[wasm][simd] Fix SpillAdjacentFpRegisters...

...to honor the {pinned} list under all circumstances.

Drive-by: DEBUG-mode helpers to print FunctionSig and LiftoffRegList
objects to stdout.

Fixed: chromium:1356718
Change-Id: I487db12294f687790cec1d658d7a7d754f3c2f99
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3859752
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Auto-Submit: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82815}

src/wasm/baseline/liftoff-assembler.cc

@@ -1274,6 +1274,14 @@ void LiftoffAssembler::MoveToReturnLocations(
 #endif
 }
 
+#if DEBUG
+void LiftoffRegList::Print() const {
+  std::ostringstream os;
+  os << *this << "\n";
+  PrintF("%s", os.str().c_str());
+}
+#endif
+
 #ifdef ENABLE_SLOW_DCHECKS
 bool LiftoffAssembler::ValidateCacheState() const {
   uint32_t register_use_count[kAfterMaxLiftoffRegCode] = {0};
@@ -1337,6 +1345,10 @@ LiftoffRegister LiftoffAssembler::SpillAdjacentFpRegisters(
   if (last_fp.fp().code() % 2 == 0) {
     pinned.set(last_fp);
   }
+  // If half of an adjacent pair is pinned, consider the whole pair pinned.
+  // Otherwise the code below would potentially spill the pinned register
+  // (after first spilling the unpinned half of the pair).
+  pinned = pinned.SpreadSetBitsToAdjacentFpRegs();
 
   // We can try to optimize the spilling here:
   // 1. Try to get a free fp register, either:

src/wasm/baseline/liftoff-register.h

@@ -344,6 +344,8 @@ class LiftoffRegList {
   // Sets all even numbered fp registers.
   static constexpr uint64_t kEvenFpSetMask = uint64_t{0x5555555555555555}
                                              << kAfterMaxLiftoffGpRegCode;
+  static constexpr uint64_t kOddFpSetMask = uint64_t{0xAAAAAAAAAAAAAAAA}
+                                            << kAfterMaxLiftoffGpRegCode;
 
   constexpr LiftoffRegList() = default;
 
@@ -426,6 +428,15 @@ class LiftoffRegList {
     return !GetAdjacentFpRegsSet().is_empty();
   }
 
+  // Returns a list where if any part of an adjacent pair of FP regs was set,
+  // both are set in the result. For example, [1, 4] is turned into [0, 1, 4, 5]
+  // because (0, 1) and (4, 5) are adjacent pairs.
+  constexpr LiftoffRegList SpreadSetBitsToAdjacentFpRegs() const {
+    storage_t odd_regs = regs_ & kOddFpSetMask;
+    storage_t even_regs = regs_ & kEvenFpSetMask;
+    return FromBits(regs_ | (odd_regs >> 1) | ((even_regs << 1) & kFpMask));
+  }
+
   constexpr bool operator==(const LiftoffRegList other) const {
     return regs_ == other.regs_;
   }
@@ -461,7 +472,7 @@ class LiftoffRegList {
   inline Iterator begin() const;
   inline Iterator end() const;
 
-  static LiftoffRegList FromBits(storage_t bits) {
+  static constexpr LiftoffRegList FromBits(storage_t bits) {
     DCHECK_EQ(bits, bits & (kGpMask | kFpMask));
     return LiftoffRegList(bits);
   }
@@ -472,6 +483,10 @@ class LiftoffRegList {
     return LiftoffRegList{bits};
   }
 
+#if DEBUG
+  void Print() const;
+#endif
+
  private:
   // Unchecked constructor. Only use for valid bits.
   explicit constexpr LiftoffRegList(storage_t bits) : regs_(bits) {}

src/wasm/value-type.cc

@@ -29,6 +29,21 @@ base::Optional<wasm::ValueKind> WasmReturnTypeFromSignature(
   }
 }
 
+#if DEBUG
+V8_EXPORT_PRIVATE extern void PrintFunctionSig(const wasm::FunctionSig* sig) {
+  std::ostringstream os;
+  os << sig->parameter_count() << " parameters:\n";
+  for (size_t i = 0; i < sig->parameter_count(); i++) {
+    os << "  " << i << ": " << sig->GetParam(i) << "\n";
+  }
+  os << sig->return_count() << " returns:\n";
+  for (size_t i = 0; i < sig->return_count(); i++) {
+    os << "  " << i << ": " << sig->GetReturn() << "\n";
+  }
+  PrintF("%s", os.str().c_str());
+}
+#endif
+
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8

test/mjsunit/regress/wasm/regress-crbug-1356718.js

@@ -0,0 +1,14 @@
+// Copyright 2022 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.
+
+d8.file.execute("test/mjsunit/wasm/wasm-module-builder.js");
+
+let builder = new WasmModuleBuilder();
+
+builder.addFunction('crash', makeSig([
+    kWasmF64, kWasmS128, kWasmS128, kWasmS128, kWasmS128, kWasmS128, kWasmS128,
+    kWasmF64, kWasmI32
+  ], [])).addBody([kExprNop]);
+
+builder.instantiate();

test/unittests/wasm/liftoff-register-unittests.cc

@@ -25,7 +25,8 @@
 #include "src/execution/riscv/frame-constants-riscv.h"
 #endif
 
-#include "src/base/macros.h"
+#include "src/wasm/baseline/liftoff-register.h"
+#include "testing/gtest/include/gtest/gtest.h"
 
 namespace v8 {
 namespace internal {
@@ -38,6 +39,32 @@ static_assert(kLiftoffAssemblerGpCacheRegs ==
 
 static_assert(kLiftoffAssemblerFpCacheRegs ==
               WasmDebugBreakFrameConstants::kPushedFpRegs);
+
+class WasmRegisterTest : public ::testing::Test {};
+
+TEST_F(WasmRegisterTest, SpreadSetBitsToAdjacentFpRegs) {
+  LiftoffRegList input(
+  // GP reg selection criteria: an even and an odd register belonging to
+  // separate adjacent pairs, and contained in kLiftoffAssemblerGpCacheRegs
+  // for the given platform.
+#if V8_TARGET_ARCH_S390X || V8_TARGET_ARCH_PPC64
+      LiftoffRegister::from_code(kGpReg, 4),
+      LiftoffRegister::from_code(kGpReg, 7),
+#else
+      LiftoffRegister::from_code(kGpReg, 1),
+      LiftoffRegister::from_code(kGpReg, 2),
+#endif
+      LiftoffRegister::from_code(kFpReg, 1),
+      LiftoffRegister::from_code(kFpReg, 4));
+  // GP regs are left alone, FP regs are spread to adjacent pairs starting
+  // at an even index: 1 → (0, 1) and 4 → (4, 5).
+  LiftoffRegList expected =
+      input | LiftoffRegList(LiftoffRegister::from_code(kFpReg, 0),
+                             LiftoffRegister::from_code(kFpReg, 5));
+  LiftoffRegList actual = input.SpreadSetBitsToAdjacentFpRegs();
+  EXPECT_EQ(expected, actual);
+}
+
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8