JIT: Seed stress modes by string hash (#83771)

Instead of using the numeric value of each stress mode inside the enum,
calculate a hash based on the string name. This has the benefit that it
won't change based on new members being added/reordered and reduces
correlation of which stress modes get enabled together.

Fix #83733

diff --git a/src/coreclr/jit/compiler.cpp b/src/coreclr/jit/compiler.cpp
index e3d3e03..60b43f3 100644 (file)
--- a/src/coreclr/jit/compiler.cpp
+++ b/src/coreclr/jit/compiler.cpp
@@ -3409,13 +3409,20 @@ bool Compiler::compJitHaltMethod()
  *    It should reflect the usefulness:overhead ratio.
  */
 
-const LPCWSTR Compiler::s_compStressModeNames[STRESS_COUNT + 1] = {
+const LPCWSTR Compiler::s_compStressModeNamesW[STRESS_COUNT + 1] = {
 #define STRESS_MODE(mode) W("STRESS_") W(#mode),
 
     STRESS_MODES
 #undef STRESS_MODE
 };
 
+const char* Compiler::s_compStressModeNames[STRESS_COUNT + 1] = {
+#define STRESS_MODE(mode) "STRESS_" #mode,
+
+    STRESS_MODES
+#undef STRESS_MODE
+};
+
 //------------------------------------------------------------------------
 // compStressCompile: determine if a stress mode should be enabled
 //
@@ -3459,7 +3466,7 @@ bool Compiler::compStressCompile(compStressArea stressArea, unsigned weight)
     {
         if (verbose)
         {
-            printf("\n\n*** JitStress: %ws ***\n\n", s_compStressModeNames[stressArea]);
+            printf("\n\n*** JitStress: %s ***\n\n", s_compStressModeNames[stressArea]);
         }
         compActiveStressModes[stressArea] = 1;
     }
@@ -3468,6 +3475,35 @@ bool Compiler::compStressCompile(compStressArea stressArea, unsigned weight)
 }
 
 //------------------------------------------------------------------------
+// compStressAreaHash: Get (or compute) a hash code for a stress area.
+//
+// Arguments:
+//   stressArea - stress mode
+//
+// Returns:
+//   A hash code for the specific stress area.
+//
+unsigned Compiler::compStressAreaHash(compStressArea area)
+{
+    static LONG s_hashCodes[STRESS_COUNT];
+    assert(static_cast<unsigned>(area) < ArrLen(s_hashCodes));
+
+    unsigned result = (unsigned)s_hashCodes[area];
+    if (result == 0)
+    {
+        result = HashStringA(s_compStressModeNames[area]);
+        if (result == 0)
+        {
+            result = 1;
+        }
+
+        InterlockedExchange(&s_hashCodes[area], (LONG)result);
+    }
+
+    return result;
+}
+
+//------------------------------------------------------------------------
 // compStressCompileHelper: helper to determine if a stress mode should be enabled
 //
 // Arguments:
@@ -3497,7 +3533,7 @@ bool Compiler::compStressCompileHelper(compStressArea stressArea, unsigned weigh
     // Does user explicitly prevent using this STRESS_MODE through the command line?
     const WCHAR* strStressModeNamesNot = JitConfig.JitStressModeNamesNot();
     if ((strStressModeNamesNot != nullptr) &&
-        (wcsstr(strStressModeNamesNot, s_compStressModeNames[stressArea]) != nullptr))
+        (wcsstr(strStressModeNamesNot, s_compStressModeNamesW[stressArea]) != nullptr))
     {
         return false;
     }
@@ -3506,7 +3542,7 @@ bool Compiler::compStressCompileHelper(compStressArea stressArea, unsigned weigh
     const WCHAR* strStressModeNames = JitConfig.JitStressModeNames();
     if (strStressModeNames != nullptr)
     {
-        if (wcsstr(strStressModeNames, s_compStressModeNames[stressArea]) != nullptr)
+        if (wcsstr(strStressModeNames, s_compStressModeNamesW[stressArea]) != nullptr)
         {
             return true;
         }
@@ -3548,7 +3584,7 @@ bool Compiler::compStressCompileHelper(compStressArea stressArea, unsigned weigh
 
     // Get a hash which can be compared with 'weight'
     assert(stressArea != 0);
-    const unsigned hash = (info.compMethodHash() ^ stressArea ^ stressLevel) % MAX_STRESS_WEIGHT;
+    const unsigned hash = (info.compMethodHash() ^ compStressAreaHash(stressArea) ^ stressLevel) % MAX_STRESS_WEIGHT;
 
     assert(hash < MAX_STRESS_WEIGHT && weight <= MAX_STRESS_WEIGHT);
     return (hash < weight);

diff --git a/src/coreclr/jit/compiler.h b/src/coreclr/jit/compiler.h
index b731e5e..53deac2 100644 (file)
--- a/src/coreclr/jit/compiler.h
+++ b/src/coreclr/jit/compiler.h
@@ -9675,7 +9675,6 @@ public:
         STRESS_MODE(MAKE_CSE)                                                                   \
         STRESS_MODE(LEGACY_INLINE)                                                              \
         STRESS_MODE(CLONE_EXPR)                                                                 \
-        STRESS_MODE(USE_CMOV)                                                                   \
         STRESS_MODE(FOLD)                                                                       \
         STRESS_MODE(MERGED_RETURNS)                                                             \
         STRESS_MODE(BB_PROFILE)                                                                 \
@@ -9731,7 +9730,8 @@ public:
 // clang-format on
 
 #ifdef DEBUG
-    static const LPCWSTR s_compStressModeNames[STRESS_COUNT + 1];
+    static const LPCWSTR s_compStressModeNamesW[STRESS_COUNT + 1];
+    static const char*   s_compStressModeNames[STRESS_COUNT + 1];
     BYTE                 compActiveStressModes[STRESS_COUNT];
 #endif // DEBUG
 
@@ -9739,6 +9739,7 @@ public:
 
     bool compStressCompile(compStressArea stressArea, unsigned weightPercentage);
     bool compStressCompileHelper(compStressArea stressArea, unsigned weightPercentage);
+    static unsigned compStressAreaHash(compStressArea area);
 
 #ifdef DEBUG