[PATCH] InstCombineCompare with constant return false if we know it is never going to be equal

[David Majnemer]

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Comment at: lib/Transforms/InstCombine/InstCombineCompares.cpp:2445
@@ +2444,3 @@
+    const APInt *AP1;
+    if (I.getPredicate() == ICmpInst::ICMP_EQ && match(Op1, m_APInt(AP1)) &&
+        CI->isOne()) {
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What about the `ICmpInst::ICMP_NE` case? We should be able to handle this case just as well.

Can we optimize any of the other predicates?

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Comment at: lib/Transforms/InstCombine/InstCombineCompares.cpp:2451
@@ +2450,3 @@
+      if (Op0KnownZero.countTrailingOnes() >= 1)
+        return ReplaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
+    }
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If you always transform to true or false, you should probably move this to InstSimplify.

http://reviews.llvm.org/D3868