RFC: PATCH: Add -maddress-mode=short|long for x86

diff --git a/gcc/config/i386/i386-opts.h b/gcc/config/i386/i386-opts.h
index 3cc2253..eea85fd 100644
--- a/gcc/config/i386/i386-opts.h
+++ b/gcc/config/i386/i386-opts.h
@@ -71,6 +71,11 @@  enum cmodel {
   CM_LARGE_PIC	/* No assumptions.  */
 };
 
+enum pmode {
+  PMODE_SI,	/* Pmode == SImode. */
+  PMODE_DI 	/* Pmode == DImode. */
+};
+
 enum asm_dialect {
   ASM_ATT,
   ASM_INTEL
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index dbcf5a9..8d9c801 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -3172,6 +3172,17 @@  ix86_option_override_internal (bool main_args_p)
   else
     ix86_arch_specified = 1;
 
+  if (global_options_set.x_ix86_pmode)
+    {
+      if ((TARGET_LP64 && ix86_pmode == PMODE_SI)
+	   || (!TARGET_64BIT && ix86_pmode == PMODE_DI))
+	error ("address mode %qs not supported in the %s bit mode",
+	       TARGET_64BIT ? "short" : "long",
+	       TARGET_64BIT ? "64" : "32");
+    }
+  else
+    ix86_pmode = TARGET_LP64 ? PMODE_DI : PMODE_SI;
+
   if (!global_options_set.x_ix86_abi)
     ix86_abi = DEFAULT_ABI;
 
diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
index c77070b..3fcd209 100644
--- a/gcc/config/i386/i386.h
+++ b/gcc/config/i386/i386.h
@@ -1745,7 +1745,7 @@  do {							\
 /* Specify the machine mode that pointers have.
    After generation of rtl, the compiler makes no further distinction
    between pointers and any other objects of this machine mode.  */
-#define Pmode (TARGET_64BIT ? DImode : SImode)
+#define Pmode (ix86_pmode == PMODE_DI ? DImode : SImode)
 
 /* A C expression whose value is zero if pointers that need to be extended
    from being `POINTER_SIZE' bits wide to `Pmode' are sign-extended and
diff --git a/gcc/config/i386/i386.opt b/gcc/config/i386/i386.opt
index 1d8dc44..29f1082 100644
--- a/gcc/config/i386/i386.opt
+++ b/gcc/config/i386/i386.opt
@@ -159,6 +159,20 @@  Enum(cmodel) String(32) Value(CM_32)
 EnumValue
 Enum(cmodel) String(kernel) Value(CM_KERNEL)
 
+maddress-mode=
+Target RejectNegative Joined Enum(pmode) Var(ix86_pmode) Init(PMODE_SI)
+Use given address mode
+
+Enum
+Name(pmode) Type(enum pmode)
+Known address mode (for use with the -maddress-mode= option):
+
+EnumValue
+Enum(pmode) String(short) Value(PMODE_SI)
+
+EnumValue
+Enum(pmode) String(long) Value(PMODE_DI)
+
 mcpu=
 Target RejectNegative Joined Undocumented Alias(mtune=) Warn(%<-mcpu=%> is deprecated; use %<-mtune=%> or %<-march=%> instead)
 
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 5f5397b..e9188db 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -634,7 +634,7 @@  Objective-C and Objective-C++ Dialects}.
 -mveclibabi=@var{type} -mvect8-ret-in-mem @gol
 -mpc32 -mpc64 -mpc80 -mstackrealign @gol
 -momit-leaf-frame-pointer  -mno-red-zone -mno-tls-direct-seg-refs @gol
--mcmodel=@var{code-model} -mabi=@var{name} @gol
+-mcmodel=@var{code-model} -mabi=@var{name} -maddress-mode=@var{mode} @gol
 -m32 -m64 -mx32 -mlarge-data-threshold=@var{num} @gol
 -msse2avx -mfentry -m8bit-idiv @gol
 -mavx256-split-unaligned-load -mavx256-split-unaligned-store}
@@ -13938,6 +13938,18 @@  be statically or dynamically linked.
 @opindex mcmodel=large
 Generate code for the large model.  This model makes no assumptions
 about addresses and sizes of sections.
+
+@item -maddress-mode=long
+@opindex maddress-mode=long
+Generate code for long address mode.  It is only supported for 64-bit
+and x32 environments.  This is the default address mode for 64-bit
+environment.
+
+@item -maddress-mode=short
+@opindex maddress-mode=short
+Generate code for short address mode.  It is only supported for 32-bit
+and x32 environments.  This is the default address mode for 32-bit and
+x32 environments.
 @end table
 
 @node i386 and x86-64 Windows Options