target/arm: Introduce PREDDESC field definitions

SVE predicate operations cannot use the "usual" simd_desc
encoding, because the lengths are not a multiple of 8.
But we were abusing the SIMD_* fields to store values anyway.
This abuse broke when SIMD_OPRSZ_BITS was modified in e2e7168a214.

Introduce a new set of field definitions for exclusive use
of predicates, so that it is obvious what kind of predicate
we are manipulating.  To be used in future patches.

Cc: qemu-stable@nongnu.org
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210113062650.593824-2-richard.henderson@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

diff --git a/target/arm/internals.h b/target/arm/internals.h
index 27cc93f..853fa88 100644 (file)
--- a/target/arm/internals.h
+++ b/target/arm/internals.h
@@ -1349,6 +1349,15 @@ void arm_log_exception(int idx);
 #define TAG_GRANULE      (1 << LOG2_TAG_GRANULE)
 
 /*
+ * SVE predicates are 1/8 the size of SVE vectors, and cannot use
+ * the same simd_desc() encoding due to restrictions on size.
+ * Use these instead.
+ */
+FIELD(PREDDESC, OPRSZ, 0, 6)
+FIELD(PREDDESC, ESZ, 6, 2)
+FIELD(PREDDESC, DATA, 8, 24)
+
+/*
  * The SVE simd_data field, for memory ops, contains either
  * rd (5 bits) or a shift count (2 bits).
  */