[Qemu-devel] [RFC 13/14] tcg-aarch64: Use adrp in tcg_out_movi

[Richard Henderson <rth@twiddle.net>]

Loading an qemu pointer as an immediate happens often:

- 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 | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/tcg/aarch64/tcg-target.c b/tcg/aarch64/tcg-target.c
index 3ea5db7..a03da58 100644
--- a/tcg/aarch64/tcg-target.c
+++ b/tcg/aarch64/tcg-target.c
@@ -298,6 +298,10 @@ typedef enum {
     INSN_RET   = 0xd65f0000,
     INSN_B_C   = 0x54000000,
 
+    /* PC relative addressing instructions */
+    INSN_ADR   = 0x10000000,
+    INSN_ADRP  = 0x90000000,
+
     /* System instructions */
     INSN_NOP   = 0xd503201f,
 } AArch64Insn;
@@ -554,6 +558,20 @@ 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 data structures.  */
+    valid = (value >> 12) - ((intptr_t)s->code_ptr >> 12);
+    if (valid == sextract64(valid, 0, 21)) {
+        insn  = INSN_ADRP | rd;
+        insn |= (valid & 3) << 29;
+        insn |= (valid & 0x1ffffc) << (5 - 2);
+        tcg_out32(s, insn);
+        if (value & 0xfff) {
+            tcg_out_aimm(s, INSN_ADDI, ext, rd, rd, value & 0xfff);
+        }
+        return;
+    }
+
     /* Would it take fewer insns to load the inverse?  */
     wantinv = 0;
     for (i = 0; i < 64; i += 16) {
-- 
1.8.3.1