Remove support for the x86 compat JIT from .NET Core.

These changes remove support for the x86 compat JIT from the build, the
runtime, and the various perf/test scripts.

Fixes #10733, #10734.

5 files changed, 2 insertions, 136 deletions

diff --git a/src/vm/codeman.cpp b/src/vm/codeman.cpp
index a30e70e7fa..d934b824f6 100644
--- a/src/vm/codeman.cpp
+++ b/src/vm/codeman.cpp
@@ -1219,7 +1219,6 @@ EEJitManager::EEJitManager()
 #if defined(_TARGET_X86_) || defined(_TARGET_AMD64_)
     m_JITCompilerOther = NULL;
 #endif
-    m_fLegacyJitUsed   = FALSE;
 
 #ifdef ALLOW_SXS_JIT
     m_alternateJit     = NULL;
@@ -1371,8 +1370,8 @@ void EEJitManager::SetCpuInfo()
 enum JIT_LOAD_JIT_ID
 {
     JIT_LOAD_MAIN = 500,    // The "main" JIT. Normally, this is named "clrjit.dll". Start at a number that is somewhat uncommon (i.e., not zero or 1) to help distinguish from garbage, in process dumps.
-    JIT_LOAD_LEGACY,        // The "legacy" JIT. Normally, this is named "compatjit.dll". This applies to AMD64 on Windows desktop, or x86 on Windows .NET Core.
-    JIT_LOAD_ALTJIT         // An "altjit". By default, named "protojit.dll". Used both internally, as well as externally for JIT CTP builds.
+    // 501 is JIT_LOAD_LEGACY on some platforms; please do not reuse this value.
+    JIT_LOAD_ALTJIT = 502   // An "altjit". By default, named "protojit.dll". Used both internally, as well as externally for JIT CTP builds.
 };
 
 enum JIT_LOAD_STATUS
@@ -1628,80 +1627,6 @@ BOOL EEJitManager::LoadJIT()
 
     // Set as a courtesy to code:CorCompileGetRuntimeDll
     s_ngenCompilerDll = m_JITCompiler;
-
-#if defined(_TARGET_X86_)
-    // If COMPlus_UseLegacyJit=1, then we fall back to compatjit.dll.
-    //
-    // This fallback mechanism was introduced for Visual Studio "14" Preview, when JIT64 (the legacy JIT) was replaced with
-    // RyuJIT. It was desired to provide a fallback mechanism in case comptibility problems (or other bugs)
-    // were discovered by customers. Setting this COMPLUS variable to 1 does not affect NGEN: existing NGEN images continue
-    // to be used, and all subsequent NGEN compilations continue to use the new JIT.
-    //
-    // If this is a compilation process, then we don't allow specifying a fallback JIT. This is a case where, when NGEN'ing,
-    // we sometimes need to JIT some things (such as when we are NGEN'ing mscorlib). In that case, we want to use exactly
-    // the same JIT as NGEN uses. And NGEN doesn't follow the COMPlus_UseLegacyJit=1 switch -- it always uses clrjit.dll.
-    //
-    // Note that we always load and initialize the default JIT. This is to handle cases where obfuscators rely on
-    // LoadLibrary("clrjit.dll") returning the module handle of the JIT, and then they call GetProcAddress("getJit") to get
-    // the EE-JIT interface. They also do this without also calling sxsJitStartup()!
-    //
-    // In addition, for reasons related to servicing, we only use RyuJIT when the registry value UseRyuJIT (type DWORD), under
-    // key HKLM\SOFTWARE\Microsoft\.NETFramework, is set to 1. Otherwise, we fall back to JIT64. Note that if this value
-    // is set, we also must use JIT64 for all NGEN compilations as well.
-    //
-    // See the document "RyuJIT Compatibility Fallback Specification.docx" for details.
-    //
-    // For .NET Core 1.2, RyuJIT for x86 is the primary jit (clrjit.dll) and JIT32 for x86 is the fallback, legacy JIT (compatjit.dll).
-    // Thus, the COMPlus_useLegacyJit=1 mechanism has been enabled for x86 CoreCLR. This scenario does not have the UseRyuJIT
-    // registry key, nor the AppX binder mode.
-
-    bool fUseRyuJit = true;
-
-    if ((!IsCompilationProcess() || !fUseRyuJit) &&     // Use RyuJIT for all NGEN, unless we're falling back to JIT64 for everything.
-        (newJitCompiler != nullptr))    // the main JIT must successfully load before we try loading the fallback JIT
-    {
-        BOOL fUsingCompatJit = FALSE;
-
-        if (!fUseRyuJit)
-        {
-            fUsingCompatJit = TRUE;
-        }
-
-        if (!fUsingCompatJit)
-        {
-            DWORD useLegacyJit = Configuration::GetKnobBooleanValue(W("System.JIT.UseWindowsX86CoreLegacyJit"), CLRConfig::EXTERNAL_UseWindowsX86CoreLegacyJit);
-            if (useLegacyJit == 1)
-            {
-                fUsingCompatJit = TRUE;
-            }
-        }
-
-
-        if (fUsingCompatJit)
-        {
-            // Now, load the compat jit and initialize it.
-
-            LPCWSTR pwzJitName = MAKEDLLNAME_W(W("compatjit"));
-
-            // Note: if the compatjit fails to load, we ignore it, and continue to use the main JIT for
-            // everything. You can imagine a policy where if the user requests the compatjit, and we fail
-            // to load it, that we fail noisily. We don't do that currently.
-            ICorJitCompiler* fallbackICorJitCompiler;
-            g_JitLoadData.jld_id = JIT_LOAD_LEGACY;
-            LoadAndInitializeJIT(pwzJitName, &m_JITCompilerOther, &fallbackICorJitCompiler, &g_JitLoadData);
-            if (fallbackICorJitCompiler != nullptr)
-            {
-                // Tell the main JIT to fall back to the "fallback" JIT compiler, in case some
-                // obfuscator tries to directly call the main JIT's getJit() function.
-                newJitCompiler->setRealJit(fallbackICorJitCompiler);
-
-                // Now, the compat JIT will be used.
-                m_fLegacyJitUsed = TRUE;
-            }
-        }
-    }
-#endif // (defined(_TARGET_AMD64_) && !defined(CROSSGEN_COMPILE)) || (defined(_TARGET_X86_) )
-
 #endif // !FEATURE_MERGE_JIT_AND_ENGINE
 
 #ifdef ALLOW_SXS_JIT
diff --git a/src/vm/codeman.h b/src/vm/codeman.h
index 9d7ed4d62f..cca5f5e2d2 100644
--- a/src/vm/codeman.h
+++ b/src/vm/codeman.h
@@ -1201,12 +1201,6 @@ public:
     HINSTANCE           m_JITCompilerOther; // Stores the handle of the legacy JIT, if one is loaded.
 #endif
 
-    // TRUE if the legacy/compat JIT was loaded successfully and will be used.
-    // This is available in all builds so if COMPlus_RequireLegacyJit=1 is set in a test,
-    // the test will fail in any build where the legacy JIT is not loaded, even if legacy
-    // fallback is not available in that build. This prevents unexpected silent successes.
-    BOOL                m_fLegacyJitUsed;
-
 #ifdef ALLOW_SXS_JIT
     //put these at the end so that we don't mess up the offsets in the DAC.
     ICorJitCompiler *   m_alternateJit;
diff --git a/src/vm/eeconfig.cpp b/src/vm/eeconfig.cpp
index 812d1df671..81f3957951 100644
--- a/src/vm/eeconfig.cpp
+++ b/src/vm/eeconfig.cpp
@@ -327,10 +327,6 @@ HRESULT EEConfig::Init()
 
     iRequireZaps = REQUIRE_ZAPS_NONE;
 
-#ifdef _TARGET_AMD64_
-    pDisableNativeImageLoadList = NULL;
-#endif
-
     // new loader behavior switches
 
     m_fDeveloperInstallation = false;
@@ -489,11 +485,6 @@ HRESULT EEConfig::Cleanup()
         delete pForbidZapsExcludeList;
 #endif
 
-#ifdef _TARGET_AMD64_
-    if (pDisableNativeImageLoadList)
-        delete pDisableNativeImageLoadList;
-#endif
-
 #ifdef FEATURE_COMINTEROP
     if (pszLogCCWRefCountChange)
         delete [] pszLogCCWRefCountChange;
@@ -996,16 +987,6 @@ HRESULT EEConfig::sync()
     }
 #endif
 
-#ifdef _TARGET_AMD64_
-    if (!IsCompilationProcess())
-    {
-        NewArrayHolder<WCHAR> wszDisableNativeImageLoadList;
-        IfFailRet(CLRConfig::GetConfigValue(CLRConfig::EXTERNAL_DisableNativeImageLoadList, &wszDisableNativeImageLoadList));
-        if (wszDisableNativeImageLoadList)
-            pDisableNativeImageLoadList = new AssemblyNamesList(wszDisableNativeImageLoadList);
-    }
-#endif
-
 #ifdef FEATURE_LOADER_OPTIMIZATION
     dwSharePolicy           = GetConfigDWORD_DontUse_(CLRConfig::EXTERNAL_LoaderOptimization, dwSharePolicy);
 #endif
@@ -1455,18 +1436,6 @@ bool EEConfig::ExcludeReadyToRun(LPCUTF8 assemblyName) const
     return false;
 }
 
-#ifdef _TARGET_AMD64_
-bool EEConfig::DisableNativeImageLoad(LPCUTF8 assemblyName) const
-{
-    LIMITED_METHOD_CONTRACT;
-
-    if (pDisableNativeImageLoadList != NULL && pDisableNativeImageLoadList->IsInList(assemblyName))
-        return true;
-
-    return false;
-}
-#endif
-
 /**************************************************************/
 #ifdef _DEBUG
 /**************************************************************/
diff --git a/src/vm/eeconfig.h b/src/vm/eeconfig.h
index e97385e3da..ae23f74755 100644
--- a/src/vm/eeconfig.h
+++ b/src/vm/eeconfig.h
@@ -758,11 +758,6 @@ public:
     bool    ForbidZap(LPCUTF8 assemblyName) const;
 #endif
     bool    ExcludeReadyToRun(LPCUTF8 assemblyName) const;
-
-#ifdef _TARGET_AMD64_
-    bool    DisableNativeImageLoad(LPCUTF8 assemblyName) const;
-    bool    IsDisableNativeImageLoadListNonEmpty() const { LIMITED_METHOD_CONTRACT; return (pDisableNativeImageLoadList != NULL); }
-#endif
     
     LPCWSTR ZapSet()                        const { LIMITED_METHOD_CONTRACT; return pZapSet; }
 
@@ -1122,16 +1117,6 @@ private: //----------------------------------------------------------------
     AssemblyNamesList * pForbidZapsExcludeList;
 #endif
 
-#ifdef _TARGET_AMD64_
-    // Assemblies for which we will not load a native image. This is from the COMPlus_DisableNativeImageLoadList
-    // variable / reg key. It performs the same function as the config file key "<disableNativeImageLoad>" (except
-    // that is it just a list of assembly names, which the config file key can specify full assembly identities).
-    // This was added to support COMPlus_UseLegacyJit, to support the rollout of RyuJIT to replace JIT64, where
-    // the user can cause the CLR to fall back to JIT64 for JITting but not for NGEN. This allows the user to
-    // force JITting for a specified list of NGEN assemblies.
-    AssemblyNamesList * pDisableNativeImageLoadList;
-#endif
-
     LPCWSTR pZapSet;
 
     bool fNgenBindOptimizeNonGac;
diff --git a/src/vm/jitinterface.cpp b/src/vm/jitinterface.cpp
index 5ef7700896..da803badcf 100644
--- a/src/vm/jitinterface.cpp
+++ b/src/vm/jitinterface.cpp
@@ -12614,13 +12614,6 @@ PCODE UnsafeJitFunction(MethodDesc* ftn, COR_ILMETHOD_DECODER* ILHeader, CORJIT_
         EEPOLICY_HANDLE_FATAL_ERROR_WITH_MESSAGE(COR_E_EXECUTIONENGINE, W("Failed to load JIT compiler"));
 #endif // ALLOW_SXS_JIT
     }
-
-    // If no compatjit wasn't used, but the user (normally a test case) requires that one is used, then fail.
-    // This is analogous to ZapRequire.
-    if (!jitMgr->m_fLegacyJitUsed && (CLRConfig::GetConfigValue(CLRConfig::EXTERNAL_RequireLegacyJit) == 1))
-    {
-        EEPOLICY_HANDLE_FATAL_ERROR_WITH_MESSAGE(COR_E_EXECUTIONENGINE, W("Failed to use legacy JIT compiler with RequireLegacyJit set"));
-    }
 #endif // CROSSGEN_COMPILE
 
 #ifdef _DEBUG