[gem5-dev] Change in gem5/gem5[develop]: arch-riscv: rvc instruction is mistaken as branch

[Jin Cui (Gerrit) via gem5-dev]

Jin Cui has uploaded this change for review. (  
https://gem5-review.googlesource.com/c/public/gem5/+/54644 )

Change subject: arch-riscv: rvc instruction is mistaken as branch
......................................................................

arch-riscv: rvc instruction is mistaken as branch

Fetch in O3CPU mistakes the normal non-branchign compressed
instructions, and regards it as a branch. This issue brokes
the consecutive instruction stream, thus affecting performance
of cpu front-end.
This fix sets the compressed for PCState during decoding.

Jira Issue: https://gem5.atlassian.net/browse/GEM5-1137

Change-Id: I7607d563bba8a08869e104877fc3c11c94cbe904
---
M src/arch/riscv/decoder.cc
1 file changed, 19 insertions(+), 0 deletions(-)



diff --git a/src/arch/riscv/decoder.cc b/src/arch/riscv/decoder.cc
index 4fbcc64..a02415f 100644
--- a/src/arch/riscv/decoder.cc
+++ b/src/arch/riscv/decoder.cc
@@ -105,8 +105,10 @@

     if (compressed(emi)) {
         next_pc.npc(next_pc.instAddr() + sizeof(machInst) / 2);
+        next_pc.compressed(true);
     } else {
         next_pc.npc(next_pc.instAddr() + sizeof(machInst));
+        next_pc.compressed(false);
     }

     return decode(emi, next_pc.instAddr());

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Gerrit-Project: public/gem5
Gerrit-Branch: develop
Gerrit-Change-Id: I7607d563bba8a08869e104877fc3c11c94cbe904
Gerrit-Change-Number: 54644
Gerrit-PatchSet: 1
Gerrit-Owner: Jin Cui <cuijinb...@gmail.com>
Gerrit-MessageType: newchange
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