Sanjay Patel
e12d734be3
[InstCombine] narrow truncated add/sub/mul with constant
...
Name: narrow_sub
%sub = sub i32 C1, %x
%r = trunc i32 %sub to i8
=>
%xn = trunc i32 %x to i8
%narrowC = trunc i32 C1 to i8
%r = sub i8 %narrowC, %xn
Name: narrow_add
%add = add i32 %x, C1
%r = trunc i32 %add to i8
=>
%xn = trunc i32 %x to i8
%narrowC = trunc i32 C1 to i8
%r = add i8 %xn, %narrowC
Name: narrow_mul
%mul = mul i32 %x, C1
%r = trunc i32 %mul to i8
=>
%xn = trunc i32 %x to i8
%narrowC = trunc i32 C1 to i8
%r = mul i8 %xn, %narrowC
http://rise4fun.com/Alive/QpS
This doesn't solve PR34046 (failure to recognize rotate):
https://bugs.llvm.org/show_bug.cgi?id=34046
...but it reduces an extra complication in the description examples
to a form that we can more easily match.
llvm-svn: 310141
2017-08-04 22:30:34 +00:00