Fuse long and FP compare & condition on ARM in Optimizing.

Also:
- Stylistic changes in corresponding parts on the x86 and
  x86-64 code generators.
- Update and improve the documentation of
  art::arm::Condition.

Bug: 21120453
Change-Id: If144772046e7d21362c3c2086246cb7d011d49ce
diff --git a/compiler/optimizing/instruction_simplifier.cc b/compiler/optimizing/instruction_simplifier.cc
index 337cf5b..017b678 100644
--- a/compiler/optimizing/instruction_simplifier.cc
+++ b/compiler/optimizing/instruction_simplifier.cc
@@ -517,10 +517,10 @@
 void InstructionSimplifierVisitor::VisitCondition(HCondition* condition) {
   // Try to fold an HCompare into this HCondition.
 
-  // This simplification is currently only supported on x86 and x86_64.
-  // TODO: Implement it for ARM, ARM64 and MIPS64.
+  // This simplification is currently only supported on x86, x86_64 and ARM.
+  // TODO: Implement it for ARM64 and MIPS64.
   InstructionSet instruction_set = GetGraph()->GetInstructionSet();
-  if (instruction_set != kX86 && instruction_set != kX86_64) {
+  if (instruction_set != kX86 && instruction_set != kX86_64 && instruction_set != kThumb2) {
     return;
   }