arch-arm: Add warning when DVM is enabled in the decoder

DVM Ops instructions are micro-architecturally modelled as loads. This
will tamper the effective number of loads stat, so a user should
be careful when interpreting stat results

JIRA: https://gem5.atlassian.net/browse/GEM5-1097

Change-Id: I526cd542ef804111cf6919359c1ce02df6d4710d
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/56605
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/arch/arm/decoder.cc

@@ -65,6 +65,13 @@ Decoder::Decoder(const ArmDecoderParams &params)
     // Initialize SVE vector length
     sveLen = (dynamic_cast<ISA *>(params.isa)
             ->getCurSveVecLenInBitsAtReset() >> 7) - 1;
+
+    if (dvmEnabled) {
+        warn_once(
+            "DVM Ops instructions are micro-architecturally "
+            "modelled as loads. This will tamper the effective "
+            "number of loads stat\n");
+    }
 }
 
 void