RFR: 8368897: RISC-V: Cleanup RV_EXT_FEATURE_FLAGS & RV_NON_EXT_FEATURE_FLAGS

[Hamlin Li]

On Tue, 30 Sep 2025 03:03:04 GMT, Fei Yang <fyang at openjdk.org> wrote:

> Hi, You need merge and rebase :-) 

Thanks for reminding :) I think my forked master needs to be adjusted in some way, as seems I previously accidently pushed some commit to master instead of branch, I'll figure out it later.

> But the order of the detection of these extesions (the order in `RiscvHwprobe::add_features_from_query_result()`) still matters, right? Say we must detect `ext_v` before `ext_Zvbb`.

Yes, you're right.
But seems previous way (assert introduced in https://github.com/openjdk/jdk/pull/24094) does not work as expected, I moved ext_V below other ext_Zv ones, the assert was not triggerred, it's verified in a commit before (https://github.com/openjdk/jdk/pull/27152, https://github.com/openjdk/jdk/pull/27171), check below for a simple patch. I'll do more investigation and find out a way to catch the out of order detections in another PR.


diff --git a/src/hotspot/cpu/riscv/vm_version_riscv.hpp b/src/hotspot/cpu/riscv/vm_version_riscv.hpp
index a0a42fb5463..17e9635d0b6 100644
--- a/src/hotspot/cpu/riscv/vm_version_riscv.hpp
+++ b/src/hotspot/cpu/riscv/vm_version_riscv.hpp
@@ -169,7 +169,6 @@ class VM_Version : public Abstract_VM_Version {
   decl(ext_C           , "c"           ,    ('C' - 'A'), true , UPDATE_DEFAULT(UseRVC))             \
   decl(ext_Q           , "q"           ,    ('Q' - 'A'), true , NO_UPDATE_DEFAULT)                  \
   decl(ext_H           , "h"           ,    ('H' - 'A'), true , NO_UPDATE_DEFAULT)                  \
-  decl(ext_V           , "v"           ,    ('V' - 'A'), true , UPDATE_DEFAULT(UseRVV))             \
   decl(ext_Zicbom      , "Zicbom"      , RV_NO_FLAG_BIT, true , UPDATE_DEFAULT(UseZicbom))          \
   decl(ext_Zicboz      , "Zicboz"      , RV_NO_FLAG_BIT, true , UPDATE_DEFAULT(UseZicboz))          \
   decl(ext_Zicbop      , "Zicbop"      , RV_NO_FLAG_BIT, true , UPDATE_DEFAULT(UseZicbop))          \
@@ -193,6 +192,7 @@ class VM_Version : public Abstract_VM_Version {
   decl(ext_Zvbc        , "Zvbc"        , RV_NO_FLAG_BIT, true , UPDATE_DEFAULT_DEP(UseZvbc, ext_V)) \
   decl(ext_Zvfh        , "Zvfh"        , RV_NO_FLAG_BIT, true , UPDATE_DEFAULT_DEP(UseZvfh, ext_V)) \
   decl(ext_Zvkn        , "Zvkn"        , RV_NO_FLAG_BIT, true , UPDATE_DEFAULT_DEP(UseZvkn, ext_V)) \
+  decl(ext_V           , "v"           ,    ('V' - 'A'), true , UPDATE_DEFAULT(UseRVV))             \
   decl(ext_Zicond      , "Zicond"      , RV_NO_FLAG_BIT, true , UPDATE_DEFAULT(UseZicond))          \
   decl(mvendorid       , "VendorId"    , RV_NO_FLAG_BIT, false, NO_UPDATE_DEFAULT)                  \
   decl(marchid         , "ArchId"      , RV_NO_FLAG_BIT, false, NO_UPDATE_DEFAULT)                  \

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PR Comment: https://git.openjdk.org/jdk/pull/27562#issuecomment-3350827288