[wasm] Optimize out redundant null checks in the jiterpreter (#81811)

* Optimize out duplicate null checks in the jiterpreter * Fix the last opcode of a jiterpreter trace sometimes executing again after the end of the trace
dotnet · Feb 9, 2023 · 2b70123 · 2b70123
1 parent 4570167
commit 2b70123
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Showing 4 changed files with 213 additions and 74 deletions.
diff --git a/src/mono/mono/utils/options-def.h b/src/mono/mono/utils/options-def.h
@@ -106,6 +106,8 @@ DEFINE_BOOL(jiterpreter_dump_traces, "jiterpreter-dump-traces", FALSE, "Dump the
 // Use runtime imports for pointer constants
 // Currently reduces performance significantly :(
 DEFINE_BOOL(jiterpreter_use_constants, "jiterpreter-use-constants", FALSE, "Use runtime imports for pointer constants")
+// Attempt to eliminate redundant null checks in compiled traces
+DEFINE_BOOL(jiterpreter_eliminate_null_checks, "jiterpreter-eliminate-null-checks", TRUE, "Attempt to eliminate redundant null checks in traces")
 // When compiling a jit_call wrapper, bypass sharedvt wrappers if possible by inlining their
 //  logic into the compiled wrapper and calling the target AOTed function with native call convention
 DEFINE_BOOL(jiterpreter_direct_jit_call, "jiterpreter-direct-jit-calls", TRUE, "Bypass gsharedvt wrappers when compiling JIT call wrappers")

diff --git a/src/mono/wasm/runtime/jiterpreter-support.ts b/src/mono/wasm/runtime/jiterpreter-support.ts
@@ -694,7 +694,8 @@ export const counters = {
     jitCallsCompiled: 0,
     directJitCallsCompiled: 0,
     failures: 0,
-    bytesGenerated: 0
+    bytesGenerated: 0,
+    nullChecksEliminated: 0,
 };
 
 export const _now = (globalThis.performance && globalThis.performance.now)
@@ -946,6 +947,7 @@ export type JiterpreterOptions = {
     useConstants: boolean;
     // Unwrap gsharedvt wrappers when compiling jitcalls if possible
     directJitCalls: boolean;
+    eliminateNullChecks: boolean;
     minimumTraceLength: number;
     minimumTraceHitCount: number;
     jitCallHitCount: number;
@@ -969,6 +971,7 @@ const optionNames : { [jsName: string] : string } = {
     "countBailouts": "jiterpreter-count-bailouts",
     "dumpTraces": "jiterpreter-dump-traces",
     "useConstants": "jiterpreter-use-constants",
+    "eliminateNullChecks": "jiterpreter-eliminate-null-checks",
     "directJitCalls": "jiterpreter-direct-jit-calls",
     "minimumTraceLength": "jiterpreter-minimum-trace-length",
     "minimumTraceHitCount": "jiterpreter-minimum-trace-hit-count",