Add the select optimization recently added to instcombine to constant folding.

This is the one where one of the branches of the select is another select on
the same condition.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124547 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/VMCore/ConstantFold.cpp b/lib/VMCore/ConstantFold.cpp
index 3fea1910ffe153b1c8325f4a255d51e34384af61..c3be1197d3c3a5791a62555ed3c9f2a12de59cca 100644 (file)
--- a/lib/VMCore/ConstantFold.cpp
+++ b/lib/VMCore/ConstantFold.cpp
@@ -693,6 +693,18 @@ Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond,
   if (isa<UndefValue>(V2)) return V1;
   if (isa<UndefValue>(Cond)) return V1;
   if (V1 == V2) return V1;
+
+  if (ConstantExpr *TrueVal = dyn_cast<ConstantExpr>(V1)) {
+    if (TrueVal->getOpcode() == Instruction::Select)
+      if (TrueVal->getOperand(0) == Cond)
+       return ConstantExpr::getSelect(Cond, TrueVal->getOperand(1), V2);
+  }
+  if (ConstantExpr *FalseVal = dyn_cast<ConstantExpr>(V2)) {
+    if (FalseVal->getOpcode() == Instruction::Select)
+      if (FalseVal->getOperand(0) == Cond)
+       return ConstantExpr::getSelect(Cond, V1, FalseVal->getOperand(2));
+  }
+
   return 0;
 }
 

diff --git a/test/Transforms/ConstProp/constant-expr.ll b/test/Transforms/ConstProp/constant-expr.ll
index 33ed1a53c3e0110a145a0f9fc4a92a443dae7e19..1088fa6959ad909ce95f5502e8ed388e264ad8b4 100644 (file)
--- a/test/Transforms/ConstProp/constant-expr.ll
+++ b/test/Transforms/ConstProp/constant-expr.ll
@@ -100,3 +100,12 @@
 ; CHECK: pr9011_14 = constant i128 0
 @pr9011_15 = constant i128 bitcast (<4 x i32> zeroinitializer to i128)
 ; CHECK: pr9011_15 = constant i128 0
+
+@select = internal constant
+          i32 select (i1 icmp ult (i32 ptrtoint (i8* @X to i32),
+                                   i32 ptrtoint (i8* @Y to i32)),
+            i32 select (i1 icmp ult (i32 ptrtoint (i8* @X to i32),
+                                     i32 ptrtoint (i8* @Y to i32)),
+               i32 10, i32 20),
+            i32 30)
+; CHECK: select = internal constant i32 select {{.*}} i32 10, i32 30