From a454ea1e6d40bbd4632e4e66de90e802ae47a68e Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Mon, 14 Jun 2021 16:09:19 +0100 Subject: [PATCH] target/arm: Implement MVE LETP insn Implement the MVE LETP insn. This is like the existing LE loop-end insn, but it must perform an FPU-enabled check, and on loop-exit it resets LTPSIZE to 4. To accommodate the requirement to do something on loop-exit, we drop the use of condlabel and instead manage both the TB exits manually, in the same way we already do in trans_WLS(). The other MVE-specific change to the LE insn is that we must raise an INVSTATE UsageFault insn if LTPSIZE is not 4. Signed-off-by: Peter Maydell Reviewed-by: Richard Henderson Message-id: 20210614151007.4545-10-peter.maydell@linaro.org --- target/arm/t32.decode | 2 +- target/arm/translate.c | 104 +++++++++++++++++++++++++++++++++++++---- 2 files changed, 97 insertions(+), 9 deletions(-) diff --git a/target/arm/t32.decode b/target/arm/t32.decode index 1b75db5065..0f9326c724 100644 --- a/target/arm/t32.decode +++ b/target/arm/t32.decode @@ -674,7 +674,7 @@ BL 1111 0. .......... 11.1 ............ @branch24 DLS 1111 0 0000 100 rn:4 1110 0000 0000 0001 size=4 WLS 1111 0 0000 100 rn:4 1100 . .......... 1 imm=%lob_imm size=4 { - LE 1111 0 0000 0 f:1 0 1111 1100 . .......... 1 imm=%lob_imm + LE 1111 0 0000 0 f:1 tp:1 1111 1100 . .......... 1 imm=%lob_imm # This is WLSTP WLS 1111 0 0000 0 size:2 rn:4 1100 . .......... 1 imm=%lob_imm } diff --git a/target/arm/translate.c b/target/arm/translate.c index 1ad0e61fac..a51e882b86 100644 --- a/target/arm/translate.c +++ b/target/arm/translate.c @@ -8223,25 +8223,113 @@ static bool trans_LE(DisasContext *s, arg_LE *a) * any faster. */ TCGv_i32 tmp; + TCGLabel *loopend; + bool fpu_active; if (!dc_isar_feature(aa32_lob, s)) { return false; } + if (a->f && a->tp) { + return false; + } + if (s->condexec_mask) { + /* + * LE in an IT block is CONSTRAINED UNPREDICTABLE; + * we choose to UNDEF, because otherwise our use of + * gen_goto_tb(1) would clash with the use of TB exit 1 + * in the dc->condjmp condition-failed codepath in + * arm_tr_tb_stop() and we'd get an assertion. + */ + return false; + } + if (a->tp) { + /* LETP */ + if (!dc_isar_feature(aa32_mve, s)) { + return false; + } + if (!vfp_access_check(s)) { + s->eci_handled = true; + return true; + } + } /* LE/LETP is OK with ECI set and leaves it untouched */ s->eci_handled = true; - if (!a->f) { - /* Not loop-forever. If LR <= 1 this is the last loop: do nothing. */ - arm_gen_condlabel(s); - tcg_gen_brcondi_i32(TCG_COND_LEU, cpu_R[14], 1, s->condlabel); - /* Decrement LR */ - tmp = load_reg(s, 14); - tcg_gen_addi_i32(tmp, tmp, -1); - store_reg(s, 14, tmp); + /* + * With MVE, LTPSIZE might not be 4, and we must emit an INVSTATE + * UsageFault exception for the LE insn in that case. Note that we + * are not directly checking FPSCR.LTPSIZE but instead check the + * pseudocode LTPSIZE() function, which returns 4 if the FPU is + * not currently active (ie ActiveFPState() returns false). We + * can identify not-active purely from our TB state flags, as the + * FPU is active only if: + * the FPU is enabled + * AND lazy state preservation is not active + * AND we do not need a new fp context (this is the ASPEN/FPCA check) + * + * Usually we don't need to care about this distinction between + * LTPSIZE and FPSCR.LTPSIZE, because the code in vfp_access_check() + * will either take an exception or clear the conditions that make + * the FPU not active. But LE is an unusual case of a non-FP insn + * that looks at LTPSIZE. + */ + fpu_active = !s->fp_excp_el && !s->v7m_lspact && !s->v7m_new_fp_ctxt_needed; + + if (!a->tp && dc_isar_feature(aa32_mve, s) && fpu_active) { + /* Need to do a runtime check for LTPSIZE != 4 */ + TCGLabel *skipexc = gen_new_label(); + tmp = load_cpu_field(v7m.ltpsize); + tcg_gen_brcondi_i32(TCG_COND_EQ, tmp, 4, skipexc); + tcg_temp_free_i32(tmp); + gen_exception_insn(s, s->pc_curr, EXCP_INVSTATE, syn_uncategorized(), + default_exception_el(s)); + gen_set_label(skipexc); + } + + if (a->f) { + /* Loop-forever: just jump back to the loop start */ + gen_jmp(s, read_pc(s) - a->imm); + return true; + } + + /* + * Not loop-forever. If LR <= loop-decrement-value this is the last loop. + * For LE, we know at this point that LTPSIZE must be 4 and the + * loop decrement value is 1. For LETP we need to calculate the decrement + * value from LTPSIZE. + */ + loopend = gen_new_label(); + if (!a->tp) { + tcg_gen_brcondi_i32(TCG_COND_LEU, cpu_R[14], 1, loopend); + tcg_gen_addi_i32(cpu_R[14], cpu_R[14], -1); + } else { + /* + * Decrement by 1 << (4 - LTPSIZE). We need to use a TCG local + * so that decr stays live after the brcondi. + */ + TCGv_i32 decr = tcg_temp_local_new_i32(); + TCGv_i32 ltpsize = load_cpu_field(v7m.ltpsize); + tcg_gen_sub_i32(decr, tcg_constant_i32(4), ltpsize); + tcg_gen_shl_i32(decr, tcg_constant_i32(1), decr); + tcg_temp_free_i32(ltpsize); + + tcg_gen_brcond_i32(TCG_COND_LEU, cpu_R[14], decr, loopend); + + tcg_gen_sub_i32(cpu_R[14], cpu_R[14], decr); + tcg_temp_free_i32(decr); } /* Jump back to the loop start */ gen_jmp(s, read_pc(s) - a->imm); + + gen_set_label(loopend); + if (a->tp) { + /* Exits from tail-pred loops must reset LTPSIZE to 4 */ + tmp = tcg_const_i32(4); + store_cpu_field(tmp, v7m.ltpsize); + } + /* End TB, continuing to following insn */ + gen_jmp_tb(s, s->base.pc_next, 1); return true; }