MIPS32R2: Share address computation

For array accesses the element address has the following structure:
Address = CONST_OFFSET + base_addr + index << ELEM_SHIFT

The address part (index << ELEM_SHIFT) can be shared across array
accesses with the same data type and index.

For example, in the following loop 5 accesses can share address
computation:

void foo(int[] a, int[] b, int[] c) {
  for (i...) {
    a[i] = a[i] + 5;
    b[i] = b[i] + c[i];
  }
}

Test: test-art-host, test-art-target
Change-Id: Id09fa782934aad4ee47669275e7e1a4d7d23b0fa

1 files changed, 40 insertions, 0 deletions

diff --git a/compiler/optimizing/nodes_mips.h b/compiler/optimizing/nodes_mips.h
index 80e652eaa7..ef388c30d5 100644
--- a/compiler/optimizing/nodes_mips.h
+++ b/compiler/optimizing/nodes_mips.h
@@ -69,6 +69,46 @@ class HMipsPackedSwitch FINAL : public HTemplateInstruction<2> {
   DISALLOW_COPY_AND_ASSIGN(HMipsPackedSwitch);
 };
 
+// This instruction computes part of the array access offset (index offset).
+//
+// For array accesses the element address has the following structure:
+// Address = CONST_OFFSET + base_addr + index << ELEM_SHIFT. The address part
+// (index << ELEM_SHIFT) can be shared across array accesses with
+// the same data type and index. For example, in the following loop 5 accesses can share address
+// computation:
+//
+// void foo(int[] a, int[] b, int[] c) {
+//   for (i...) {
+//     a[i] = a[i] + 5;
+//     b[i] = b[i] + c[i];
+//   }
+// }
+//
+// Note: as the instruction doesn't involve base array address into computations it has no side
+// effects.
+class HIntermediateArrayAddressIndex FINAL : public HExpression<2> {
+ public:
+  HIntermediateArrayAddressIndex(HInstruction* index, HInstruction* shift, uint32_t dex_pc)
+      : HExpression(DataType::Type::kInt32, SideEffects::None(), dex_pc) {
+    SetRawInputAt(0, index);
+    SetRawInputAt(1, shift);
+  }
+
+  bool CanBeMoved() const OVERRIDE { return true; }
+  bool InstructionDataEquals(const HInstruction* other ATTRIBUTE_UNUSED) const OVERRIDE {
+    return true;
+  }
+  bool IsActualObject() const OVERRIDE { return false; }
+
+  HInstruction* GetIndex() const { return InputAt(0); }
+  HInstruction* GetShift() const { return InputAt(1); }
+
+  DECLARE_INSTRUCTION(IntermediateArrayAddressIndex);
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(HIntermediateArrayAddressIndex);
+};
+
 }  // namespace art
 
 #endif  // ART_COMPILER_OPTIMIZING_NODES_MIPS_H_