From: Nick Lewycky <nicholas@mxc.ca>
Date: Sun, 20 Sep 2009 05:48:50 +0000 (+0000)
Subject: Try turning icmp(bitcast(x), bitcast(y)) into icmp(bitcast(bitcast(x)), y) in
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=55a722bf6a08c684e49f5b56301bfc66d6dc9fd4;p=oota-llvm.git

Try turning icmp(bitcast(x), bitcast(y)) into icmp(bitcast(bitcast(x)), y) in
the hopes that the two bitcasts will merge.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82371 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/VMCore/ConstantFold.cpp b/lib/VMCore/ConstantFold.cpp
index 8c65b563570..3f5c7efbb9a 100644
--- a/lib/VMCore/ConstantFold.cpp
+++ b/lib/VMCore/ConstantFold.cpp
@@ -1627,6 +1627,16 @@ Constant *llvm::ConstantFoldCompareInstruction(LLVMContext &Context,
     if (Result != -1)
       return ConstantInt::get(Type::getInt1Ty(Context), Result);
 
+    // If the right hand side is a bitcast, try using its inverse to simplify
+    // it by moving it to the left hand side.
+    if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(C2)) {
+      if (CE2->getOpcode() == Instruction::BitCast) {
+        Constant *CE2Op0 = CE2->getOperand(0);
+        Constant *Inverse = ConstantExpr::getBitCast(C1, CE2Op0->getType());
+        return ConstantExpr::getICmp(pred, Inverse, CE2Op0);
+      }
+    }
+
     if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) {
       // If C2 is a constant expr and C1 isn't, flip them around and fold the
       // other way if possible.
diff --git a/test/Transforms/ConstProp/2009-09-19-ConstFold-i1-ConstExpr.ll b/test/Transforms/ConstProp/2009-09-19-ConstFold-i1-ConstExpr.ll
index debf9a8e5cd..0a40c0ce2c4 100644
--- a/test/Transforms/ConstProp/2009-09-19-ConstFold-i1-ConstExpr.ll
+++ b/test/Transforms/ConstProp/2009-09-19-ConstFold-i1-ConstExpr.ll
@@ -23,3 +23,8 @@ global i1 srem (i1 icmp ult (i8* @X, i8* @Y), i1 icmp ult (i8* @X, i8* @Z))
 global i1 urem (i1 icmp ult (i8* @X, i8* @Y), i1 icmp ult (i8* @X, i8* @Z))
 ; CHECK-NOT: icmp
 ; CHECK: i1 false
+
+global i1 icmp ule (i32* bitcast (i8* @X to i32*), i32* bitcast (i8* @Y to i32*))
+; CHECK-NOT: bitcast
+; CHECK: icmp
+