MIPS: tlbex: Avoid unnecessary _PAGE_PRESENT shifts

Commit c5b367835cfc ("MIPS: Add support for XPA.") added generation of a
shift by _PAGE_PRESENT_SHIFT in build_pte_present() and
build_pte_writable(), however except for the XPA case this is always
zero making it unnecessary.

Make the shift conditional upon _PAGE_PRESENT_SHIFT being non-zero to
save an instruction in those cases.

Fixes: c5b367835cfc ("MIPS: Add support for XPA.")
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9889/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
index 5029287..323d1d3 100644 (file)
--- a/arch/mips/mm/tlbex.c
+++ b/arch/mips/mm/tlbex.c
@@ -1608,22 +1608,29 @@ build_pte_present(u32 **p, struct uasm_reloc **r,
                  int pte, int ptr, int scratch, enum label_id lid)
 {
        int t = scratch >= 0 ? scratch : pte;
+       int cur = pte;
 
        if (cpu_has_rixi) {
                if (use_bbit_insns()) {
                        uasm_il_bbit0(p, r, pte, ilog2(_PAGE_PRESENT), lid);
                        uasm_i_nop(p);
                } else {
-                       uasm_i_srl(p, t, pte, _PAGE_PRESENT_SHIFT);
-                       uasm_i_andi(p, t, t, 1);
+                       if (_PAGE_PRESENT_SHIFT) {
+                               uasm_i_srl(p, t, cur, _PAGE_PRESENT_SHIFT);
+                               cur = t;
+                       }
+                       uasm_i_andi(p, t, cur, 1);
                        uasm_il_beqz(p, r, t, lid);
                        if (pte == t)
                                /* You lose the SMP race :-(*/
                                iPTE_LW(p, pte, ptr);
                }
        } else {
-               uasm_i_srl(p, t, pte, _PAGE_PRESENT_SHIFT);
-               uasm_i_andi(p, t, t,
+               if (_PAGE_PRESENT_SHIFT) {
+                       uasm_i_srl(p, t, cur, _PAGE_PRESENT_SHIFT);
+                       cur = t;
+               }
+               uasm_i_andi(p, t, cur,
                        (_PAGE_PRESENT | _PAGE_READ) >> _PAGE_PRESENT_SHIFT);
                uasm_i_xori(p, t, t,
                        (_PAGE_PRESENT | _PAGE_READ) >> _PAGE_PRESENT_SHIFT);
@@ -1654,9 +1661,13 @@ build_pte_writable(u32 **p, struct uasm_reloc **r,
                   enum label_id lid)
 {
        int t = scratch >= 0 ? scratch : pte;
+       int cur = pte;
 
-       uasm_i_srl(p, t, pte, _PAGE_PRESENT_SHIFT);
-       uasm_i_andi(p, t, t,
+       if (_PAGE_PRESENT_SHIFT) {
+               uasm_i_srl(p, t, cur, _PAGE_PRESENT_SHIFT);
+               cur = t;
+       }
+       uasm_i_andi(p, t, cur,
                    (_PAGE_PRESENT | _PAGE_WRITE) >> _PAGE_PRESENT_SHIFT);
        uasm_i_xori(p, t, t,
                    (_PAGE_PRESENT | _PAGE_WRITE) >> _PAGE_PRESENT_SHIFT);