ARM: Add comments to clarify conditionally executed code dealing with d16-d31

src/arm/deoptimizer-arm.cc

Index: src/arm/deoptimizer-arm.cc
diff --git a/src/arm/deoptimizer-arm.cc b/src/arm/deoptimizer-arm.cc
index f4cab9dd624075c22ac57936c4d8f5311e5feffe..0cca5fdadcb33c72d47498488f6d7a2cf0b7ef93 100644
--- a/src/arm/deoptimizer-arm.cc
+++ b/src/arm/deoptimizer-arm.cc
@@ -1011,6 +1011,7 @@ void Deoptimizer::EntryGenerator::Generate() {
     __ CheckFor32DRegs(ip);
 
     // Push registers d0-d13, and possibly d16-d31, on the stack.
+    // If d16-d31 are not pushed, decrease the stack pointer instead.
     __ vstm(db_w, sp, d16, d31, ne);
     __ sub(sp, sp, Operand(16 * kDoubleSize), LeaveCC, eq);
     __ vstm(db_w, sp, d0, d13);