Fix pattern matching for comparison with BTC

Following Commit 870f753 a broadcast is materialized for the BTC, so
update our pattern-matching logic to look for a comparison with a
broadcast of the BTC rather than the BTC itself.

Author: hazzlim

llvm/lib/Transforms/Vectorize/VPlanPatternMatch.h

@@ -246,6 +246,12 @@ m_BranchOnCond(const Op0_t &Op0) {
   return m_VPInstruction<VPInstruction::BranchOnCond>(Op0);
 }
 
+template <typename Op0_t>
+inline UnaryVPInstruction_match<Op0_t, VPInstruction::Broadcast>
+m_Broadcast(const Op0_t &Op0) {
+  return m_VPInstruction<VPInstruction::Broadcast>(Op0);
+}
+
 template <typename Op0_t, typename Op1_t>
 inline BinaryVPInstruction_match<Op0_t, Op1_t, VPInstruction::ActiveLaneMask>
 m_ActiveLaneMask(const Op0_t &Op0, const Op1_t &Op1) {

llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp

@@ -1059,10 +1059,11 @@ static bool optimizeVectorInductionWidthForTCAndVFUF(VPlan &Plan,
     // Currently only handle cases where the single user is a header-mask
     // comparison with the backedge-taken-count.
     using namespace VPlanPatternMatch;
-    if (!match(*WideIV->user_begin(),
-               m_Binary<Instruction::ICmp>(
-                   m_Specific(WideIV),
-                   m_Specific(Plan.getOrCreateBackedgeTakenCount()))))
+    if (!match(
+            *WideIV->user_begin(),
+            m_Binary<Instruction::ICmp>(
+                m_Specific(WideIV),
+                m_Broadcast(m_Specific(Plan.getOrCreateBackedgeTakenCount())))))
       continue;
 
     // Update IV operands and comparison bound to use new narrower type.