ARM: Port instr simplification of array accesses.
After changing the addressing mode for array accesses (in
https://android-review.googlesource.com/248406) the 'add'
instruction that calculates the base address for the array can be
shared across accesses to the same array.
Before https://android-review.googlesource.com/248406:
add IP, r[Array], r[Index0], LSL #2
ldr r0, [IP, #12]
add IP, r[Array], r[Index1], LSL #2
ldr r0, [IP, #12]
Before this CL:
add IP. r[Array], #12
ldr r0, [IP, r[Index0], LSL #2]
add IP. r[Array], #12
ldr r0, [IP, r[Index1], LSL #2]
After this CL:
add IP. r[Array], #12
ldr r0, [IP, r[Index0], LSL #2]
ldr r0, [IP, r[Index1], LSL #2]
Link to the original optimization:
https://android-review.googlesource.com/#/c/127310/
Test: Run ART test suite on Nexus 6.
Change-Id: Iee26f9a0a7ca46abb90e3f60d19d22dc8dee4d8f
diff --git a/compiler/optimizing/instruction_simplifier_shared.cc b/compiler/optimizing/instruction_simplifier_shared.cc
index dab1ebc..8f7778f 100644
--- a/compiler/optimizing/instruction_simplifier_shared.cc
+++ b/compiler/optimizing/instruction_simplifier_shared.cc
@@ -226,4 +226,59 @@
return false;
}
+
+bool TryExtractArrayAccessAddress(HInstruction* access,
+ HInstruction* array,
+ HInstruction* index,
+ size_t data_offset) {
+ if (kEmitCompilerReadBarrier) {
+ // The read barrier instrumentation does not support the
+ // HIntermediateAddress instruction yet.
+ //
+ // TODO: Handle this case properly in the ARM64 and ARM code generator and
+ // re-enable this optimization; otherwise, remove this TODO.
+ // b/26601270
+ return false;
+ }
+ if (index->IsConstant() ||
+ (index->IsBoundsCheck() && index->AsBoundsCheck()->GetIndex()->IsConstant())) {
+ // When the index is a constant all the addressing can be fitted in the
+ // memory access instruction, so do not split the access.
+ return false;
+ }
+ if (access->IsArraySet() &&
+ access->AsArraySet()->GetValue()->GetType() == Primitive::kPrimNot) {
+ // The access may require a runtime call or the original array pointer.
+ return false;
+ }
+
+ // Proceed to extract the base address computation.
+ HGraph* graph = access->GetBlock()->GetGraph();
+ ArenaAllocator* arena = graph->GetArena();
+
+ HIntConstant* offset = graph->GetIntConstant(data_offset);
+ HIntermediateAddress* address =
+ new (arena) HIntermediateAddress(array, offset, kNoDexPc);
+ address->SetReferenceTypeInfo(array->GetReferenceTypeInfo());
+ access->GetBlock()->InsertInstructionBefore(address, access);
+ access->ReplaceInput(address, 0);
+ // Both instructions must depend on GC to prevent any instruction that can
+ // trigger GC to be inserted between the two.
+ access->AddSideEffects(SideEffects::DependsOnGC());
+ DCHECK(address->GetSideEffects().Includes(SideEffects::DependsOnGC()));
+ DCHECK(access->GetSideEffects().Includes(SideEffects::DependsOnGC()));
+ // TODO: Code generation for HArrayGet and HArraySet will check whether the input address
+ // is an HIntermediateAddress and generate appropriate code.
+ // We would like to replace the `HArrayGet` and `HArraySet` with custom instructions (maybe
+ // `HArm64Load` and `HArm64Store`,`HArmLoad` and `HArmStore`). We defer these changes
+ // because these new instructions would not bring any advantages yet.
+ // Also see the comments in
+ // `InstructionCodeGeneratorARM::VisitArrayGet()`
+ // `InstructionCodeGeneratorARM::VisitArraySet()`
+ // `InstructionCodeGeneratorARM64::VisitArrayGet()`
+ // `InstructionCodeGeneratorARM64::VisitArraySet()`.
+ return true;
+}
+
+
} // namespace art