[wasm-simd] Scalar lowering to convert i8x16 to f32x4

Implement conversion of an i8x16 node to a f32x4 node.

Bug: v8:10507
Change-Id: Ifefffb779dbf25b57eae278afe41c11b41c949ac
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2185472Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67659}

src/compiler/simd-scalar-lowering.cc

@@ -1833,6 +1833,9 @@ Node** SimdScalarLowering::GetReplacementsWithType(Node* node, SimdType type) {
       Int32ToFloat32(replacements, result);
     } else if (ReplacementType(node) == SimdType::kInt16x8) {
       UNIMPLEMENTED();
+    } else if (ReplacementType(node) == SimdType::kInt8x16) {
+      SmallerIntToInt32<int8_t>(replacements, result);
+      Int32ToFloat32(result, result);
     } else {
       UNREACHABLE();
     }

test/cctest/BUILD.gn

@@ -290,6 +290,7 @@ v8_source_set("cctest_sources") {
     "wasm/test-run-wasm-module.cc",
     "wasm/test-run-wasm-sign-extension.cc",
     "wasm/test-run-wasm-simd-liftoff.cc",
+    "wasm/test-run-wasm-simd-scalar-lowering.cc",
     "wasm/test-run-wasm-simd.cc",
     "wasm/test-run-wasm.cc",
     "wasm/test-streaming-compilation.cc",

test/cctest/cctest.status

@@ -484,6 +484,7 @@
   'test-run-wasm-module/*': [SKIP],
   'test-run-wasm-sign-extension/*': [SKIP],
   'test-run-wasm-simd-liftoff/*': [SKIP],
+  'test-run-wasm-simd-scalar-lowering/*': [SKIP],
   'test-run-wasm-simd/*': [SKIP],
   'test-streaming-compilation/*': [SKIP],
   'test-wasm-breakpoints/*': [SKIP],

test/cctest/wasm/test-run-wasm-simd-scalar-lowering.cc

+// Copyright 2020 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "src/wasm/compilation-environment.h"
+#include "src/wasm/wasm-tier.h"
+#include "test/cctest/cctest.h"
+#include "test/cctest/wasm/wasm-run-utils.h"
+#include "test/common/wasm/flag-utils.h"
+#include "test/common/wasm/wasm-macro-gen.h"
+
+namespace v8 {
+namespace internal {
+namespace wasm {
+namespace test_run_wasm_simd {
+
+#define WASM_SIMD_TEST(name)                                     \
+  void RunWasm_##name##_Impl(LowerSimd lower_simd,               \
+                             ExecutionTier execution_tier);      \
+  TEST(RunWasm_##name##_simd_lowered) {                          \
+    EXPERIMENTAL_FLAG_SCOPE(simd);                               \
+    RunWasm_##name##_Impl(kLowerSimd, ExecutionTier::kTurbofan); \
+  }                                                              \
+  void RunWasm_##name##_Impl(LowerSimd lower_simd, ExecutionTier execution_tier)
+
+WASM_SIMD_TEST(I8x16ToF32x4) {
+  WasmRunner<int32_t, int32_t> r(execution_tier, lower_simd);
+  float* g = r.builder().AddGlobal<float>(kWasmS128);
+  byte param1 = 0;
+  BUILD(r,
+        WASM_SET_GLOBAL(
+            0, WASM_SIMD_UNOP(kExprF32x4Sqrt,
+                              WASM_SIMD_I8x16_SPLAT(WASM_GET_LOCAL(param1)))),
+        WASM_ONE);
+
+  // Arbitrary pattern that doesn't end up creating a NaN.
+  r.Call(0x5b);
+  float f = bit_cast<float>(0x5b5b5b5b);
+  float actual = ReadLittleEndianValue<float>(&g[0]);
+  float expected = std::sqrt(f);
+  CHECK_EQ(expected, actual);
+}
+
+}  // namespace test_run_wasm_simd
+}  // namespace wasm
+}  // namespace internal
+}  // namespace v8