[Qemu-devel] [PATCH v4 6/7] target/arm: Try pc-relative addresses for movi

[Richard Henderson <rth@twiddle.net>]

Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 tcg/arm/tcg-target.inc.c | 44 +++++++++++++++++++++++++++++---------------
 1 file changed, 29 insertions(+), 15 deletions(-)

diff --git a/tcg/arm/tcg-target.inc.c b/tcg/arm/tcg-target.inc.c
index fce382f..18708b1 100644
--- a/tcg/arm/tcg-target.inc.c
+++ b/tcg/arm/tcg-target.inc.c
@@ -418,25 +418,39 @@ static inline void tcg_out_dat_imm(TCGContext *s,
 
 static void tcg_out_movi32(TCGContext *s, int cond, int rd, uint32_t arg)
 {
-    int rot, opc, rn;
-
-    /* For armv7, make sure not to use movw+movt when mov/mvn would do.
-       Speed things up by only checking when movt would be required.
-       Prior to armv7, have one go at fully rotated immediates before
-       doing the decomposition thing below.  */
-    if (!use_armv7_instructions || (arg & 0xffff0000)) {
-        rot = encode_imm(arg);
+    int rot, opc, rn, diff;
+
+    /* Check a single MOV/MVN before anything else.  */
+    rot = encode_imm(arg);
+    if (rot >= 0) {
+        tcg_out_dat_imm(s, cond, ARITH_MOV, rd, 0,
+                        rotl(arg, rot) | (rot << 7));
+        return;
+    }
+    rot = encode_imm(~arg);
+    if (rot >= 0) {
+        tcg_out_dat_imm(s, cond, ARITH_MVN, rd, 0,
+                        rotl(~arg, rot) | (rot << 7));
+        return;
+    }
+
+    /* Check for a pc-relative address.  This will usually be the TB,
+       or within the TB, which is immediately before the code block.  */
+    diff = arg - ((intptr_t)s->code_ptr + 8);
+    if (diff >= 0) {
+        rot = encode_imm(diff);
         if (rot >= 0) {
-            tcg_out_dat_imm(s, cond, ARITH_MOV, rd, 0,
-                            rotl(arg, rot) | (rot << 7));
+            tcg_out_dat_imm(s, cond, ARITH_ADD, rd, TCG_REG_PC,
+                            rotl(diff, rot) | (rot << 7));
             return;
-        }
-        rot = encode_imm(~arg);
+	}
+    } else {
+        rot = encode_imm(-diff);
         if (rot >= 0) {
-            tcg_out_dat_imm(s, cond, ARITH_MVN, rd, 0,
-                            rotl(~arg, rot) | (rot << 7));
+            tcg_out_dat_imm(s, cond, ARITH_SUB, rd, TCG_REG_PC,
+                            rotl(-diff, rot) | (rot << 7));
             return;
-        }
+	}
     }
 
     /* Use movw + movt.  */
-- 
2.9.4