Basic SIMD reduction support.

Rationale:
Enables vectorization of x += .... for very basic (simple, same-type)
constructs. Paves the way for more complex (narrower and/or mixed-type)
constructs, which will be handled by the next CL.

This is  a revert   of Icb5d6c805516db0a1d911c3ede9a246ccef89a22
and thus a revert^2 of I2454778dd0ef1da915c178c7274e1cf33e271d0f
and thus a revert^3 of I1c1c87b6323e01442e8fbd94869ddc9e760ea1fc
and thus a revert^4 of I7880c135aee3ed0a39da9ae5b468cbf80e613766

PS1-2 shows what needed to change

Test: test-art-host test-art-target

Bug: 64091002
Change-Id: I647889e0da0959ca405b70081b79c7d3c9bcb2e9
diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index f60d532..869fdd4 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -1374,7 +1374,8 @@
   M(UShr, BinaryOperation)                                              \
   M(Xor, BinaryOperation)                                               \
   M(VecReplicateScalar, VecUnaryOperation)                              \
-  M(VecSumReduce, VecUnaryOperation)                                    \
+  M(VecExtractScalar, VecUnaryOperation)                                \
+  M(VecReduce, VecUnaryOperation)                                       \
   M(VecCnv, VecUnaryOperation)                                          \
   M(VecNeg, VecUnaryOperation)                                          \
   M(VecAbs, VecUnaryOperation)                                          \
@@ -7030,6 +7031,17 @@
   return false;
 }
 
+// Returns true iff instruction is the given integral constant.
+inline bool IsInt64Value(HInstruction* instruction, int64_t value) {
+  int64_t val = 0;
+  return IsInt64AndGet(instruction, &val) && val == value;
+}
+
+// Returns true iff instruction is a zero bit pattern.
+inline bool IsZeroBitPattern(HInstruction* instruction) {
+  return instruction->IsConstant() && instruction->AsConstant()->IsZeroBitPattern();
+}
+
 #define INSTRUCTION_TYPE_CHECK(type, super)                                    \
   inline bool HInstruction::Is##type() const { return GetKind() == k##type; }  \
   inline const H##type* HInstruction::As##type() const {                       \