Ensure `MacroAssembler::Nop` generates a single `nop`.

The `MacroAssembler` is allowed to emit any code that is functionally
equivalent to what is requested by the user, and is expected to
generate 'good' code.  The user can expect calls such as
`masm.Add(r0, r0, 0)` to be optimized away (think that `0` may be the
value of a variable).
Following this we *could* generate no code for calls to `Nop()`. But
`Nop()` will likely not be used by mistake, so we ensure it generates
at least one `nop` instruction. This is useful for tests where we want
to generate 'some' code.

Change-Id: Iecf31b5cfd151a77b1633ea5158ff54fef9f8908

1 files changed, 16 insertions, 3 deletions

diff --git a/test/aarch64/test-assembler-aarch64.cc b/test/aarch64/test-assembler-aarch64.cc
index c4594e9c..f0720f3c 100644
--- a/test/aarch64/test-assembler-aarch64.cc
+++ b/test/aarch64/test-assembler-aarch64.cc
@@ -22596,11 +22596,11 @@ TEST(optimised_mov_register) {
   Label start;
   __ Bind(&start);
   __ Mov(x0, x0);
-  VIXL_CHECK(__ GetSizeOfCodeGeneratedSince(&start) == 0);
+  VIXL_CHECK(masm.GetSizeOfCodeGeneratedSince(&start) == 0);
   __ Mov(w0, w0, kDiscardForSameWReg);
-  VIXL_CHECK(__ GetSizeOfCodeGeneratedSince(&start) == 0);
+  VIXL_CHECK(masm.GetSizeOfCodeGeneratedSince(&start) == 0);
   __ Mov(w0, w0);
-  VIXL_CHECK(__ GetSizeOfCodeGeneratedSince(&start) == kInstructionSize);
+  VIXL_CHECK(masm.GetSizeOfCodeGeneratedSince(&start) == kInstructionSize);
 
   END();
 
@@ -22610,5 +22610,18 @@ TEST(optimised_mov_register) {
 }
 
 
+TEST(nop) {
+  MacroAssembler masm;
+
+  Label start;
+  __ Bind(&start);
+  __ Nop();
+  // `MacroAssembler::Nop` must generate at least one nop.
+  VIXL_CHECK(masm.GetSizeOfCodeGeneratedSince(&start) >= kInstructionSize);
+
+  masm.FinalizeCode();
+}
+
+
 }  // namespace aarch64
 }  // namespace vixl