[PATCH] ppc: Add optimization to generate endian-swapping load opcodes

[Paul Cercueil]

When generating endian-swap code with jit_bswapr_us() or
jit_bswapr_ui(), look at the last opcode generated. If it's a LHZX or
LWZX, it can be replaced with a LHBRX or LWBRX opcode, which will
perform the endian swap directly.

If it's a LHZ or LWZ, then we can just move the immediate value into a
temporary register, and emit a LHBRX or LWBRX opcode.

The "no flag" check is needed, because we must ensure that no branch
will jump between the load opcode that we want to modify, and the
jit_bswapr opcode.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
---
 lib/jit_ppc-cpu.c | 63 +++++++++++++++++++++++++++++++++++++++++------
 lib/jit_ppc.c     | 11 +++++++--
 2 files changed, 64 insertions(+), 10 deletions(-)

diff --git a/lib/jit_ppc-cpu.c b/lib/jit_ppc-cpu.c
index cab085f..3769a61 100644
--- a/lib/jit_ppc-cpu.c
+++ b/lib/jit_ppc-cpu.c
@@ -260,7 +260,7 @@ static void _FXS(jit_state_t*,int,int,int,int,int,int,int);
 #  define LHAU(d,a,s)                  FDs(43,d,a,s)
 #  define LHAUX(d,a,b)                 FX(31,d,a,b,375)
 #  define LHAX(d,a,b)                  FX(31,d,a,b,343)
-#  define LHRBX(d,a,b)                 FX(31,d,a,b,790)
+#  define LHBRX(d,a,b)                 FX(31,d,a,b,790)
 #  define LHZ(d,a,s)                   FDs(40,d,a,s)
 #  define LHZU(d,a,s)                  FDs(41,d,a,s)
 #  define LHZUX(d,a,b)                 FX(31,d,a,b,311)
@@ -521,10 +521,12 @@ static jit_word_t 
_movi_p(jit_state_t*,jit_int32_t,jit_word_t);
 #    define extr_i(r0,r1)              EXTSW(r0,r1)
 #    define extr_ui(r0,r1)             CLRLDI(r0,r1,32)
 #  endif
-#  define bswapr_us(r0,r1)             _bswapr_us(_jit,r0,r1)
-static void _bswapr_us(jit_state_t*,jit_int32_t,jit_int32_t);
-#  define bswapr_ui(r0,r1)             _bswapr_ui(_jit,r0,r1)
-static void _bswapr_ui(jit_state_t*,jit_int32_t,jit_int32_t);
+#  define bswapr_us_lh(r0,r1,no_flag)  _bswapr_us(_jit,r0,r1,no_flag)
+#  define bswapr_us(r0,r1)             _bswapr_us(_jit,r0,r1,0)
+static void _bswapr_us(jit_state_t*,jit_int32_t,jit_int32_t,jit_bool_t);
+#  define bswapr_ui_lw(r0,r1,no_flag)  _bswapr_ui(_jit,r0,r1,no_flag)
+#  define bswapr_ui(r0,r1)             _bswapr_ui(_jit,r0,r1,0)
+static void _bswapr_ui(jit_state_t*,jit_int32_t,jit_int32_t,jit_bool_t);
 #  if __WORDSIZE == 64
 #    define bswapr_ul(r0,r1)           generic_bswapr_ul(_jit,r0,r1)
 #  endif
@@ -1148,8 +1150,31 @@ _movi_p(jit_state_t *_jit, jit_int32_t r0, jit_word_t i0)
 }
 
 static void
-_bswapr_us(jit_state_t *_jit, jit_int32_t r0, jit_int32_t r1)
+_bswapr_us(jit_state_t *_jit, jit_int32_t r0, jit_int32_t r1, jit_bool_t 
no_flag)
 {
+    jit_int32_t                reg, addr_reg;
+
+    if (no_flag && r0 == r1) {
+        if ((*(_jit->pc.ui - 1) & 0xffe007ff) == (0x7c00022e | r0 << 21)) {
+            /* Convert LHZX to LHBRX */
+            _jit->pc.ui--;
+            LHBRX(r0, (*_jit->pc.ui >> 16) & 0x1f, (*_jit->pc.ui >> 11) & 
0x1f);
+            return;
+        }
+
+        if ((*(_jit->pc.ui - 1) & 0xffe00000) == (0xa0000000 | r0 << 21)) {
+            /* Convert LHZ to LHBRX */
+            _jit->pc.ui--;
+            addr_reg = (*_jit->pc.ui >> 16) & 0x1f;
+
+            reg = jit_get_reg(jit_class_gpr);
+            LI(rn(reg), (short)*_jit->pc.ui);
+            LHBRX(r0, rn(reg), addr_reg);
+            jit_unget_reg(reg);
+            return;
+        }
+    }
+
     if (r0 == r1) {
         RLWIMI(r0, r0, 16, 8, 15);
         RLWINM(r0, r0, 24, 16, 31);
@@ -1160,9 +1185,31 @@ _bswapr_us(jit_state_t *_jit, jit_int32_t r0, 
jit_int32_t r1)
 }
 
 static void
-_bswapr_ui(jit_state_t *_jit, jit_int32_t r0, jit_int32_t r1)
+_bswapr_ui(jit_state_t *_jit, jit_int32_t r0, jit_int32_t r1, jit_bool_t 
no_flag)
 {
-    jit_int32_t                reg;
+    jit_int32_t                reg, addr_reg;
+
+    if (no_flag && r0 == r1) {
+        if ((*(_jit->pc.ui - 1) & 0xffe007ff) == (0x7c00002e | r0 << 21)) {
+            /* Convert LWZX to LWBRX */
+            _jit->pc.ui--;
+            LWBRX(r0, (*_jit->pc.ui >> 16) & 0x1f, (*_jit->pc.ui >> 11) & 
0x1f);
+            return;
+        }
+
+        if ((*(_jit->pc.ui - 1) & 0xffe00000) == (0x80000000 | r0 << 21)) {
+            /* Convert LWZ to LWBRX */
+            _jit->pc.ui--;
+            addr_reg = (*_jit->pc.ui >> 16) & 0x1f;
+
+            reg = jit_get_reg(jit_class_gpr);
+            LI(rn(reg), (short)*_jit->pc.ui);
+            LWBRX(r0, rn(reg), addr_reg);
+            jit_unget_reg(reg);
+            return;
+        }
+    }
+
     reg = jit_get_reg(jit_class_gpr);
     ROTLWI(rn(reg), r1, 8);
     RLWIMI(rn(reg), r1, 24, 0, 7);
diff --git a/lib/jit_ppc.c b/lib/jit_ppc.c
index e94d1a5..28975be 100644
--- a/lib/jit_ppc.c
+++ b/lib/jit_ppc.c
@@ -1148,6 +1148,7 @@ _emit_code(jit_state_t *_jit)
     jit_word_t          word;
     jit_int32_t                 value;
     jit_int32_t                 offset;
+    jit_bool_t       no_flag = 0;
     struct {
        jit_node_t      *node;
        jit_word_t       word;
@@ -1356,8 +1357,12 @@ _emit_code(jit_state_t *_jit)
 #  if __WORDSIZE == 64
                case_rr(hton, _ul);
 #  endif
-               case_rr(bswap, _us);
-               case_rr(bswap, _ui);
+           case jit_code_bswapr_us:
+               bswapr_us_lh(rn(node->u.w), rn(node->v.w), no_flag);
+               break;
+           case jit_code_bswapr_ui:
+               bswapr_ui_lw(rn(node->u.w), rn(node->v.w), no_flag);
+               break;
 #  if __WORDSIZE == 64
                case_rr(bswap, _ul);
 #  endif
@@ -1823,6 +1828,8 @@ _emit_code(jit_state_t *_jit)
        assert(_jitc->regarg == 0 && _jitc->synth == 0);
        /* update register live state */
        jit_reglive(node);
+
+        no_flag = !(node->flag & jit_flag_patch);
     }
 #undef case_brf
 #undef case_brw
-- 
2.35.1