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    • Dan Gohman's avatar
      Teach IndVarSimplify to optimize code using the C "int" type for · eb6be650
      Dan Gohman authored
      loop induction on LP64 targets. When the induction variable is
      used in addressing, IndVars now is usually able to inserst a
      64-bit induction variable and eliminates the sign-extending cast.
      This is also useful for code using C "short" types for
      induction variables on targets with 32-bit addressing.
      
      Inserting a wider induction variable is easy; the tricky part is
      determining when trunc(sext(i)) expressions are no-ops. This
      requires range analysis of the loop trip count. A common case is
      when the original loop iteration starts at 0 and exits when the
      induction variable is signed-less-than a fixed value; this case
      is now handled.
      
      This replaces IndVarSimplify's OptimizeCanonicalIVType. It was
      doing the same optimization, but it was limited to loops with
      constant trip counts, because it was running after the loop
      rewrite, and the information about the original induction
      variable is lost by that point.
      
      Rename ScalarEvolution's executesAtLeastOnce to
      isLoopGuardedByCond, generalize it to be able to test for
      ICMP_NE conditions, and move it to be a public function so that
      IndVars can use it.
      
      llvm-svn: 64407
      eb6be650
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