From d2b6fdbc319b753a63c20d3e4512652835f2ee6d Mon Sep 17 00:00:00 2001
From: Michael Kuperstein <michael.m.kuperstein@intel.com>
Date: Thu, 5 Feb 2015 09:15:37 +0000
Subject: [PATCH] Teach isDereferenceablePointer() to look through bitcast
 constant expressions. This fixes a LICM regression due to the new load+store
 pair canonicalization.

Differential Revision: http://reviews.llvm.org/D7411

llvm-svn: 228284
---
 llvm/include/llvm/IR/Operator.h        | 14 ++++++++
 llvm/lib/IR/Value.cpp                  |  2 +-
 llvm/test/Transforms/LICM/constexpr.ll | 46 ++++++++++++++++++++++++++
 3 files changed, 61 insertions(+), 1 deletion(-)
 create mode 100644 llvm/test/Transforms/LICM/constexpr.ll

diff --git a/llvm/include/llvm/IR/Operator.h b/llvm/include/llvm/IR/Operator.h
index 0933f2170236..0fa3101f8bf7 100644
--- a/llvm/include/llvm/IR/Operator.h
+++ b/llvm/include/llvm/IR/Operator.h
@@ -504,6 +504,20 @@ public:
   }
 };
 
+class BitCastOperator
+    : public ConcreteOperator<Operator, Instruction::BitCast> {
+  friend class BitCastInst;
+  friend class ConstantExpr;
+
+public:
+  Type *getSrcTy() const {
+    return getOperand(0)->getType();
+  }
+
+  Type *getDestTy() const {
+    return getType();
+  }
+};
 
 } // End llvm namespace
 
diff --git a/llvm/lib/IR/Value.cpp b/llvm/lib/IR/Value.cpp
index 5f7e258441a8..52dcd6311ff8 100644
--- a/llvm/lib/IR/Value.cpp
+++ b/llvm/lib/IR/Value.cpp
@@ -496,7 +496,7 @@ static bool isDereferenceablePointer(const Value *V, const DataLayout *DL,
   // is at least as large as for the resulting pointer type, then
   // we can look through the bitcast.
   if (DL)
-    if (const BitCastInst* BC = dyn_cast<BitCastInst>(V)) {
+    if (const BitCastOperator *BC = dyn_cast<BitCastOperator>(V)) {
       Type *STy = BC->getSrcTy()->getPointerElementType(),
            *DTy = BC->getDestTy()->getPointerElementType();
       if (STy->isSized() && DTy->isSized() &&
diff --git a/llvm/test/Transforms/LICM/constexpr.ll b/llvm/test/Transforms/LICM/constexpr.ll
new file mode 100644
index 000000000000..f78878716aae
--- /dev/null
+++ b/llvm/test/Transforms/LICM/constexpr.ll
@@ -0,0 +1,46 @@
+; RUN: opt < %s -S -basicaa -licm | FileCheck %s
+; This fixes PR22460
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc"
+
+@in = internal unnamed_addr global i32* null, align 8
+@out = internal unnamed_addr global i32* null, align 8
+
+; CHECK-LABEL: @bar
+; CHECK: entry:
+; CHECK: load i64* bitcast (i32** @in to i64*)
+; CHECK: do.body:
+; CHECK-NOT: load
+
+define i64 @bar(i32 %N) {
+entry:
+  br label %do.body
+
+do.body:                                          ; preds = %l2, %entry
+  %i.0 = phi i32 [ 0, %entry ], [ %inc, %l2 ]
+  %total = phi i64 [ 0, %entry ], [ %next, %l2 ]
+  %c = icmp eq i32 %N, 6
+  br i1 %c, label %l1, label %do.body.l2_crit_edge
+
+do.body.l2_crit_edge:                             ; preds = %do.body
+  %inval.pre = load i32** @in, align 8
+  br label %l2
+
+l1:                                               ; preds = %do.body
+  %v1 = load i64* bitcast (i32** @in to i64*), align 8
+  store i64 %v1, i64* bitcast (i32** @out to i64*), align 8
+  %0 = inttoptr i64 %v1 to i32*
+  br label %l2
+
+l2:                                               ; preds = %do.body.l2_crit_edge, %l1
+  %inval = phi i32* [ %inval.pre, %do.body.l2_crit_edge ], [ %0, %l1 ]
+  %int = ptrtoint i32* %inval to i64
+  %next = add i64 %total, %int
+  %inc = add nsw i32 %i.0, 1
+  %cmp = icmp slt i32 %inc, %N
+  br i1 %cmp, label %do.body, label %do.end
+
+do.end:                                           ; preds = %l2
+  ret i64 %total
+}