegal();
+                (RETIRE_FAIL, true)
+               }
+            }
           },
           F_Base(w) => {
             instbits = zero_extend(w);
@@ -131,8 +137,14 @@ function step(step_no : int) -> bool = {
             then {
               print_instr("[" ^ string_of_int(step_no) ^ "] [" ^ to_str(cur_privilege) ^ "]: " ^ BitStr(PC) ^ " (" ^ BitStr(w) ^ ") " ^ to_str(ast));
             };
-            nextPC = PC + 4;
-            (execute(ast), true)
+            /* Zicfilp requires a aligned lpad if elp is LP_EXPECTED */
+            if zicfilp_is_elp_violated() then {
+              handle_sw_check_exception(LANDING_PAD_FAULT);
+              (RETIRE_FAIL, true)
+            } else {
+              nextPC = PC + 4;
+              (execute(ast), true)
+            }
           }
         }
       }