target/riscv: Fix LMUL check to use VLEN
The previous check was failing with:
VLEN=128 ELEN = 64 SEW = 16 and LMUL = 1/8 which is a
valid combination.
Fix the check to allow valid combinations when VLEN is a multiple of
ELEN.
From the specification:
"In general, the requirement is to support LMUL ≥ SEWMIN/ELEN, where
SEWMIN is the narrowest supported SEW value and ELEN is the widest
supported SEW value. In the standard extensions, SEWMIN=8. For standard
vector extensions with ELEN=32, fractional LMULs of 1/2 and 1/4 must be
supported. For standard vector extensions with ELEN=64, fractional LMULs
of 1/2, 1/4, and 1/8 must be supported." Elsewhere in the specification
it makes clear that VLEN>=ELEN.
From inspection this new check allows:
VLEN=ELEN=64 1/2, 1/4, 1/8 for SEW >=8
VLEN=ELEN=32 1/2, 1/4 for SEW >=8
Fixes: d9b7609a1fb2 ("target/riscv: rvv-1.0: configure instructions")
Signed-off-by: Rob Bradford <rbradford@rivosinc.com>
Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
Message-Id: <20230718131316.12283-2-rbradford@rivosinc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
diff --git a/target/riscv/vector_helper.c b/target/riscv/vector_helper.c
index cfacf2e..4d06754 100644
--- a/target/riscv/vector_helper.c
+++ b/target/riscv/vector_helper.c
@@ -43,9 +43,9 @@
xlen - 1 - R_VTYPE_RESERVED_SHIFT);
if (lmul & 4) {
- /* Fractional LMUL. */
+ /* Fractional LMUL - check LMUL * VLEN >= SEW */
if (lmul == 4 ||
- cpu->cfg.elen >> (8 - lmul) < sew) {
+ cpu->cfg.vlen >> (8 - lmul) < sew) {
vill = true;
}
}
