arm: Add support for armv8 CRC32 instructions

This patch introduces the ARM A32/T32/A64 CRC Instructions, which are
mandatory since ARMv8.1. The UNPREDICTABLE behaviours are implemented as
follows:
1) CRC32(C)X (64 bit) instructions are decoded as Undefined in Aarch32
2) The instructions support predication in Aarch32
3) Using R15(PC) as source/dest operand is permitted in Aarch32

Change-Id: Iaf29b05874e1370c7615da79a07f111ded17b6cc
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Giacomo Gabrielli <giacomo.gabrielli@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/5521
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

1 files changed, 31 insertions, 0 deletions

diff --git a/src/arch/arm/isa/formats/misc.isa b/src/arch/arm/isa/formats/misc.isa
index 43a7cc975..26681e40f 100644
--- a/src/arch/arm/isa/formats/misc.isa
+++ b/src/arch/arm/isa/formats/misc.isa
@@ -38,6 +38,37 @@
 // Authors: Gabe Black
 //          Giacomo Gabrielli
 
+def format Crc32() {{
+    decode_block = '''
+    {
+        const IntRegIndex rm = (IntRegIndex)(uint32_t)bits(machInst, 3, 0);
+        const IntRegIndex rn = (IntRegIndex)(uint32_t)bits(machInst, 19, 16);
+        const IntRegIndex rd = (IntRegIndex)(uint32_t)bits(machInst, 15, 12);
+
+        uint8_t c_poly = bits(machInst, 9);
+        uint8_t sz = bits(machInst, 22, 21);
+        uint8_t crc_select = (c_poly << 2) | sz;
+
+        switch(crc_select) {
+          case 0x0:
+            return new Crc32b(machInst, rd, rn, rm);
+          case 0x1:
+            return new Crc32h(machInst, rd, rn, rm);
+          case 0x2:
+            return new Crc32w(machInst, rd, rn, rm);
+          case 0x4:
+            return new Crc32cb(machInst, rd, rn, rm);
+          case 0x5:
+            return new Crc32ch(machInst, rd, rn, rm);
+          case 0x6:
+            return new Crc32cw(machInst, rd, rn, rm);
+          default:
+            return new Unknown(machInst);
+        }
+    }
+    '''
+}};
+
 def format ArmERet() {{
     decode_block = "return new Eret(machInst);"
 }};