arch-arm: Add FP16 support introduced by Armv8.2-A

This changeset adds support for FP/SIMD instructions with
half-precision floating-point operands.

Change-Id: I4957f111c9c5e5d6a3747fe9d169d394d642fee8
Signed-off-by: Giacomo Gabrielli <giacomo.gabrielli@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/13084
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

1 files changed, 34 insertions, 8 deletions

diff --git a/src/arch/arm/insts/pred_inst.hh b/src/arch/arm/insts/pred_inst.hh
index d2a9f7080..62d1c09ab 100644
--- a/src/arch/arm/insts/pred_inst.hh
+++ b/src/arch/arm/insts/pred_inst.hh
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2010, 2012-2013 ARM Limited
+ * Copyright (c) 2010, 2012-2013, 2017-2018 ARM Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
@@ -158,25 +158,51 @@ simd_modified_imm(bool op, uint8_t cmode, uint8_t data, bool &immValid,
     return bigData;
 }
 
+/** Floating point data types. */
+enum class FpDataType { Fp16, Fp32, Fp64 };
+
 static inline uint64_t
-vfp_modified_imm(uint8_t data, bool wide)
+vfp_modified_imm(uint8_t data, FpDataType dtype)
 {
     uint64_t bigData = data;
     uint64_t repData;
-    if (wide) {
-        repData = bits(data, 6) ? 0xFF : 0;
-        bigData = (bits(bigData, 5, 0) << 48) |
-                  (repData << 54) | (bits(~bigData, 6) << 62) |
-                  (bits(bigData, 7) << 63);
-    } else {
+    switch (dtype) {
+      case FpDataType::Fp16:
+        repData = bits(data, 6) ? 0x3 : 0;
+        bigData = (bits(bigData, 5, 0) << 6) |
+                  (repData << 12) | (bits(~bigData, 6) << 14) |
+                  (bits(bigData, 7) << 15);
+        break;
+      case FpDataType::Fp32:
         repData = bits(data, 6) ? 0x1F : 0;
         bigData = (bits(bigData, 5, 0) << 19) |
                   (repData << 25) | (bits(~bigData, 6) << 30) |
                   (bits(bigData, 7) << 31);
+        break;
+      case FpDataType::Fp64:
+        repData = bits(data, 6) ? 0xFF : 0;
+        bigData = (bits(bigData, 5, 0) << 48) |
+                  (repData << 54) | (bits(~bigData, 6) << 62) |
+                  (bits(bigData, 7) << 63);
+        break;
+      default:
+        assert(0);
     }
     return bigData;
 }
 
+static inline FpDataType
+decode_fp_data_type(uint8_t encoding)
+{
+    switch (encoding) {
+      case 1: return FpDataType::Fp16;
+      case 2: return FpDataType::Fp32;
+      case 3: return FpDataType::Fp64;
+      default:
+        panic(
+            "Invalid floating point data type in VFP/SIMD or SVE instruction");
+    }
+}
 
 /**
  * Base class for predicated integer operations.