[liftoff] Fix implicit conversion to LiftoffRegList

According to the style guide, the implicit conversion of any number of
registers to a LiftoffRegList should not be there. This CL removes it,
and fixes two subideal call sites to use SpillRegister (receiving a
single register) instead of SpillOneRegister (receiving a register list
to choose from).

Plus some semantics-preserving rewrites.

R=jkummerow@chromium.org

Bug: chromium:1337221
Change-Id: Id22043ac1c185bc794dbde7baa4b1d5ab7cce56e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3707286Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81250}

src/wasm/baseline/arm/liftoff-assembler-arm.h

@@ -192,7 +192,7 @@ inline void I64Shiftop(LiftoffAssembler* assm, LiftoffRegister dst,
   // Left shift writes {dst_high} then {dst_low}, right shifts write {dst_low}
   // then {dst_high}.
   Register clobbered_dst_reg = is_left_shift ? dst_high : dst_low;
-  LiftoffRegList pinned = {clobbered_dst_reg, src};
+  LiftoffRegList pinned{clobbered_dst_reg, src};
   Register amount_capped =
       pinned.set(assm->GetUnusedRegister(kGpReg, pinned)).gp();
   assm->and_(amount_capped, amount, Operand(0x3F));
@@ -951,7 +951,7 @@ inline void AtomicBinop32(LiftoffAssembler* lasm, Register dst_addr,
                           StoreType type,
                           void (*op)(LiftoffAssembler*, Register, Register,
                                      Register)) {
-  LiftoffRegList pinned = {dst_addr, offset_reg, value, result};
+  LiftoffRegList pinned{dst_addr, offset_reg, value, result};
   switch (type.value()) {
     case StoreType::kI64Store8:
       __ LoadConstant(result.high(), WasmValue(0));
@@ -1002,8 +1002,8 @@ inline void AtomicOp64(LiftoffAssembler* lasm, Register dst_addr,
   // Make sure {dst_low} and {dst_high} are not occupied by any other value.
   Register value_low = value.low_gp();
   Register value_high = value.high_gp();
-  LiftoffRegList pinned = {dst_addr,   offset_reg, value_low,
-                           value_high, dst_low,    dst_high};
+  LiftoffRegList pinned{dst_addr,   offset_reg, value_low,
+                        value_high, dst_low,    dst_high};
   __ ClearRegister(dst_low, {&dst_addr, &offset_reg, &value_low, &value_high},
                    pinned);
   pinned = pinned | LiftoffRegList{dst_addr, offset_reg, value_low, value_high};
@@ -1273,7 +1273,7 @@ void LiftoffAssembler::AtomicCompareExchange(
   void (Assembler::*load)(Register, Register, Condition) = nullptr;
   void (Assembler::*store)(Register, Register, Register, Condition) = nullptr;
 
-  LiftoffRegList pinned = {dst_addr, offset_reg};
+  LiftoffRegList pinned{dst_addr, offset_reg};
   // We need to remember the high word of {result}, so we can set it to zero in
   // the end if necessary.
   Register result_high = no_reg;
@@ -1612,7 +1612,7 @@ inline void GeneratePopCnt(Assembler* assm, Register dst, Register src,
 }  // namespace liftoff
 
 bool LiftoffAssembler::emit_i32_popcnt(Register dst, Register src) {
-  LiftoffRegList pinned = {dst};
+  LiftoffRegList pinned{dst};
   Register scratch1 = pinned.set(GetUnusedRegister(kGpReg, pinned)).gp();
   Register scratch2 = GetUnusedRegister(kGpReg, pinned).gp();
   liftoff::GeneratePopCnt(this, dst, src, scratch1, scratch2);
@@ -1853,7 +1853,7 @@ bool LiftoffAssembler::emit_i64_popcnt(LiftoffRegister dst,
   // overwrite the second src register before using it.
   Register src1 = src.high_gp() == dst.low_gp() ? src.high_gp() : src.low_gp();
   Register src2 = src.high_gp() == dst.low_gp() ? src.low_gp() : src.high_gp();
-  LiftoffRegList pinned = {dst, src2};
+  LiftoffRegList pinned{dst, src2};
   Register scratch1 = pinned.set(GetUnusedRegister(kGpReg, pinned)).gp();
   Register scratch2 = GetUnusedRegister(kGpReg, pinned).gp();
   liftoff::GeneratePopCnt(this, dst.low_gp(), src1, scratch1, scratch2);
@@ -2996,7 +2996,7 @@ void LiftoffAssembler::emit_i64x2_mul(LiftoffRegister dst, LiftoffRegister lhs,
   if (used_plus_dst.has(lhs) && used_plus_dst.has(rhs)) {
     tmp1 = temps.AcquireQ();
     // We only have 1 scratch Q register, so acquire another ourselves.
-    LiftoffRegList pinned = {dst};
+    LiftoffRegList pinned{dst};
     LiftoffRegister unused_pair = GetUnusedRegister(kFpRegPair, pinned);
     tmp2 = liftoff::GetSimd128Register(unused_pair);
   } else if (used_plus_dst.has(lhs)) {
@@ -3122,7 +3122,7 @@ void LiftoffAssembler::emit_i32x4_bitmask(LiftoffRegister dst,
 
   if (cache_state()->is_used(src)) {
     // We only have 1 scratch Q register, so try and reuse src.
-    LiftoffRegList pinned = {src};
+    LiftoffRegList pinned{src};
     LiftoffRegister unused_pair = GetUnusedRegister(kFpRegPair, pinned);
     mask = liftoff::GetSimd128Register(unused_pair);
   }
@@ -3307,7 +3307,7 @@ void LiftoffAssembler::emit_i16x8_bitmask(LiftoffRegister dst,
 
   if (cache_state()->is_used(src)) {
     // We only have 1 scratch Q register, so try and reuse src.
-    LiftoffRegList pinned = {src};
+    LiftoffRegList pinned{src};
     LiftoffRegister unused_pair = GetUnusedRegister(kFpRegPair, pinned);
     mask = liftoff::GetSimd128Register(unused_pair);
   }
@@ -3643,7 +3643,7 @@ void LiftoffAssembler::emit_i8x16_bitmask(LiftoffRegister dst,
 
   if (cache_state()->is_used(src)) {
     // We only have 1 scratch Q register, so try and reuse src.
-    LiftoffRegList pinned = {src};
+    LiftoffRegList pinned{src};
     LiftoffRegister unused_pair = GetUnusedRegister(kFpRegPair, pinned);
     mask = liftoff::GetSimd128Register(unused_pair);
   }

src/wasm/baseline/arm64/liftoff-assembler-arm64.h

@@ -634,7 +634,7 @@ inline void AtomicBinop(LiftoffAssembler* lasm, Register dst_addr,
                         Register offset_reg, uintptr_t offset_imm,
                         LiftoffRegister value, LiftoffRegister result,
                         StoreType type, Binop op) {
-  LiftoffRegList pinned = {dst_addr, offset_reg, value, result};
+  LiftoffRegList pinned{dst_addr, offset_reg, value, result};
   Register store_result = pinned.set(__ GetUnusedRegister(kGpReg, pinned)).gp();
 
   // {LiftoffCompiler::AtomicBinop} ensures that {result} is unique.
@@ -820,7 +820,7 @@ void LiftoffAssembler::AtomicCompareExchange(
     Register dst_addr, Register offset_reg, uintptr_t offset_imm,
     LiftoffRegister expected, LiftoffRegister new_value, LiftoffRegister result,
     StoreType type) {
-  LiftoffRegList pinned = {dst_addr, offset_reg, expected, new_value};
+  LiftoffRegList pinned{dst_addr, offset_reg, expected, new_value};
 
   Register result_reg = result.gp();
   if (pinned.has(result)) {

src/wasm/baseline/ia32/liftoff-assembler-ia32.h

@@ -676,7 +676,7 @@ inline void AtomicAddOrSubOrExchange32(LiftoffAssembler* lasm, Binop binop,
   Register result_reg = is_64_bit_op ? result.low_gp() : result.gp();
 
   bool is_byte_store = type.size() == 1;
-  LiftoffRegList pinned = {dst_addr, value_reg, offset_reg};
+  LiftoffRegList pinned{dst_addr, value_reg, offset_reg};
 
   // Ensure that {value_reg} is a valid register.
   if (is_byte_store && !liftoff::kByteRegs.has(value_reg)) {
@@ -1041,7 +1041,7 @@ void LiftoffAssembler::AtomicCompareExchange(
     }
 
     bool is_byte_store = type.size() == 1;
-    LiftoffRegList pinned = {dst_addr, value_reg, expected_reg};
+    LiftoffRegList pinned{dst_addr, value_reg, expected_reg};
 
     // Ensure that {value_reg} is a valid register.
     if (is_byte_store && !liftoff::kByteRegs.has(value_reg)) {
@@ -1467,7 +1467,7 @@ namespace liftoff {
 inline void EmitShiftOperation(LiftoffAssembler* assm, Register dst,
                                Register src, Register amount,
                                void (Assembler::*emit_shift)(Register)) {
-  LiftoffRegList pinned = {dst, src, amount};
+  LiftoffRegList pinned{dst, src, amount};
   // If dst is ecx, compute into a tmp register first, then move to ecx.
   if (dst == ecx) {
     Register tmp = assm->GetUnusedRegister(kGpReg, pinned).gp();
@@ -1698,7 +1698,7 @@ inline void Emit64BitShiftOperation(
     LiftoffAssembler* assm, LiftoffRegister dst, LiftoffRegister src,
     Register amount, void (TurboAssembler::*emit_shift)(Register, Register)) {
   // Temporary registers cannot overlap with {dst}.
-  LiftoffRegList pinned = {dst};
+  LiftoffRegList pinned{dst};
 
   constexpr size_t kMaxRegMoves = 3;
   base::SmallVector<LiftoffAssembler::ParallelRegisterMoveTuple, kMaxRegMoves>
@@ -2241,7 +2241,7 @@ inline bool EmitTruncateFloatToInt(LiftoffAssembler* assm, Register dst,
   }
   CpuFeatureScope feature(assm, SSE4_1);
 
-  LiftoffRegList pinned = {src, dst};
+  LiftoffRegList pinned{src, dst};
   DoubleRegister rounded =
       pinned.set(__ GetUnusedRegister(kFpReg, pinned)).fp();
   DoubleRegister converted_back =
@@ -2280,7 +2280,7 @@ inline bool EmitSatTruncateFloatToInt(LiftoffAssembler* assm, Register dst,
   Label not_nan;
   Label src_positive;
 
-  LiftoffRegList pinned = {src, dst};
+  LiftoffRegList pinned{src, dst};
   DoubleRegister rounded =
       pinned.set(__ GetUnusedRegister(kFpReg, pinned)).fp();
   DoubleRegister converted_back =
@@ -2388,7 +2388,7 @@ bool LiftoffAssembler::emit_type_conversion(WasmOpcode opcode,
       cvtsi2ss(dst.fp(), src.gp());
       return true;
     case kExprF32UConvertI32: {
-      LiftoffRegList pinned = {dst, src};
+      LiftoffRegList pinned{dst, src};
       Register scratch = GetUnusedRegister(kGpReg, pinned).gp();
       Cvtui2ss(dst.fp(), src.gp(), scratch);
       return true;
@@ -2403,7 +2403,7 @@ bool LiftoffAssembler::emit_type_conversion(WasmOpcode opcode,
       Cvtsi2sd(dst.fp(), src.gp());
       return true;
     case kExprF64UConvertI32: {
-      LiftoffRegList pinned = {dst, src};
+      LiftoffRegList pinned{dst, src};
       Register scratch = GetUnusedRegister(kGpReg, pinned).gp();
       Cvtui2sd(dst.fp(), src.gp(), scratch);
       return true;

src/wasm/baseline/liftoff-assembler.h

@@ -470,15 +470,11 @@ class LiftoffAssembler : public TurboAssembler {
     if (slot.is_reg()) {
       cache_state_.dec_used(slot.reg());
       if (slot.reg() == reg) return;
-      if (cache_state_.is_used(reg)) {
-        SpillOneRegister(reg);
-      }
+      if (cache_state_.is_used(reg)) SpillRegister(reg);
       Move(reg, slot.reg(), slot.kind());
       return;
     }
-    if (cache_state_.is_used(reg)) {
-      SpillOneRegister(reg);
-    }
+    if (cache_state_.is_used(reg)) SpillRegister(reg);
     LoadToRegister(slot, reg);
   }
 

src/wasm/baseline/liftoff-compiler.cc

@@ -1557,7 +1557,7 @@ class LiftoffCompiler {
                               : __ GetUnusedRegister(result_rc, {});
     CallEmitFn(fn, dst, src);
     if (V8_UNLIKELY(nondeterminism_)) {
-      LiftoffRegList pinned = {dst};
+      LiftoffRegList pinned{dst};
       if (result_kind == ValueKind::kF32 || result_kind == ValueKind::kF64) {
         CheckNan(dst, pinned, result_kind);
       } else if (result_kind == ValueKind::kS128 &&
@@ -1782,7 +1782,7 @@ class LiftoffCompiler {
       LiftoffRegister lhs = __ PopToRegister();
       // Either reuse {lhs} for {dst}, or choose a register (pair) which does
       // not overlap, for easier code generation.
-      LiftoffRegList pinned = {lhs};
+      LiftoffRegList pinned{lhs};
       LiftoffRegister dst = src_rc == result_rc
                                 ? __ GetUnusedRegister(result_rc, {lhs}, pinned)
                                 : __ GetUnusedRegister(result_rc, pinned);
@@ -1813,7 +1813,7 @@ class LiftoffCompiler {
 
     CallEmitFn(fn, dst, lhs, rhs);
     if (V8_UNLIKELY(nondeterminism_)) {
-      LiftoffRegList pinned = {dst};
+      LiftoffRegList pinned{dst};
       if (result_kind == ValueKind::kF32 || result_kind == ValueKind::kF64) {
         CheckNan(dst, pinned, result_kind);
       } else if (result_kind == ValueKind::kS128 &&
@@ -3011,7 +3011,7 @@ class LiftoffCompiler {
       if (index == no_reg) return;
 
       CODE_COMMENT("load from memory");
-      LiftoffRegList pinned = {index};
+      LiftoffRegList pinned{index};
 
       // Load the memory start address only now to reduce register pressure
       // (important on ia32).
@@ -3055,7 +3055,7 @@ class LiftoffCompiler {
     if (index == no_reg) return;
 
     uintptr_t offset = imm.offset;
-    LiftoffRegList pinned = {index};
+    LiftoffRegList pinned{index};
     CODE_COMMENT("load with transformation");
     Register addr = GetMemoryStart(pinned);
     LiftoffRegister value = __ GetUnusedRegister(reg_class_for(kS128), {});
@@ -3434,7 +3434,7 @@ class LiftoffCompiler {
                  LiftoffRegister src2, LiftoffRegister src3) {
     CallEmitFn(fn, dst, src1, src2, src3);
     if (V8_UNLIKELY(nondeterminism_)) {
-      LiftoffRegList pinned = {dst};
+      LiftoffRegList pinned{dst};
       if (result_kind == ValueKind::kF32 || result_kind == ValueKind::kF64) {
         CheckNan(dst, pinned, result_kind);
       } else if (result_kind == ValueKind::kS128 &&
@@ -3524,7 +3524,7 @@ class LiftoffCompiler {
       GenerateCCall(&dst, &sig_v_s, kS128, &src, ext_ref());
     }
     if (V8_UNLIKELY(nondeterminism_)) {
-      LiftoffRegList pinned = {dst};
+      LiftoffRegList pinned{dst};
       CheckS128Nan(dst, pinned, result_lane_kind);
     }
     __ PushRegister(kS128, dst);
@@ -3532,9 +3532,10 @@ class LiftoffCompiler {
 
   template <typename EmitFn>
   void EmitSimdFmaOp(EmitFn emit_fn) {
-    LiftoffRegister src3 = __ PopToRegister();
-    LiftoffRegister src2 = __ PopToRegister({src3});
-    LiftoffRegister src1 = __ PopToRegister({src2, src3});
+    LiftoffRegList pinned;
+    LiftoffRegister src3 = pinned.set(__ PopToRegister(pinned));
+    LiftoffRegister src2 = pinned.set(__ PopToRegister(pinned));
+    LiftoffRegister src1 = pinned.set(__ PopToRegister(pinned));
     RegClass dst_rc = reg_class_for(kS128);
     LiftoffRegister dst = __ GetUnusedRegister(dst_rc, {});
     (asm_.*emit_fn)(dst, src1, src2, src3);
@@ -4098,9 +4099,10 @@ class LiftoffCompiler {
         // There is no helper for an instruction with 3 SIMD operands
         // and we do not expect to add any more, so inlining it here.
         static constexpr RegClass res_rc = reg_class_for(kS128);
-        LiftoffRegister acc = __ PopToRegister();
-        LiftoffRegister rhs = __ PopToRegister(LiftoffRegList{acc});
-        LiftoffRegister lhs = __ PopToRegister(LiftoffRegList{rhs, acc});
+        LiftoffRegList pinned;
+        LiftoffRegister acc = pinned.set(__ PopToRegister(pinned));
+        LiftoffRegister rhs = pinned.set(__ PopToRegister(pinned));
+        LiftoffRegister lhs = pinned.set(__ PopToRegister(pinned));
         LiftoffRegister dst = __ GetUnusedRegister(res_rc, {lhs, rhs, acc}, {});
 
         __ emit_i32x4_dot_i8x16_i7x16_add_s(dst, lhs, rhs, acc);
@@ -4225,8 +4227,9 @@ class LiftoffCompiler {
       return unsupported(decoder, kSimd, "simd");
     }
     static constexpr RegClass result_rc = reg_class_for(kS128);
-    LiftoffRegister rhs = __ PopToRegister();
-    LiftoffRegister lhs = __ PopToRegister(LiftoffRegList{rhs});
+    LiftoffRegList pinned;
+    LiftoffRegister rhs = pinned.set(__ PopToRegister(pinned));
+    LiftoffRegister lhs = pinned.set(__ PopToRegister(pinned));
     LiftoffRegister dst = __ GetUnusedRegister(result_rc, {lhs, rhs}, {});
 
     uint8_t shuffle[kSimd128Size];
@@ -4578,7 +4581,7 @@ class LiftoffCompiler {
                                     full_index, {}, kDoForceCheck);
     if (index == no_reg) return;
 
-    LiftoffRegList pinned = {index};
+    LiftoffRegList pinned{index};
     AlignmentCheckMem(decoder, type.size(), imm.offset, index, pinned);
     uintptr_t offset = imm.offset;
     CODE_COMMENT("atomic load from memory");
@@ -4647,7 +4650,7 @@ class LiftoffCompiler {
     Register index = BoundsCheckMem(decoder, type.size(), imm.offset,
                                     full_index, {}, kDoForceCheck);
     if (index == no_reg) return;
-    LiftoffRegList pinned = {index};
+    LiftoffRegList pinned{index};
     AlignmentCheckMem(decoder, type.size(), imm.offset, index, pinned);
 
     uintptr_t offset = imm.offset;
@@ -4676,7 +4679,7 @@ class LiftoffCompiler {
 #else
     ValueKind result_kind = type.value_type().kind();
     LiftoffRegList pinned;
-    LiftoffRegister new_value = pinned.set(__ PopToRegister());
+    LiftoffRegister new_value = pinned.set(__ PopToRegister(pinned));
     LiftoffRegister expected = pinned.set(__ PopToRegister(pinned));
     LiftoffRegister full_index = __ PopToRegister(pinned);
     Register index = BoundsCheckMem(decoder, type.size(), imm.offset,
@@ -4727,7 +4730,7 @@ class LiftoffCompiler {
         BoundsCheckMem(decoder, value_kind_size(kind), imm.offset, full_index,
                        {}, kDoForceCheck);
     if (index_reg == no_reg) return;
-    LiftoffRegList pinned = {index_reg};
+    LiftoffRegList pinned{index_reg};
     AlignmentCheckMem(decoder, value_kind_size(kind), imm.offset, index_reg,
                       pinned);
 
@@ -4774,7 +4777,7 @@ class LiftoffCompiler {
     Register index_reg = BoundsCheckMem(decoder, kInt32Size, imm.offset,
                                         full_index, {}, kDoForceCheck);
     if (index_reg == no_reg) return;
-    LiftoffRegList pinned = {index_reg};
+    LiftoffRegList pinned{index_reg};
     AlignmentCheckMem(decoder, kInt32Size, imm.offset, index_reg, pinned);
 
     uintptr_t offset = imm.offset;
@@ -4982,7 +4985,7 @@ class LiftoffCompiler {
                   const Value&, const Value&) {
     Register mem_offsets_high_word = no_reg;
     LiftoffRegList pinned;
-    LiftoffRegister size = pinned.set(__ PopToRegister());
+    LiftoffRegister size = pinned.set(__ PopToRegister(pinned));
     LiftoffRegister src = pinned.set(__ PopToRegister(pinned));
     LiftoffRegister dst =
         PopMemTypeToRegister(decoder, &mem_offsets_high_word, &pinned);
@@ -5303,10 +5306,10 @@ class LiftoffCompiler {
       i--;
       int offset = StructFieldOffset(imm.struct_type, i);
       ValueKind field_kind = imm.struct_type->field(i).kind();
-      LiftoffRegister value = initial_values_on_stack
-                                  ? pinned.set(__ PopToRegister(pinned))
-                                  : pinned.set(__ GetUnusedRegister(
-                                        reg_class_for(field_kind), pinned));
+      LiftoffRegister value = pinned.set(
+          initial_values_on_stack
+              ? __ PopToRegister(pinned)
+              : __ GetUnusedRegister(reg_class_for(field_kind), pinned));
       if (!initial_values_on_stack) {
         if (!CheckSupportedType(decoder, field_kind, "default value")) return;
         SetDefaultValue(value, field_kind, pinned);
@@ -5395,7 +5398,7 @@ class LiftoffCompiler {
     }
 
     LiftoffRegister obj(kReturnRegister0);
-    LiftoffRegList pinned = {obj};
+    LiftoffRegList pinned{obj};
     LiftoffRegister length = pinned.set(__ PopToModifiableRegister(pinned));
     LiftoffRegister value =
         pinned.set(__ GetUnusedRegister(reg_class_for(elem_kind), pinned));
@@ -5550,7 +5553,7 @@ class LiftoffCompiler {
     LiftoffRegister array(kReturnRegister0);
     if (!CheckSupportedType(decoder, elem_kind, "array.init")) return;
     for (int i = static_cast<int>(elements.size()) - 1; i >= 0; i--) {
-      LiftoffRegList pinned = {array};
+      LiftoffRegList pinned{array};
       LiftoffRegister element = pinned.set(__ PopToRegister(pinned));
       LiftoffRegister offset_reg =
           pinned.set(__ GetUnusedRegister(kGpReg, pinned));
@@ -6486,7 +6489,7 @@ class LiftoffCompiler {
     // Pop the index. We'll modify the register's contents later.
     Register index = __ PopToModifiableRegister().gp();
 
-    LiftoffRegList pinned = {index};
+    LiftoffRegList pinned{index};
     // Get three temporary registers.
     Register table = pinned.set(__ GetUnusedRegister(kGpReg, pinned)).gp();
     Register tmp_const = pinned.set(__ GetUnusedRegister(kGpReg, pinned)).gp();

src/wasm/baseline/liftoff-register.h

@@ -354,7 +354,7 @@ class LiftoffRegList {
       typename = std::enable_if_t<std::conjunction_v<std::disjunction<
           std::is_same<Register, Regs>, std::is_same<DoubleRegister, Regs>,
           std::is_same<LiftoffRegister, Regs>>...>>>
-  constexpr LiftoffRegList(Regs... regs) {
+  constexpr explicit LiftoffRegList(Regs... regs) {
     (..., set(regs));
   }