From 55ee75d57114c17460d364121a2ec3a5cf40e1d2 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Tue, 30 Nov 2010 19:12:10 +0000
Subject: [PATCH] enhance isRemovable to refuse to delete volatile mem
 transfers now that DSE hacks on them.  This fixes a regression I introduced,
 by generalizing DSE to hack on transfers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120445 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../Scalar/DeadStoreElimination.cpp           | 23 +++++++++++++++----
 .../Transforms/DeadStoreElimination/simple.ll | 20 ++++++++++++----
 2 files changed, 35 insertions(+), 8 deletions(-)

diff --git a/lib/Transforms/Scalar/DeadStoreElimination.cpp b/lib/Transforms/Scalar/DeadStoreElimination.cpp
index cb4d482a634..d05f57f0d02 100644
--- a/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ b/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -152,12 +152,27 @@ getLocForWrite(Instruction *Inst, AliasAnalysis &AA) {
 /// isRemovable - If the value of this instruction and the memory it writes to
 /// is unused, may we delete this instruction?
 static bool isRemovable(Instruction *I) {
-  assert(hasMemoryWrite(I));
-  if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
-    return II->getIntrinsicID() != Intrinsic::lifetime_end;
+  // Don't remove volatile stores.
   if (StoreInst *SI = dyn_cast<StoreInst>(I))
     return !SI->isVolatile();
-  return true;
+  
+  IntrinsicInst *II = cast<IntrinsicInst>(I);
+  switch (II->getIntrinsicID()) {
+  default: assert(0 && "doesn't pass 'hasMemoryWrite' predicate");
+  case Intrinsic::lifetime_end:
+    // Never remove dead lifetime_end's, e.g. because it is followed by a
+    // free.
+    return false;
+  case Intrinsic::init_trampoline:
+    // Always safe to remove init_trampoline.
+    return true;
+    
+  case Intrinsic::memset:
+  case Intrinsic::memmove:
+  case Intrinsic::memcpy:
+    // Don't remove volatile memory intrinsics.
+    return !cast<MemIntrinsic>(II)->isVolatile();
+  }
 }
 
 /// getPointerOperand - Return the pointer that is being written to.
diff --git a/test/Transforms/DeadStoreElimination/simple.ll b/test/Transforms/DeadStoreElimination/simple.ll
index 0c05b153571..203cf37193b 100644
--- a/test/Transforms/DeadStoreElimination/simple.ll
+++ b/test/Transforms/DeadStoreElimination/simple.ll
@@ -1,6 +1,12 @@
 ; RUN: opt < %s -basicaa -dse -S | FileCheck %s
 target datalayout = "E-p:64:64:64-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128"
 
+declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1) nounwind
+declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture, i64, i32, i1) nounwind
+declare void @llvm.memset.i64(i8*, i8, i64, i32)
+declare void @llvm.memcpy.i64(i8*, i8*, i64, i32)
+declare i8* @llvm.init.trampoline(i8*, i8*, i8*)
+
 define void @test1(i32* %Q, i32* %P) {
         %DEAD = load i32* %Q
         store i32 %DEAD, i32* %P
@@ -55,9 +61,6 @@ define void @test5(i32* %Q) {
 ; CHECK-NEXT: ret void
 }
 
-declare void @llvm.memset.i64(i8*, i8, i64, i32)
-declare void @llvm.memcpy.i64(i8*, i8*, i64, i32)
-
 ; Should delete store of 10 even though memset is a may-store to P (P and Q may
 ; alias).
 define void @test6(i32 *%p, i8 *%q) {
@@ -116,7 +119,6 @@ define double @test10(i8* %X) {
 
 
 ; DSE should delete the dead trampoline.
-declare i8* @llvm.init.trampoline(i8*, i8*, i8*)
 declare void @test11f()
 define void @test11() {
 ; CHECK: @test11
@@ -210,3 +212,13 @@ define void @test17(i8* %P, i8* %Q) nounwind ssp {
 ; CHECK-NEXT: ret
 }
 
+; Should not delete the volatile memset.
+define void @test17v(i8* %P, i8* %Q) nounwind ssp {
+  tail call void @llvm.memset.p0i8.i64(i8* %P, i8 42, i64 8, i32 1, i1 true)
+  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+  ret void
+; CHECK: @test17v
+; CHECK-NEXT: call void @llvm.memset
+; CHECK-NEXT: call void @llvm.memcpy
+; CHECK-NEXT: ret
+}