[PATCH] [InstCombine] Canonicalize min/max expressions correctly.

[James Molloy]

Hi majnemer, reames,

This patch introduces a canonical form for min/max idioms where one operand
is extended or truncated. This often happens when the other operand is a
constant. For example:

  %1 = icmp slt i32 %a, i32 0
  %2 = sext i32 %a to i64
  %3 = select i1 %1, i64 %2, i64 0

Would now be canonicalized into:

  %1 = icmp slt i32 %a, i32 0
  %2 = select i1 %1, i32 %a, i32 0
  %3 = sext i32 %2 to i64

This builds upon a patch posted by David Majenemer
(https://www.marc.info/?l=llvm-commits&m=143008038714141&w=2). That pass
passively stopped instcombine from ruining canonical patterns. This
patch additionally actively makes instcombine canonicalize too.

REPOSITORY
  rL LLVM

http://reviews.llvm.org/D9749

Files:
  lib/Transforms/InstCombine/InstCombineCompares.cpp
  lib/Transforms/InstCombine/InstCombineSelect.cpp
  lib/Transforms/InstCombine/InstructionCombining.cpp
  test/Transforms/InstCombine/minmax-fold.ll

EMAIL PREFERENCES
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