Optimize ValueSet::Kill

Skip calling DeleteAllImpureWhich for side effects which
MayDependOn will always return false, which happened 65-75% of
the times. In fact, SideEffects::None() was passed on ~50% of
the calls to Kill.

Based on local compiles, this CL improves GVN runtime by ~15% and
overall dex2oat runtime by ~1%.

Bug: 393108375
Test: art/test/testrunner/testrunner.py --host --64 -b --optimizing
Change-Id: Ib5cdb33c9caa5f2cfffbc1a650dabbda185a3c6d

1 files changed, 7 insertions, 3 deletions

diff --git a/compiler/optimizing/gvn.cc b/compiler/optimizing/gvn.cc
index 8a5a4742ba..d088e02132 100644
--- a/compiler/optimizing/gvn.cc
+++ b/compiler/optimizing/gvn.cc
@@ -125,9 +125,13 @@ class ValueSet : public ArenaObject<kArenaAllocGvn> {
 
   // Removes all instructions in the set affected by the given side effects.
   void Kill(SideEffects side_effects) {
-    DeleteAllImpureWhich([side_effects](Node* node) {
-      return node->GetSideEffects().MayDependOn(side_effects);
-    });
+    // Nothing to do if the side effects don't have any change bit set, as MayDependOn will always
+    // return false.
+    if (side_effects.HasSideEffects()) {
+      DeleteAllImpureWhich([side_effects](Node* node) {
+        return node->GetSideEffects().MayDependOn(side_effects);
+      });
+    }
   }
 
   void Clear() {