Roman Lebedev
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4d8e47ca18
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[InstCombine] Sink sub into hands of select if one hand becomes zero (PR44426)
This decreases use count of %Op1, makes one hand of select to be 0,
and possibly exposes further folding potential.
Name: sub (select %Cond, %Op1, %FalseVal), %Op1 -> select %Cond, 0, (sub %FalseVal, %Op1)
%Op1 = %TrueVal
%o = select i1 %Cond, i8 %Op1, i8 %FalseVal
%r = sub i8 %o, %Op1
=>
%n = sub i8 %FalseVal, %Op1
%r = select i1 %Cond, i8 0, i8 %n
Name: sub (select %Cond, %TrueVal, %Op1), %Op1 -> select %Cond, (sub %TrueVal, %Op1), 0
%Op1 = %FalseVal
%o = select i1 %Cond, i8 %TrueVal, i8 %Op1
%r = sub i8 %o, %Op1
=>
%n = sub i8 %TrueVal, %Op1
%r = select i1 %Cond, i8 %n, i8 0
https://rise4fun.com/Alive/avL
https://bugs.llvm.org/show_bug.cgi?id=44426
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2020-01-04 17:30:51 +03:00 |