8335191: RISC-V: verify perf of chacha20

Hamlin Li · Hamlin Li · commit 9d8791864ec4 · 2024-07-25T07:47:45.000Z
Reviewed-by: fyang
diff --git a/src/hotspot/cpu/riscv/vm_version_riscv.cpp b/src/hotspot/cpu/riscv/vm_version_riscv.cpp
@@ -252,7 +252,9 @@ void VM_Version::initialize() {
   }
 
   // ChaCha20
-  if (UseRVV) {
+  if (UseRVV && MaxVectorSize >= 32) {
+    // performance tests on hardwares (MaxVectorSize == 16, 32) show that
+    // it brings regression when MaxVectorSize == 16.
     if (FLAG_IS_DEFAULT(UseChaCha20Intrinsics)) {
       FLAG_SET_DEFAULT(UseChaCha20Intrinsics, true);
     }

Original file line number	Diff line number	Diff line change
`@@ -252,7 +252,9 @@ void VM_Version::initialize() {`
`252`	`252`	`}`
`253`	`253`
`254`	`254`	`// ChaCha20`
`255`		`- if (UseRVV) {`
	`255`	`+ if (UseRVV && MaxVectorSize >= 32) {`
	`256`	`+ // performance tests on hardwares (MaxVectorSize == 16, 32) show that`
	`257`	`+ // it brings regression when MaxVectorSize == 16.`
`256`	`258`	`if (FLAG_IS_DEFAULT(UseChaCha20Intrinsics)) {`
`257`	`259`	`FLAG_SET_DEFAULT(UseChaCha20Intrinsics, true);`
`258`	`260`	`}`