Allocate space for siLatestTrackedScopes on demand

By the time siLatestTrackedScopes is needed the number of tracked variables is known so we can allocate an array of suitable size. Defaulting to lclMAX_TRACKED requires 4 kbytes and for many small methods that's a waste.

Commit migrated from https://github.com/dotnet/coreclr/commit/2e0cc331a72b2473317f9652646bcc6796ece449

diff --git a/src/coreclr/src/jit/codegen.h b/src/coreclr/src/jit/codegen.h
index 755859a..ef20943 100644 (file)
--- a/src/coreclr/src/jit/codegen.h
+++ b/src/coreclr/src/jit/codegen.h
@@ -626,7 +626,7 @@ protected:
 
     // Tracks the last entry for each tracked register variable
 
-    siScope* siLatestTrackedScopes[lclMAX_TRACKED];
+    siScope** siLatestTrackedScopes;
 
     IL_OFFSET siLastEndOffs; // IL offset of the (exclusive) end of the last block processed
 

diff --git a/src/coreclr/src/jit/scopeinfo.cpp b/src/coreclr/src/jit/scopeinfo.cpp
index 366a060..41c3435 100644 (file)
--- a/src/coreclr/src/jit/scopeinfo.cpp
+++ b/src/coreclr/src/jit/scopeinfo.cpp
@@ -377,19 +377,33 @@ void CodeGen::siInit()
 
     if (compiler->info.compVarScopesCount == 0)
     {
-        return;
+        siLatestTrackedScopes = nullptr;
     }
-
+    else
+    {
 #if FEATURE_EH_FUNCLETS
-    siInFuncletRegion = false;
+        siInFuncletRegion = false;
 #endif // FEATURE_EH_FUNCLETS
 
-    for (unsigned i = 0; i < lclMAX_TRACKED; i++)
-    {
-        siLatestTrackedScopes[i] = nullptr;
-    }
+        unsigned scopeCount = compiler->lvaTrackedCount;
 
-    compiler->compResetScopeLists();
+        if (scopeCount == 0)
+        {
+            siLatestTrackedScopes = nullptr;
+        }
+        else
+        {
+            siLatestTrackedScopes =
+                static_cast<siScope**>(compiler->compGetMemArray(scopeCount, sizeof(siScope*), CMK_SiScope));
+
+            for (unsigned i = 0; i < scopeCount; i++)
+            {
+                siLatestTrackedScopes[i] = nullptr;
+            }
+        }
+
+        compiler->compResetScopeLists();
+    }
 }
 
 /*****************************************************************************
@@ -669,8 +683,6 @@ void CodeGen::siUpdate()
         LclVarDsc* lclVar = &compiler->lvaTable[lclNum];
         assert(lclVar->lvTracked);
 #endif
-
-        siScope* scope = siLatestTrackedScopes[varIndex];
         siEndTrackedScope(varIndex);
     }