rvv: add new rs1 = zero feature to vsetvl

Signed-off-by: Chih-Min Chao <chihmin.chao@sifive.com>

2 files changed, 14 insertions, 3 deletions

diff --git a/riscv/processor.cc b/riscv/processor.cc
index 583affb..1700fba 100644
--- a/riscv/processor.cc
+++ b/riscv/processor.cc
@@ -211,7 +211,7 @@ void vectorUnit_t::reset(){
   set_vl(-1, 0, -1); // default to illegal configuration
 }
 
-reg_t vectorUnit_t::set_vl(uint64_t regId, reg_t reqVL, reg_t newType){
+reg_t vectorUnit_t::set_vl(int regId, reg_t reqVL, reg_t newType){
   if (vtype != newType){
     vtype = newType;
     vsew = 1 << (BITS(newType, 4, 2) + 3);
@@ -227,7 +227,18 @@ reg_t vectorUnit_t::set_vl(uint64_t regId, reg_t reqVL, reg_t newType){
       vtype = UINT64_MAX << (p->get_xlen() - 1);
     }
   }
-  vl = vlmax == 0 ? vlmax : (reqVL <= vlmax && regId != 0) ? reqVL : vlmax;
+
+  // set vl
+  if (vlmax == 0) {
+    vl = 0;
+  } else if (regId == 0) {
+    vl = vl > vlmax ? 0 : vl;
+  } else if (regId == -1) {
+    vl = vlmax;
+  } else if (regId >= 0) {
+    vl = reqVL > vlmax ? vlmax : reqVL;
+  }
+
   vstart = 0;
   setvl_count++;
   return vl;
diff --git a/riscv/processor.h b/riscv/processor.h
index 1591645..ef0319f 100644
--- a/riscv/processor.h
+++ b/riscv/processor.h
@@ -196,7 +196,7 @@ class vectorUnit_t {
       reg_file = 0;
     }
 
-    reg_t set_vl(uint64_t regId, reg_t reqVL, reg_t newType);
+    reg_t set_vl(int regId, reg_t reqVL, reg_t newType);
 
     reg_t get_vlen() { return VLEN; }
     reg_t get_elen() { return ELEN; }