target/arm: Change gen_jmp* to work on displacements

In preparation for TARGET_TB_PCREL, reduce reliance on absolute values.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20221020030641.2066807-7-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/translate.c

@@ -266,6 +266,12 @@ static uint32_t read_pc(DisasContext *s)
     return s->pc_curr + (s->thumb ? 4 : 8);
 }
 
+/* The pc_curr difference for an architectural jump. */
+static target_long jmp_diff(DisasContext *s, target_long diff)
+{
+    return diff + (s->thumb ? 4 : 8);
+}
+
 /* Set a variable to the value of a CPU register.  */
 void load_reg_var(DisasContext *s, TCGv_i32 var, int reg)
 {
@@ -2592,7 +2598,7 @@ static void gen_goto_ptr(void)
  * cpu_loop_exec. Any live exit_requests will be processed as we
  * enter the next TB.
  */
-static void gen_goto_tb(DisasContext *s, int n, int diff)
+static void gen_goto_tb(DisasContext *s, int n, target_long diff)
 {
     target_ulong dest = s->pc_curr + diff;
 
@@ -2608,10 +2614,8 @@ static void gen_goto_tb(DisasContext *s, int n, int diff)
 }
 
 /* Jump, specifying which TB number to use if we gen_goto_tb() */
-static inline void gen_jmp_tb(DisasContext *s, uint32_t dest, int tbno)
+static void gen_jmp_tb(DisasContext *s, target_long diff, int tbno)
 {
-    int diff = dest - s->pc_curr;
-
     if (unlikely(s->ss_active)) {
         /* An indirect jump so that we still trigger the debug exception.  */
         gen_update_pc(s, diff);
@@ -2653,9 +2657,9 @@ static inline void gen_jmp_tb(DisasContext *s, uint32_t dest, int tbno)
     }
 }
 
-static inline void gen_jmp(DisasContext *s, uint32_t dest)
+static inline void gen_jmp(DisasContext *s, target_long diff)
 {
-    gen_jmp_tb(s, dest, 0);
+    gen_jmp_tb(s, diff, 0);
 }
 
 static inline void gen_mulxy(TCGv_i32 t0, TCGv_i32 t1, int x, int y)
@@ -8322,7 +8326,7 @@ static bool trans_CLRM(DisasContext *s, arg_CLRM *a)
 
 static bool trans_B(DisasContext *s, arg_i *a)
 {
-    gen_jmp(s, read_pc(s) + a->imm);
+    gen_jmp(s, jmp_diff(s, a->imm));
     return true;
 }
 
@@ -8337,14 +8341,14 @@ static bool trans_B_cond_thumb(DisasContext *s, arg_ci *a)
         return true;
     }
     arm_skip_unless(s, a->cond);
-    gen_jmp(s, read_pc(s) + a->imm);
+    gen_jmp(s, jmp_diff(s, a->imm));
     return true;
 }
 
 static bool trans_BL(DisasContext *s, arg_i *a)
 {
     tcg_gen_movi_i32(cpu_R[14], s->base.pc_next | s->thumb);
-    gen_jmp(s, read_pc(s) + a->imm);
+    gen_jmp(s, jmp_diff(s, a->imm));
     return true;
 }
 
@@ -8364,7 +8368,8 @@ static bool trans_BLX_i(DisasContext *s, arg_BLX_i *a)
     }
     tcg_gen_movi_i32(cpu_R[14], s->base.pc_next | s->thumb);
     store_cpu_field_constant(!s->thumb, thumb);
-    gen_jmp(s, (read_pc(s) & ~3) + a->imm);
+    /* This jump is computed from an aligned PC: subtract off the low bits. */
+    gen_jmp(s, jmp_diff(s, a->imm - (s->pc_curr & 3)));
     return true;
 }
 
@@ -8525,10 +8530,10 @@ static bool trans_WLS(DisasContext *s, arg_WLS *a)
          * when we take this upcoming exit from this TB, so gen_jmp_tb() is OK.
          */
     }
-    gen_jmp_tb(s, s->base.pc_next, 1);
+    gen_jmp_tb(s, curr_insn_len(s), 1);
 
     gen_set_label(nextlabel);
-    gen_jmp(s, read_pc(s) + a->imm);
+    gen_jmp(s, jmp_diff(s, a->imm));
     return true;
 }
 
@@ -8608,7 +8613,7 @@ static bool trans_LE(DisasContext *s, arg_LE *a)
 
     if (a->f) {
         /* Loop-forever: just jump back to the loop start */
-        gen_jmp(s, read_pc(s) - a->imm);
+        gen_jmp(s, jmp_diff(s, -a->imm));
         return true;
     }
 
@@ -8639,7 +8644,7 @@ static bool trans_LE(DisasContext *s, arg_LE *a)
         tcg_temp_free_i32(decr);
     }
     /* Jump back to the loop start */
-    gen_jmp(s, read_pc(s) - a->imm);
+    gen_jmp(s, jmp_diff(s, -a->imm));
 
     gen_set_label(loopend);
     if (a->tp) {
@@ -8647,7 +8652,7 @@ static bool trans_LE(DisasContext *s, arg_LE *a)
         store_cpu_field(tcg_constant_i32(4), v7m.ltpsize);
     }
     /* End TB, continuing to following insn */
-    gen_jmp_tb(s, s->base.pc_next, 1);
+    gen_jmp_tb(s, curr_insn_len(s), 1);
     return true;
 }
 
@@ -8746,7 +8751,7 @@ static bool trans_CBZ(DisasContext *s, arg_CBZ *a)
     tcg_gen_brcondi_i32(a->nz ? TCG_COND_EQ : TCG_COND_NE,
                         tmp, 0, s->condlabel);
     tcg_temp_free_i32(tmp);
-    gen_jmp(s, read_pc(s) + a->imm);
+    gen_jmp(s, jmp_diff(s, a->imm));
     return true;
 }