riscv64,exec: fix sra with shift amount >= 32

* the LSB of funct7 may be "1" due to the shift amount can be >= 32

src/isa/riscv64/exec/compute.c

@@ -24,8 +24,8 @@ make_EHelper(sll) {
 
 make_EHelper(srl) {
   rtl_andi(&id_src2->val, &id_src2->val, 0x3f);
-
-  if (decinfo.isa.instr.funct7 == 32) {
+  // the LSB of funct7 may be "1" due to the shift amount can be >= 32
+  if ((decinfo.isa.instr.funct7 & ~0x1) == 32) {
     // sra
     rtl_sar(&s0, &id_src->val, &id_src2->val);
     print_asm_template3(sra);
@@ -34,7 +34,6 @@ make_EHelper(srl) {
     rtl_shr(&s0, &id_src->val, &id_src2->val);
     print_asm_template3(srl);
   }
-
   rtl_sr(id_dest->reg, &s0, 4);
 }
 
@@ -118,6 +117,7 @@ make_EHelper(sllw) {
 
 make_EHelper(srlw) {
   rtl_andi(&id_src2->val, &id_src2->val, 0x1f);
+  assert((decinfo.isa.instr.funct7 & 0x1) == 0);
   if (decinfo.isa.instr.funct7 == 32) {
     // sraw
     rtl_sext(&id_src->val, &id_src->val, 4);