diff --git a/glx/indirect_reqsize.h b/glx/indirect_reqsize.h
index 632a85b1c..809681931 100644
--- a/glx/indirect_reqsize.h
+++ b/glx/indirect_reqsize.h
@@ -30,7 +30,7 @@
 
 #include <X11/Xfuncproto.h>
 
-#if defined(__GNUC__) || (defined(__SUNPRO_C) && (__SUNPRO_C >= 0x590))
+#if defined(__GNUC__)
 #define PURE __attribute__((pure))
 #else
 #define PURE
diff --git a/glx/indirect_size.h b/glx/indirect_size.h
index 6a3d14cc4..e36c22ab3 100644
--- a/glx/indirect_size.h
+++ b/glx/indirect_size.h
@@ -38,7 +38,7 @@
 
 #include <X11/Xfuncproto.h>
 
-#if defined(__GNUC__) || (defined(__SUNPRO_C) && (__SUNPRO_C >= 0x590))
+#if defined(__GNUC__)
 #define PURE __attribute__((pure))
 #else
 #define PURE
diff --git a/glx/indirect_size_get.c b/glx/indirect_size_get.c
index 7e81e6288..46d068769 100644
--- a/glx/indirect_size_get.c
+++ b/glx/indirect_size_get.c
@@ -33,7 +33,7 @@
 #include "indirect_util.h"
 #include "indirect_size.h"
 
-#if defined(__GNUC__) || (defined(__SUNPRO_C) && (__SUNPRO_C >= 0x590))
+#if defined(__GNUC__)
 #define PURE __attribute__((pure))
 #else
 #define PURE
diff --git a/glx/indirect_size_get.h b/glx/indirect_size_get.h
index 5af11d378..587e4148a 100644
--- a/glx/indirect_size_get.h
+++ b/glx/indirect_size_get.h
@@ -38,7 +38,7 @@
 
 #include <X11/Xfuncproto.h>
 
-#if defined(__GNUC__) || (defined(__SUNPRO_C) && (__SUNPRO_C >= 0x590))
+#if defined(__GNUC__)
 #define PURE __attribute__((pure))
 #else
 #define PURE
diff --git a/hw/kdrive/ephyr/hostx.c b/hw/kdrive/ephyr/hostx.c
index 5baa3e781..be894bd36 100644
--- a/hw/kdrive/ephyr/hostx.c
+++ b/hw/kdrive/ephyr/hostx.c
@@ -420,11 +420,6 @@ hostx_set_title(char *title)
     ephyrTitle = title;
 }
 
-#ifdef __SUNPRO_C
-/* prevent "Function has no return statement" error for x_io_error_handler */
-#pragma does_not_return(exit)
-#endif
-
 static void
 hostx_init_shm(void)
 {
diff --git a/hw/xfree86/common/compiler.h b/hw/xfree86/common/compiler.h
index eb788d3fd..af2f1490c 100644
--- a/hw/xfree86/common/compiler.h
+++ b/hw/xfree86/common/compiler.h
@@ -51,10 +51,6 @@
 
 #define _COMPILER_H
 
-#if defined(__SUNPRO_C)
-#define DO_PROTOTYPES
-#endif
-
 /* Map Sun compiler platform defines to gcc-style used in the code */
 #if defined(__amd64) && !defined(__amd64__)
 #define __amd64__
@@ -95,45 +91,6 @@
 #define __FUNCTION__ __func__   /* C99 */
 #endif
 
-#if defined(DO_PROTOTYPES)
-#if !defined(__arm__)
-#if !defined(__sparc__) && !defined(__arm32__) && !defined(__nds32__) \
-      && !(defined(__alpha__) && defined(__linux__)) \
-      && !(defined(__ia64__) && defined(__linux__)) \
-      && !(defined(__mips64) && defined(__linux__)) \
-
-extern _X_EXPORT void outb(unsigned short, unsigned char);
-extern _X_EXPORT void outw(unsigned short, unsigned short);
-extern _X_EXPORT void outl(unsigned short, unsigned int);
-extern _X_EXPORT unsigned int inb(unsigned short);
-extern _X_EXPORT unsigned int inw(unsigned short);
-extern _X_EXPORT unsigned int inl(unsigned short);
-
-#else                           /* __sparc__,  __arm32__, __alpha__, __nds32__ */
-extern _X_EXPORT void outb(unsigned long, unsigned char);
-extern _X_EXPORT void outw(unsigned long, unsigned short);
-extern _X_EXPORT void outl(unsigned long, unsigned int);
-extern _X_EXPORT unsigned int inb(unsigned long);
-extern _X_EXPORT unsigned int inw(unsigned long);
-extern _X_EXPORT unsigned int inl(unsigned long);
-
-#ifdef __SUNPRO_C
-extern _X_EXPORT unsigned char  xf86ReadMmio8    (void *, unsigned long);
-extern _X_EXPORT unsigned short xf86ReadMmio16Be (void *, unsigned long);
-extern _X_EXPORT unsigned short xf86ReadMmio16Le (void *, unsigned long);
-extern _X_EXPORT unsigned int   xf86ReadMmio32Be (void *, unsigned long);
-extern _X_EXPORT unsigned int   xf86ReadMmio32Le (void *, unsigned long);
-extern _X_EXPORT void xf86WriteMmio8    (void *, unsigned long, unsigned int);
-extern _X_EXPORT void xf86WriteMmio16Be (void *, unsigned long, unsigned int);
-extern _X_EXPORT void xf86WriteMmio16Le (void *, unsigned long, unsigned int);
-extern _X_EXPORT void xf86WriteMmio32Be (void *, unsigned long, unsigned int);
-extern _X_EXPORT void xf86WriteMmio32Le (void *, unsigned long, unsigned int);
-#endif                          /* _SUNPRO_C */
-#endif                          /* __sparc__,  __arm32__, __alpha__, __nds32__ */
-#endif                          /* __arm__ */
-
-#endif                          /* NO_INLINE || DO_PROTOTYPES */
-
 #ifdef __GNUC__
 #ifdef __i386__
 
@@ -265,8 +222,7 @@ inl(unsigned long port)
 
 #endif                          /* __linux__ */
 
-#if (defined(__FreeBSD__) || defined(__OpenBSD__)) \
-      && !defined(DO_PROTOTYPES)
+#if (defined(__FreeBSD__) || defined(__OpenBSD__))
 
 /* for FreeBSD and OpenBSD on Alpha, we use the libio (resp. libalpha) */
 /*  inx/outx routines */
@@ -280,7 +236,7 @@ extern _X_EXPORT unsigned char inb(unsigned int port);
 extern _X_EXPORT unsigned short inw(unsigned int port);
 extern _X_EXPORT unsigned int inl(unsigned int port);
 
-#endif                          /* (__FreeBSD__ || __OpenBSD__ ) && !DO_PROTOTYPES */
+#endif                          /* (__FreeBSD__ || __OpenBSD__ ) */
 
 #if defined(__NetBSD__)
 #include <machine/pio.h>
@@ -941,9 +897,7 @@ inl(unsigned PORT_SIZE port)
 #define asm __asm
 #endif
 #endif
-#if !defined(__SUNPRO_C)
 #include <sys/inline.h>
-#endif
 #endif                          /* __GNUC__ */
 
 #if !defined(MMIO_IS_BE) && \
diff --git a/hw/xfree86/int10/vbe.h b/hw/xfree86/int10/vbe.h
index 8024f5102..1f43d68ca 100644
--- a/hw/xfree86/int10/vbe.h
+++ b/hw/xfree86/int10/vbe.h
@@ -59,13 +59,13 @@ typedef struct vbeControllerInfoBlock {
     CARD8 OemData[256];
 } vbeControllerInfoRec, *vbeControllerInfoPtr;
 
-#if defined(__GNUC__) || defined(__USLC__) || defined(__SUNPRO_C)
+#if defined(__GNUC__) || defined(__USLC__)
 #pragma pack()                  /* All GCC versions recognise this syntax */
 #else
 #pragma pack(0)
 #endif
 
-#if !( defined(__GNUC__) || (defined(__SUNPRO_C) && (__SUNPRO_C >= 0x590)) )
+#if !( defined(__GNUC__))
 #define __attribute__(a)
 #endif
 
diff --git a/hw/xnest/Display.c b/hw/xnest/Display.c
index dc59c6b91..e6fa4ba30 100644
--- a/hw/xnest/Display.c
+++ b/hw/xnest/Display.c
@@ -54,11 +54,6 @@ Pixmap xnestScreenSaverPixmap;
 XlibGC xnestBitmapGC;
 unsigned long xnestEventMask;
 
-#ifdef __SUNPRO_C
-/* prevent "Function has no return statement" error for x_io_error_handler */
-#pragma does_not_return(exit)
-#endif
-
 static int _X_NORETURN
 x_io_error_handler(Display * dpy)
 {
diff --git a/include/misc.h b/include/misc.h
index 50efaba3c..14c645b4b 100644
--- a/include/misc.h
+++ b/include/misc.h
@@ -290,7 +290,7 @@ wrong_size(void)
 }
 #endif
 
-#if !(defined(__GNUC__) || (defined(__SUNPRO_C) && (__SUNPRO_C >= 0x590)))
+#if !(defined(__GNUC__))
 static inline int
 __builtin_constant_p(int x)
 {