[PATCH] D78190: Add Bfloat IR type

Wed Apr 15 10:57:06 PDT 2020

craig.topper added a comment.

Is this missing support in SelectionDAG's type system? MachineValueType.h and ValueType.h or is that coming in another patch?

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Comment at: llvm/docs/LangRef.rst:2896
+   * - ``bfloat``
+     - 16-bit brain floating-point value (10-bit mantissa)
+
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bfloat doesn't have 10-bits of mantissa. its 1 bit of sign, 8-bits of exponent and 7-bits of mantissa.

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Comment at: llvm/lib/Support/APFloat.cpp:4837

 APFloat APFloat::getAllOnesValue(unsigned BitWidth, bool isIEEE) {
   if (isIEEE) {
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This is a bit of strange interace. I wonder if it wouldn't be possible to have the callers pass the semantics instead of the bitwidth and then this function could get the bitwidth from the semantics. It looks like there aren't many callers. I believe the one in Constants.cpp could get the semantics from getFltSemantics on the Type. Probably similar could be done at other callers?

Repository:
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  https://reviews.llvm.org/D78190/new/

https://reviews.llvm.org/D78190