Hans Wennborg 800b12f90a Switch lowering: exploit unreachable fall-through when lowering case range cluster ...

In the example below, we would previously emit two range checks, one for cases
1--3 and one for 4--6. This patch makes us exploit the fact that the
fall-through is unreachable and only one range check is necessary.

  switch i32 %i, label %default [
    i32 1,  label %bb1
    i32 2,  label %bb1
    i32 3,  label %bb1
    i32 4,  label %bb2
    i32 5,  label %bb2
    i32 6,  label %bb2
  ]
  default: unreachable

llvm-svn: 357252

2019-03-29 13:40:05 +00:00

418 KiB

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