ARCv2: Adhere to Zero Delay loop restriction

Branch insn can't be scheduled as last insn of Zero Overhead loop

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

3 files changed, 41 insertions, 15 deletions

diff --git a/arch/arc/include/asm/delay.h b/arch/arc/include/asm/delay.h
index 43de30256981..08e7e2a16ac1 100644
--- a/arch/arc/include/asm/delay.h
+++ b/arch/arc/include/asm/delay.h
@@ -22,11 +22,10 @@
 static inline void __delay(unsigned long loops)
 {
         __asm__ __volatile__(
-        "1:     sub.f %0, %0, 1 \n"
-        "       jpnz 1b         \n"
-        : "+r"(loops)
-        :
-        : "cc");
+        "       lp  1f  \n"
+        "       nop     \n"
+        "1:             \n"
+        : "+l"(loops));
 }
 
 extern void __bad_udelay(void);
diff --git a/arch/arc/include/asm/uaccess.h b/arch/arc/include/asm/uaccess.h
index 30c9baffa96f..d1da6032b715 100644
--- a/arch/arc/include/asm/uaccess.h
+++ b/arch/arc/include/asm/uaccess.h
@@ -659,31 +659,30 @@ static inline unsigned long __arc_clear_user(void __user *to, unsigned long n)
 static inline long
 __arc_strncpy_from_user(char *dst, const char __user *src, long count)
 {
-        long res = count;
+        long res = 0;
         char val;
-        unsigned int hw_count;
 
         if (count == 0)
                 return 0;
 
         __asm__ __volatile__(
-        "       lp 2f           \n"
+        "       lp      3f                      \n"
         "1:     ldb.ab  %3, [%2, 1]             \n"
-        "       breq.d  %3, 0, 2f               \n"
+        "       breq.d  %3, 0, 3f               \n"
         "       stb.ab  %3, [%1, 1]             \n"
-        "2:     sub %0, %6, %4                  \n"
-        "3:     ;nop                            \n"
+        "       add     %0, %0, 1       # Num of NON NULL bytes copied  \n"
+        "3:                                                             \n"
         "       .section .fixup, \"ax\"         \n"
         "       .align 4                        \n"
-        "4:     mov %0, %5                      \n"
+        "4:     mov %0, %4              # sets @res as -EFAULT  \n"
         "       j   3b                          \n"
         "       .previous                       \n"
         "       .section __ex_table, \"a\"      \n"
         "       .align 4                        \n"
         "       .word   1b, 4b                  \n"
         "       .previous                       \n"
-        : "=r"(res), "+r"(dst), "+r"(src), "=&r"(val), "=l"(hw_count)
-        : "g"(-EFAULT), "ir"(count), "4"(count) /* this "4" seeds lp_count */
+        : "+r"(res), "+r"(dst), "+r"(src), "=r"(val)
+        : "g"(-EFAULT), "l"(count)
         : "memory");
 
         return res;
diff --git a/arch/arc/lib/memcmp.S b/arch/arc/lib/memcmp.S
index 978bf8314dfb..a4015e7d9ab7 100644
--- a/arch/arc/lib/memcmp.S
+++ b/arch/arc/lib/memcmp.S
@@ -24,14 +24,32 @@ ENTRY(memcmp)
         ld      r4,[r0,0]
         ld      r5,[r1,0]
         lsr.f   lp_count,r3,3
+#ifdef CONFIG_ISA_ARCV2
+        /* In ARCv2 a branch can't be the last instruction in a zero overhead
+         * loop.
+         * So we move the branch to the start of the loop, duplicate it
+         * after the end, and set up r12 so that the branch isn't taken
+         *  initially.
+         */
+        mov_s   r12,WORD2
+        lpne    .Loop_end
+        brne    WORD2,r12,.Lodd
+        ld      WORD2,[r0,4]
+#else
         lpne    .Loop_end
         ld_s    WORD2,[r0,4]
+#endif
         ld_s    r12,[r1,4]
         brne    r4,r5,.Leven
         ld.a    r4,[r0,8]
         ld.a    r5,[r1,8]
+#ifdef CONFIG_ISA_ARCV2
+.Loop_end:
+        brne    WORD2,r12,.Lodd
+#else
         brne    WORD2,r12,.Lodd
 .Loop_end:
+#endif
         asl_s   SHIFT,SHIFT,3
         bhs_s   .Last_cmp
         brne    r4,r5,.Leven
@@ -89,7 +107,6 @@ ENTRY(memcmp)
         bset.cs r0,r0,31
 .Lodd:
         cmp_s   WORD2,r12
-
         mov_s   r0,1
         j_s.d   [blink]
         bset.cs r0,r0,31
@@ -100,14 +117,25 @@ ENTRY(memcmp)
         ldb     r4,[r0,0]
         ldb     r5,[r1,0]
         lsr.f   lp_count,r3
+#ifdef CONFIG_ISA_ARCV2
+        mov     r12,r3
         lpne    .Lbyte_end
+        brne    r3,r12,.Lbyte_odd
+#else
+        lpne    .Lbyte_end
+#endif
         ldb_s   r3,[r0,1]
         ldb     r12,[r1,1]
         brne    r4,r5,.Lbyte_even
         ldb.a   r4,[r0,2]
         ldb.a   r5,[r1,2]
+#ifdef CONFIG_ISA_ARCV2
+.Lbyte_end:
+        brne    r3,r12,.Lbyte_odd
+#else
         brne    r3,r12,.Lbyte_odd
 .Lbyte_end:
+#endif
         bcc     .Lbyte_even
         brne    r4,r5,.Lbyte_even
         ldb_s   r3,[r0,1]