Remove implicit 64 to 32 bit narrowing

This patch fixes cases of implicit 64 to 32 bit narrowing. The issue is
that `CodeBuffer` represents code offsets with `ptrdiff_t`, which will
be 64 bit on a 64 bit system. However, we want to support generating 32
bit code from a 64 bit program, therefore the 32 bit part of VIXL works
with `int32_t` for code offsets. We had implicit conversions happening
due to this.

We solve this by explicitely casting to `int32_t` in the AArch32
assembler when calling `GetCursorOffset`. If you are working with the
`CodeBuffer` directly, you are dealing with a code buffer on the host
and so will work with offsets as `ptrdiff_t`. But, when working with the
AArch32 assembler itself you will get offsets as `int32_t`. The
assembler is in charge of checking that the offsets it gets from the
code buffer fit into `int32_t`.

Additionally, we had narrowing cases when generally wrapping host
pointers into an Operand. This can only work if the pointer fits into 32
bits. This patch introduces a Operand::From() factory method that can be
used for converting any integral or pointer type to an immediate
operand.

Change-Id: Icc15711b34c2477ed997eef238e25496d86ea9aa

1 files changed, 0 insertions, 2 deletions

diff --git a/SConstruct b/SConstruct
index 07f9f037..7214699e 100644
--- a/SConstruct
+++ b/SConstruct
@@ -260,8 +260,6 @@ def ConfigureEnvironmentForCompiler(env):
     if not using_clang3_4:
       env.Append(CPPFLAGS = ['-Wunreachable-code'])
 
-    env.Append(CPPFLAGS = ['-Wno-shorten-64-to-32'])
-
   # GCC 4.8 has a bug which produces a warning saying that an anonymous Operand
   # object might be used uninitialized:
   #   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57045