InstCombine: (icmp eq B, 0) | (icmp ult A, B) -> (icmp ule A, B-1)
This transform allows us to turn IR that looks like:
%1 = icmp eq i64 %b, 0
%2 = icmp ult i64 %a, %b
%3 = or i1 %1, %2
ret i1 %3
into:
%0 = add i64 %b, -1
%1 = icmp uge i64 %0, %a
ret i1 %1
which means we go from lowering:
cmpq %rsi, %rdi
setb %cl
testq %rsi, %rsi
sete %al
orb %cl, %al
ret
to lowering:
decq %rsi
cmpq %rdi, %rsi
setae %al
ret
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185677
91177308-0d34-0410-b5e6-
96231b3b80d8