Fuzzing: Keep AVX flags enabled for Winch (bytecodealliance#10052)

* Fuzzing: Keep AVX flags enabled for Winch

* Check that SIMD is enabled

* Inspect flags in wast oracle

* Add log statement

Author: jeffcharles

crates/fuzzing/src/generators/codegen_settings.rs

@@ -31,6 +31,15 @@ impl CodegenSettings {
             }
         }
     }
+
+    /// Returns the flags used for codegen.
+    pub(crate) fn flags(&self) -> &[(String, String)] {
+        if let Self::Target { flags, .. } = self {
+            flags
+        } else {
+            &[]
+        }
+    }
 }
 
 impl<'a> Arbitrary<'a> for CodegenSettings {

crates/fuzzing/src/generators/config.rs

@@ -685,6 +685,17 @@ impl WasmtimeConfig {
         Ok(())
     }
 
+    /// Returns the codegen flag value, if any, for `name`.
+    pub(crate) fn codegen_flag(&self, name: &str) -> Option<&str> {
+        self.codegen.flags().iter().find_map(|(n, value)| {
+            if n == name {
+                Some(value.as_str())
+            } else {
+                None
+            }
+        })
+    }
+
     /// Helper to switch `MemoryConfig::CustomUnaligned` to
     /// `MemoryConfig::Normal`
     fn avoid_custom_unaligned_memory(&mut self, u: &mut Unstructured<'_>) -> arbitrary::Result<()> {

crates/fuzzing/src/oracles.rs

@@ -21,7 +21,7 @@ mod stacks;
 
 use self::diff_wasmtime::WasmtimeInstance;
 use self::engine::{DiffEngine, DiffInstance};
-use crate::generators::{self, DiffValue, DiffValueType};
+use crate::generators::{self, CompilerStrategy, DiffValue, DiffValueType};
 use crate::single_module_fuzzer::KnownValid;
 use arbitrary::Arbitrary;
 pub use stacks::check_stacks;
@@ -672,6 +672,25 @@ pub fn wast_test(mut fuzz_config: generators::Config, test: generators::WastTest
         return;
     }
 
+    // Winch requires AVX and AVX2 for SIMD tests to pass so don't run the test
+    // if either isn't enabled.
+    if fuzz_config.wasmtime.compiler_strategy == CompilerStrategy::Winch
+        && test.config.simd()
+        && (fuzz_config
+            .wasmtime
+            .codegen_flag("has_avx")
+            .is_some_and(|value| value == "false")
+            || fuzz_config
+                .wasmtime
+                .codegen_flag("has_avx2")
+                .is_some_and(|value| value == "false"))
+    {
+        log::warn!(
+            "Skipping Wast test because Winch doesn't support SIMD tests with AVX or AVX2 disabled"
+        );
+        return;
+    }
+
     // Fuel and epochs don't play well with threads right now, so exclude any
     // thread-spawning test if it looks like threads are spawned in that case.
     if fuzz_config.wasmtime.consume_fuel || fuzz_config.wasmtime.epoch_interruption {