diff --git a/lib/Makefile b/lib/Makefile
index 4827e3ad478d..9b687827bf3d 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -40,7 +40,7 @@ _csu=csu/${MACHINE_ARCH}
 _csu=csu
 .endif
 
-.if !defined(NOLIBC_R) && ${MACHINE_ARCH} != ia64
+.if !defined(NOLIBC_R)
 _libc_r=	libc_r
 .endif
 
diff --git a/lib/libc_r/uthread/pthread_private.h b/lib/libc_r/uthread/pthread_private.h
index e8e85b0a3ea0..b2f7a61afa4a 100644
--- a/lib/libc_r/uthread/pthread_private.h
+++ b/lib/libc_r/uthread/pthread_private.h
@@ -102,6 +102,21 @@
 	(jb)[0]._jb[R_RA + 4] = (long)(ra);		\
 	(jb)[0]._jb[R_T12 + 4] = (long)(ra);		\
 } while (0)
+#elif defined(__ia64__)
+#define	GET_BSP_JB(jb)		(*((unsigned long*)JMPBUF_ADDR_OF(jb,J_BSP)))
+#define	GET_STACK_JB(jb)	(*((unsigned long*)JMPBUF_ADDR_OF(jb,J_SP)))
+#define	GET_STACK_SJB(sjb)	GET_STACK_JB(sjb)
+#define	SET_RETURN_ADDR_JB(jb, ra)			\
+do {							\
+	*((unsigned long*)JMPBUF_ADDR_OF(jb,J_B0)) = ((long*)(ra))[0];	\
+	*((unsigned long*)JMPBUF_ADDR_OF(jb,J_PFS)) &= ~0x1FFFFFFFFFUL;	\
+} while (0)
+#define SET_STACK_JB(jb, stk, sz)			\
+do {							\
+	UPD_STACK_JB(jb, stk + sz - 16);		\
+	GET_BSP_JB(jb) = (long)(stk);			\
+} while (0)
+#define UPD_STACK_JB(jb, stk)	GET_STACK_JB(jb) = (long)(stk)
 #elif	defined(__sparc64__)
 #include <machine/frame.h>
 
@@ -432,7 +447,11 @@ struct pthread_attr {
 /*
  * Miscellaneous definitions.
  */
+#if !defined(__ia64__)
 #define PTHREAD_STACK_DEFAULT			65536
+#else
+#define PTHREAD_STACK_DEFAULT			0x40000
+#endif
 /*
  * Size of default red zone at the end of each stack.  In actuality, this "red
  * zone" is merely an unmapped region, except in the case of the initial stack.
@@ -450,7 +469,11 @@ extern int _pthread_page_size;
  * than the stacks of other threads, since many applications are likely to run
  * almost entirely on this stack.
  */
+#if !defined(__ia64__)
 #define PTHREAD_STACK_INITIAL			0x100000
+#else
+#define PTHREAD_STACK_INITIAL			0x400000
+#endif
 
 /*
  * Define the different priority ranges.  All applications have thread
diff --git a/lib/libc_r/uthread/uthread_create.c b/lib/libc_r/uthread/uthread_create.c
index d101721c9b78..2ea87b297cdd 100644
--- a/lib/libc_r/uthread/uthread_create.c
+++ b/lib/libc_r/uthread/uthread_create.c
@@ -144,10 +144,15 @@ _pthread_create(pthread_t *thread, const pthread_attr_t *attr,
 			 */
 			SET_RETURN_ADDR_JB(new_thread->ctx.jb, _thread_start);
 
+#if !defined(__ia64__)
 			/* The stack starts high and builds down: */
 			SET_STACK_JB(new_thread->ctx.jb,
 			    (long)new_thread->stack + pattr->stacksize_attr
 			    - sizeof(double));
+#else
+			SET_STACK_JB(new_thread->ctx.jb,
+			    (long)new_thread->stack, pattr->stacksize_attr);
+#endif
 
 			/* Copy the thread attributes: */
 			memcpy(&new_thread->attr, pattr, sizeof(struct pthread_attr));
diff --git a/lib/libc_r/uthread/uthread_init.c b/lib/libc_r/uthread/uthread_init.c
index d1d116e25ede..41737b198b77 100644
--- a/lib/libc_r/uthread/uthread_init.c
+++ b/lib/libc_r/uthread/uthread_init.c
@@ -373,8 +373,13 @@ _thread_init(void)
 
 		/* Setup the context for the scheduler: */
 		_setjmp(_thread_kern_sched_jb);
+#if !defined(__ia64__)
 		SET_STACK_JB(_thread_kern_sched_jb, _thread_kern_sched_stack +
 		    sched_stack_size - sizeof(double));
+#else
+		SET_STACK_JB(_thread_kern_sched_jb, _thread_kern_sched_stack,
+		    sched_stack_size);
+#endif
 		SET_RETURN_ADDR_JB(_thread_kern_sched_jb, _thread_kern_scheduler);
 
 		/*
diff --git a/lib/libc_r/uthread/uthread_sig.c b/lib/libc_r/uthread/uthread_sig.c
index 5e3c9b955f40..b99c64d440ff 100644
--- a/lib/libc_r/uthread/uthread_sig.c
+++ b/lib/libc_r/uthread/uthread_sig.c
@@ -1043,15 +1043,20 @@ thread_sigframe_add(struct pthread *thread, int sig, int has_args)
  	/* Get the top of the threads stack: */
 	stackp = GET_STACK_JB(thread->ctx.jb);
 
+#if !defined(__ia64__)
 	/*
 	 * Leave a little space on the stack and round down to the
 	 * nearest aligned word:
 	 */
 	stackp -= sizeof(double);
 	stackp &= ~0x3UL;
+#endif
 
 	/* Allocate room on top of the stack for a new signal frame: */
 	stackp -= sizeof(struct pthread_signal_frame);
+#if defined(__ia64__)
+	stackp &= ~0xFUL;
+#endif
 
 	psf = (struct pthread_signal_frame *) stackp;
 
@@ -1080,9 +1085,15 @@ thread_sigframe_add(struct pthread *thread, int sig, int has_args)
 	/*
 	 * Set up the context:
 	 */
+#if !defined(__ia64__)
 	stackp -= sizeof(double);
+#endif
 	_setjmp(thread->ctx.jb);
+#if !defined(__ia64__)
 	SET_STACK_JB(thread->ctx.jb, stackp);
+#else
+	UPD_STACK_JB(thread->ctx.jb, stackp - 16);
+#endif
 	SET_RETURN_ADDR_JB(thread->ctx.jb, _thread_sig_wrapper);
 }