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02d4601fcf
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
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