[wasm] Reduce SIMD, branch and branchif generator weights

Branch and branchif generators might generate many endless loops.
Otherwise, the simd instructions got maybe a too high weight (which
makes sense in the beginning).

Change-Id: I92c15162aeaac5ab8941721febeb4c93b03a6b28
Reviewed-on: https://chrome-internal-review.googlesource.com/c/v8/fuzzilli/+/7977729
Commit-Queue: Eva Herencsárová <evih@google.com>
Reviewed-by: Carl Smith <cffsmith@google.com>

Author: evicy

Sources/Fuzzilli/CodeGen/CodeGeneratorWeights.swift

@@ -279,20 +279,20 @@ public let codeGeneratorWeights = [
     "WasmLegacyTryDelegateGenerator":           8,
     "WasmThrowGenerator":                       2,
     "WasmRethrowGenerator":                     10,
-    "WasmBranchGenerator":                      10,
-    "WasmBranchIfGenerator":                    10,
+    "WasmBranchGenerator":                      6,
+    "WasmBranchIfGenerator":                    6,
     "WasmJsCallGenerator":                      30,
 
     // Simd Generators
-    "ConstSimd128Generator":                    10,
-    "WasmSimd128IntegerUnOpGenerator":          10,
-    "WasmSimd128IntegerBinOpGenerator":         10,
-    "WasmSimd128FloatUnOpGenerator":            10,
-    "WasmSimd128FloatBinOpGenerator":           10,
-    "WasmSimd128CompareGenerator":              10,
-    "WasmI64x2SplatGenerator":                  10,
-    "WasmI64x2ExtractLaneGenerator":            10,
-    "WasmI64x2LoadSplatGenerator":              10,
+    "ConstSimd128Generator":                    5,
+    "WasmSimd128IntegerUnOpGenerator":          5,
+    "WasmSimd128IntegerBinOpGenerator":         5,
+    "WasmSimd128FloatUnOpGenerator":            5,
+    "WasmSimd128FloatBinOpGenerator":           5,
+    "WasmSimd128CompareGenerator":              5,
+    "WasmI64x2SplatGenerator":                  5,
+    "WasmI64x2ExtractLaneGenerator":            5,
+    "WasmI64x2LoadSplatGenerator":              5,
 
     "WasmSelectGenerator":                      10,
 ]

Tests/FuzzilliTests/LiveTests.swift

@@ -97,7 +97,6 @@ class LiveTests: XCTestCase {
             }
         }
 
-        // TODO(cffsmith): Try to lower this
         // We expect a maximum of 25% of Wasm execution attempts to fail.
         checkFailureRate(testResults: results, maxFailureRate: 0.25)
     }