arch-riscv: Fix disassembling of operand list for compressed instructions

In disassembling compressed instructions, the original Gem5 gives needless
operands, such as register or immediate. This patch fixes the problem.
- Existing formats fixed: CIOp, CJOp, CBOp and Jump.
- New formats added: CIAddi4spnOp (for c.addi4spn only) and CompressedROp (with
  templates CBasicDeclare and CBasicExecute)

Change-Id: Ic293836983256a59d3a7aca091c8184b410516a4
Signed-off-by: Ian Jiang <ianjiang.ict@gmail.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/22566
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Alec Roelke <alec.roelke@gmail.com>
Maintainer: Alec Roelke <alec.roelke@gmail.com>

3 files changed, 78 insertions, 13 deletions

diff --git a/src/arch/riscv/isa/decoder.isa b/src/arch/riscv/isa/decoder.isa
index 78cb78ce6..fd9c574e1 100644
--- a/src/arch/riscv/isa/decoder.isa
+++ b/src/arch/riscv/isa/decoder.isa
@@ -36,7 +36,7 @@
 
 decode QUADRANT default Unknown::unknown() {
     0x0: decode COPCODE {
-        0x0: CIOp::c_addi4spn({{
+        0x0: CIAddi4spnOp::c_addi4spn({{
             imm = CIMM8<1:1> << 2 |
                   CIMM8<0:0> << 3 |
                   CIMM8<7:6> << 4 |
@@ -197,7 +197,7 @@ decode QUADRANT default Unknown::unknown() {
                     Rp1 = Rp1 & imm;
                 }}, uint64_t);
             }
-            format ROp {
+            format CompressedROp {
                 0x3: decode CFUNCT1 {
                     0x0: decode CFUNCT2LOW {
                         0x0: c_sub({{
@@ -328,7 +328,7 @@ decode QUADRANT default Unknown::unknown() {
                         ra = NPC;
                         NPC = Rc1;
                     }}, IsIndirectControl, IsUncondControl, IsCall);
-                    default: ROp::c_add({{
+                    default: CompressedROp::c_add({{
                         Rc1_sd = Rc1_sd + Rc2_sd;
                     }});
                 }
diff --git a/src/arch/riscv/isa/formats/compressed.isa b/src/arch/riscv/isa/formats/compressed.isa
index b520d53eb..9c812e886 100644
--- a/src/arch/riscv/isa/formats/compressed.isa
+++ b/src/arch/riscv/isa/formats/compressed.isa
@@ -36,8 +36,8 @@ def format CROp(code, *opt_flags) {{
     exec_output = BasicExecute.subst(iop)
 }};
 
-def format CIOp(imm_code, code, imm_type='int64_t', *opt_flags) {{
-    regs = ['_destRegIdx[0]','_srcRegIdx[0]']
+def format CIAddi4spnOp(imm_code, code, imm_type='int64_t', *opt_flags) {{
+    regs = ['_destRegIdx[0]', '_srcRegIdx[0]']
     iop = InstObjParams(name, Name, 'ImmOp<%s>' % imm_type,
         {'code': code, 'imm_code': imm_code,
          'regs': ','.join(regs)}, opt_flags)
@@ -47,8 +47,17 @@ def format CIOp(imm_code, code, imm_type='int64_t', *opt_flags) {{
     exec_output = ImmExecute.subst(iop)
 }};
 
+def format CIOp(imm_code, code, imm_type='int64_t', *opt_flags) {{
+    iop = InstObjParams(name, Name, 'ImmOp<%s>' % imm_type,
+        {'code': code, 'imm_code': imm_code,
+         'regs': '_destRegIdx[0]'}, opt_flags)
+    header_output = ImmDeclare.subst(iop)
+    decoder_output = ImmConstructor.subst(iop)
+    decode_block = BasicDecode.subst(iop)
+    exec_output = ImmExecute.subst(iop)
+}};
+
 def format CJOp(code, *opt_flags) {{
-    regs = ['_destRegIdx[0]', '_srcRegIdx[0]']
     imm_code = """
            imm =             CJUMPIMM3TO1 << 1 |
                              CJUMPIMM4TO4 << 4 |
@@ -62,7 +71,7 @@ def format CJOp(code, *opt_flags) {{
     """
     iop = InstObjParams(name, Name, 'ImmOp<int64_t>',
         {'code': code, 'imm_code': imm_code,
-         'regs': ','.join(regs)}, opt_flags)
+         'regs': ''}, opt_flags)
     header_output = BranchDeclare.subst(iop)
     decoder_output = ImmConstructor.subst(iop)
     decode_block = BasicDecode.subst(iop)
@@ -78,10 +87,10 @@ def format CBOp(code, *opt_flags) {{
                 if (CIMM3<2:2> > 0)
                     imm |= ~((int64_t)0xFF);
                """
-    regs = ['_srcRegIdx[0]','_srcRegIdx[1]']
+    regs = '_srcRegIdx[0]'
     iop = InstObjParams(name, Name, 'ImmOp<int64_t>',
         {'code': code, 'imm_code': imm_code,
-         'regs': ','.join(regs)}, opt_flags)
+         'regs': '_srcRegIdx[0]'}, opt_flags)
     header_output = BranchDeclare.subst(iop)
     decoder_output = ImmConstructor.subst(iop)
     decode_block = BasicDecode.subst(iop)
@@ -101,3 +110,61 @@ def format CompressedStore(sdisp_code, memacc_code,
         LoadStoreBase(name, Name, sdisp_code, ea_code, memacc_code, mem_flags,
         inst_flags, 'Store', exec_template_base='Store')
 }};
+
+// Compressed basic instruction class declaration template.
+def template CBasicDeclare {{
+    //
+    // Static instruction class for "%(mnemonic)s".
+    //
+    class %(class_name)s : public %(base_class)s
+    {
+      public:
+        /// Constructor.
+        %(class_name)s(MachInst machInst);
+        Fault execute(ExecContext *, Trace::InstRecord *) const override;
+        std::string generateDisassembly(Addr pc,
+            const SymbolTable *symtab) const override;
+    };
+}};
+
+// Compressed basic instruction class execute method template.
+def template CBasicExecute {{
+    Fault
+    %(class_name)s::execute(ExecContext *xc,
+        Trace::InstRecord *traceData) const
+    {
+        Fault fault = NoFault;
+
+        %(op_decl)s;
+        %(op_rd)s;
+        if (fault == NoFault) {
+            %(code)s;
+            if (fault == NoFault) {
+                %(op_wb)s;
+            }
+        }
+        return fault;
+    }
+
+    std::string
+    %(class_name)s::generateDisassembly(Addr pc,
+            const SymbolTable *symtab) const
+    {
+        std::vector<RegId> indices = {%(regs)s};
+        std::stringstream ss;
+        ss << mnemonic << ' ';
+        ss << registerName(indices[0]) << ", ";
+        ss << registerName(indices[1]);
+        return ss.str();
+    }
+}};
+
+def format CompressedROp(code, *opt_flags) {{
+    regs = ['_destRegIdx[0]','_srcRegIdx[1]']
+    iop = InstObjParams(name, Name, 'RegOp',
+        {'code': code, 'regs': ','.join(regs)}, opt_flags)
+    header_output = CBasicDeclare.subst(iop)
+    decoder_output = BasicConstructor.subst(iop)
+    decode_block = BasicDecode.subst(iop)
+    exec_output = CBasicExecute.subst(iop)
+}};
diff --git a/src/arch/riscv/isa/formats/standard.isa b/src/arch/riscv/isa/formats/standard.isa
index 3c71fc8fb..e67fdfcbd 100644
--- a/src/arch/riscv/isa/formats/standard.isa
+++ b/src/arch/riscv/isa/formats/standard.isa
@@ -203,9 +203,7 @@ def template JumpExecute {{
         std::vector<RegId> indices = {%(regs)s};
         std::stringstream ss;
         ss << mnemonic << ' ';
-        for (const RegId& idx: indices)
-            ss << registerName(idx) << ", ";
-        ss << imm;
+        ss << registerName(indices[0]);
         return ss.str();
     }
 }};
@@ -328,7 +326,7 @@ def format BOp(code, *opt_flags) {{
 }};
 
 def format Jump(code, *opt_flags) {{
-    regs = ['_destRegIdx[0]', '_srcRegIdx[0]']
+    regs = ['_srcRegIdx[0]']
     iop = InstObjParams(name, Name, 'ImmOp<int64_t>',
         {'code': code, 'imm_code': 'imm = sext<12>(IMM12);',
          'regs': ','.join(regs)}, opt_flags)