[ptr-compr][cleanup] Remove branchy decompression implementation

... as the smi-corrupting decompression seems to be stable enough.

Bug: v8:9706
Change-Id: I404924ec4a12b37d8bc3e521c5563aa7e6357dc6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1835544Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64107}

src/codegen/arm64/macro-assembler-arm64-inl.h

@@ -1025,11 +1025,7 @@ void TurboAssembler::SmiUntag(Register dst, const MemOperand& src) {
   } else {
     DCHECK(SmiValuesAre31Bits());
     if (COMPRESS_POINTERS_BOOL) {
-      if (kUseSmiCorruptingPtrDecompression) {
-        Ldr(dst.W(), src);
-      } else {
-        Ldrsw(dst, src);
-      }
+      Ldr(dst.W(), src);
     } else {
       Ldr(dst, src);
     }

src/codegen/arm64/macro-assembler-arm64.cc

@@ -2736,29 +2736,14 @@ void TurboAssembler::DecompressAnyTagged(const Register& destination,
                                          const MemOperand& field_operand) {
   RecordComment("[ DecompressAnyTagged");
   Ldrsw(destination, field_operand);
-  if (kUseSmiCorruptingPtrDecompression) {
-    Add(destination, kRootRegister, destination);
-  } else {
-    Label done;
-    JumpIfSmi(destination, &done);
-    Add(destination, kRootRegister, destination);
-    bind(&done);
-  }
+  Add(destination, kRootRegister, destination);
   RecordComment("]");
 }
 
 void TurboAssembler::DecompressAnyTagged(const Register& destination,
                                          const Register& source) {
   RecordComment("[ DecompressAnyTagged");
-  if (kUseSmiCorruptingPtrDecompression) {
-    Add(destination, kRootRegister, Operand(source, SXTW));
-  } else {
-    Label done;
-    Sxtw(destination, source);
-    JumpIfSmi(destination, &done);
-    Add(destination, kRootRegister, destination);
-    bind(&done);
-  }
+  Add(destination, kRootRegister, Operand(source, SXTW));
   RecordComment("]");
 }
 

src/codegen/code-stub-assembler.cc

@@ -749,7 +749,7 @@ TNode<Smi> CodeStubAssembler::NormalizeSmiIndex(TNode<Smi> smi_index) {
 }
 
 TNode<Smi> CodeStubAssembler::SmiFromInt32(SloppyTNode<Int32T> value) {
-  if (COMPRESS_POINTERS_BOOL && kUseSmiCorruptingPtrDecompression) {
+  if (COMPRESS_POINTERS_BOOL) {
     static_assert(!COMPRESS_POINTERS_BOOL || (kSmiShiftSize + kSmiTagSize == 1),
                   "Use shifting instead of add");
     return BitcastWordToTaggedSigned(
@@ -781,7 +781,7 @@ TNode<Smi> CodeStubAssembler::SmiTag(SloppyTNode<IntPtrT> value) {
   if (ToInt32Constant(value, &constant_value) && Smi::IsValid(constant_value)) {
     return SmiConstant(constant_value);
   }
-  if (COMPRESS_POINTERS_BOOL && kUseSmiCorruptingPtrDecompression) {
+  if (COMPRESS_POINTERS_BOOL) {
     return SmiFromInt32(TruncateIntPtrToInt32(value));
   }
   TNode<Smi> smi =
@@ -794,7 +794,7 @@ TNode<IntPtrT> CodeStubAssembler::SmiUntag(SloppyTNode<Smi> value) {
   if (ToIntPtrConstant(value, &constant_value)) {
     return IntPtrConstant(constant_value >> (kSmiShiftSize + kSmiTagSize));
   }
-  if (COMPRESS_POINTERS_BOOL && kUseSmiCorruptingPtrDecompression) {
+  if (COMPRESS_POINTERS_BOOL) {
     return ChangeInt32ToIntPtr(SmiToInt32(value));
   }
   return Signed(WordSar(BitcastTaggedToWordForTagAndSmiBits(value),
@@ -802,7 +802,7 @@ TNode<IntPtrT> CodeStubAssembler::SmiUntag(SloppyTNode<Smi> value) {
 }
 
 TNode<Int32T> CodeStubAssembler::SmiToInt32(SloppyTNode<Smi> value) {
-  if (COMPRESS_POINTERS_BOOL && kUseSmiCorruptingPtrDecompression) {
+  if (COMPRESS_POINTERS_BOOL) {
     return Signed(Word32Sar(
         TruncateIntPtrToInt32(BitcastTaggedToWordForTagAndSmiBits(value)),
         SmiShiftBitsConstant32()));
@@ -9702,11 +9702,7 @@ TNode<IntPtrT> CodeStubAssembler::ElementOffsetFromIndex(
       index = smi_index.value();
     } else {
       if (COMPRESS_POINTERS_BOOL) {
-        if (kUseSmiCorruptingPtrDecompression) {
-          smi_index_node = NormalizeSmiIndex(smi_index_node);
-        } else {
-          CSA_ASSERT(this, IsValidSmiIndex(smi_index_node));
-        }
+        smi_index_node = NormalizeSmiIndex(smi_index_node);
       }
     }
     intptr_index_node = BitcastTaggedToWordForTagAndSmiBits(smi_index_node);

src/codegen/x64/macro-assembler-x64.cc

@@ -313,14 +313,7 @@ void TurboAssembler::DecompressTaggedPointer(Register destination,
 
 void TurboAssembler::DecompressRegisterAnyTagged(Register destination,
                                                  Register scratch) {
-  if (kUseSmiCorruptingPtrDecompression) {
-    addq(destination, kRootRegister);
-  } else {
-    Label done;
-    JumpIfSmi(destination, &done);
-    addq(destination, kRootRegister);
-    bind(&done);
-  }
+  addq(destination, kRootRegister);
 }
 
 void TurboAssembler::DecompressAnyTagged(Register destination,

src/common/globals.h

@@ -246,10 +246,6 @@ using AtomicTagged_t = base::AtomicWord;
 
 #endif  // V8_COMPRESS_POINTERS
 
-// Defines whether to use smi-corrupting or branchful implementation of pointer
-// decompression should be used.
-constexpr bool kUseSmiCorruptingPtrDecompression = true;
-
 STATIC_ASSERT(kTaggedSize == (1 << kTaggedSizeLog2));
 STATIC_ASSERT((kTaggedSize == 8) == TAGGED_SIZE_8_BYTES);
 

src/common/ptr-compr-inl.h

@@ -65,12 +65,7 @@ V8_INLINE Address DecompressTaggedPointer(TOnHeapAddress on_heap_addr,
 template <typename TOnHeapAddress>
 V8_INLINE Address DecompressTaggedAny(TOnHeapAddress on_heap_addr,
                                       Tagged_t raw_value) {
-  if (kUseSmiCorruptingPtrDecompression) {
-    return DecompressTaggedPointer(on_heap_addr, raw_value);
-  }
-  return HAS_SMI_TAG(raw_value)
-             ? DecompressTaggedSigned(raw_value)
-             : DecompressTaggedPointer(on_heap_addr, raw_value);
+  return DecompressTaggedPointer(on_heap_addr, raw_value);
 }
 
 #ifdef V8_COMPRESS_POINTERS

src/compiler/graph-assembler.cc

@@ -99,12 +99,11 @@ Node* GraphAssembler::IntPtrEqual(Node* left, Node* right) {
 }
 
 Node* GraphAssembler::TaggedEqual(Node* left, Node* right) {
-#ifdef V8_COMPRESS_POINTERS
-  return Word32Equal(ChangeTaggedToCompressed(left),
-                     ChangeTaggedToCompressed(right));
-#else
+  if (COMPRESS_POINTERS_BOOL) {
+    return Word32Equal(ChangeTaggedToCompressed(left),
+                       ChangeTaggedToCompressed(right));
+  }
   return WordEqual(left, right);
-#endif
 }
 
 Node* GraphAssembler::Float64RoundDown(Node* value) {

src/compiler/representation-change.cc

@@ -1272,7 +1272,7 @@ Node* RepresentationChanger::GetBitRepresentationFor(
       }
     }
   } else if (output_rep == MachineRepresentation::kTaggedSigned) {
-    if (COMPRESS_POINTERS_BOOL && kUseSmiCorruptingPtrDecompression) {
+    if (COMPRESS_POINTERS_BOOL) {
       node = jsgraph()->graph()->NewNode(machine()->Word32Equal(), node,
                                          jsgraph()->Int32Constant(0));
     } else {

src/compiler/simplified-lowering.cc

@@ -2667,7 +2667,7 @@ class RepresentationSelector {
       case IrOpcode::kReferenceEqual: {
         VisitBinop(node, UseInfo::AnyTagged(), MachineRepresentation::kBit);
         if (lower()) {
-          if (COMPRESS_POINTERS_BOOL && kUseSmiCorruptingPtrDecompression) {
+          if (COMPRESS_POINTERS_BOOL) {
             NodeProperties::ChangeOp(node, lowering->machine()->Word32Equal());
           } else {
             NodeProperties::ChangeOp(node, lowering->machine()->WordEqual());

src/compiler/wasm-compiler.cc

@@ -3046,7 +3046,7 @@ Node* WasmGraphBuilder::BuildChangeInt32ToIntPtr(Node* value) {
 }
 
 Node* WasmGraphBuilder::BuildChangeInt32ToSmi(Node* value) {
-  if (COMPRESS_POINTERS_BOOL && kUseSmiCorruptingPtrDecompression) {
+  if (COMPRESS_POINTERS_BOOL) {
     return graph()->NewNode(mcgraph()->machine()->Word32Shl(), value,
                             BuildSmiShiftBitsConstant32());
   }
@@ -3056,7 +3056,7 @@ Node* WasmGraphBuilder::BuildChangeInt32ToSmi(Node* value) {
 }
 
 Node* WasmGraphBuilder::BuildChangeUint31ToSmi(Node* value) {
-  if (COMPRESS_POINTERS_BOOL && kUseSmiCorruptingPtrDecompression) {
+  if (COMPRESS_POINTERS_BOOL) {
     return graph()->NewNode(mcgraph()->machine()->Word32Shl(), value,
                             BuildSmiShiftBitsConstant32());
   }
@@ -3073,7 +3073,7 @@ Node* WasmGraphBuilder::BuildSmiShiftBitsConstant32() {
 }
 
 Node* WasmGraphBuilder::BuildChangeSmiToInt32(Node* value) {
-  if (COMPRESS_POINTERS_BOOL && kUseSmiCorruptingPtrDecompression) {
+  if (COMPRESS_POINTERS_BOOL) {
     value =
         graph()->NewNode(mcgraph()->machine()->TruncateInt64ToInt32(), value);
     value = graph()->NewNode(mcgraph()->machine()->Word32Sar(), value,
@@ -3086,7 +3086,7 @@ Node* WasmGraphBuilder::BuildChangeSmiToInt32(Node* value) {
 }
 
 Node* WasmGraphBuilder::BuildChangeSmiToIntPtr(Node* value) {
-  if (COMPRESS_POINTERS_BOOL && kUseSmiCorruptingPtrDecompression) {
+  if (COMPRESS_POINTERS_BOOL) {
     value = BuildChangeSmiToInt32(value);
     return BuildChangeInt32ToIntPtr(value);
   }