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[InstCombine] reduce more unsigned saturated add with 'not' op
We want to use the sum in the icmp to allow matching with m_UAddWithOverflow and eliminate the 'not'. This is discussed in D51929 and is another step towards solving PR14613: https://bugs.llvm.org/show_bug.cgi?id=14613 Name: not op %notx = xor i32 %x, -1 %a = add i32 %x, %y %c = icmp ult i32 %notx, %y %r = select i1 %c, i32 -1, i32 %a => %a = add i32 %x, %y %c2 = icmp ult i32 %a, %y %r = select i1 %c2, i32 -1, i32 %a Name: not op ugt %notx = xor i32 %x, -1 %a = add i32 %x, %y %c = icmp ugt i32 %y, %notx %r = select i1 %c, i32 -1, i32 %a => %a = add i32 %x, %y %c2 = icmp ult i32 %a, %y %r = select i1 %c2, i32 -1, i32 %a https://rise4fun.com/Alive/niom (The matching here is still incomplete.) llvm-svn: 354224
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