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 <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20201119215617.29887-21-peter.maydell@linaro.org
diff --git a/target/arm/m-nocp.decode b/target/arm/m-nocp.decode
index ccd62e8..6699626 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 808b407..0db9360 100644
--- a/target/arm/translate-vfp.c.inc
+++ b/target/arm/translate-vfp.c.inc
@@ -3721,6 +3721,31 @@
!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
