From 24dbc420aae556649f50e645bd94489dab2cc75a Mon Sep 17 00:00:00 2001
From: James Ward <james.ward@arm.com>
Date: Wed, 19 Oct 2022 12:20:31 +0100
Subject: Add BF16 support to reference model

* Upgrade Eigen to 3.4.0 (for bfloat16 support) and add work-
  arounds for reduce.any() and reduce.all() bugs (introduced
  between 3.3.7 and 3.4.0)
* Truncation to bfloat16 now performed in eval() methods

Signed-off-by: James Ward <james.ward@arm.com>
Signed-off-by: Jeremy Johnson <jeremy.johnson@arm.com>
Change-Id: If5f5c988d76d3d30790acf3b97081726b89205fe
---
 reference_model/src/arith_util.h | 89 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)

(limited to 'reference_model/src/arith_util.h')

diff --git a/reference_model/src/arith_util.h b/reference_model/src/arith_util.h
index 554a7a2..33bdeed 100644
--- a/reference_model/src/arith_util.h
+++ b/reference_model/src/arith_util.h
@@ -31,13 +31,18 @@
 #include <math.h>
 #define __STDC_LIMIT_MACROS    //enable min/max of plain data type
 #include "func_debug.h"
+#include "func_config.h"
 #include "inttypes.h"
+#include "tosa_generated.h"
 #include <cassert>
 #include <iostream>
 #include <limits>
 #include <stdint.h>
 #include <typeinfo>
+#include <Eigen/Core>
+#include <bitset>
 
+using namespace tosa;
 using namespace std;
 
 inline size_t _count_one(uint64_t val)
@@ -191,4 +196,88 @@ constexpr T saturate(const uint32_t width, const intmax_t value)
     // clang-format on
 }
 
+inline void float_trunc_bytes(float* src)
+{
+    /* Set the least significant two bytes to zero for the input float value.*/
+    char src_as_bytes[sizeof(float)];
+    memcpy(src_as_bytes, src, sizeof(float));
+
+    if (g_func_config.float_is_big_endian)
+    {
+        src_as_bytes[2] = '\000';
+        src_as_bytes[3] = '\000';
+    }
+    else
+    {
+        src_as_bytes[0] = '\000';
+        src_as_bytes[1] = '\000';
+    }
+
+    memcpy(src, &src_as_bytes, sizeof(float));
+}
+
+inline void truncateFloatToBFloat(float* src, int64_t size) {
+    /* Set the least significant two bytes to zero for each float
+    value in the input src buffer. */
+    ASSERT_MEM(src);
+    ASSERT_MSG(size > 0, "Size of src (representing number of values in src) must be a positive integer.");
+    for (; size != 0; src++, size--)
+    {
+        float_trunc_bytes(src);
+    }
+}
+
+inline bool checkValidBFloat(float src)
+{
+    /* Checks if the least significant two bytes are zero. */
+    ASSERT_MEM(src);
+    char src_as_bytes[sizeof(float)];
+    memcpy(src_as_bytes, &src, sizeof(float));
+
+    if (g_func_config.float_is_big_endian)
+    {
+        return (src_as_bytes[2] == '\000' && src_as_bytes[3] == '\000');
+    }
+    else
+    {
+        return (src_as_bytes[0] == '\000' && src_as_bytes[1] == '\000');
+    }
+}
+
+inline bool float_is_big_endian()
+{
+    /* Compares float values 1.0 and -1.0 by checking whether the
+    negation causes the first or the last byte to change.
+    First byte changing would indicate the float representation
+    is big-endian.*/
+    float f = 1.0;
+    char f_as_bytes[sizeof(float)];
+    memcpy(f_as_bytes, &f, sizeof(float));
+    f = -f;
+    char f_neg_as_bytes[sizeof(float)];
+    memcpy(f_neg_as_bytes, &f, sizeof(float));
+    return f_as_bytes[0] != f_neg_as_bytes[0];
+}
+
+template <DType Dtype>
+float fpTrunc(float f_in)
+{
+    /* Truncates a float value based on the DType it represents.*/
+    switch (Dtype)
+    {
+        case DType_BF16:
+            truncateFloatToBFloat(&f_in, 1);
+            break;
+        case DType_FP16:
+            // TODO(jw): implement FP16 truncate function (no-op placeholder for now)
+            break;
+        case DType_FP32:
+            // No-op for fp32
+            break;
+        default:
+            ASSERT_MSG(false, "DType %s should not be float-truncated.", EnumNameDType(Dtype));
+    }
+    return f_in;
+}
+
 #endif /* _ARITH_UTIL_H */
-- 
cgit v1.2.1