Add instcombine transforms to optimize tests of multiple bits of the same value into a single larger comparison.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@108378 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 25 insertions, 0 deletions

diff --git a/lib/Transforms/InstCombine/InstCombineSelect.cpp b/lib/Transforms/InstCombine/InstCombineSelect.cpp
index c44fe9db6e..c85d74ad7d 100644
--- a/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -699,6 +699,31 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
     SI.setOperand(2, TrueVal);
     return &SI;
   }
+  
+  // select (or (A == 0) (B == 0)) T, F--> select (and (A != 0) (B != 0)) F, T
+  // Note: This is a canonicalization rather than an optimization, and is used
+  // to expose opportunities to other instcombine transforms.
+  Instruction* CondInst = dyn_cast<Instruction>(CondVal);
+  if (CondInst && CondInst->getOpcode() == Instruction::Or) {
+    ICmpInst *LHSCmp = dyn_cast<ICmpInst>(CondInst->getOperand(0));
+    ICmpInst *RHSCmp = dyn_cast<ICmpInst>(CondInst->getOperand(1));
+    if (LHSCmp && LHSCmp->getPredicate() == ICmpInst::ICMP_EQ &&
+        RHSCmp && RHSCmp->getPredicate() == ICmpInst::ICMP_EQ) {
+      ConstantInt* C1 = dyn_cast<ConstantInt>(LHSCmp->getOperand(1));
+      ConstantInt* C2 = dyn_cast<ConstantInt>(RHSCmp->getOperand(1));
+      if (C1 && C1->isZero() && C2 && C2->isZero()) {
+        LHSCmp->setPredicate(ICmpInst::ICMP_NE);
+        RHSCmp->setPredicate(ICmpInst::ICMP_NE);
+        Value *And =
+          InsertNewInstBefore(BinaryOperator::CreateAnd(LHSCmp, RHSCmp,
+                                             "and."+CondVal->getName()), SI);
+        SI.setOperand(0, And);
+        SI.setOperand(1, FalseVal);
+        SI.setOperand(2, TrueVal);
+        return &SI;
+      }
+    }
+  }
 
   return 0;
 }