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don't read CSR in csrrw(i) with rd=0 #1628

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don't read CSR in csrrw(i) with rd=0 #1628

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5 changes: 4 additions & 1 deletion riscv/insns/csrrw.h
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Original file line number Diff line number Diff line change
@@ -1,5 +1,8 @@
int csr = validate_csr(insn.csr(), true);
reg_t old = p->get_csr(csr, insn, true);
reg_t old = (insn.rd() != 0) ? p->get_csr(csr, insn, true) : 0; // don't if rd = 0
auto &csrmap = p->get_state()->csrmap;
// permission on write
csrmap.count(csr) ? csrmap[csr]->verify_permissions(insn, true) : throw trap_illegal_instruction(insn.bits());
p->put_csr(csr, RS1);
WRITE_RD(sext_xlen(old));
serialize();
5 changes: 4 additions & 1 deletion riscv/insns/csrrwi.h
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Original file line number Diff line number Diff line change
@@ -1,5 +1,8 @@
int csr = validate_csr(insn.csr(), true);
reg_t old = p->get_csr(csr, insn, true);
reg_t old = (insn.rd() != 0) ? p->get_csr(csr, insn, true) : 0; // don't if rd = 0
auto &csrmap = p->get_state()->csrmap;
// permission on write
csrmap.count(csr) ? csrmap[csr]->verify_permissions(insn, true) : throw trap_illegal_instruction(insn.bits());
p->put_csr(csr, insn.rs1());
WRITE_RD(sext_xlen(old));
serialize();