bf16_to_float: Fix strict aliasing violation

* This function was accessing a uint32_t with a pointer to float which
violates the strict aliasing rules. With GCC 11, this leads to a
-Wuninitialized warning, which causes the build to fail.

* This change uses memcpy instead of type punning which fixes the strict
aliasing violation, thereby fixing the build with GCC 11.

* Resolves MLCE-420

Change-Id: I9fda5f1e68ac68490b244bd40380910adae00bf3
Signed-off-by: Pablo Marquez Tello <pablo.tello@arm.com>
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/5318
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Manuel Bottini <manuel.bottini@arm.com>
Reviewed-by: Georgios Pinitas <georgios.pinitas@arm.com>

1 files changed, 6 insertions, 5 deletions

diff --git a/support/Bfloat16.h b/support/Bfloat16.h
index d57d8ce9ee..173f2d16e2 100644
--- a/support/Bfloat16.h
+++ b/support/Bfloat16.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020 Arm Limited.
+ * Copyright (c) 2020-2021 Arm Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -25,6 +25,7 @@
 #define ARM_COMPUTE_BFLOAT16_H
 
 #include <cstdint>
+#include <cstring>
 
 namespace arm_compute
 {
@@ -70,9 +71,9 @@ inline uint16_t float_to_bf16(const float v)
 inline float bf16_to_float(const uint16_t &v)
 {
     const uint32_t lv = (v << 16);
-    const float   *fp = reinterpret_cast<const float *>(&lv);
-
-    return *fp;
+    float          fp;
+    memcpy(&fp, &lv, sizeof(lv));
+    return fp;
 }
 }
 
@@ -137,4 +138,4 @@ private:
     uint16_t value;
 };
 } // namespace arm_compute
-#endif /* ARM_COMPUTE_BFLOAT16_H */
\ No newline at end of file
+#endif /* ARM_COMPUTE_BFLOAT16_H */