[Qemu-devel] [PATCH 2/2] target/hppa: Optimize blr r0,rn

[Richard Henderson]

We can eliminate an extra TB in this case, which merely
loads a "return address" into rn.

Signed-off-by: Richard Henderson <address@hidden>
---
 target/hppa/translate.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/target/hppa/translate.c b/target/hppa/translate.c
index dad8ce563c..dc5636fe94 100644
--- a/target/hppa/translate.c
+++ b/target/hppa/translate.c
@@ -3488,12 +3488,16 @@ static bool trans_b_gate(DisasContext *ctx, arg_b_gate 
*a)
 
 static bool trans_blr(DisasContext *ctx, arg_blr *a)
 {
-    TCGv_reg tmp = get_temp(ctx);
-
-    tcg_gen_shli_reg(tmp, load_gpr(ctx, a->x), 3);
-    tcg_gen_addi_reg(tmp, tmp, ctx->iaoq_f + 8);
-    /* The computation here never changes privilege level.  */
-    return do_ibranch(ctx, tmp, a->l, a->n);
+    if (a->x) {
+        TCGv_reg tmp = get_temp(ctx);
+        tcg_gen_shli_reg(tmp, load_gpr(ctx, a->x), 3);
+        tcg_gen_addi_reg(tmp, tmp, ctx->iaoq_f + 8);
+        /* The computation here never changes privilege level.  */
+        return do_ibranch(ctx, tmp, a->l, a->n);
+    } else {
+        /* BLR R0,RX is a good way to load PC+8 into RX.  */
+        return do_dbranch(ctx, ctx->iaoq_f + 8, a->l, a->n);
+    }
 }
 
 static bool trans_bv(DisasContext *ctx, arg_bv *a)
-- 
2.17.2