From b4f150b44b10efd07b2a88484830602476bd8d7a Mon Sep 17 00:00:00 2001
From: Nick Lewycky <nicholas@mxc.ca>
Date: Sun, 20 Sep 2009 05:48:50 +0000
Subject: 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
---
lib/VMCore/ConstantFold.cpp | 10 ++++++++++
1 file changed, 10 insertions(+)
(limited to 'lib/VMCore')
diff --git a/lib/VMCore/ConstantFold.cpp b/lib/VMCore/ConstantFold.cpp
index 8c65b56..3f5c7ef 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.
--
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