[wasm][fuzzer] Generate more and longer sequences

In Liftoff, bugs often happen only if specific cache states are
constructed. For this, longer sequences of instructions are needed.
Thus, add a few rules to increase the chance of generating longer
sequences.

R=ahaas@chromium.org

Change-Id: I8f112edf0280282bf275585e8a15772013c25245
Reviewed-on: https://chromium-review.googlesource.com/1158695Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54927}

test/fuzzer/wasm-compile.cc

@@ -382,9 +382,9 @@ class WasmGenerator {
 
   void set_global(DataRange& data) { global_op<kWasmStmt>(data); }
 
-  template <ValueType T1, ValueType T2>
+  template <ValueType... Types>
   void sequence(DataRange& data) {
-    Generate<T1, T2>(data);
+    Generate<Types...>(data);
   }
 
   void current_memory(DataRange& data) {
@@ -474,6 +474,9 @@ void WasmGenerator::Generate<kWasmStmt>(DataRange& data) {
 
   constexpr generate_fn alternates[] = {
       &WasmGenerator::sequence<kWasmStmt, kWasmStmt>,
+      &WasmGenerator::sequence<kWasmStmt, kWasmStmt, kWasmStmt, kWasmStmt>,
+      &WasmGenerator::sequence<kWasmStmt, kWasmStmt, kWasmStmt, kWasmStmt,
+                               kWasmStmt, kWasmStmt, kWasmStmt, kWasmStmt>,
       &WasmGenerator::block<kWasmStmt>,
       &WasmGenerator::loop<kWasmStmt>,
       &WasmGenerator::if_<kWasmStmt, kIf>,
@@ -510,7 +513,9 @@ void WasmGenerator::Generate<kWasmI32>(DataRange& data) {
   }
 
   constexpr generate_fn alternates[] = {
+      &WasmGenerator::sequence<kWasmI32, kWasmStmt>,
       &WasmGenerator::sequence<kWasmStmt, kWasmI32>,
+      &WasmGenerator::sequence<kWasmStmt, kWasmI32, kWasmStmt>,
 
       &WasmGenerator::op<kExprI32Eqz, kWasmI32>,
       &WasmGenerator::op<kExprI32Eq, kWasmI32, kWasmI32>,
@@ -599,7 +604,9 @@ void WasmGenerator::Generate<kWasmI64>(DataRange& data) {
   }
 
   constexpr generate_fn alternates[] = {
+      &WasmGenerator::sequence<kWasmI64, kWasmStmt>,
       &WasmGenerator::sequence<kWasmStmt, kWasmI64>,
+      &WasmGenerator::sequence<kWasmStmt, kWasmI64, kWasmStmt>,
 
       &WasmGenerator::op<kExprI64Add, kWasmI64, kWasmI64>,
       &WasmGenerator::op<kExprI64Sub, kWasmI64, kWasmI64>,
@@ -654,7 +661,9 @@ void WasmGenerator::Generate<kWasmF32>(DataRange& data) {
   }
 
   constexpr generate_fn alternates[] = {
+      &WasmGenerator::sequence<kWasmF32, kWasmStmt>,
       &WasmGenerator::sequence<kWasmStmt, kWasmF32>,
+      &WasmGenerator::sequence<kWasmStmt, kWasmF32, kWasmStmt>,
 
       &WasmGenerator::op<kExprF32Add, kWasmF32, kWasmF32>,
       &WasmGenerator::op<kExprF32Sub, kWasmF32, kWasmF32>,
@@ -685,7 +694,9 @@ void WasmGenerator::Generate<kWasmF64>(DataRange& data) {
   }
 
   constexpr generate_fn alternates[] = {
+      &WasmGenerator::sequence<kWasmF64, kWasmStmt>,
       &WasmGenerator::sequence<kWasmStmt, kWasmF64>,
+      &WasmGenerator::sequence<kWasmStmt, kWasmF64, kWasmStmt>,
 
       &WasmGenerator::op<kExprF64Add, kWasmF64, kWasmF64>,
       &WasmGenerator::op<kExprF64Sub, kWasmF64, kWasmF64>,