[Qemu-devel] [PULL 35/49] target/arm: Tidy TBI handling in gen_a64_set_pc

[Peter Maydell]

From: Richard Henderson <address@hidden>

We can perform this with fewer operations.

Reviewed-by: Peter Maydell <address@hidden>
Signed-off-by: Richard Henderson <address@hidden>
Message-id: address@hidden
Signed-off-by: Peter Maydell <address@hidden>
---
 target/arm/translate-a64.c | 62 +++++++++++++-------------------------
 1 file changed, 21 insertions(+), 41 deletions(-)

diff --git a/target/arm/translate-a64.c b/target/arm/translate-a64.c
index f49fe1de3a8..4d28a27c3bd 100644
--- a/target/arm/translate-a64.c
+++ b/target/arm/translate-a64.c
@@ -261,7 +261,7 @@ void gen_a64_set_pc_im(uint64_t val)
 /* Load the PC from a generic TCG variable.
  *
  * If address tagging is enabled via the TCR TBI bits, then loading
- * an address into the PC will clear out any tag in the it:
+ * an address into the PC will clear out any tag in it:
  *  + for EL2 and EL3 there is only one TBI bit, and if it is set
  *    then the address is zero-extended, clearing bits [63:56]
  *  + for EL0 and EL1, TBI0 controls addresses with bit 55 == 0
@@ -280,54 +280,34 @@ static void gen_a64_set_pc(DisasContext *s, TCGv_i64 src)
     int tbi = s->tbii;
 
     if (s->current_el <= 1) {
-        /* Test if NEITHER or BOTH TBI values are set.  If so, no need to
-         * examine bit 55 of address, can just generate code.
-         * If mixed, then test via generated code
-         */
-        if (tbi == 3) {
-            TCGv_i64 tmp_reg = tcg_temp_new_i64();
-            /* Both bits set, sign extension from bit 55 into [63:56] will
-             * cover both cases
-             */
-            tcg_gen_shli_i64(tmp_reg, src, 8);
-            tcg_gen_sari_i64(cpu_pc, tmp_reg, 8);
-            tcg_temp_free_i64(tmp_reg);
-        } else if (tbi == 0) {
-            /* Neither bit set, just load it as-is */
-            tcg_gen_mov_i64(cpu_pc, src);
-        } else {
-            TCGv_i64 tcg_tmpval = tcg_temp_new_i64();
-            TCGv_i64 tcg_bit55  = tcg_temp_new_i64();
-            TCGv_i64 tcg_zero   = tcg_const_i64(0);
+        if (tbi != 0) {
+            /* Sign-extend from bit 55.  */
+            tcg_gen_sextract_i64(cpu_pc, src, 0, 56);
 
-            tcg_gen_andi_i64(tcg_bit55, src, (1ull << 55));
+            if (tbi != 3) {
+                TCGv_i64 tcg_zero = tcg_const_i64(0);
 
-            if (tbi == 1) {
-                /* tbi0==1, tbi1==0, so 0-fill upper byte if bit 55 = 0 */
-                tcg_gen_andi_i64(tcg_tmpval, src,
-                                 0x00FFFFFFFFFFFFFFull);
-                tcg_gen_movcond_i64(TCG_COND_EQ, cpu_pc, tcg_bit55, tcg_zero,
-                                    tcg_tmpval, src);
-            } else {
-                /* tbi0==0, tbi1==1, so 1-fill upper byte if bit 55 = 1 */
-                tcg_gen_ori_i64(tcg_tmpval, src,
-                                0xFF00000000000000ull);
-                tcg_gen_movcond_i64(TCG_COND_NE, cpu_pc, tcg_bit55, tcg_zero,
-                                    tcg_tmpval, src);
+                /*
+                 * The two TBI bits differ.
+                 * If tbi0, then !tbi1: only use the extension if positive.
+                 * if !tbi0, then tbi1: only use the extension if negative.
+                 */
+                tcg_gen_movcond_i64(tbi == 1 ? TCG_COND_GE : TCG_COND_LT,
+                                    cpu_pc, cpu_pc, tcg_zero, cpu_pc, src);
+                tcg_temp_free_i64(tcg_zero);
             }
-            tcg_temp_free_i64(tcg_zero);
-            tcg_temp_free_i64(tcg_bit55);
-            tcg_temp_free_i64(tcg_tmpval);
+            return;
         }
-    } else {  /* EL > 1 */
+    } else {
         if (tbi != 0) {
             /* Force tag byte to all zero */
-            tcg_gen_andi_i64(cpu_pc, src, 0x00FFFFFFFFFFFFFFull);
-        } else {
-            /* Load unmodified address */
-            tcg_gen_mov_i64(cpu_pc, src);
+            tcg_gen_extract_i64(cpu_pc, src, 0, 56);
+            return;
         }
     }
+
+    /* Load unmodified address */
+    tcg_gen_mov_i64(cpu_pc, src);
 }
 
 typedef struct DisasCompare64 {
-- 
2.20.1