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[RFC] [AARCH64] Add support for new control bits CTR_EL0.DIC and CTR_EL0.IDC


The DCache clean & ICache invalidation requirements for instructions
to be data coherence are discoverable through new fields in CTR_EL0.
Let's support the two bits if they are enabled, then we can get some
performance benefit from this feature.

2019-08-22  Shaokun Zhang  <zhangshaokun@hisilicon.com>

    * config/aarch64/sync-cache.c: Support CTR_EL0.IDC and CTR_EL0.DIC

---
 libgcc/config/aarch64/sync-cache.c | 56 ++++++++++++++++++++++++--------------
 1 file changed, 35 insertions(+), 21 deletions(-)

diff --git a/libgcc/config/aarch64/sync-cache.c b/libgcc/config/aarch64/sync-cache.c
index 791f5e42ff44..0b057efbdcab 100644
--- a/libgcc/config/aarch64/sync-cache.c
+++ b/libgcc/config/aarch64/sync-cache.c
@@ -23,6 +23,9 @@ a copy of the GCC Runtime Library Exception along with this program;
 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 <http://www.gnu.org/licenses/>.  */
 
+#define CTR_IDC_SHIFT           28
+#define CTR_DIC_SHIFT           29
+
 void __aarch64_sync_cache_range (const void *, const void *);
 
 void
@@ -41,32 +44,43 @@ __aarch64_sync_cache_range (const void *base, const void *end)
   icache_lsize = 4 << (cache_info & 0xF);
   dcache_lsize = 4 << ((cache_info >> 16) & 0xF);
 
-  /* Loop over the address range, clearing one cache line at once.
-     Data cache must be flushed to unification first to make sure the
-     instruction cache fetches the updated data.  'end' is exclusive,
-     as per the GNU definition of __clear_cache.  */
+  /* If CTR_EL0.IDC is enabled, Data cache clean to the Point of Unification is
+     not required for instruction to data coherence.  */
+
+  if ((cache_info >> CTR_IDC_SHIFT) & 0x1 == 0x0) {
+    /* Loop over the address range, clearing one cache line at once.
+       Data cache must be flushed to unification first to make sure the
+       instruction cache fetches the updated data.  'end' is exclusive,
+       as per the GNU definition of __clear_cache.  */
 
-  /* Make the start address of the loop cache aligned.  */
-  address = (const char*) ((__UINTPTR_TYPE__) base
-			   & ~ (__UINTPTR_TYPE__) (dcache_lsize - 1));
+    /* Make the start address of the loop cache aligned.  */
+    address = (const char*) ((__UINTPTR_TYPE__) base
+			     & ~ (__UINTPTR_TYPE__) (dcache_lsize - 1));
 
-  for (; address < (const char *) end; address += dcache_lsize)
-    asm volatile ("dc\tcvau, %0"
-		  :
-		  : "r" (address)
-		  : "memory");
+    for (; address < (const char *) end; address += dcache_lsize)
+      asm volatile ("dc\tcvau, %0"
+		    :
+		    : "r" (address)
+		    : "memory");
+  }
 
   asm volatile ("dsb\tish" : : : "memory");
 
-  /* Make the start address of the loop cache aligned.  */
-  address = (const char*) ((__UINTPTR_TYPE__) base
-			   & ~ (__UINTPTR_TYPE__) (icache_lsize - 1));
+  /* If CTR_EL0.DIC is enabled, Instruction cache cleaning to the Point of
+     Unification is not required for instruction to data coherence.  */
+
+  if ((cache_info >> CTR_DIC_SHIFT) & 0x1 == 0x0) {
+    /* Make the start address of the loop cache aligned.  */
+    address = (const char*) ((__UINTPTR_TYPE__) base
+			     & ~ (__UINTPTR_TYPE__) (icache_lsize - 1));
 
-  for (; address < (const char *) end; address += icache_lsize)
-    asm volatile ("ic\tivau, %0"
-		  :
-		  : "r" (address)
-		  : "memory");
+    for (; address < (const char *) end; address += icache_lsize)
+      asm volatile ("ic\tivau, %0"
+		    :
+		    : "r" (address)
+		    : "memory");
 
-  asm volatile ("dsb\tish; isb" : : : "memory");
+    asm volatile ("dsb\tish" : : : "memory");
+  }
+  asm volatile("isb" : : : "memory")
 }
-- 
2.7.4


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