[Qemu-devel] [PATCH for-next 12/15] tcg-ppc64: Use TCG_REG_TB in tcg_out_movi and tcg_out_mem_long

[Richard Henderson <rth@twiddle.net>]

This results in significant code size reductions when manipulating
pointers into TCG's own data structures.  E.g.

-OUT: [size=180]
+OUT: [size=132]
...
-xxx:  li      r2,16383			# goto_tb
-xxx:  rldicr  r2,r2,32,31
-xxx:  oris    r2,r2,39128
-xxx:  ori     r2,r2,376
-xxx:  ldx     r30,0,r2
+xxx:  addis   r30,r30,-544
+xxx:  ld      r30,-8(r30)
...
-xxx:  li      r3,16383			# exit_tb
-xxx:  rldicr  r3,r3,32,31
-xxx:  oris    r3,r3,39128
-xxx:  ori     r3,r3,288
+xxx:  addis   r3,r30,-544
+xxx:  addi    r3,r3,-96

Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 tcg/ppc64/tcg-target.c | 164 +++++++++++++++++++++++++++++--------------------
 1 file changed, 99 insertions(+), 65 deletions(-)

diff --git a/tcg/ppc64/tcg-target.c b/tcg/ppc64/tcg-target.c
index e01d8bc..d4e1efc 100644
--- a/tcg/ppc64/tcg-target.c
+++ b/tcg/ppc64/tcg-target.c
@@ -548,6 +548,78 @@ static inline void tcg_out_shri64(TCGContext *s, TCGReg dst, TCGReg src, int c)
     tcg_out_rld(s, RLDICL, dst, src, 64 - c, c);
 }
 
+static void tcg_out_mem_long(TCGContext *s, PowerOpcode opi, PowerOpcode opx,
+                             TCGReg rt, TCGReg base, tcg_target_long offset)
+{
+    tcg_target_long orig = offset, l0, l1, extra = 0, align = 0;
+    TCGReg rs = TCG_REG_R2;
+
+    assert(rt != TCG_REG_R2 && base != TCG_REG_R2);
+
+    switch (opi) {
+    case LD: case LWA:
+        align = 3;
+        /* FALLTHRU */
+    default:
+        if (rt != TCG_REG_R0) {
+            rs = rt;
+        }
+        break;
+    case STD:
+        align = 3;
+        break;
+    case STB: case STH: case STW:
+        break;
+    }
+
+    /* For unaligned, use the indexed form.  */
+    if (offset & align) {
+    do_indexed:
+        tcg_out_movi(s, TCG_TYPE_I64, TCG_REG_R2, orig);
+        tcg_out32(s, opx | TAB(rt, base, TCG_REG_R2));
+        return;
+    }
+
+    if (base == TCG_REG_R0) {
+        /* For absolute addresses, avoid indexed form.  First try turning
+           it into an offset from a known base register, then just fold
+           the low 16 bits. */
+        offset -= (tcg_target_long)s->code_buf;
+        if (offset == (int32_t)offset) {
+            orig = offset;
+            base = TCG_REG_TB;
+        } else {
+            offset = (int16_t)orig;
+            tcg_out_movi(s, TCG_TYPE_I64, TCG_REG_R2, orig - offset);
+            orig = offset;
+            base = TCG_REG_R2;
+        }
+    } else if (offset != (int32_t)offset) {
+        /* For very large offsets off a real base register, use indexed.  */
+        goto do_indexed;
+    }
+
+    l0 = (int16_t)offset;
+    offset = (offset - l0) >> 16;
+    l1 = (int16_t)offset;
+
+    if (l1 < 0 && orig >= 0) {
+        extra = 0x4000;
+        l1 = (int16_t)(offset - 0x4000);
+    }
+    if (l1) {
+        tcg_out32(s, ADDIS | TAI(rs, base, l1));
+        base = rs;
+    }
+    if (extra) {
+        tcg_out32(s, ADDIS | TAI(rs, base, extra));
+        base = rs;
+    }
+    if (opi != ADDI || base != rt || l0 != 0) {
+        tcg_out32(s, opi | TAI(rt, base, l0));
+    }
+}
+
 static void tcg_out_movi32(TCGContext *s, TCGReg ret, int32_t arg)
 {
     if (arg == (int16_t) arg) {
@@ -563,23 +635,37 @@ static void tcg_out_movi32(TCGContext *s, TCGReg ret, int32_t arg)
 static void tcg_out_movi(TCGContext *s, TCGType type, TCGReg ret,
                          tcg_target_long arg)
 {
+    tcg_target_long tmp;
+
+    /* Two attempts at 1 or 2 insn sequence for 32-bit constant.  */
     if (type == TCG_TYPE_I32 || arg == (int32_t)arg) {
         tcg_out_movi32(s, ret, arg);
-    } else if (arg == (uint32_t)arg && !(arg & 0x8000)) {
+        return;
+    }
+    if (arg == (uint32_t)arg && !(arg & 0x8000)) {
         tcg_out32(s, ADDI | TAI(ret, 0, arg));
         tcg_out32(s, ORIS | SAI(ret, ret, arg >> 16));
-    } else {
-        int32_t high = arg >> 32;
-        tcg_out_movi32(s, ret, high);
-        if (high) {
-            tcg_out_shli64(s, ret, ret, 32);
-        }
-        if (arg & 0xffff0000) {
-            tcg_out32(s, ORIS | SAI(ret, ret, arg >> 16));
-        }
-        if (arg & 0xffff) {
-            tcg_out32(s, ORI | SAI(ret, ret, arg));
-        }
+        return;
+    }
+
+    /* See if we can turn a address constant into a TB offset.  */
+    tmp = arg - (uintptr_t)s->code_buf;
+    if (tmp == (int32_t)tmp) {
+        tcg_out_mem_long(s, ADDI, ADD, ret, TCG_REG_TB, tmp);
+        return;
+    }
+
+    /* Full 64-bit constant load.  */
+    tmp = arg >> 32;
+    tcg_out_movi32(s, ret, tmp);
+    if (tmp) {
+        tcg_out_shli64(s, ret, ret, 32);
+    }
+    if (arg & 0xffff0000) {
+        tcg_out32(s, ORIS | SAI(ret, ret, arg >> 16));
+    }
+    if (arg & 0xffff) {
+        tcg_out32(s, ORI | SAI(ret, ret, arg));
     }
 }
 
@@ -746,58 +832,6 @@ static void tcg_out_call(TCGContext *s, tcg_target_long arg,
 #endif
 }
 
-static void tcg_out_mem_long(TCGContext *s, PowerOpcode opi, PowerOpcode opx,
-                             TCGReg rt, TCGReg base, tcg_target_long offset)
-{
-    tcg_target_long orig = offset, l0, l1, extra = 0, align = 0;
-    TCGReg rs = TCG_REG_R2;
-
-    assert(rt != TCG_REG_R2 && base != TCG_REG_R2);
-
-    switch (opi) {
-    case LD: case LWA:
-        align = 3;
-        /* FALLTHRU */
-    default:
-        if (rt != TCG_REG_R0) {
-            rs = rt;
-        }
-        break;
-    case STD:
-        align = 3;
-        break;
-    case STB: case STH: case STW:
-        break;
-    }
-
-    /* For unaligned, or very large offsets, use the indexed form.  */
-    if (offset & align || offset != (int32_t)offset) {
-        tcg_out_movi(s, TCG_TYPE_I64, TCG_REG_R2, orig);
-        tcg_out32(s, opx | TAB(rt, base, TCG_REG_R2));
-        return;
-    }
-
-    l0 = (int16_t)offset;
-    offset = (offset - l0) >> 16;
-    l1 = (int16_t)offset;
-
-    if (l1 < 0 && orig >= 0) {
-        extra = 0x4000;
-        l1 = (int16_t)(offset - 0x4000);
-    }
-    if (l1) {
-        tcg_out32(s, ADDIS | TAI(rs, base, l1));
-        base = rs;
-    }
-    if (extra) {
-        tcg_out32(s, ADDIS | TAI(rs, base, extra));
-        base = rs;
-    }
-    if (opi != ADDI || base != rt || l0 != 0) {
-        tcg_out32(s, opi | TAI(rt, base, l0));
-    }
-}
-
 #if defined (CONFIG_SOFTMMU)
 
 #include "exec/softmmu_defs.h"
-- 
1.8.3.1