JIT: random partial compilation stress mode (#107561)

When JitRandomPartialCompilation is nonzero, allow partial compilation patchpoints at the start of randomly chosen patchpoint-eligible blocks. Enable this stress mode in the jit-experimental pipeline.
dotnet · Sep 13, 2024 · f722e5c · f722e5c
1 parent cf9c995
commit f722e5c
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Showing 4 changed files with 32 additions and 6 deletions.
diff --git a/eng/pipelines/common/templates/runtimes/run-test-job.yml b/eng/pipelines/common/templates/runtimes/run-test-job.yml
@@ -539,6 +539,7 @@ jobs:
             scenarios:
             - jitosr_stress
             - jitpartialcompilation_pgo
+            - jitpartialcompilation_pgo_stress_random
             - jitoptrepeat
             - jitoldlayout
           ${{ else }}:
@@ -548,6 +549,7 @@ jobs:
             - jit_stress_splitting
             - jitpartialcompilation
             - jitpartialcompilation_pgo
+            - jitpartialcompilation_pgo_stress_random
             - jitobjectstackallocation
             - jitphysicalpromotion_only
             - jitphysicalpromotion_full

diff --git a/src/coreclr/jit/importer.cpp b/src/coreclr/jit/importer.cpp
@@ -6238,17 +6238,36 @@ void Compiler::impImportBlockCode(BasicBlock* block)
     //
     // Note unlike OSR, it's ok to forgo these.
     //
-    // Todo: stress mode...
-    //
     if (opts.jitFlags->IsSet(JitFlags::JIT_FLAG_TIER0) && (JitConfig.TC_PartialCompilation() > 0) &&
-        compCanHavePatchpoints() && !compTailPrefixSeen)
+        compCanHavePatchpoints() && !compTailPrefixSeen && (verCurrentState.esStackDepth == 0) &&
+        !block->HasFlag(BBF_PATCHPOINT) && !block->hasHndIndex())
     {
         // Is this block a good place for partial compilation?
         //
-        if ((block != fgFirstBB) && block->isRunRarely() && (verCurrentState.esStackDepth == 0) &&
-            !block->HasFlag(BBF_PATCHPOINT) && !block->hasHndIndex())
+        bool addPartialCompilationPatchpoint = (block != fgFirstBB) && block->isRunRarely();
+
+#ifdef DEBUG
+        // Stress mode
+        //
+        const char* reason                   = "rarely run";
+        const int   randomPartialCompilation = JitConfig.JitRandomPartialCompilation();
+        if (randomPartialCompilation > 0)
+        {
+            // Reuse the random inliner's random state.
+            // Note m_inlineStrategy is always created, even if we're not inlining.
+            //
+            CLRRandom* const random      = impInlineRoot()->m_inlineStrategy->GetRandom(randomPartialCompilation);
+            const int        randomValue = (int)random->Next(100);
+
+            addPartialCompilationPatchpoint = (randomValue < randomPartialCompilation);
+            reason                          = "randomly chosen";
+        }
+#endif
+
+        if (addPartialCompilationPatchpoint)
         {
-            JITDUMP("\nBlock " FMT_BB " will be a partial compilation patchpoint -- not importing\n", block->bbNum);
+            JITDUMP("\nBlock " FMT_BB " (%s) will be a partial compilation patchpoint -- not importing\n", block->bbNum,
+                    reason);
             block->SetFlags(BBF_PARTIAL_COMPILATION_PATCHPOINT);
             setMethodHasPartialCompilationPatchpoint();
 

diff --git a/src/coreclr/jit/jitconfigvalues.h b/src/coreclr/jit/jitconfigvalues.h
@@ -683,6 +683,9 @@ RELEASE_CONFIG_INTEGER(TC_OnStackReplacement_InitialCounter, W("TC_OnStackReplac
 // Enable partial compilation for Tier0 methods
 RELEASE_CONFIG_INTEGER(TC_PartialCompilation, W("TC_PartialCompilation"), 0)
 
+// If partial compilation is enabled, use random heuristic for patchpoint placement
+CONFIG_INTEGER(JitRandomPartialCompilation, W("JitRandomPartialCompilation"), 0)
+
 // Patchpoint strategy:
 // 0 - backedge sources
 // 1 - backedge targets

diff --git a/src/tests/Common/testenvironment.proj b/src/tests/Common/testenvironment.proj
@@ -70,6 +70,7 @@
       DOTNET_JitRandomGuardedDevirtualization;
       DOTNET_JitRandomEdgeCounts;
       DOTNET_JitRandomOnStackReplacement;
+      DOTNET_JitRandomPartialComplation;
       DOTNET_JitRandomlyCollect64BitCounts;
       DOTNET_JitStressModeNames;
       DOTNET_JitGuardedDevirtualizationMaxTypeChecks;
@@ -225,6 +226,7 @@
     <TestEnvironment Include="jit_stress_splitting" JitFakeProcedureSplitting="1" JitStressProcedureSplitting="1" />
     <TestEnvironment Include="jitpartialcompilation" TC_PartialCompilation="1" TC_QuickJitForLoops="1" TieredCompilation="1" />
     <TestEnvironment Include="jitpartialcompilation_pgo" TC_PartialCompilation="1" TC_QuickJitForLoops="1" TieredCompilation="1" TieredPGO="1" />
+    <TestEnvironment Include="jitpartialcompilation_pgo_stress_random" TC_PartialCompilation="1" TC_QuickJitForLoops="1" TieredCompilation="1" TieredPGO="1" JitRandomPartialCompilation="15" />
     <TestEnvironment Include="jitobjectstackallocation" JitObjectStackAllocation="1" TieredCompilation="0" />
     <TestEnvironment Include="jitphysicalpromotion_only" JitStressModeNames="STRESS_NO_OLD_PROMOTION" TieredCompilation="0" />
     <TestEnvironment Include="jitphysicalpromotion_full" JitStressModeNames="STRESS_PHYSICAL_PROMOTION_COST STRESS_NO_OLD_PROMOTION" TieredCompilation="0" />