[PATCH] powerpc: Cleanup LOADADDR etc. asm macros

This patch consolidates the variety of macros used for loading 32 or
64-bit constants in assembler (LOADADDR, LOADBASE, SET_REG_TO_*).  The
idea is to make the set of macros consistent across 32 and 64 bit and
to make it more obvious which is the appropriate one to use in a given
situation.  The new macros and their semantics are described in the
comments in ppc_asm.h.

In the process, we change several places that were unnecessarily using
immediate loads on ppc64 to use the GOT/TOC.  Likewise we cleanup a
couple of places where we were clumsily subtracting PAGE_OFFSET with
asm instructions to use assemble-time arithmetic or the toreal() macro
instead.

Signed-off-by: David Gibson <dwg@au1.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 40 insertions, 36 deletions

diff --git a/include/asm-powerpc/ppc_asm.h b/include/asm-powerpc/ppc_asm.h
index 0dc798d46ea4..ab8688d39024 100644
--- a/include/asm-powerpc/ppc_asm.h
+++ b/include/asm-powerpc/ppc_asm.h
@@ -156,52 +156,56 @@ n:
 #endif
 
 /* 
- * LOADADDR( rn, name )
- *   loads the address of 'name' into 'rn'
+ * LOAD_REG_IMMEDIATE(rn, expr)
+ *   Loads the value of the constant expression 'expr' into register 'rn'
+ *   using immediate instructions only.  Use this when it's important not
+ *   to reference other data (i.e. on ppc64 when the TOC pointer is not
+ *   valid).
  *
- * LOADBASE( rn, name )
- *   loads the address (possibly without the low 16 bits) of 'name' into 'rn'
- *   suitable for base+disp addressing
+ * LOAD_REG_ADDR(rn, name)
+ *   Loads the address of label 'name' into register 'rn'.  Use this when
+ *   you don't particularly need immediate instructions only, but you need
+ *   the whole address in one register (e.g. it's a structure address and
+ *   you want to access various offsets within it).  On ppc32 this is
+ *   identical to LOAD_REG_IMMEDIATE.
+ *
+ * LOAD_REG_ADDRBASE(rn, name)
+ * ADDROFF(name)
+ *   LOAD_REG_ADDRBASE loads part of the address of label 'name' into
+ *   register 'rn'.  ADDROFF(name) returns the remainder of the address as
+ *   a constant expression.  ADDROFF(name) is a signed expression < 16 bits
+ *   in size, so is suitable for use directly as an offset in load and store
+ *   instructions.  Use this when loading/storing a single word or less as:
+ *      LOAD_REG_ADDRBASE(rX, name)
+ *      ld      rY,ADDROFF(name)(rX)
  */
 #ifdef __powerpc64__
-#define LOADADDR(rn,name) \
-        lis     rn,name##@highest;      \
-        ori     rn,rn,name##@higher;    \
-        rldicr  rn,rn,32,31;            \
-        oris    rn,rn,name##@h;         \
-        ori     rn,rn,name##@l
-
-#define LOADBASE(rn,name)               \
-        ld      rn,name@got(r2)
-
-#define OFF(name)       0
-
-#define SET_REG_TO_CONST(reg, value)                    \
-        lis     reg,(((value)>>48)&0xFFFF);             \
-        ori     reg,reg,(((value)>>32)&0xFFFF);         \
-        rldicr  reg,reg,32,31;                          \
-        oris    reg,reg,(((value)>>16)&0xFFFF);         \
-        ori     reg,reg,((value)&0xFFFF);
-
-#define SET_REG_TO_LABEL(reg, label)                    \
-        lis     reg,(label)@highest;                    \
-        ori     reg,reg,(label)@higher;                 \
-        rldicr  reg,reg,32,31;                          \
-        oris    reg,reg,(label)@h;                      \
-        ori     reg,reg,(label)@l;
+#define LOAD_REG_IMMEDIATE(reg,expr)            \
+        lis     (reg),(expr)@highest;           \
+        ori     (reg),(reg),(expr)@higher;      \
+        rldicr  (reg),(reg),32,31;              \
+        oris    (reg),(reg),(expr)@h;           \
+        ori     (reg),(reg),(expr)@l;
+
+#define LOAD_REG_ADDR(reg,name)                 \
+        ld      (reg),name@got(r2)
+
+#define LOAD_REG_ADDRBASE(reg,name)     LOAD_REG_ADDR(reg,name)
+#define ADDROFF(name)                   0
 
 /* offsets for stack frame layout */
 #define LRSAVE  16
 
 #else /* 32-bit */
-#define LOADADDR(rn,name) \
-        lis     rn,name@ha;     \
-        addi    rn,rn,name@l
 
-#define LOADBASE(rn,name)       \
-        lis     rn,name@ha
+#define LOAD_REG_IMMEDIATE(reg,expr)            \
+        lis     (reg),(expr)@ha;                \
+        addi    (reg),(reg),(expr)@l;
+
+#define LOAD_REG_ADDR(reg,name)         LOAD_REG_IMMEDIATE(reg, name)
 
-#define OFF(name)       name@l
+#define LOAD_REG_ADDRBASE(reg, name)    lis     (reg),name@ha
+#define ADDROFF(name)                   name@l
 
 /* offsets for stack frame layout */
 #define LRSAVE  4