[gem5-dev] [S] Change in gem5/gem5[develop]: arch-riscv: Revert CSR instruction fixes

[Melissa Jost (Gerrit) via gem5-dev]

Melissa Jost has uploaded this change for review. (  
https://gem5-review.googlesource.com/c/public/gem5/+/68637?usp=email )

Change subject: arch-riscv: Revert CSR instruction fixes
......................................................................

arch-riscv: Revert CSR instruction fixes

This reverts commit 4b1c24542065380c6cff7ab2baa25e216a0ad38e
and commit 89c49d1ab06ea5364ab1f80586f8b01c0297cb12 because
they are causing the RISC-V Ubuntu boot test within the
nightly tests to hang and time out.

Change-Id: Ia4d8098ec940cb5900256c8cede0146256c851e5
---
M src/arch/riscv/insts/standard.hh
M src/arch/riscv/isa/formats/standard.isa
2 files changed, 8 insertions(+), 26 deletions(-)



diff --git a/src/arch/riscv/insts/standard.hh  
b/src/arch/riscv/insts/standard.hh
index 2dfe73a..5b0e8c2 100644
--- a/src/arch/riscv/insts/standard.hh
+++ b/src/arch/riscv/insts/standard.hh
@@ -91,33 +91,18 @@
   protected:
     uint64_t csr;
     uint64_t uimm;
-    bool read;
-    bool write;

     /// Constructor
     CSROp(const char *mnem, ExtMachInst _machInst, OpClass __opClass)
         : RiscvStaticInst(mnem, _machInst, __opClass),
-            csr(FUNCT12), uimm(CSRIMM), read(true), write(true)
+            csr(FUNCT12), uimm(CSRIMM)
     {
         if (csr == CSR_SATP) {
             flags[IsSquashAfter] = true;
         }
-        if (strcmp(mnemonic, "csrrw") == 0 ||
-            strcmp(mnemonic, "csrrwi") == 0) {
-          if (RD == 0){
-            read = false;
-          }
-        } else if (strcmp(mnemonic, "csrrs") == 0 ||
-                   strcmp(mnemonic, "csrrc") == 0 ||
-                   strcmp(mnemonic, "csrrsi") == 0 ||
-                   strcmp(mnemonic, "csrrci") == 0 ){
-          if (RS1 == 0 || uimm == 0) {
-            write = false;
-          }
-        }
     }

-  std::string generateDisassembly(
+    std::string generateDisassembly(
         Addr pc, const loader::SymbolTable *symtab) const override;
 };

diff --git a/src/arch/riscv/isa/formats/standard.isa  
b/src/arch/riscv/isa/formats/standard.isa
index c94a0bc..bb500f5 100644
--- a/src/arch/riscv/isa/formats/standard.isa
+++ b/src/arch/riscv/isa/formats/standard.isa
@@ -358,7 +358,7 @@
         %(op_decl)s;
         %(op_rd)s;

-        RegVal data = 0, olddata = 0, nonmaskdata = 0;
+        RegVal data, olddata;
         auto lowestAllowedMode = (PrivilegeMode)bits(csr, 9, 8);
         auto pm = (PrivilegeMode)xc->readMiscReg(MISCREG_PRV);
         if (pm < lowestAllowedMode) {
@@ -380,13 +380,11 @@
             break;
         }

-        if (read) {
-          if (csr == CSR_FCSR) {
+        if (csr == CSR_FCSR) {
             olddata = xc->readMiscReg(MISCREG_FFLAGS) |
-              (xc->readMiscReg(MISCREG_FRM) << FRM_OFFSET);
-          } else {
+                      (xc->readMiscReg(MISCREG_FRM) << FRM_OFFSET);
+        } else {
             olddata = xc->readMiscReg(midx);
-          }
         }
         olddata = rvZext(olddata);
         auto olddata_all = olddata;
@@ -397,9 +395,8 @@

         %(code)s;

-        nonmaskdata = data & ~maskVal;
         data &= maskVal;
-        if (write) {
+        if (data != olddata) {
             if (bits(csr, 11, 10) == 0x3) {
                 return std::make_shared<IllegalInstFault>(
                         csprintf("CSR %s is read-only\n", csrName),  
machInst);
@@ -420,7 +417,7 @@
               case CSR_SIP: case CSR_SIE:
               case CSR_UIP: case CSR_UIE:
               case CSR_MSTATUS: case CSR_SSTATUS: case CSR_USTATUS:
-                if (nonmaskdata == 0) {
+                if (newdata_all != olddata_all) {
                     xc->setMiscReg(midx, newdata_all);
                 } else {
                     return std::make_shared<IllegalInstFault>(

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Gerrit-Project: public/gem5
Gerrit-Branch: develop
Gerrit-Change-Id: Ia4d8098ec940cb5900256c8cede0146256c851e5
Gerrit-Change-Number: 68637
Gerrit-PatchSet: 1
Gerrit-Owner: Melissa Jost <melissakj...@gmail.com>
Gerrit-MessageType: newchange
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