[Qemu-devel] [PATCH v4 25/33] tcg-aarch64: Use adrp in tcg_out_movi

[Richard Henderson <rth@twiddle.net>]

Loading an qemu pointer as an immediate happens often.  E.g.

- exit_tb $0x7fa8140013
+ exit_tb $0x7f81ee0013
...
- :  d2800260        mov     x0, #0x13
- :  f2b50280        movk    x0, #0xa814, lsl #16
- :  f2c00fe0        movk    x0, #0x7f, lsl #32
+ :  90ff1000        adrp    x0, 0x7f81ee0000
+ :  91004c00        add     x0, x0, #0x13

Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 tcg/aarch64/tcg-target.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/tcg/aarch64/tcg-target.c b/tcg/aarch64/tcg-target.c
index e50abcb..5691cc3 100644
--- a/tcg/aarch64/tcg-target.c
+++ b/tcg/aarch64/tcg-target.c
@@ -323,6 +323,10 @@ typedef enum {
     /* Conditional select instructions */
     INSN_CSEL  = 0x1a800000,
     INSN_CSINC = 0x1a800400,
+
+    /* PC relative addressing instructions */
+    INSN_ADR   = 0x10000000,
+    INSN_ADRP  = 0x90000000,
 } AArch64Insn;
 
 static inline enum aarch64_ldst_op_data
@@ -510,6 +514,12 @@ static inline void tcg_fmt_Rd_uimm(TCGContext *s, AArch64Insn insn,
     tcg_out32(s, insn | sf << 31 | shift << (21 - 4) | half << 5 | rd);
 }
 
+static inline void tcg_fmt_Rd_disp21(TCGContext *s, AArch64Insn insn,
+                                     TCGReg rd, tcg_target_long disp)
+{
+    tcg_out32(s, insn | (disp & 3) << 29 | (disp & 0x1ffffc) << (5 - 2) | rd);
+}
+
 static inline void tcg_out_ldst_9(TCGContext *s,
                                   enum aarch64_ldst_op_data op_data,
                                   enum aarch64_ldst_op_type op_type,
@@ -561,7 +571,7 @@ static void tcg_out_movi(TCGContext *s, TCGType type, TCGReg rd,
     AArch64Insn insn;
     int i, wantinv, shift;
     tcg_target_long svalue = value;
-    tcg_target_long ivalue, imask;
+    tcg_target_long ivalue, imask, disp;
 
     /* For 32-bit values, discard potential garbage in value.  For 64-bit
        values within [2**31, 2**32-1], we can create smaller sequences by
@@ -593,6 +603,17 @@ static void tcg_out_movi(TCGContext *s, TCGType type, TCGReg rd,
         return;
     }
 
+    /* Look for host pointer values within 4G of the PC.  This happens
+       often when loading pointers to QEMU's own data structures.  */
+    disp = (value >> 12) - ((intptr_t)s->code_ptr >> 12);
+    if (disp == sextract64(disp, 0, 21)) {
+        tcg_fmt_Rd_disp21(s, INSN_ADRP, rd, disp);
+        if (value & 0xfff) {
+            tcg_fmt_Rdn_aimm(s, INSN_ADDI, type, rd, rd, value & 0xfff);
+        }
+        return;
+    }
+
     /* Would it take fewer insns to begin with MOVN?  For the value and its
        inverse, count the number of 16-bit lanes that are 0.  For the benefit
        of 32-bit quantities, compare the zero-extended normal value vs the
-- 
1.8.3.1