[InstCombine] reduce more checks for power-of-2-or-zero using ctpop

Extends the transform from:
rL364341
...to include another (more common?) pattern that tests whether a
value is a power-of-2 (including or excluding zero).

llvm-svn: 364856

1 files changed, 7 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 664edc7c9e5..4c818193ced 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -3926,9 +3926,15 @@ Instruction *InstCombiner::foldICmpEquality(ICmpInst &I) {
     return new ICmpInst(Pred, A, B);
 
   // Canonicalize checking for a power-of-2-or-zero value:
+  // (A & (A-1)) == 0 --> ctpop(A) < 2 (two commuted variants)
+  // ((A-1) & A) != 0 --> ctpop(A) > 1 (two commuted variants)
+  if (!match(Op0, m_OneUse(m_c_And(m_Add(m_Value(A), m_AllOnes()),
+                                   m_Deferred(A)))) ||
+      !match(Op1, m_ZeroInt()))
+    A = nullptr;
+
   // (A & -A) == A --> ctpop(A) < 2 (four commuted variants)
   // (-A & A) != A --> ctpop(A) > 1 (four commuted variants)
-  A = nullptr;
   if (match(Op0, m_OneUse(m_c_And(m_Neg(m_Specific(Op1)), m_Specific(Op1)))))
     A = Op1;
   else if (match(Op1,