From fe6fa228a71f0eb8b8ee315452e6a7736c537b1f Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Thu, 19 Nov 2020 21:56:09 +0000 Subject: [PATCH] target/arm: Implement new v8.1M VLLDM and VLSTM encodings v8.1M adds new encodings of VLLDM and VLSTM (where bit 7 is set). The only difference is that: * the old T1 encodings UNDEF if the implementation implements 32 Dregs (this is currently architecturally impossible for M-profile) * the new T2 encodings have the implementation-defined option to read from memory (discarding the data) or write UNKNOWN values to memory for the stack slots that would be D16-D31 We choose not to make those accesses, so for us the two instructions behave identically assuming they don't UNDEF. Signed-off-by: Peter Maydell Reviewed-by: Richard Henderson Message-id: 20201119215617.29887-21-peter.maydell@linaro.org --- target/arm/m-nocp.decode | 2 +- target/arm/translate-vfp.c.inc | 25 +++++++++++++++++++++++++ 2 files changed, 26 insertions(+), 1 deletion(-) diff --git a/target/arm/m-nocp.decode b/target/arm/m-nocp.decode index ccd62e8739..6699626d7c 100644 --- a/target/arm/m-nocp.decode +++ b/target/arm/m-nocp.decode @@ -36,7 +36,7 @@ { # Special cases which do not take an early NOCP: VLLDM and VLSTM - VLLDM_VLSTM 1110 1100 001 l:1 rn:4 0000 1010 0000 0000 + VLLDM_VLSTM 1110 1100 001 l:1 rn:4 0000 1010 op:1 000 0000 # VSCCLRM (new in v8.1M) is similar: VSCCLRM 1110 1100 1.01 1111 .... 1011 imm:7 0 vd=%vd_dp size=3 VSCCLRM 1110 1100 1.01 1111 .... 1010 imm:8 vd=%vd_sp size=2 diff --git a/target/arm/translate-vfp.c.inc b/target/arm/translate-vfp.c.inc index 808b407705..0db936084b 100644 --- a/target/arm/translate-vfp.c.inc +++ b/target/arm/translate-vfp.c.inc @@ -3721,6 +3721,31 @@ static bool trans_VLLDM_VLSTM(DisasContext *s, arg_VLLDM_VLSTM *a) !arm_dc_feature(s, ARM_FEATURE_V8)) { return false; } + + if (a->op) { + /* + * T2 encoding ({D0-D31} reglist): v8.1M and up. We choose not + * to take the IMPDEF option to make memory accesses to the stack + * slots that correspond to the D16-D31 registers (discarding + * read data and writing UNKNOWN values), so for us the T2 + * encoding behaves identically to the T1 encoding. + */ + if (!arm_dc_feature(s, ARM_FEATURE_V8_1M)) { + return false; + } + } else { + /* + * T1 encoding ({D0-D15} reglist); undef if we have 32 Dregs. + * This is currently architecturally impossible, but we add the + * check to stay in line with the pseudocode. Note that we must + * emit code for the UNDEF so it takes precedence over the NOCP. + */ + if (dc_isar_feature(aa32_simd_r32, s)) { + unallocated_encoding(s); + return true; + } + } + /* * If not secure, UNDEF. We must emit code for this * rather than returning false so that this takes