Added InstCombine for "select cond, ~cond, x" type patterns

These can be reduced to "~cond & x" or "~cond | x"

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@146624 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 27 insertions, 0 deletions

diff --git a/lib/Transforms/InstCombine/InstCombineSelect.cpp b/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 84f80f0d74..f1ea8ead1f 100644
--- a/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -682,6 +682,13 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
       return BinaryOperator::CreateOr(CondVal, FalseVal);
     else if (CondVal == FalseVal)
       return BinaryOperator::CreateAnd(CondVal, TrueVal);
+
+    // select a, ~a, b -> (~a)&b
+    // select a, b, ~a -> (~a)|b
+    if (match(TrueVal, m_Not(m_Specific(CondVal))))
+      return BinaryOperator::CreateAnd(TrueVal, FalseVal);
+    else if (match(FalseVal, m_Not(m_Specific(CondVal))))
+      return BinaryOperator::CreateOr(TrueVal, FalseVal);
   }
 
   // Selecting between two integer constants?
diff --git a/test/Transforms/InstCombine/select.ll b/test/Transforms/InstCombine/select.ll
index 46615613eb..4baae2618d 100644
--- a/test/Transforms/InstCombine/select.ll
+++ b/test/Transforms/InstCombine/select.ll
@@ -809,3 +809,23 @@ define i32 @test61(i32* %ptr) {
 ; CHECK: @test61
 ; CHECK: ret i32 10
 }
+
+define i1 @test62(i1 %A, i1 %B) {
+        %not = xor i1 %A, true
+        %C = select i1 %A, i1 %not, i1 %B             
+        ret i1 %C
+; CHECK: @test62
+; CHECK: %not = xor i1 %A, true
+; CHECK: %C = and i1 %not, %B
+; CHECK: ret i1 %C
+}
+
+define i1 @test63(i1 %A, i1 %B) {
+        %not = xor i1 %A, true
+        %C = select i1 %A, i1 %B, i1 %not         
+        ret i1 %C
+; CHECK: @test63
+; CHECK: %not = xor i1 %A, true
+; CHECK: %C = or i1 %B, %not
+; CHECK: ret i1 %C
+}