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CodeGen: extend f16 conversions to permit types > float.

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This makes the two intrinsics @llvm.convert.from.f16 and
@llvm.convert.to.f16 accept types other than simple "float". This is
only strictly needed for the truncate operation, since otherwise
double rounding occurs and there's no way to represent the strict IEEE
conversion. However, for symmetry we allow larger types in the extend
too.

During legalization, we can expand an "fp16_to_double" operation into
two extends for convenience, but abort when the truncate isn't legal. A new
libcall is probably needed here.

Even after this commit, various target tweaks are needed to actually use the
extended intrinsics. I've put these into separate commits for clarity, so there
are no actual tests of f64 conversion here.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213248 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Tim Northover
2014-07-17 10:51:23 +00:00
parent f33a30cdd0
commit 3e61ccdded
23 changed files with 140 additions and 115 deletions
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20
docs/LangRef.rst
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@@ -8653,14 +8653,14 @@ Syntax:
::
declare i16 @llvm.convert.to.fp16(float %a)
declare i16 @llvm.convert.to.fp16.f32(float %a)
declare i16 @llvm.convert.to.fp16.f64(double %a)
Overview:
"""""""""
The '``llvm.convert.to.fp16``' intrinsic function performs a conversion
from single precision floating point format to half precision floating
point format.
The '``llvm.convert.to.fp16``' intrinsic function performs a conversion from a
conventional floating point type to half precision floating point format.
Arguments:
""""""""""
@@ -8671,17 +8671,16 @@ converted.
Semantics:
""""""""""
The '``llvm.convert.to.fp16``' intrinsic function performs a conversion
from single precision floating point format to half precision floating
point format. The return value is an ``i16`` which contains the
converted number.
The '``llvm.convert.to.fp16``' intrinsic function performs a conversion from a
conventional floating point format to half precision floating point format. The
return value is an ``i16`` which contains the converted number.
Examples:
"""""""""
.. code-block:: llvm
%res = call i16 @llvm.convert.to.fp16(float %a)
%res = call i16 @llvm.convert.to.fp16.f32(float %a)
store i16 %res, i16* @x, align 2
.. _int_convert_from_fp16:
@@ -8694,7 +8693,8 @@ Syntax:
::
declare float @llvm.convert.from.fp16(i16 %a)
declare float @llvm.convert.from.fp16.f32(i16 %a)
declare double @llvm.convert.from.fp16.f64(i16 %a)
Overview:
"""""""""