From a5f533909e746ca6e534b232fb42c9c6fd81b468 Mon Sep 17 00:00:00 2001 From: Leon Alrae Date: Thu, 29 Jan 2015 16:15:00 +0000 Subject: target-mips: fix hflags modified in delay / forbidden slot All instructions which may change hflags terminate tb. However, this doesn't work if such an instruction is placed in delay or forbidden slot. gen_branch() clears MIPS_HFLAG_BMASK in ctx->hflags and then generates code to overwrite hflags with ctx->hflags, consequently we loose any execution-time hflags modifications. For example, in the following scenario hflag related to Status.CU1 will not be updated: /* Set Status.CU1 in delay slot */ mfc0 $24, $12, 0 lui $25, 0x2000 or $25, $25, $24 b check_Status_CU1 mtc0 $25, $12, 0 With this change we clear MIPS_HFLAG_BMASK in execution-time hflags if instruction in delay or forbidden slot wants to terminate tb for some reason (i.e. ctx->bstate != BS_NONE). Also, die early and loudly if "unknown branch" is encountered as this should never happen. Signed-off-by: Leon Alrae --- target-mips/translate.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) (limited to 'target-mips') diff --git a/target-mips/translate.c b/target-mips/translate.c index 0e2443a..a91e503 100644 --- a/target-mips/translate.c +++ b/target-mips/translate.c @@ -10531,14 +10531,25 @@ static void gen_rdhwr(DisasContext *ctx, int rt, int rd) tcg_temp_free(t0); } +static inline void clear_branch_hflags(DisasContext *ctx) +{ + ctx->hflags &= ~MIPS_HFLAG_BMASK; + if (ctx->bstate == BS_NONE) { + save_cpu_state(ctx, 0); + } else { + /* it is not safe to save ctx->hflags as hflags may be changed + in execution time by the instruction in delay / forbidden slot. */ + tcg_gen_andi_i32(hflags, hflags, ~MIPS_HFLAG_BMASK); + } +} + static void gen_branch(DisasContext *ctx, int insn_bytes) { if (ctx->hflags & MIPS_HFLAG_BMASK) { int proc_hflags = ctx->hflags & MIPS_HFLAG_BMASK; /* Branches completion */ - ctx->hflags &= ~MIPS_HFLAG_BMASK; + clear_branch_hflags(ctx); ctx->bstate = BS_BRANCH; - save_cpu_state(ctx, 0); /* FIXME: Need to clear can_do_io. */ switch (proc_hflags & MIPS_HFLAG_BMASK_BASE) { case MIPS_HFLAG_FBNSLOT: @@ -10596,8 +10607,8 @@ static void gen_branch(DisasContext *ctx, int insn_bytes) tcg_gen_exit_tb(0); break; default: - MIPS_DEBUG("unknown branch"); - break; + fprintf(stderr, "unknown branch 0x%x\n", proc_hflags); + abort(); } } } -- cgit v1.1