aco: compact aco::span<T> to use uint16_t offset and size instead of pointer and size_t.

This reduces the size of the Instruction base class
from 40 bytes to 16 bytes. No pipelinedb changes.

Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3332>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3332>

src/amd/compiler/aco_instruction_selection.cpp

@@ -7964,7 +7964,7 @@ void split_arguments(isel_context *ctx, Pseudo_instruction *startpgm)
    /* Split all arguments except for the first (ring_offsets) and the last
     * (exec) so that the dead channels don't stay live throughout the program.
     */
-   for (unsigned i = 1; i < startpgm->definitions.size() - 1; i++) {
+   for (int i = 1; i < startpgm->definitions.size() - 1; i++) {
       if (startpgm->definitions[i].regClass().size() > 1) {
          emit_split_vector(ctx, startpgm->definitions[i].getTemp(),
                            startpgm->definitions[i].regClass().size());

src/amd/compiler/aco_ir.h

@@ -929,8 +929,10 @@ T* create_instruction(aco_opcode opcode, Format format, uint32_t num_operands, u
    inst->opcode = opcode;
    inst->format = format;
 
-   inst->operands = aco::span<Operand>((Operand*)(data + sizeof(T)), num_operands);
-   inst->definitions = aco::span<Definition>((Definition*)inst->operands.end(), num_definitions);
+   uint16_t operands_offset = data + sizeof(T) - (char*)&inst->operands;
+   inst->operands = aco::span<Operand>(operands_offset, num_operands);
+   uint16_t definitions_offset = (char*)inst->operands.end() - (char*)&inst->definitions;
+   inst->definitions = aco::span<Definition>(definitions_offset, num_definitions);
 
    return inst;
 }

src/amd/compiler/aco_optimizer.cpp

@@ -829,7 +829,8 @@ void label_instruction(opt_ctx &ctx, Block& block, aco_ptr<Instruction>& instr)
          Format format = is_vgpr ? Format::VOP1 : Format::SOP1;
          instr->opcode = opcode;
          instr->format = format;
-         instr->operands = {instr->operands.begin(), 1 };
+         while (instr->operands.size() > 1)
+            instr->operands.pop_back();
          instr->operands[0] = vec_op;
 
          if (vec_op.isConstant()) {

src/amd/compiler/aco_util.h

@@ -47,8 +47,8 @@ public:
    using const_iterator         = const_pointer;
    using reverse_iterator       = std::reverse_iterator<iterator>;
    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
-   using size_type              = std::size_t;
-   using difference_type        = std::ptrdiff_t;
+   using size_type              = uint16_t;
+   using difference_type        = ptrdiff_t;
 
    /*! \brief                  Compiler generated default constructor
    */
@@ -58,49 +58,49 @@ public:
    *   \param[in]   data      Pointer to the underlying data array
    *   \param[in]   length    The size of the span
    */
-   constexpr span(pointer data, const size_type length)
-       : data{ data } , length{ length } {}
+   constexpr span(uint16_t offset, const size_type length)
+       : offset{ offset } , length{ length } {}
 
    /*! \brief                 Returns an iterator to the begin of the span
    *   \return                data
    */
    constexpr iterator begin() noexcept {
-      return data;
+      return (pointer)((char*)this + offset);
    }
 
    /*! \brief                 Returns a const_iterator to the begin of the span
    *   \return                data
    */
    constexpr const_iterator begin() const noexcept {
-      return data;
+      return (const_pointer)((const char *)this + offset);
    }
 
    /*! \brief                 Returns an iterator to the end of the span
    *   \return                data + length
    */
    constexpr iterator end() noexcept {
-      return std::next(data, length);
+      return std::next(begin(), length);
    }
 
    /*! \brief                 Returns a const_iterator to the end of the span
    *   \return                data + length
    */
    constexpr const_iterator end() const noexcept {
-      return std::next(data, length);
+      return std::next(begin(), length);
    }
 
    /*! \brief                 Returns a const_iterator to the begin of the span
    *   \return                data
    */
    constexpr const_iterator cbegin() const noexcept {
-      return data;
+      return begin();
    }
 
    /*! \brief                 Returns a const_iterator to the end of the span
    *   \return                data + length
    */
    constexpr const_iterator cend() const noexcept {
-      return std::next(data, length);
+      return std::next(begin(), length);
    }
 
    /*! \brief                 Returns a reverse_iterator to the end of the span
@@ -151,7 +151,7 @@ public:
    */
    constexpr reference operator[](const size_type index) noexcept {
       assert(length > index);
-      return *(std::next(data, index));
+      return *(std::next(begin(), index));
    }
 
    /*! \brief                 Unchecked const access operator
@@ -160,7 +160,7 @@ public:
    */
    constexpr const_reference operator[](const size_type index) const noexcept {
       assert(length > index);
-      return *(std::next(data, index));
+      return *(std::next(begin(), index));
    }
 
    /*! \brief                 Returns a reference to the last element of the span
@@ -168,7 +168,7 @@ public:
    */
    constexpr reference back() noexcept {
       assert(length > 0);
-      return *(std::next(data, length - 1));
+      return *(std::next(begin(), length - 1));
    }
 
    /*! \brief                 Returns a const_reference to the last element of the span
@@ -176,7 +176,7 @@ public:
    */
    constexpr const_reference back() const noexcept {
       assert(length > 0);
-      return *(std::next(data, length - 1));
+      return *(std::next(begin(), length - 1));
    }
 
    /*! \brief                 Returns a reference to the first element of the span
@@ -219,15 +219,15 @@ public:
    /*! \brief                 Clears the span
    */
    constexpr void clear() noexcept {
-      data = nullptr;
+      offset = 0;
       length = 0;
    }
 
 private:
-   pointer data{ nullptr };   //!> Pointer to the underlying data array
+   uint16_t offset{ 0 };      //!> Byte offset from span to data
    size_type length{ 0 };     //!> Size of the span
 };
 
 } // namespace aco
 
-#endif // ACO_UTIL_H
+#endif // ACO_UTIL_H