In vfp.decode we have the names of the VFNMA and VFNMS instructions the wrong way around. The architecture says that bit 6 is the 'op' bit, which is 1 for VFNMA and 0 for VFNMS, but we label these two lines of decode the other way around. This doesn't cause any user-visible problem because in the handling of these functions in translate-vfp.c we give VFNMA the behaviour specified for VFNMS and vice-versa, but it's confusing when reading the code.
Switch the names of the VFP VFNMA and VFNMS instructions in the decode file and flip the behaviour also. NB: the instructions VFMA and VFMS *are* decoded with op=0 for VFMA and op=1 for VFMS; the confusion probably arose because we assumed VFNMA and VFNMS to be the same way around. Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2536 Signed-off-by: Peter Maydell <peter.mayd...@linaro.org> Message-id: 20240830152156.2046590-1-peter.mayd...@linaro.org Reviewed-by: Richard Henderson <richard.hender...@linaro.org> --- target/arm/tcg/vfp.decode | 12 ++++++------ target/arm/tcg/translate-vfp.c | 8 ++++---- 2 files changed, 10 insertions(+), 10 deletions(-) diff --git a/target/arm/tcg/vfp.decode b/target/arm/tcg/vfp.decode index 5405e80197b..2dd87a27089 100644 --- a/target/arm/tcg/vfp.decode +++ b/target/arm/tcg/vfp.decode @@ -141,18 +141,18 @@ VDIV_dp ---- 1110 1.00 .... .... 1011 .0.0 .... @vfp_dnm_d VFMA_hp ---- 1110 1.10 .... .... 1001 .0. 0 .... @vfp_dnm_s VFMS_hp ---- 1110 1.10 .... .... 1001 .1. 0 .... @vfp_dnm_s -VFNMA_hp ---- 1110 1.01 .... .... 1001 .0. 0 .... @vfp_dnm_s -VFNMS_hp ---- 1110 1.01 .... .... 1001 .1. 0 .... @vfp_dnm_s +VFNMS_hp ---- 1110 1.01 .... .... 1001 .0. 0 .... @vfp_dnm_s +VFNMA_hp ---- 1110 1.01 .... .... 1001 .1. 0 .... @vfp_dnm_s VFMA_sp ---- 1110 1.10 .... .... 1010 .0. 0 .... @vfp_dnm_s VFMS_sp ---- 1110 1.10 .... .... 1010 .1. 0 .... @vfp_dnm_s -VFNMA_sp ---- 1110 1.01 .... .... 1010 .0. 0 .... @vfp_dnm_s -VFNMS_sp ---- 1110 1.01 .... .... 1010 .1. 0 .... @vfp_dnm_s +VFNMS_sp ---- 1110 1.01 .... .... 1010 .0. 0 .... @vfp_dnm_s +VFNMA_sp ---- 1110 1.01 .... .... 1010 .1. 0 .... @vfp_dnm_s VFMA_dp ---- 1110 1.10 .... .... 1011 .0.0 .... @vfp_dnm_d VFMS_dp ---- 1110 1.10 .... .... 1011 .1.0 .... @vfp_dnm_d -VFNMA_dp ---- 1110 1.01 .... .... 1011 .0.0 .... @vfp_dnm_d -VFNMS_dp ---- 1110 1.01 .... .... 1011 .1.0 .... @vfp_dnm_d +VFNMS_dp ---- 1110 1.01 .... .... 1011 .0.0 .... @vfp_dnm_d +VFNMA_dp ---- 1110 1.01 .... .... 1011 .1.0 .... @vfp_dnm_d VMOV_imm_hp ---- 1110 1.11 .... .... 1001 0000 .... \ vd=%vd_sp imm=%vmov_imm diff --git a/target/arm/tcg/translate-vfp.c b/target/arm/tcg/translate-vfp.c index cd5b8483576..b6fa28a7bf6 100644 --- a/target/arm/tcg/translate-vfp.c +++ b/target/arm/tcg/translate-vfp.c @@ -2190,8 +2190,8 @@ static bool do_vfm_sp(DisasContext *s, arg_VFMA_sp *a, bool neg_n, bool neg_d) static bool do_vfm_dp(DisasContext *s, arg_VFMA_dp *a, bool neg_n, bool neg_d) { /* - * VFNMA : fd = muladd(-fd, fn, fm) - * VFNMS : fd = muladd(-fd, -fn, fm) + * VFNMA : fd = muladd(-fd, -fn, fm) + * VFNMS : fd = muladd(-fd, fn, fm) * VFMA : fd = muladd( fd, fn, fm) * VFMS : fd = muladd( fd, -fn, fm) * @@ -2262,8 +2262,8 @@ static bool do_vfm_dp(DisasContext *s, arg_VFMA_dp *a, bool neg_n, bool neg_d) #define MAKE_VFM_TRANS_FNS(PREC) \ MAKE_ONE_VFM_TRANS_FN(VFMA, PREC, false, false) \ MAKE_ONE_VFM_TRANS_FN(VFMS, PREC, true, false) \ - MAKE_ONE_VFM_TRANS_FN(VFNMA, PREC, false, true) \ - MAKE_ONE_VFM_TRANS_FN(VFNMS, PREC, true, true) + MAKE_ONE_VFM_TRANS_FN(VFNMS, PREC, false, true) \ + MAKE_ONE_VFM_TRANS_FN(VFNMA, PREC, true, true) MAKE_VFM_TRANS_FNS(hp) MAKE_VFM_TRANS_FNS(sp) -- 2.34.1
