Add missing file

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@5163 6f19259b-4bc3-4df7-8a09-765794883524

DuetPkg/CpuIoDxe/Ia32/CpuIoAccessGNU.c

@@ -0,0 +1,134 @@
+/*  This file is only used when not able to compile the MASM CpuIoAccess.asm
+    NOTE: Compiling with -fomit-frame-pointer would get you to roughly the exact
+    same code as the MASM file although GCC will typically include movzbl %al, %eax
+    or movzwl %ax, %eax instructions on the read functions such that the entire
+    eax result register will be valid, not just the lowest 8 or 16 bits.
+ */
+#ifdef __GNUC__
+
+/*  A quick note about GCC inline asm and the GNU assembler:
+    When gas encounters an instruction with a suffix (e.g. inb, inw, or inl vs. just in) it will
+    warn if the operand corresponding to the suffix is not of the correct size and will assume you
+    meant what you said when you specified the suffix.
+
+    Because GCC does not enable us to see whether it is replacing %0 with %al, %ax, or %eax it is
+    helpful to have the assembler warn us that GCC is making an incorrect assumption.  The actual
+    in or out instruction will always be generated correctly in this case since the assembler is
+    correct in assuming we meant what we said when we specified the suffix.  However, GCC might
+    generate incorrect surrounding code.  For example, if we were to incorrectly specify the
+    output size of an in instruction as UINT32, GCC would potentially fail to issue movz(b|w)l after
+    it under the assumption that the in instruction filled the entire eax register and not just
+    the al or ax portion.
+
+    GCC determines which size of register to use based on the C data type.  So for in instructions
+    the interesting type is that of the automatic variable named Data which is specified as an
+    output operand to the inline assembly statement.  For example:
+
+      UINT8     Data;
+      asm ( "inb %1, %0"
+          : "=a"(Data)
+          : "d"(Port)
+          );
+      return Data;
+
+    In this case, GCC will replace %0 with %al.  If Data had been specified as UINT16, it would replace
+    %0 with %ax, and for UINT32 with %eax.
+
+    Likewise in the case of IA32 out instructions, GCC will replace %0 with the appropriately sized
+    register based on the size of the input operand.  There is one gotcha though.  The CpuIoWrite
+    series of functions all use UINT32 as the type of the second (Data) argument.  This means that
+    for GCC to output the correct register size we must cast it appropriately.
+
+    The Port number is always a UINT16 so GCC will always ouput %dx.
+ */
+
+#include "CpuIoAccess.h"
+
+UINT8
+IA32API
+CpuIoRead8 (
+  IN  UINT16  Port
+  )
+{
+  UINT8     Data;
+  asm ( "inb %1, %0"
+      : "=a"(Data)
+      : "d"(Port)
+      );
+  return Data;
+}
+
+UINT16
+IA32API
+CpuIoRead16 (
+  IN  UINT16  Port
+  )
+{
+  UINT16    Data;
+  asm ( "inw %1, %0"
+      : "=a"(Data)
+      : "d"(Port)
+      );
+  return Data;
+}
+
+UINT32
+IA32API
+CpuIoRead32 (
+  IN  UINT16  Port
+  )
+{
+  UINT32    Data;
+  asm ( "inl %1, %0"
+      : "=a"(Data)
+      : "d"(Port)
+      );
+  return Data;
+}
+
+VOID
+IA32API
+CpuIoWrite8 (
+  IN  UINT16  Port,
+  IN  UINT32  Data
+  )
+{
+  asm ( "outb %1, %0"
+      : /* No outputs */
+      : "d"(Port)
+      , "a"((UINT8)Data)
+      );
+}
+
+VOID
+IA32API
+CpuIoWrite16 (
+  IN  UINT16  Port,
+  IN  UINT32  Data
+  )
+{
+  asm ( "outw %1, %0"
+      : /* No outputs */
+      : "d"(Port)
+      , "a"((UINT16)Data)
+      );
+}
+
+VOID
+IA32API
+CpuIoWrite32 (
+  IN  UINT16  Port,
+  IN  UINT32  Data
+  )
+{
+  asm ( "outl %1, %0"
+      : /* No outputs */
+      : "d"(Port)
+      /*  NOTE: Cast is technically unnecessary but we use it to illustrate
+          that we always want to output a UINT32 and never anything else.
+       */
+      , "a"((UINT32)Data) 
+      );
+}
+
+#endif /* def __GNUC__ */