refactor bit extensions.

source/opt/const_folding_rules.cpp

@@ -21,59 +21,6 @@ namespace opt {
 namespace {
 constexpr uint32_t kExtractCompositeIdInIdx = 0;
 
-// Returns the value obtained by extracting the |number_of_bits| least
-// significant bits from |value|, and sign-extending it to 64-bits.
-uint64_t SignExtendValue(uint64_t value, uint32_t number_of_bits) {
-  if (number_of_bits == 64) return value;
-
-  uint64_t mask_for_sign_bit = 1ull << (number_of_bits - 1);
-  uint64_t mask_for_significant_bits = (mask_for_sign_bit << 1) - 1ull;
-  if (value & mask_for_sign_bit) {
-    // Set upper bits to 1
-    value |= ~mask_for_significant_bits;
-  } else {
-    // Clear the upper bits
-    value &= mask_for_significant_bits;
-  }
-  return value;
-}
-
-// Returns the value obtained by extracting the |number_of_bits| least
-// significant bits from |value|, and zero-extending it to 64-bits.
-uint64_t ZeroExtendValue(uint64_t value, uint32_t number_of_bits) {
-  if (number_of_bits == 64) return value;
-
-  uint64_t mask_for_first_bit_to_clear = 1ull << (number_of_bits);
-  uint64_t mask_for_bits_to_keep = mask_for_first_bit_to_clear - 1;
-  value &= mask_for_bits_to_keep;
-  return value;
-}
-
-// Returns a constant whose value is `value` and type is `type`. This constant
-// will be generated by `const_mgr`. The type must be a scalar integer type.
-const analysis::Constant* GenerateIntegerConstant(
-    const analysis::Integer* integer_type, uint64_t result,
-    analysis::ConstantManager* const_mgr) {
-  assert(integer_type != nullptr);
-
-  std::vector<uint32_t> words;
-  if (integer_type->width() == 64) {
-    // In the 64-bit case, two words are needed to represent the value.
-    words = {static_cast<uint32_t>(result),
-             static_cast<uint32_t>(result >> 32)};
-  } else {
-    // In all other cases, only a single word is needed.
-    assert(integer_type->width() <= 32);
-    if (integer_type->IsSigned()) {
-      result = SignExtendValue(result, integer_type->width());
-    } else {
-      result = ZeroExtendValue(result, integer_type->width());
-    }
-    words = {static_cast<uint32_t>(result)};
-  }
-  return const_mgr->GetConstant(integer_type, words);
-}
-
 // Returns a constants with the value NaN of the given type.  Only works for
 // 32-bit and 64-bit float point types.  Returns |nullptr| if an error occurs.
 const analysis::Constant* GetNan(const analysis::Type* type,
@@ -1730,7 +1677,7 @@ BinaryScalarFoldingRule FoldBinaryIntegerOperation(uint64_t (*op)(uint64_t,
         uint64_t result = op(ia, ib);
 
         const analysis::Constant* result_constant =
-            GenerateIntegerConstant(integer_type, result, const_mgr);
+            const_mgr->GenerateIntegerConstant(integer_type, result);
         return result_constant;
       };
 }
@@ -1745,7 +1692,7 @@ const analysis::Constant* FoldScalarSConvert(
   const analysis::Integer* integer_type = result_type->AsInteger();
   assert(integer_type && "The result type of an SConvert");
   int64_t value = a->GetSignExtendedValue();
-  return GenerateIntegerConstant(integer_type, value, const_mgr);
+  return const_mgr->GenerateIntegerConstant(integer_type, value);
 }
 
 // A scalar folding rule that folds OpUConvert.
@@ -1762,8 +1709,8 @@ const analysis::Constant* FoldScalarUConvert(
   // If the operand was an unsigned value with less than 32-bit, it would have
   // been sign extended earlier, and we need to clear those bits.
   auto* operand_type = a->type()->AsInteger();
-  value = ZeroExtendValue(value, operand_type->width());
-  return GenerateIntegerConstant(integer_type, value, const_mgr);
+  value = utils::ClearHighBits(value, 64-operand_type->width());
+  return const_mgr->GenerateIntegerConstant(integer_type, value);
 }
 }  // namespace
 

source/opt/constants.cpp

@@ -20,6 +20,32 @@
 
 namespace spvtools {
 namespace opt {
+
+namespace {
+// Returns the value obtained by extracting the |number_of_bits| least
+// significant bits from |value|, and sign-extending it to 64-bits.
+uint64_t SignExtendValue(uint64_t value, uint32_t number_of_bits) {
+  const uint32_t width = sizeof(value) * 8;
+  if (number_of_bits == width) return value;
+
+  bool is_negative = utils::IsBitAtPositionSet(value, number_of_bits-1);
+  if (is_negative) {
+    value = utils::SetHighBits(value, width-number_of_bits);
+  } else {
+    value = utils::ClearHighBits(value, width-number_of_bits);
+  }
+  return value;
+}
+
+// Returns the value obtained by extracting the |number_of_bits| least
+// significant bits from |value|, and zero-extending it to 64-bits.
+uint64_t ZeroExtendValue(uint64_t value, uint32_t number_of_bits) {
+  const uint32_t width = sizeof(value) * 8;
+  if (number_of_bits == width) return value;
+  return utils::ClearHighBits(value, width-number_of_bits);
+}
+}
+
 namespace analysis {
 
 float Constant::GetFloat() const {
@@ -525,6 +551,28 @@ uint32_t ConstantManager::GetNullConstId(const Type* type) {
   return GetDefiningInstruction(c)->result_id();
 }
 
+const Constant* ConstantManager::GenerateIntegerConstant(
+    const analysis::Integer* integer_type, uint64_t result) {
+  assert(integer_type != nullptr);
+
+  std::vector<uint32_t> words;
+  if (integer_type->width() == 64) {
+    // In the 64-bit case, two words are needed to represent the value.
+    words = {static_cast<uint32_t>(result),
+             static_cast<uint32_t>(result >> 32)};
+  } else {
+    // In all other cases, only a single word is needed.
+    assert(integer_type->width() <= 32);
+    if (integer_type->IsSigned()) {
+      result = SignExtendValue(result, integer_type->width());
+    } else {
+      result = ZeroExtendValue(result, integer_type->width());
+    }
+    words = {static_cast<uint32_t>(result)};
+  }
+  return GetConstant(integer_type, words);
+}
+
 std::vector<const analysis::Constant*> Constant::GetVectorComponents(
     analysis::ConstantManager* const_mgr) const {
   std::vector<const analysis::Constant*> components;

source/opt/constants.h

@@ -671,6 +671,11 @@ class ConstantManager {
   // Returns the id of a OpConstantNull with type of |type|.
   uint32_t GetNullConstId(const Type* type);
 
+  // Returns a constant whose value is `value` and type is `type`. This constant
+  // will be generated by `const_mgr`. The type must be a scalar integer type.
+  const Constant* GenerateIntegerConstant(const analysis::Integer* integer_type,
+                                          uint64_t result);
+
  private:
   // Creates a Constant instance with the given type and a vector of constant
   // defining words. Returns a unique pointer to the created Constant instance