ARM: improve compiler's ability to optimize page tables

Allow the compiler to better optimize the page table walking code
by avoiding over-complex pmd_addr_end() calculations.  These
calculations prevent the compiler spotting that we'll never iterate
over the PMD table, causing it to create double nested loops where
a single loop will do.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h
index b155414..53d1d5d 100644 (file)
--- a/arch/arm/include/asm/pgtable.h
+++ b/arch/arm/include/asm/pgtable.h
@@ -374,6 +374,9 @@ static inline pte_t *pmd_page_vaddr(pmd_t pmd)
 
 #define pmd_page(pmd)          pfn_to_page(__phys_to_pfn(pmd_val(pmd)))
 
+/* we don't need complex calculations here as the pmd is folded into the pgd */
+#define pmd_addr_end(addr,end) (end)
+
 /*
  * Conversion functions: convert a page and protection to a page entry,
  * and a page entry and page directory to the page they refer to.