[Mono-dev] Proposed endian optimization - s390x

[Neale Ferguson]

Hi,
 I am proposing the following changes to mono-endian.h to optimize
little-endian to big-endian processing for s390x. The architecture defines
instructions for just this purpose so instead of doing shifts etc. we can
just do this:

--- a/mono/metadata/mono-endian.h
+++ b/mono/metadata/mono-endian.h
@@ -14,7 +14,49 @@ typedef union {
        unsigned char cval [8];
 } mono_rdouble;
 
-#if NO_UNALIGNED_ACCESS
+#if defined(__s390x__)
+
+#define read16(x)      s390x_read16(*(guint16 *)(x))
+#define read32(x)      s390x_read32(*(guint32 *)(x))
+#define read64(x)      s390x_read64(*(guint64 *)(x))
+
+static __inline__ guint16
+s390x_read16(guint16 x)
+{
+       guint16 ret;
+
+       __asm__ ("      lrvr    %0,%1\n"
+                "      sra     %0,16\n"
+                : "=r" (ret) : "r" (x));
+
+       return(ret);
+}
+
+static __inline__ guint32
+s390x_read32(guint32 x)
+{
+       guint32 ret;
+
+       __asm__ ("      lrvr    %0,%1\n"
+                : "=r" (ret) : "r" (x));
+
+       return(ret);

+}
+
+static __inline__ guint64
+s390x_read64(guint64 x)
+{
+       guint64 ret;
+
+       __asm__ ("      lrvgr   %0,%1\n"
+                : "=r" (ret) : "r" (x));
+
+       return(ret);
+}
+
+#else
+
+# if NO_UNALIGNED_ACCESS
 
 guint16 mono_read16 (const unsigned char *x);
 guint32 mono_read32 (const unsigned char *x);
@@ -24,12 +66,14 @@ guint64 mono_read64 (const unsigned char *x);
 #define read32(x) (mono_read32 ((const unsigned char *)(x)))
 #define read64(x) (mono_read64 ((const unsigned char *)(x)))
 
-#else
+# else
 
 #define read16(x) GUINT16_FROM_LE (*((const guint16 *) (x)))
 #define read32(x) GUINT32_FROM_LE (*((const guint32 *) (x)))
 #define read64(x) GUINT64_FROM_LE (*((const guint64 *) (x)))
 
+# endif
+
 #endif
 
 #define readr4(x,dest) \


Any objections?

Neale