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[docs] Clarify semantics of ordered fadd/fmul reductions. 

Differential Revision: https://reviews.llvm.org/D82034
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Amara Emerson 2020-06-17 11:13:22 -07:00
parent 1ec469cf4c
commit 84167a8d58
1 changed files with 22 additions and 2 deletions
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24
llvm/docs/LangRef.rst
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@ -15131,7 +15131,17 @@ matches the element-type of the vector input.
If the intrinsic call has the 'reassoc' or 'fast' flags set, then the
reduction will not preserve the associativity of an equivalent scalarized
counterpart. Otherwise the reduction will be *ordered*, thus implying that
the operation respects the associativity of a scalarized reduction.
the operation respects the associativity of a scalarized reduction. That is, the
reduction begins with the start value and performs an fadd operation with consecutively
increasing vector element indices. See the following pseudocode:
::
float ordered_fadd(start_value, input_vector)
result = start_value
for i = 0 to length(input_vector)
result = result + input_vector[i]
return result
Arguments:
@ -15192,7 +15202,17 @@ matches the element-type of the vector input.
If the intrinsic call has the 'reassoc' or 'fast' flags set, then the
reduction will not preserve the associativity of an equivalent scalarized
counterpart. Otherwise the reduction will be *ordered*, thus implying that
the operation respects the associativity of a scalarized reduction.
the operation respects the associativity of a scalarized reduction. That is, the
reduction begins with the start value and performs an fmul operation with consecutively
increasing vector element indices. See the following pseudocode:
::
float ordered_fmul(start_value, input_vector)
result = start_value
for i = 0 to length(input_vector)
result = result * input_vector[i]
return result
Arguments: