[Qemu-devel] [PATCH for-next 03/15] tcg-ppc64: Use the branch absolute instruction when possible

[Richard Henderson <rth@twiddle.net>]

... before falling back to an indirect branch.

Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 tcg/ppc64/tcg-target.c | 31 ++++++++++++++++++-------------
 1 file changed, 18 insertions(+), 13 deletions(-)

diff --git a/tcg/ppc64/tcg-target.c b/tcg/ppc64/tcg-target.c
index 94960a3..fce3e5d 100644
--- a/tcg/ppc64/tcg-target.c
+++ b/tcg/ppc64/tcg-target.c
@@ -173,13 +173,17 @@ static const int tcg_target_callee_save_regs[] = {
     TCG_REG_R31
 };
 
+static inline bool in_range_b(intptr_t disp)
+{
+    return disp >= -0x4000000 && disp < 0x4000000;
+}
+
 static uint32_t reloc_pc24_val (void *pc, tcg_target_long target)
 {
     tcg_target_long disp;
 
     disp = target - (tcg_target_long) pc;
-    if ((disp << 38) >> 38 != disp)
-        tcg_abort ();
+    assert(in_range_b(disp));
 
     return disp & 0x3fffffc;
 }
@@ -195,8 +199,7 @@ static uint16_t reloc_pc14_val (void *pc, tcg_target_long target)
     tcg_target_long disp;
 
     disp = target - (tcg_target_long) pc;
-    if (disp != (int16_t) disp)
-        tcg_abort ();
+    assert(disp == (int16_t)disp);
 
     return disp & 0xfffc;
 }
@@ -454,6 +457,7 @@ static int tcg_target_const_match (tcg_target_long val,
 #define FXM(b) (1 << (19 - (b)))
 
 #define LK    1
+#define AA    2
 
 #define TAB(t, a, b) (RT(t) | RA(a) | RB(b))
 #define SAB(s, a, b) (RS(s) | RA(a) | RB(b))
@@ -688,17 +692,18 @@ static void tcg_out_xori32(TCGContext *s, TCGReg dst, TCGReg src, uint32_t c)
     tcg_out_zori32(s, dst, src, c, XORI, XORIS);
 }
 
-static void tcg_out_b (TCGContext *s, int mask, tcg_target_long target)
+static void tcg_out_b(TCGContext *s, int lk, tcg_target_long target)
 {
-    tcg_target_long disp;
+    tcg_target_long disp = target - (tcg_target_long) s->code_ptr;
 
-    disp = target - (tcg_target_long) s->code_ptr;
-    if ((disp << 38) >> 38 == disp)
-        tcg_out32 (s, B | (disp & 0x3fffffc) | mask);
-    else {
-        tcg_out_movi (s, TCG_TYPE_I64, 0, (tcg_target_long) target);
-        tcg_out32 (s, MTSPR | RS (0) | CTR);
-        tcg_out32 (s, BCCTR | BO_ALWAYS | mask);
+    if (in_range_b(disp)) {
+        tcg_out32(s, B | (disp & 0x3fffffc) | lk);
+    } else if (in_range_b(target)) {
+        tcg_out32(s, B | AA | target | lk);
+    } else {
+        tcg_out_movi(s, TCG_TYPE_PTR, TCG_REG_R0, target);
+        tcg_out32 (s, MTSPR | RS(TCG_REG_R0) | CTR);
+        tcg_out32 (s, BCCTR | BO_ALWAYS | lk);
     }
 }
 
-- 
1.8.3.1