[PATCH] Ignore lifetime intrinsics in use list for MemCpyOptimizer.

[Luqman Aden]

Lifetime intrinsics were preventing various optimizations like turning memset+memcpy to just memset.

http://reviews.llvm.org/D5020

Files:
  lib/Transforms/Scalar/MemCpyOptimizer.cpp
  test/Transforms/MemCpyOpt/memcpy-to-memset-with-lifetimes.ll

Index: lib/Transforms/Scalar/MemCpyOptimizer.cpp
===================================================================
--- lib/Transforms/Scalar/MemCpyOptimizer.cpp
+++ lib/Transforms/Scalar/MemCpyOptimizer.cpp
@@ -679,6 +679,10 @@
           srcUseList.push_back(UU);
       else
         return false;
+    } else if (const IntrinsicInst *IT = dyn_cast<IntrinsicInst>(U)) {
+      if (IT->getIntrinsicID() != Intrinsic::lifetime_start &&
+          IT->getIntrinsicID() != Intrinsic::lifetime_end)
+        continue;
     } else if (U != C && U != cpy) {
       return false;
     }
Index: test/Transforms/MemCpyOpt/memcpy-to-memset-with-lifetimes.ll
===================================================================
--- test/Transforms/MemCpyOpt/memcpy-to-memset-with-lifetimes.ll
+++ test/Transforms/MemCpyOpt/memcpy-to-memset-with-lifetimes.ll
@@ -0,0 +1,28 @@
+; RUN: opt -basicaa -memcpyopt -instcombine -S < %s | FileCheck %s
+
+target datalayout = "e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @foo([8 x i64]* noalias nocapture sret dereferenceable(64)) {
+entry-block:
+  %a = alloca [8 x i64], align 8
+  %1 = bitcast [8 x i64]* %a to i8*
+  call void @llvm.lifetime.start(i64 64, i8* %1)
+  call void @llvm.memset.p0i8.i64(i8* %1, i8 0, i64 64, i32 8, i1 false)
+  %2 = bitcast [8 x i64]* %0 to i8*
+  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %2, i8* %1, i64 64, i32 8, i1 false)
+  call void @llvm.lifetime.end(i64 64, i8* %1)
+  ret void
+
+; CHECK-LABEL: @foo(
+; CHECK: %1 = bitcast
+; CHECK: call void @llvm.memset
+; CHECK-NOT: call void @llvm.memcpy
+; CHECK: ret void
+}
+
+declare void @llvm.lifetime.start(i64, i8* nocapture) nounwind
+declare void @llvm.lifetime.end(i64, i8* nocapture) nounwind
+
+declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture readonly, i64, i32, i1) nounwind
+declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1) nounwind
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