[Qemu-riscv] [Qemu-devel] [PATCH v5 11/15] memory: Single byte swap along the I/O path

[<tony.nguyen@bt.com>]

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Now that MemOp has been pushed down into the memory API, we can
collapse the two byte swaps adjust_endianness and handle_bswap into
the former.

Collapsing byte swaps along the I/O path enables additional endian
inversion logic, e.g. SPARC64 Invert Endian TTE bit, with redundant
byte swaps cancelling out.

Signed-off-by: Tony Nguyen <tony.nguyen@bt.com>
---
 accel/tcg/cputlb.c | 41 +++++++++++++++++++----------------------
 memory.c           | 30 +++++++++++++++++-------------
 2 files changed, 36 insertions(+), 35 deletions(-)

diff --git a/accel/tcg/cputlb.c b/accel/tcg/cputlb.c
index 5d88cec..e61b1eb 100644
--- a/accel/tcg/cputlb.c
+++ b/accel/tcg/cputlb.c
@@ -1209,26 +1209,13 @@ static void *atomic_mmu_lookup(CPUArchState *env, target_ulong addr,
 #endif

 /*
- * Byte Swap Helper
+ * Byte Swap Checker
  *
- * This should all dead code away depending on the build host and
- * access type.
+ * Dead code should all go away depending on the build host and access type.
  */
-
-static inline uint64_t handle_bswap(uint64_t val, int size, bool big_endian)
+static inline bool need_bswap(bool big_endian)
 {
-    if ((big_endian && NEED_BE_BSWAP) || (!big_endian && NEED_LE_BSWAP)) {
-        switch (size) {
-        case 1: return val;
-        case 2: return bswap16(val);
-        case 4: return bswap32(val);
-        case 8: return bswap64(val);
-        default:
-            g_assert_not_reached();
-        }
-    } else {
-        return val;
-    }
+    return (big_endian && NEED_BE_BSWAP) || (!big_endian && NEED_LE_BSWAP);
 }

 /*
@@ -1259,6 +1246,7 @@ load_helper(CPUArchState *env, target_ulong addr, TCGMemOpIdx oi,
     unsigned a_bits = get_alignment_bits(get_memop(oi));
     void *haddr;
     uint64_t res;
+    MemOp op;

     /* Handle CPU specific unaligned behaviour */
     if (addr & ((1 << a_bits) - 1)) {
@@ -1304,9 +1292,13 @@ load_helper(CPUArchState *env, target_ulong addr, TCGMemOpIdx oi,
             }
         }

-        res = io_readx(env, &env_tlb(env)->d[mmu_idx].iotlb[index],
-                       mmu_idx, addr, retaddr, access_type, SIZE_MEMOP(size));
-        return handle_bswap(res, size, big_endian);
+        op = SIZE_MEMOP(size);
+        if (need_bswap(big_endian)) {
+            op ^= MO_BSWAP;
+        }
+
+        return io_readx(env, &env_tlb(env)->d[mmu_idx].iotlb[index],
+                       mmu_idx, addr, retaddr, access_type, op);
     }

     /* Handle slow unaligned access (it spans two pages or IO).  */
@@ -1507,6 +1499,7 @@ store_helper(CPUArchState *env, target_ulong addr, uint64_t val,
     const size_t tlb_off = offsetof(CPUTLBEntry, addr_write);
     unsigned a_bits = get_alignment_bits(get_memop(oi));
     void *haddr;
+    MemOp op;

     /* Handle CPU specific unaligned behaviour */
     if (addr & ((1 << a_bits) - 1)) {
@@ -1552,9 +1545,13 @@ store_helper(CPUArchState *env, target_ulong addr, uint64_t val,
             }
         }

+        op = SIZE_MEMOP(size);
+        if (need_bswap(big_endian)) {
+            op ^= MO_BSWAP;
+        }
+
         io_writex(env, &env_tlb(env)->d[mmu_idx].iotlb[index], mmu_idx,
-                  handle_bswap(val, size, big_endian),
-                  addr, retaddr, SIZE_MEMOP(size));
+                  val, addr, retaddr, op);
         return;
     }

diff --git a/memory.c b/memory.c
index 6982e19..0277d3d 100644
--- a/memory.c
+++ b/memory.c
@@ -352,7 +352,7 @@ static bool memory_region_big_endian(MemoryRegion *mr)
 #endif
 }

-static bool memory_region_wrong_endianness(MemoryRegion *mr)
+static bool memory_region_endianness_inverted(MemoryRegion *mr)
 {
 #ifdef TARGET_WORDS_BIGENDIAN
     return mr->ops->endianness == DEVICE_LITTLE_ENDIAN;
@@ -361,23 +361,27 @@ static bool memory_region_wrong_endianness(MemoryRegion *mr)
 #endif
 }

-static void adjust_endianness(MemoryRegion *mr, uint64_t *data, unsigned size)
+static void adjust_endianness(MemoryRegion *mr, uint64_t *data, MemOp op)
 {
-    if (memory_region_wrong_endianness(mr)) {
-        switch (size) {
-        case 1:
+    if (memory_region_endianness_inverted(mr)) {
+        op ^= MO_BSWAP;
+    }
+
+    if (op & MO_BSWAP) {
+        switch (op & MO_SIZE) {
+        case MO_8:
             break;
-        case 2:
+        case MO_16:
             *data = bswap16(*data);
             break;
-        case 4:
+        case MO_32:
             *data = bswap32(*data);
             break;
-        case 8:
+        case MO_64:
             *data = bswap64(*data);
             break;
         default:
-            abort();
+            g_assert_not_reached();
         }
     }
 }
@@ -1451,7 +1455,7 @@ MemTxResult memory_region_dispatch_read(MemoryRegion *mr,
     }

     r = memory_region_dispatch_read1(mr, addr, pval, size, attrs);
-    adjust_endianness(mr, pval, size);
+    adjust_endianness(mr, pval, op);
     return r;
 }

@@ -1494,7 +1498,7 @@ MemTxResult memory_region_dispatch_write(MemoryRegion *mr,
         return MEMTX_DECODE_ERROR;
     }

-    adjust_endianness(mr, &data, size);
+    adjust_endianness(mr, &data, op);

     if ((!kvm_eventfds_enabled()) &&
         memory_region_dispatch_write_eventfds(mr, addr, data, size, attrs)) {
@@ -2340,7 +2344,7 @@ void memory_region_add_eventfd(MemoryRegion *mr,
     }

     if (size) {
-        adjust_endianness(mr, &mrfd.data, size);
+        adjust_endianness(mr, &mrfd.data, SIZE_MEMOP(size));
     }
     memory_region_transaction_begin();
     for (i = 0; i < mr->ioeventfd_nb; ++i) {
@@ -2375,7 +2379,7 @@ void memory_region_del_eventfd(MemoryRegion *mr,
     unsigned i;

     if (size) {
-        adjust_endianness(mr, &mrfd.data, size);
+        adjust_endianness(mr, &mrfd.data, SIZE_MEMOP(size));
     }
     memory_region_transaction_begin();
     for (i = 0; i < mr->ioeventfd_nb; ++i) {
--
1.8.3.1




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