[Qemu-devel] [PATCH v8 52/87] target/mips: Add handling of branch delay slots for nanoMIPS

[Aleksandar Markovic]

From: Matthew Fortune <address@hidden>

ISA mode bit (LSB of address) is no longer required but is also
masked to allow for tools transition. The flag has_isa_mode has the
key role in the implementation.

Signed-off-by: Yongbok Kim <address@hidden>
Signed-off-by: Aleksandar Markovic <address@hidden>
Signed-off-by: Stefan Markovic <address@hidden>
---
 target/mips/translate.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/target/mips/translate.c b/target/mips/translate.c
index 3282fca..e4427e4 100644
--- a/target/mips/translate.c
+++ b/target/mips/translate.c
@@ -1471,6 +1471,7 @@ typedef struct DisasContext {
     bool mrp;
     bool nan2008;
     bool abs2008;
+    bool has_isa_mode;
 } DisasContext;
 
 #define DISAS_STOP       DISAS_TARGET_0
@@ -4674,7 +4675,7 @@ static void gen_compute_branch (DisasContext *ctx, 
uint32_t opc,
 
     if (blink > 0) {
         int post_delay = insn_bytes + delayslot_size;
-        int lowbit = !!(ctx->hflags & MIPS_HFLAG_M16);
+        int lowbit = ctx->has_isa_mode && !!(ctx->hflags & MIPS_HFLAG_M16);
 
         tcg_gen_movi_tl(cpu_gpr[blink],
                         ctx->base.pc_next + post_delay + lowbit);
@@ -11171,7 +11172,7 @@ static void gen_compute_compact_branch(DisasContext 
*ctx, uint32_t opc,
     int bcond_compute = 0;
     TCGv t0 = tcg_temp_new();
     TCGv t1 = tcg_temp_new();
-    int m16_lowbit = (ctx->hflags & MIPS_HFLAG_M16) != 0;
+    int m16_lowbit = ctx->has_isa_mode && ((ctx->hflags & MIPS_HFLAG_M16) != 
0);
 
     if (ctx->hflags & MIPS_HFLAG_BMASK) {
 #ifdef MIPS_DEBUG_DISAS
@@ -24970,6 +24971,7 @@ static void mips_tr_init_disas_context(DisasContextBase 
*dcbase, CPUState *cs)
     ctx->mrp = (env->CP0_Config5 >> CP0C5_MRP) & 1;
     ctx->nan2008 = (env->active_fpu.fcr31 >> FCR31_NAN2008) & 1;
     ctx->abs2008 = (env->active_fpu.fcr31 >> FCR31_ABS2008) & 1;
+    ctx->has_isa_mode = ((env->CP0_Config3 >> CP0C3_MMAR) & 0x7) < 3;
     restore_cpu_state(env, ctx);
 #ifdef CONFIG_USER_ONLY
         ctx->mem_idx = MIPS_HFLAG_UM;
-- 
2.7.4