From eb20dafdbff92063a88624176fdc396e01961bf3 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Thu, 10 Dec 2020 20:14:32 +0000 Subject: [PATCH] target/arm: Implement FPCXT_NS fp system register Implement the v8.1M FPCXT_NS floating-point system register. This is a little more complicated than FPCXT_S, because it has specific handling for "current FP state is inactive", and it only wants to do PreserveFPState(), not the full set of actions done by ExecuteFPCheck() which vfp_access_check() implements. Signed-off-by: Peter Maydell Reviewed-by: Richard Henderson Message-id: 20201210201433.26262-4-peter.maydell@linaro.org --- target/arm/translate-vfp.c.inc | 102 ++++++++++++++++++++++++++++++++- 1 file changed, 99 insertions(+), 3 deletions(-) diff --git a/target/arm/translate-vfp.c.inc b/target/arm/translate-vfp.c.inc index 8b4cfd68ca..10766f210c 100644 --- a/target/arm/translate-vfp.c.inc +++ b/target/arm/translate-vfp.c.inc @@ -663,6 +663,7 @@ static FPSysRegCheckResult fp_sysreg_checks(DisasContext *s, int regno) } break; case ARM_VFP_FPCXT_S: + case ARM_VFP_FPCXT_NS: if (!arm_dc_feature(s, ARM_FEATURE_V8_1M)) { return false; } @@ -674,13 +675,48 @@ static FPSysRegCheckResult fp_sysreg_checks(DisasContext *s, int regno) return FPSysRegCheckFailed; } - if (!vfp_access_check(s)) { + /* + * FPCXT_NS is a special case: it has specific handling for + * "current FP state is inactive", and must do the PreserveFPState() + * but not the usual full set of actions done by ExecuteFPCheck(). + * So we don't call vfp_access_check() and the callers must handle this. + */ + if (regno != ARM_VFP_FPCXT_NS && !vfp_access_check(s)) { return FPSysRegCheckDone; } - return FPSysRegCheckContinue; } +static void gen_branch_fpInactive(DisasContext *s, TCGCond cond, + TCGLabel *label) +{ + /* + * FPCXT_NS is a special case: it has specific handling for + * "current FP state is inactive", and must do the PreserveFPState() + * but not the usual full set of actions done by ExecuteFPCheck(). + * We don't have a TB flag that matches the fpInactive check, so we + * do it at runtime as we don't expect FPCXT_NS accesses to be frequent. + * + * Emit code that checks fpInactive and does a conditional + * branch to label based on it: + * if cond is TCG_COND_NE then branch if fpInactive != 0 (ie if inactive) + * if cond is TCG_COND_EQ then branch if fpInactive == 0 (ie if active) + */ + assert(cond == TCG_COND_EQ || cond == TCG_COND_NE); + + /* fpInactive = FPCCR_NS.ASPEN == 1 && CONTROL.FPCA == 0 */ + TCGv_i32 aspen, fpca; + aspen = load_cpu_field(v7m.fpccr[M_REG_NS]); + fpca = load_cpu_field(v7m.control[M_REG_S]); + tcg_gen_andi_i32(aspen, aspen, R_V7M_FPCCR_ASPEN_MASK); + tcg_gen_xori_i32(aspen, aspen, R_V7M_FPCCR_ASPEN_MASK); + tcg_gen_andi_i32(fpca, fpca, R_V7M_CONTROL_FPCA_MASK); + tcg_gen_or_i32(fpca, fpca, aspen); + tcg_gen_brcondi_i32(tcg_invert_cond(cond), fpca, 0, label); + tcg_temp_free_i32(aspen); + tcg_temp_free_i32(fpca); +} + static bool gen_M_fp_sysreg_write(DisasContext *s, int regno, fp_sysreg_loadfn *loadfn, @@ -688,6 +724,7 @@ static bool gen_M_fp_sysreg_write(DisasContext *s, int regno, { /* Do a write to an M-profile floating point system register */ TCGv_i32 tmp; + TCGLabel *lab_end = NULL; switch (fp_sysreg_checks(s, regno)) { case FPSysRegCheckFailed: @@ -721,6 +758,13 @@ static bool gen_M_fp_sysreg_write(DisasContext *s, int regno, tcg_temp_free_i32(tmp); break; } + case ARM_VFP_FPCXT_NS: + lab_end = gen_new_label(); + /* fpInactive case: write is a NOP, so branch to end */ + gen_branch_fpInactive(s, TCG_COND_NE, lab_end); + /* !fpInactive: PreserveFPState(), and reads same as FPCXT_S */ + gen_preserve_fp_state(s); + /* fall through */ case ARM_VFP_FPCXT_S: { TCGv_i32 sfpa, control; @@ -744,6 +788,9 @@ static bool gen_M_fp_sysreg_write(DisasContext *s, int regno, default: g_assert_not_reached(); } + if (lab_end) { + gen_set_label(lab_end); + } return true; } @@ -753,6 +800,8 @@ static bool gen_M_fp_sysreg_read(DisasContext *s, int regno, { /* Do a read from an M-profile floating point system register */ TCGv_i32 tmp; + TCGLabel *lab_end = NULL; + bool lookup_tb = false; switch (fp_sysreg_checks(s, regno)) { case FPSysRegCheckFailed: @@ -811,12 +860,59 @@ static bool gen_M_fp_sysreg_read(DisasContext *s, int regno, fpscr = load_cpu_field(v7m.fpdscr[M_REG_NS]); gen_helper_vfp_set_fpscr(cpu_env, fpscr); tcg_temp_free_i32(fpscr); - gen_lookup_tb(s); + lookup_tb = true; + break; + } + case ARM_VFP_FPCXT_NS: + { + TCGv_i32 control, sfpa, fpscr, fpdscr, zero; + TCGLabel *lab_active = gen_new_label(); + + lookup_tb = true; + + gen_branch_fpInactive(s, TCG_COND_EQ, lab_active); + /* fpInactive case: reads as FPDSCR_NS */ + TCGv_i32 tmp = load_cpu_field(v7m.fpdscr[M_REG_NS]); + storefn(s, opaque, tmp); + lab_end = gen_new_label(); + tcg_gen_br(lab_end); + + gen_set_label(lab_active); + /* !fpInactive: Reads the same as FPCXT_S, but side effects differ */ + gen_preserve_fp_state(s); + tmp = tcg_temp_new_i32(); + sfpa = tcg_temp_new_i32(); + fpscr = tcg_temp_new_i32(); + gen_helper_vfp_get_fpscr(fpscr, cpu_env); + tcg_gen_andi_i32(tmp, fpscr, ~FPCR_NZCV_MASK); + control = load_cpu_field(v7m.control[M_REG_S]); + tcg_gen_andi_i32(sfpa, control, R_V7M_CONTROL_SFPA_MASK); + tcg_gen_shli_i32(sfpa, sfpa, 31 - R_V7M_CONTROL_SFPA_SHIFT); + tcg_gen_or_i32(tmp, tmp, sfpa); + tcg_temp_free_i32(control); + /* Store result before updating FPSCR, in case it faults */ + storefn(s, opaque, tmp); + /* If SFPA is zero then set FPSCR from FPDSCR_NS */ + fpdscr = load_cpu_field(v7m.fpdscr[M_REG_NS]); + zero = tcg_const_i32(0); + tcg_gen_movcond_i32(TCG_COND_EQ, fpscr, sfpa, zero, fpdscr, fpscr); + gen_helper_vfp_set_fpscr(cpu_env, fpscr); + tcg_temp_free_i32(zero); + tcg_temp_free_i32(sfpa); + tcg_temp_free_i32(fpdscr); + tcg_temp_free_i32(fpscr); break; } default: g_assert_not_reached(); } + + if (lab_end) { + gen_set_label(lab_end); + } + if (lookup_tb) { + gen_lookup_tb(s); + } return true; }