[Qemu-devel] [PATCH] tcg-i386: Introduce specific deposit helpers

[Jan Kiszka <jan.kiszka@siemens.com>]

x86 cannot provide an optimized generic deposit implementation. But at
least for a few special cases, namely for writing bits 0..7, 8..15, and
0..15, a version using only a single instruction is feasible.
Introducing such helpers improves emulating 16-bit x86 code on x86, but
also rarer cases where 32-bit or 64-bit code accesses bytes or words.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 tcg/i386/tcg-target.c |   25 +++++++++++++++++++++++++
 tcg/i386/tcg-target.h |    6 ++++++
 tcg/tcg-op.h          |   12 ++++++++++++
 tcg/tcg-opc.h         |    6 ++++++
 tcg/tcg.h             |    3 +++
 5 files changed, 52 insertions(+), 0 deletions(-)

diff --git a/tcg/i386/tcg-target.c b/tcg/i386/tcg-target.c
index 281f87d..3f9d0ad 100644
--- a/tcg/i386/tcg-target.c
+++ b/tcg/i386/tcg-target.c
@@ -1747,6 +1747,19 @@ static inline void tcg_out_op(TCGContext *s, TCGOpcode opc,
         break;
 #endif
 
+    OP_32_64(deposit8l):
+        tcg_out_modrm(s, OPC_MOVB_EvGv | P_REXB_R | P_REXB_RM,
+                      args[2], args[0]);
+        break;
+
+    OP_32_64(deposit8h):
+        tcg_out_modrm(s, OPC_MOVB_EvGv, args[2], args[0] + 4);
+        break;
+
+    OP_32_64(deposit16l):
+        tcg_out_modrm(s, OPC_MOVL_EvGv | P_DATA16, args[2], args[0]);
+        break;
+
     default:
         tcg_abort();
     }
@@ -1802,6 +1815,14 @@ static const TCGTargetOpDef x86_op_defs[] = {
 
     { INDEX_op_setcond_i32, { "q", "r", "ri" } },
 
+#if TCG_TARGET_REG_BITS == 64
+    { INDEX_op_deposit8l_i32, { "r", "0", "r" } },
+#else
+    { INDEX_op_deposit8l_i32, { "abcd", "0", "abcd" } },
+#endif
+    { INDEX_op_deposit8h_i32, { "abcd", "0", "abcd" } },
+    { INDEX_op_deposit16l_i32, { "r", "0", "r" } },
+
 #if TCG_TARGET_REG_BITS == 32
     { INDEX_op_mulu2_i32, { "a", "d", "a", "r" } },
     { INDEX_op_add2_i32, { "r", "r", "0", "1", "ri", "ri" } },
@@ -1853,6 +1874,10 @@ static const TCGTargetOpDef x86_op_defs[] = {
     { INDEX_op_ext8u_i64, { "r", "r" } },
     { INDEX_op_ext16u_i64, { "r", "r" } },
     { INDEX_op_ext32u_i64, { "r", "r" } },
+
+    { INDEX_op_deposit8l_i64, { "r", "0", "r" } },
+    { INDEX_op_deposit8h_i64, { "abcd", "0", "abcd" } },
+    { INDEX_op_deposit16l_i64, { "r", "0", "r" } },
 #endif
 
 #if TCG_TARGET_REG_BITS == 64
diff --git a/tcg/i386/tcg-target.h b/tcg/i386/tcg-target.h
index 5088e47..54b2f60 100644
--- a/tcg/i386/tcg-target.h
+++ b/tcg/i386/tcg-target.h
@@ -91,6 +91,9 @@ enum {
 #define TCG_TARGET_HAS_nand_i32         0
 #define TCG_TARGET_HAS_nor_i32          0
 #define TCG_TARGET_HAS_deposit_i32      0
+#define TCG_TARGET_HAS_deposit8l_i32    1
+#define TCG_TARGET_HAS_deposit8h_i32    1
+#define TCG_TARGET_HAS_deposit16l_i32   1
 
 #if TCG_TARGET_REG_BITS == 64
 #define TCG_TARGET_HAS_div2_i64         1
@@ -112,6 +115,9 @@ enum {
 #define TCG_TARGET_HAS_nand_i64         0
 #define TCG_TARGET_HAS_nor_i64          0
 #define TCG_TARGET_HAS_deposit_i64      0
+#define TCG_TARGET_HAS_deposit8l_i64    1
+#define TCG_TARGET_HAS_deposit8h_i64    1
+#define TCG_TARGET_HAS_deposit16l_i64   1
 #endif
 
 #define TCG_TARGET_HAS_GUEST_BASE
diff --git a/tcg/tcg-op.h b/tcg/tcg-op.h
index 404b637..80ffccb 100644
--- a/tcg/tcg-op.h
+++ b/tcg/tcg-op.h
@@ -2047,6 +2047,12 @@ static inline void tcg_gen_deposit_i32(TCGv_i32 ret, TCGv_i32 arg1,
 {
     if (TCG_TARGET_HAS_deposit_i32) {
         tcg_gen_op5ii_i32(INDEX_op_deposit_i32, ret, arg1, arg2, ofs, len);
+    } else if (ofs == 0 && len == 8 && TCG_TARGET_HAS_deposit8l_i32) {
+        tcg_gen_op3_i32(INDEX_op_deposit8l_i32, ret, arg1, arg2);
+    } else if (ofs == 8 && len == 8 && TCG_TARGET_HAS_deposit8h_i32) {
+        tcg_gen_op3_i32(INDEX_op_deposit8h_i32, ret, arg1, arg2);
+    } else if (ofs == 0 && len == 16 && TCG_TARGET_HAS_deposit16l_i32) {
+        tcg_gen_op3_i32(INDEX_op_deposit16l_i32, ret, arg1, arg2);
     } else {
         uint32_t mask = (1u << len) - 1;
         TCGv_i32 t1 = tcg_temp_new_i32 ();
@@ -2066,6 +2072,12 @@ static inline void tcg_gen_deposit_i64(TCGv_i64 ret, TCGv_i64 arg1,
 {
     if (TCG_TARGET_HAS_deposit_i64) {
         tcg_gen_op5ii_i64(INDEX_op_deposit_i64, ret, arg1, arg2, ofs, len);
+    } else if (ofs == 0 && len == 8 && TCG_TARGET_HAS_deposit8l_i64) {
+        tcg_gen_op3_i32(INDEX_op_deposit8l_i64, ret, arg1, arg2);
+    } else if (ofs == 8 && len == 8 && TCG_TARGET_HAS_deposit8h_i64) {
+        tcg_gen_op3_i32(INDEX_op_deposit8h_i64, ret, arg1, arg2);
+    } else if (ofs == 0 && len == 16 && TCG_TARGET_HAS_deposit16l_i64) {
+        tcg_gen_op3_i32(INDEX_op_deposit16l_i64, ret, arg1, arg2);
     } else {
         uint64_t mask = (1ull << len) - 1;
         TCGv_i64 t1 = tcg_temp_new_i64 ();
diff --git a/tcg/tcg-opc.h b/tcg/tcg-opc.h
index 8e06d03..0871d15 100644
--- a/tcg/tcg-opc.h
+++ b/tcg/tcg-opc.h
@@ -80,6 +80,9 @@ DEF(sar_i32, 1, 2, 0, 0)
 DEF(rotl_i32, 1, 2, 0, IMPL(TCG_TARGET_HAS_rot_i32))
 DEF(rotr_i32, 1, 2, 0, IMPL(TCG_TARGET_HAS_rot_i32))
 DEF(deposit_i32, 1, 2, 2, IMPL(TCG_TARGET_HAS_deposit_i32))
+DEF(deposit8l_i32, 1, 2, 0, IMPL(TCG_TARGET_HAS_deposit8l_i32))
+DEF(deposit8h_i32, 1, 2, 0, IMPL(TCG_TARGET_HAS_deposit8h_i32))
+DEF(deposit16l_i32, 1, 2, 0, IMPL(TCG_TARGET_HAS_deposit16l_i32))
 
 DEF(brcond_i32, 0, 2, 2, TCG_OPF_BB_END | TCG_OPF_SIDE_EFFECTS)
 
@@ -139,6 +142,9 @@ DEF(sar_i64, 1, 2, 0, IMPL64)
 DEF(rotl_i64, 1, 2, 0, IMPL64 | IMPL(TCG_TARGET_HAS_rot_i64))
 DEF(rotr_i64, 1, 2, 0, IMPL64 | IMPL(TCG_TARGET_HAS_rot_i64))
 DEF(deposit_i64, 1, 2, 2, IMPL64 | IMPL(TCG_TARGET_HAS_deposit_i64))
+DEF(deposit8l_i64, 1, 2, 0, IMPL64 | IMPL(TCG_TARGET_HAS_deposit8l_i64))
+DEF(deposit8h_i64, 1, 2, 0, IMPL64 | IMPL(TCG_TARGET_HAS_deposit8h_i64))
+DEF(deposit16l_i64, 1, 2, 0, IMPL64 | IMPL(TCG_TARGET_HAS_deposit16l_i64))
 
 DEF(brcond_i64, 0, 2, 2, TCG_OPF_BB_END | TCG_OPF_SIDE_EFFECTS | IMPL64)
 DEF(ext8s_i64, 1, 1, 0, IMPL64 | IMPL(TCG_TARGET_HAS_ext8s_i64))
diff --git a/tcg/tcg.h b/tcg/tcg.h
index dc5e9c9..9a95d2b 100644
--- a/tcg/tcg.h
+++ b/tcg/tcg.h
@@ -69,6 +69,9 @@ typedef uint64_t TCGRegSet;
 #define TCG_TARGET_HAS_nand_i64         0
 #define TCG_TARGET_HAS_nor_i64          0
 #define TCG_TARGET_HAS_deposit_i64      0
+#define TCG_TARGET_HAS_deposit8l_i64    0
+#define TCG_TARGET_HAS_deposit8h_i64    0
+#define TCG_TARGET_HAS_deposit16l_i64   0
 #endif
 
 /* Only one of DIV or DIV2 should be defined.  */
-- 
1.7.3.4