[PATCH] riscv: Add helper to make NaN-boxing for FP register

[Ian Jiang]

The function that makes NaN-boxing when a 32-bit value is assigned
to a 64-bit FP register is split out to a helper gen_nanbox_fpr().
Then it is applied in translating of the FLW instruction.

This also applies for other instructions when the RVD extension is
present, such as FMV.W.W, FADD.S, FSUB.S and so on.

Signed-off-by: Ian Jiang <address@hidden>
---
 target/riscv/insn_trans/trans_rvf.inc.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/target/riscv/insn_trans/trans_rvf.inc.c 
b/target/riscv/insn_trans/trans_rvf.inc.c
index e23cd639a6..3bfd8881e7 100644
--- a/target/riscv/insn_trans/trans_rvf.inc.c
+++ b/target/riscv/insn_trans/trans_rvf.inc.c
@@ -23,6 +23,20 @@
         return false;                       \
 } while (0)
 
+/*
+ * RISC-V requires NaN-boxing of narrower width floating
+ * point values.  This applies when a 32-bit value is
+ * assigned to a 64-bit FP register.  Thus this does not
+ * apply when the RVD extension is not present.
+ */
+static void gen_nanbox_fpr(DisasContext *ctx, int regno)
+{
+    if (has_ext(ctx, RVD)) {
+        tcg_gen_ori_i64(cpu_fpr[regno], cpu_fpr[regno],
+                        MAKE_64BIT_MASK(32, 32));
+    }
+}
+
 static bool trans_flw(DisasContext *ctx, arg_flw *a)
 {
     TCGv t0 = tcg_temp_new();
@@ -32,8 +46,7 @@ static bool trans_flw(DisasContext *ctx, arg_flw *a)
     tcg_gen_addi_tl(t0, t0, a->imm);
 
     tcg_gen_qemu_ld_i64(cpu_fpr[a->rd], t0, ctx->mem_idx, MO_TEUL);
-    /* RISC-V requires NaN-boxing of narrower width floating point values */
-    tcg_gen_ori_i64(cpu_fpr[a->rd], cpu_fpr[a->rd], 0xffffffff00000000ULL);
+    gen_nanbox_fpr(ctx, a->rd);
 
     tcg_temp_free(t0);
     mark_fs_dirty(ctx);
-- 
2.17.1