From 7fbf95a037d79c5e923ffb51ac902dbe9599c87f Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Thu, 10 Dec 2020 20:14:31 +0000 Subject: [PATCH] target/arm: Correct store of FPSCR value via FPCXT_S In commit 64f863baeedc8659 we implemented the v8.1M FPCXT_S register, but we got the write behaviour wrong. On read, this register reads bits [27:0] of FPSCR plus the CONTROL.SFPA bit. On write, it doesn't just write back those bits -- it writes a value to the whole FPSCR, whose upper 4 bits are zeroes. We also incorrectly implemented the write-to-FPSCR as a simple store to vfp.xregs; this skips the "update the softfloat flags" part of the vfp_set_fpscr helper so the value would read back correctly but not actually take effect. Fix both of these things by doing a complete write to the FPSCR using the helper function. Signed-off-by: Peter Maydell Reviewed-by: Richard Henderson Message-id: 20201210201433.26262-3-peter.maydell@linaro.org --- target/arm/translate-vfp.c.inc | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/target/arm/translate-vfp.c.inc b/target/arm/translate-vfp.c.inc index 0db936084b..8b4cfd68ca 100644 --- a/target/arm/translate-vfp.c.inc +++ b/target/arm/translate-vfp.c.inc @@ -723,8 +723,11 @@ static bool gen_M_fp_sysreg_write(DisasContext *s, int regno, } case ARM_VFP_FPCXT_S: { - TCGv_i32 sfpa, control, fpscr; - /* Set FPSCR[27:0] and CONTROL.SFPA from value */ + TCGv_i32 sfpa, control; + /* + * Set FPSCR and CONTROL.SFPA from value; the new FPSCR takes + * bits [27:0] from value and zeroes bits [31:28]. + */ tmp = loadfn(s, opaque); sfpa = tcg_temp_new_i32(); tcg_gen_shri_i32(sfpa, tmp, 31); @@ -732,11 +735,8 @@ static bool gen_M_fp_sysreg_write(DisasContext *s, int regno, tcg_gen_deposit_i32(control, control, sfpa, R_V7M_CONTROL_SFPA_SHIFT, 1); store_cpu_field(control, v7m.control[M_REG_S]); - fpscr = load_cpu_field(vfp.xregs[ARM_VFP_FPSCR]); - tcg_gen_andi_i32(fpscr, fpscr, FPCR_NZCV_MASK); tcg_gen_andi_i32(tmp, tmp, ~FPCR_NZCV_MASK); - tcg_gen_or_i32(fpscr, fpscr, tmp); - store_cpu_field(fpscr, vfp.xregs[ARM_VFP_FPSCR]); + gen_helper_vfp_set_fpscr(cpu_env, tmp); tcg_temp_free_i32(tmp); tcg_temp_free_i32(sfpa); break;