diff --git a/include/tcg/tcg-opc.h b/include/tcg/tcg-opc.h
index 5bbec858aa..993992373e 100644
--- a/include/tcg/tcg-opc.h
+++ b/include/tcg/tcg-opc.h
@@ -96,8 +96,8 @@ DEF(ext8s_i32, 1, 1, 0, IMPL(TCG_TARGET_HAS_ext8s_i32))
 DEF(ext16s_i32, 1, 1, 0, IMPL(TCG_TARGET_HAS_ext16s_i32))
 DEF(ext8u_i32, 1, 1, 0, IMPL(TCG_TARGET_HAS_ext8u_i32))
 DEF(ext16u_i32, 1, 1, 0, IMPL(TCG_TARGET_HAS_ext16u_i32))
-DEF(bswap16_i32, 1, 1, 0, IMPL(TCG_TARGET_HAS_bswap16_i32))
-DEF(bswap32_i32, 1, 1, 0, IMPL(TCG_TARGET_HAS_bswap32_i32))
+DEF(bswap16_i32, 1, 1, 1, IMPL(TCG_TARGET_HAS_bswap16_i32))
+DEF(bswap32_i32, 1, 1, 1, IMPL(TCG_TARGET_HAS_bswap32_i32))
 DEF(not_i32, 1, 1, 0, IMPL(TCG_TARGET_HAS_not_i32))
 DEF(neg_i32, 1, 1, 0, IMPL(TCG_TARGET_HAS_neg_i32))
 DEF(andc_i32, 1, 2, 0, IMPL(TCG_TARGET_HAS_andc_i32))
@@ -165,9 +165,9 @@ DEF(ext32s_i64, 1, 1, 0, IMPL64 | IMPL(TCG_TARGET_HAS_ext32s_i64))
 DEF(ext8u_i64, 1, 1, 0, IMPL64 | IMPL(TCG_TARGET_HAS_ext8u_i64))
 DEF(ext16u_i64, 1, 1, 0, IMPL64 | IMPL(TCG_TARGET_HAS_ext16u_i64))
 DEF(ext32u_i64, 1, 1, 0, IMPL64 | IMPL(TCG_TARGET_HAS_ext32u_i64))
-DEF(bswap16_i64, 1, 1, 0, IMPL64 | IMPL(TCG_TARGET_HAS_bswap16_i64))
-DEF(bswap32_i64, 1, 1, 0, IMPL64 | IMPL(TCG_TARGET_HAS_bswap32_i64))
-DEF(bswap64_i64, 1, 1, 0, IMPL64 | IMPL(TCG_TARGET_HAS_bswap64_i64))
+DEF(bswap16_i64, 1, 1, 1, IMPL64 | IMPL(TCG_TARGET_HAS_bswap16_i64))
+DEF(bswap32_i64, 1, 1, 1, IMPL64 | IMPL(TCG_TARGET_HAS_bswap32_i64))
+DEF(bswap64_i64, 1, 1, 1, IMPL64 | IMPL(TCG_TARGET_HAS_bswap64_i64))
 DEF(not_i64, 1, 1, 0, IMPL64 | IMPL(TCG_TARGET_HAS_not_i64))
 DEF(neg_i64, 1, 1, 0, IMPL64 | IMPL(TCG_TARGET_HAS_neg_i64))
 DEF(andc_i64, 1, 2, 0, IMPL64 | IMPL(TCG_TARGET_HAS_andc_i64))
diff --git a/include/tcg/tcg.h b/include/tcg/tcg.h
index 2dad364240..899493701c 100644
--- a/include/tcg/tcg.h
+++ b/include/tcg/tcg.h
@@ -408,6 +408,18 @@ typedef TCGv_ptr TCGv_env;
 /* Used to align parameters.  See the comment before tcgv_i32_temp.  */
 #define TCG_CALL_DUMMY_ARG      ((TCGArg)0)
 
+/*
+ * Flags for the bswap opcodes.
+ * If IZ, the input is zero-extended, otherwise unknown.
+ * If OZ or OS, the output is zero- or sign-extended respectively,
+ * otherwise the high bits are undefined.
+ */
+enum {
+    TCG_BSWAP_IZ = 1,
+    TCG_BSWAP_OZ = 2,
+    TCG_BSWAP_OS = 4,
+};
+
 typedef enum TCGTempVal {
     TEMP_VAL_DEAD,
     TEMP_VAL_REG,
diff --git a/tcg/README b/tcg/README
index 8510d823e3..c2e7762a37 100644
--- a/tcg/README
+++ b/tcg/README
@@ -295,19 +295,25 @@ ext32u_i64 t0, t1
 
 8, 16 or 32 bit sign/zero extension (both operands must have the same type)
 
-* bswap16_i32/i64 t0, t1
+* bswap16_i32/i64 t0, t1, flags
 
-16 bit byte swap on a 32/64 bit value. It assumes that the two/six high order
-bytes are set to zero.
+16 bit byte swap on the low bits of a 32/64 bit input.
+If flags & TCG_BSWAP_IZ, then t1 is known to be zero-extended from bit 15.
+If flags & TCG_BSWAP_OZ, then t0 will be zero-extended from bit 15.
+If flags & TCG_BSWAP_OS, then t0 will be sign-extended from bit 15.
+If neither TCG_BSWAP_OZ nor TCG_BSWAP_OS are set, then the bits of
+t0 above bit 15 may contain any value.
 
-* bswap32_i32/i64 t0, t1
+* bswap32_i64 t0, t1, flags
 
-32 bit byte swap on a 32/64 bit value. With a 64 bit value, it assumes that
-the four high order bytes are set to zero.
+32 bit byte swap on a 64-bit value.  The flags are the same as for bswap16,
+except they apply from bit 31 instead of bit 15.
 
-* bswap64_i64 t0, t1
+* bswap32_i32 t0, t1, flags
+* bswap64_i64 t0, t1, flags
 
-64 bit byte swap
+32/64 bit byte swap.  The flags are ignored, but still present
+for consistency with the other bswap opcodes.
 
 * discard_i32/i64 t0
 
diff --git a/tcg/tcg-op.c b/tcg/tcg-op.c
index dcc2ed0bbc..dc65577e2f 100644
--- a/tcg/tcg-op.c
+++ b/tcg/tcg-op.c
@@ -1005,7 +1005,8 @@ void tcg_gen_ext16u_i32(TCGv_i32 ret, TCGv_i32 arg)
 void tcg_gen_bswap16_i32(TCGv_i32 ret, TCGv_i32 arg)
 {
     if (TCG_TARGET_HAS_bswap16_i32) {
-        tcg_gen_op2_i32(INDEX_op_bswap16_i32, ret, arg);
+        tcg_gen_op3i_i32(INDEX_op_bswap16_i32, ret, arg,
+                         TCG_BSWAP_IZ | TCG_BSWAP_OZ);
     } else {
         TCGv_i32 t0 = tcg_temp_new_i32();
 
@@ -1020,7 +1021,7 @@ void tcg_gen_bswap16_i32(TCGv_i32 ret, TCGv_i32 arg)
 void tcg_gen_bswap32_i32(TCGv_i32 ret, TCGv_i32 arg)
 {
     if (TCG_TARGET_HAS_bswap32_i32) {
-        tcg_gen_op2_i32(INDEX_op_bswap32_i32, ret, arg);
+        tcg_gen_op3i_i32(INDEX_op_bswap32_i32, ret, arg, 0);
     } else {
         TCGv_i32 t0 = tcg_temp_new_i32();
         TCGv_i32 t1 = tcg_temp_new_i32();
@@ -1661,7 +1662,8 @@ void tcg_gen_bswap16_i64(TCGv_i64 ret, TCGv_i64 arg)
         tcg_gen_bswap16_i32(TCGV_LOW(ret), TCGV_LOW(arg));
         tcg_gen_movi_i32(TCGV_HIGH(ret), 0);
     } else if (TCG_TARGET_HAS_bswap16_i64) {
-        tcg_gen_op2_i64(INDEX_op_bswap16_i64, ret, arg);
+        tcg_gen_op3i_i64(INDEX_op_bswap16_i64, ret, arg,
+                         TCG_BSWAP_IZ | TCG_BSWAP_OZ);
     } else {
         TCGv_i64 t0 = tcg_temp_new_i64();
 
@@ -1680,7 +1682,8 @@ void tcg_gen_bswap32_i64(TCGv_i64 ret, TCGv_i64 arg)
         tcg_gen_bswap32_i32(TCGV_LOW(ret), TCGV_LOW(arg));
         tcg_gen_movi_i32(TCGV_HIGH(ret), 0);
     } else if (TCG_TARGET_HAS_bswap32_i64) {
-        tcg_gen_op2_i64(INDEX_op_bswap32_i64, ret, arg);
+        tcg_gen_op3i_i64(INDEX_op_bswap32_i64, ret, arg,
+                         TCG_BSWAP_IZ | TCG_BSWAP_OZ);
     } else {
         TCGv_i64 t0 = tcg_temp_new_i64();
         TCGv_i64 t1 = tcg_temp_new_i64();
@@ -1717,7 +1720,7 @@ void tcg_gen_bswap64_i64(TCGv_i64 ret, TCGv_i64 arg)
         tcg_temp_free_i32(t0);
         tcg_temp_free_i32(t1);
     } else if (TCG_TARGET_HAS_bswap64_i64) {
-        tcg_gen_op2_i64(INDEX_op_bswap64_i64, ret, arg);
+        tcg_gen_op3i_i64(INDEX_op_bswap64_i64, ret, arg, 0);
     } else {
         TCGv_i64 t0 = tcg_temp_new_i64();
         TCGv_i64 t1 = tcg_temp_new_i64();
diff --git a/tcg/tcg.c b/tcg/tcg.c
index 5e53c3348f..5150ed700e 100644
--- a/tcg/tcg.c
+++ b/tcg/tcg.c
@@ -1778,6 +1778,14 @@ static const char * const alignment_name[(MO_AMASK >> MO_ASHIFT) + 1] = {
     [MO_ALIGN_64 >> MO_ASHIFT] = "al64+",
 };
 
+static const char bswap_flag_name[][6] = {
+    [TCG_BSWAP_IZ] = "iz",
+    [TCG_BSWAP_OZ] = "oz",
+    [TCG_BSWAP_OS] = "os",
+    [TCG_BSWAP_IZ | TCG_BSWAP_OZ] = "iz,oz",
+    [TCG_BSWAP_IZ | TCG_BSWAP_OS] = "iz,os",
+};
+
 static inline bool tcg_regset_single(TCGRegSet d)
 {
     return (d & (d - 1)) == 0;
@@ -1921,6 +1929,26 @@ static void tcg_dump_ops(TCGContext *s, bool have_prefs)
                     i = 1;
                 }
                 break;
+            case INDEX_op_bswap16_i32:
+            case INDEX_op_bswap16_i64:
+            case INDEX_op_bswap32_i32:
+            case INDEX_op_bswap32_i64:
+            case INDEX_op_bswap64_i64:
+                {
+                    TCGArg flags = op->args[k];
+                    const char *name = NULL;
+
+                    if (flags < ARRAY_SIZE(bswap_flag_name)) {
+                        name = bswap_flag_name[flags];
+                    }
+                    if (name) {
+                        col += qemu_log(",%s", name);
+                    } else {
+                        col += qemu_log(",$0x%" TCG_PRIlx, flags);
+                    }
+                    i = k = 1;
+                }
+                break;
             default:
                 i = 0;
                 break;