Support unaligned integer loads on ARM and MIPS.

runtime/vm/intermediate_language.cc

Index: runtime/vm/intermediate_language.cc
diff --git a/runtime/vm/intermediate_language.cc b/runtime/vm/intermediate_language.cc
index c3359f1f23fe46637922f5369b64a07f62f3c7f3..1b5771729ef5793424d4759acd9b598fd262995a 100644
--- a/runtime/vm/intermediate_language.cc
+++ b/runtime/vm/intermediate_language.cc
@@ -3659,6 +3659,89 @@ Definition* StringInterpolateInstr::Canonicalize(FlowGraph* flow_graph) {
 }
 
 
+LoadIndexedInstr::LoadIndexedInstr(Value* array,
+                                   Value* index,
+                                   intptr_t index_scale,
+                                   intptr_t class_id,
+                                   bool aligned,
+                                   intptr_t deopt_id,
+                                   TokenPosition token_pos)
+    : TemplateDefinition(deopt_id),
+      index_scale_(index_scale),
+      class_id_(class_id),
+      aligned_(aligned),
+      token_pos_(token_pos) {
+  SetInputAt(0, array);
+  SetInputAt(1, index);
+
+  switch (class_id) {
+    case kTypedDataInt8ArrayCid:
+    case kTypedDataUint8ArrayCid:
+    case kTypedDataUint8ClampedArrayCid:
+    case kExternalTypedDataUint8ArrayCid:
+    case kExternalTypedDataUint8ClampedArrayCid:
+    case kOneByteStringCid:
+    case kExternalOneByteStringCid:
+      // Don't need to worry about alignment for accessing bytes.
+      aligned_ = true;
+      break;
+    case kTypedDataFloat32ArrayCid:
+    case kTypedDataFloat64ArrayCid:
+    case kTypedDataFloat64x2ArrayCid:
+    case kTypedDataInt32x4ArrayCid:
+    case kTypedDataFloat32x4ArrayCid:
+      // TODO(rmacnak): Investigate alignment requirements of floating point
+      // loads.
+      aligned_ = true;
+      break;

[zra, 2016/10/26 06:59:41]

I'd sort of prefer leaving aligned_ out of the initializer list, and setting it
in a default case here. Otherwise maybe put a comment above the switch
explaining what it is for.

[Cutch, 2016/10/26 09:00:29]

I'd like to see the switch statement factored into a separate function which
returns true/false.

Something like:

bool AddressWillBeAligned(intptr_t cid, bool default_value) { ... }

Then you could put it into initializer list:

aligned_(AddressWillBeAligned(class_id, aligned)),

[rmacnak, 2016/10/31 22:57:26]

Switched to enum and separate narrowing function.

+  }
+}
+
+
+
+StoreIndexedInstr::StoreIndexedInstr(Value* array,
+                                     Value* index,
+                                     Value* value,
+                                     StoreBarrierType emit_store_barrier,
+                                     intptr_t index_scale,
+                                     intptr_t class_id,
+                                     bool aligned,
+                                     intptr_t deopt_id,
+                                     TokenPosition token_pos)
+    : TemplateDefinition(deopt_id),
+      emit_store_barrier_(emit_store_barrier),
+      index_scale_(index_scale),
+      class_id_(class_id),
+      aligned_(aligned),
+      token_pos_(token_pos) {
+  SetInputAt(kArrayPos, array);
+  SetInputAt(kIndexPos, index);
+  SetInputAt(kValuePos, value);
+
+  switch (class_id) {
+    case kTypedDataInt8ArrayCid:
+    case kTypedDataUint8ArrayCid:
+    case kTypedDataUint8ClampedArrayCid:
+    case kExternalTypedDataUint8ArrayCid:
+    case kExternalTypedDataUint8ClampedArrayCid:
+    case kOneByteStringCid:
+    case kExternalOneByteStringCid:
+      // Don't need to worry about alignment for accessing bytes.
+      aligned_ = true;
+      break;
+    case kTypedDataFloat32ArrayCid:
+    case kTypedDataFloat64ArrayCid:
+    case kTypedDataFloat64x2ArrayCid:
+    case kTypedDataInt32x4ArrayCid:
+    case kTypedDataFloat32x4ArrayCid:
+      // TODO(rmacnak): Investigate alignment requirements of floating point
+      // loads.
+      aligned_ = true;
+      break;

[zra, 2016/10/26 06:59:41]

ditto

+  }
+}
+
+
 InvokeMathCFunctionInstr::InvokeMathCFunctionInstr(
     ZoneGrowableArray<Value*>* inputs,
     intptr_t deopt_id,