Delete FEATURE_DOUBLE_ALIGNMENT_HINT for GC heap allocations (#115985)

* Delete FEATURE_DOUBLE_ALIGNMENT_HINT for allocations

This optimization is no longer relevant on current x86 hardware. The performance penalty for misaligned memory access is negligible compared to what it used to be.

Fixes #101284

* Delete tests that are no longer applicable

Author: jkotas

src/coreclr/inc/clrconfigvalues.h

@@ -749,7 +749,6 @@ CONFIG_DWORD_INFO(INTERNAL_AlwaysUseMetadataInterfaceMapLayout, W("AlwaysUseMeta
 CONFIG_DWORD_INFO(INTERNAL_AssertOnUnneededThis, W("AssertOnUnneededThis"), 0, "While the ConfigDWORD is unnecessary, the contained ASSERT should be kept. This may result in some work tracking down violating MethodDescCallSites.")
 CONFIG_DWORD_INFO(INTERNAL_AssertStacktrace, W("AssertStacktrace"), 1, "")
 RETAIL_CONFIG_DWORD_INFO(EXTERNAL_DisableConfigCache, W("DisableConfigCache"), 0, "Used to disable the \"probabilistic\" config cache, which walks through the appropriate config registry keys on init and probabilistically keeps track of which exist.")
-RETAIL_CONFIG_DWORD_INFO(UNSUPPORTED_DoubleArrayToLargeObjectHeap, W("DoubleArrayToLargeObjectHeap"), 0, "Controls double[] placement")
 CONFIG_STRING_INFO(INTERNAL_DumpOnClassLoad, W("DumpOnClassLoad"), "Dumps information about loaded class to log.")
 CONFIG_DWORD_INFO(INTERNAL_ExpandAllOnLoad, W("ExpandAllOnLoad"), 0, "")
 CONFIG_DWORD_INFO(INTERNAL_ForceRelocs, W("ForceRelocs"), 0, "")

src/coreclr/inc/switches.h

@@ -151,8 +151,7 @@
 #define FEATURE_64BIT_ALIGNMENT
 #endif
 
-// Prefer double alignment for structs and arrays with doubles. Put arrays of doubles more agressively
-// into large object heap for performance because large object heap is 8 byte aligned
+// Prefer double alignment for structs with doubles on the stack.
 #if !defined(FEATURE_64BIT_ALIGNMENT) && !defined(HOST_64BIT)
 #define FEATURE_DOUBLE_ALIGNMENT_HINT
 #endif

src/coreclr/vm/eeconfig.cpp

@@ -173,10 +173,6 @@ HRESULT EEConfig::Init()
     fConditionalContracts = false;
 #endif
 
-#ifdef FEATURE_DOUBLE_ALIGNMENT_HINT
-    DoubleArrayToLargeObjectHeapThreshold = 1000;
-#endif
-
 #ifdef _DEBUG
     // interop logging
     m_TraceWrapper = 0;
@@ -468,10 +464,6 @@ HRESULT EEConfig::sync()
     }
 #endif // defined(FEATURE_READYTORUN)
 
-#ifdef FEATURE_DOUBLE_ALIGNMENT_HINT
-    DoubleArrayToLargeObjectHeapThreshold = CLRConfig::GetConfigValue(CLRConfig::UNSUPPORTED_DoubleArrayToLargeObjectHeap, DoubleArrayToLargeObjectHeapThreshold);
-#endif
-
 #ifdef _DEBUG
     IfFailRet (CLRConfig::GetConfigValue(CLRConfig::INTERNAL_BreakOnClassLoad, (LPWSTR*) &pszBreakOnClassLoad));
     pszBreakOnClassLoad = NarrowWideChar((LPWSTR)pszBreakOnClassLoad);

src/coreclr/vm/eeconfig.h

@@ -299,14 +299,6 @@ class EEConfig
     bool ExpandModulesOnLoad(void) const { LIMITED_METHOD_CONTRACT; return fExpandAllOnLoad; }
 #endif //_DEBUG
 
-#ifdef FEATURE_DOUBLE_ALIGNMENT_HINT
-    // Because the large object heap is 8 byte aligned, we want to put
-    // arrays of doubles there more agressively than normal objects.
-    // This is the threshold for this.  It is the number of doubles,
-    // not the number of bytes in the array.
-    unsigned int  GetDoubleArrayToLargeObjectHeapThreshold() const { LIMITED_METHOD_CONTRACT; return DoubleArrayToLargeObjectHeapThreshold; }
-#endif
-
 #ifdef TEST_DATA_CONSISTENCY
     // get the value of fTestDataConsistency, which controls whether we test that we can correctly detect
     // held locks in DAC builds. This is determined by an environment variable.
@@ -517,10 +509,6 @@ class EEConfig
     bool m_fBuiltInCOMInteropSupported;   // COM built-in support
 #endif // FEATURE_COMINTEROP
 
-#ifdef FEATURE_DOUBLE_ALIGNMENT_HINT
-    unsigned int DoubleArrayToLargeObjectHeapThreshold;  // double arrays of more than this number of elems go in large object heap
-#endif
-
 #ifdef _DEBUG
     bool fExpandAllOnLoad;              // True if we want to load all types/jit all methods in an assembly
                                         // at load time.

src/coreclr/vm/gchelpers.cpp

@@ -510,15 +510,6 @@ OBJECTREF AllocateSzArray(MethodTable* pArrayMT, INT32 cElements, GC_ALLOC_FLAGS
     size_t totalSize = safeTotalSize.Value();
 #endif
 
-#ifdef FEATURE_DOUBLE_ALIGNMENT_HINT
-    if ((pArrayMT->GetArrayElementTypeHandle() == CoreLibBinder::GetElementType(ELEMENT_TYPE_R8)) &&
-        ((DWORD)cElements >= g_pConfig->GetDoubleArrayToLargeObjectHeapThreshold()))
-    {
-        STRESS_LOG2(LF_GC, LL_INFO10, "Allocating double MD array of size %d and length %d to large object heap\n", totalSize, cElements);
-        flags |= GC_ALLOC_LARGE_OBJECT_HEAP;
-    }
-#endif
-
     if (totalSize >= LARGE_OBJECT_SIZE && totalSize >= GCHeapUtilities::GetGCHeap()->GetLOHThreshold())
         flags |= GC_ALLOC_LARGE_OBJECT_HEAP;
 
@@ -533,12 +524,6 @@ OBJECTREF AllocateSzArray(MethodTable* pArrayMT, INT32 cElements, GC_ALLOC_FLAGS
     }
     else
     {
-#ifdef FEATURE_DOUBLE_ALIGNMENT_HINT
-        if (pArrayMT->GetArrayElementTypeHandle() == CoreLibBinder::GetElementType(ELEMENT_TYPE_R8))
-        {
-            flags |= GC_ALLOC_ALIGN8;
-        }
-#endif
 #ifdef FEATURE_64BIT_ALIGNMENT
         MethodTable* pElementMT = pArrayMT->GetArrayElementTypeHandle().GetMethodTable();
         if (pElementMT->RequiresAlign8() && pElementMT->IsValueType())
@@ -773,15 +758,6 @@ OBJECTREF AllocateArrayEx(MethodTable *pArrayMT, INT32 *pArgs, DWORD dwNumArgs,
     size_t totalSize = safeTotalSize.Value();
 #endif
 
-#ifdef FEATURE_DOUBLE_ALIGNMENT_HINT
-    if ((pArrayMT->GetArrayElementTypeHandle() == CoreLibBinder::GetElementType(ELEMENT_TYPE_R8)) &&
-        (cElements >= g_pConfig->GetDoubleArrayToLargeObjectHeapThreshold()))
-    {
-        STRESS_LOG2(LF_GC, LL_INFO10, "Allocating double MD array of size %d and length %d to large object heap\n", totalSize, cElements);
-        flags |= GC_ALLOC_LARGE_OBJECT_HEAP;
-    }
-#endif
-
     if (totalSize >= LARGE_OBJECT_SIZE && totalSize >= GCHeapUtilities::GetGCHeap()->GetLOHThreshold())
         flags |= GC_ALLOC_LARGE_OBJECT_HEAP;
 

src/coreclr/vm/i386/jitinterfacex86.cpp

@@ -407,15 +407,8 @@ void *JIT_TrialAlloc::GenAllocArray(Flags flags)
     // array header or alignment.
     sl.Emit16(0xfa81);
 
-
-        // The large object heap is 8 byte aligned, so for double arrays we
-        // want to bias toward putting things in the large object heap
     unsigned maxElems =  0xffff - 256;
 
-#ifdef FEATURE_DOUBLE_ALIGNMENT_HINT
-    if ((flags & ALIGN8) && g_pConfig->GetDoubleArrayToLargeObjectHeapThreshold() < maxElems)
-        maxElems = g_pConfig->GetDoubleArrayToLargeObjectHeapThreshold();
-#endif // FEATURE_DOUBLE_ALIGNMENT_HINT
     if (flags & OBJ_ARRAY)
     {
         //Since we know that the array elements are sizeof(OBJECTREF), set maxElems exactly here (use the

src/coreclr/vm/jitinterface.cpp

@@ -5701,16 +5701,6 @@ CorInfoHelpFunc CEEInfo::getNewHelperStatic(MethodTable * pMT, bool * pHasSideEf
         helper = CORINFO_HELP_NEWSFAST;
     }
 
-#ifdef FEATURE_DOUBLE_ALIGNMENT_HINT
-    // If we are use the fast allocator we also may need the
-    // specialized varion for align8
-    if (pMT->GetClass()->IsAlign8Candidate() &&
-        (helper == CORINFO_HELP_NEWSFAST))
-    {
-        helper = CORINFO_HELP_NEWSFAST_ALIGN8;
-    }
-#endif // FEATURE_DOUBLE_ALIGNMENT_HINT
-
     return helper;
 }
 
@@ -5788,13 +5778,6 @@ CorInfoHelpFunc CEEInfo::getNewArrHelperStatic(TypeHandle clsHnd)
             // Use the slow helper
             result = CORINFO_HELP_NEWARR_1_DIRECT;
         }
-#ifdef FEATURE_DOUBLE_ALIGNMENT_HINT
-        else if (elemType == ELEMENT_TYPE_R8)
-        {
-            // Use the Align8 fast helper
-            result = CORINFO_HELP_NEWARR_1_ALIGN8;
-        }
-#endif
         else
         {
             // Yea, we can do it the fast way!

src/tests/JIT/Methodical/Methodical_d1.csproj

@@ -77,9 +77,6 @@
     <Compile Include="divrem\rem\r8rem.cs" />
     <Compile Include="divrem\rem\u4rem.cs" />
     <Compile Include="divrem\rem\u8rem.cs" />
-    <Compile Include="doublearray\dblarray1.cs" />
-    <Compile Include="doublearray\dblarray2.cs" />
-    <Compile Include="doublearray\dblarray3.cs" />
     <Compile Include="eh\basics\multihandler.cs" />
     <Compile Include="eh\basics\throwincatch.cs" />
     <Compile Include="eh\basics\throwinclassconstructor.cs" />
@@ -160,4 +157,4 @@
     <Compile Include="explicit\rotate\rotarg_valref.cs" />
   </ItemGroup>
   <Import Project="$(TestSourceDir)MergedTestRunner.targets" />
-</Project>
+</Project>

src/tests/JIT/Methodical/Methodical_do.csproj

@@ -73,9 +73,6 @@
     <Compile Include="divrem\rem\r8rem.cs" />
     <Compile Include="divrem\rem\u4rem.cs" />
     <Compile Include="divrem\rem\u8rem.cs" />
-    <Compile Include="doublearray\dblarray1.cs" />
-    <Compile Include="doublearray\dblarray2.cs" />
-    <Compile Include="doublearray\dblarray3.cs" />
     <Compile Include="eh\basics\multihandler.cs" />
     <Compile Include="eh\basics\throwincatch.cs" />
     <Compile Include="eh\basics\throwinclassconstructor.cs" />
@@ -284,4 +281,4 @@
     <Compile Include="xxobj\sizeof\sizeof64.cs" />
   </ItemGroup>
   <Import Project="$(TestSourceDir)MergedTestRunner.targets" />
-</Project>
+</Project>

src/tests/JIT/Methodical/Methodical_r1.csproj

@@ -78,9 +78,6 @@
     <Compile Include="divrem\rem\r8rem.cs" />
     <Compile Include="divrem\rem\u4rem.cs" />
     <Compile Include="divrem\rem\u8rem.cs" />
-    <Compile Include="doublearray\dblarray1.cs" />
-    <Compile Include="doublearray\dblarray2.cs" />
-    <Compile Include="doublearray\dblarray3.cs" />
     <Compile Include="eh\basics\multihandler.cs" />
     <Compile Include="eh\basics\throwincatch.cs" />
     <Compile Include="eh\basics\throwinclassconstructor.cs" />
@@ -161,4 +158,4 @@
     <Compile Include="explicit\rotate\rotarg_valref.cs" />
   </ItemGroup>
   <Import Project="$(TestSourceDir)MergedTestRunner.targets" />
-</Project>
+</Project>

src/tests/JIT/Methodical/Methodical_ro.csproj

@@ -73,9 +73,6 @@
     <Compile Include="divrem\rem\r8rem.cs" />
     <Compile Include="divrem\rem\u4rem.cs" />
     <Compile Include="divrem\rem\u8rem.cs" />
-    <Compile Include="doublearray\dblarray1.cs" />
-    <Compile Include="doublearray\dblarray2.cs" />
-    <Compile Include="doublearray\dblarray3.cs" />
     <Compile Include="eh\basics\multihandler.cs" />
     <Compile Include="eh\basics\throwincatch.cs" />
     <Compile Include="eh\basics\throwinclassconstructor.cs" />
@@ -284,4 +281,4 @@
     <Compile Include="xxobj\sizeof\sizeof64.cs" />
   </ItemGroup>
   <Import Project="$(TestSourceDir)MergedTestRunner.targets" />
-</Project>
+</Project>