[llvm] r245543 - Revert "[DSE] Enable removal of lifetime intrinsics in terminating blocks"

[Bjorn Steinbrink via llvm-commits]

Author: bsteinbr
Date: Thu Aug 20 03:58:47 2015
New Revision: 245543

URL: http://llvm.org/viewvc/llvm-project?rev=245543&view=rev
Log:
Revert "[DSE] Enable removal of lifetime intrinsics in terminating blocks"

Modified:
    llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp
    llvm/trunk/test/Transforms/DeadStoreElimination/lifetime.ll

Modified: llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp?rev=245543&r1=245542&r2=245543&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp Thu Aug 20 03:58:47 2015
@@ -788,33 +788,15 @@ bool DSE::handleEndBlock(BasicBlock &BB)
 
   const DataLayout &DL = BB.getModule()->getDataLayout();
 
-  // becomes false once lifetime intrinsics are observable or useful for stack
-  // coloring
-  bool canRemoveLifetimeIntrinsics = true;
-
   // Scan the basic block backwards
   for (BasicBlock::iterator BBI = BB.end(); BBI != BB.begin(); ){
     --BBI;
 
-    Value *V = nullptr;
-    if (canRemoveLifetimeIntrinsics)
-      if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(BBI))
-        switch (II->getIntrinsicID()) {
-          default: break;
-          case Intrinsic::lifetime_start:
-          case Intrinsic::lifetime_end:
-            V = II->getArgOperand(1);
-            break;
-        }
-
-    if (!V && hasMemoryWrite(BBI, *TLI) && isRemovable(BBI))
-      V = getStoredPointerOperand(BBI);
-
-    // If we found a store, check to see if it points into a dead stack value.
-    if (V) {
+    // If we find a store, check to see if it points into a dead stack value.
+    if (hasMemoryWrite(BBI, *TLI) && isRemovable(BBI)) {
       // See through pointer-to-pointer bitcasts
       SmallVector<Value *, 4> Pointers;
-      GetUnderlyingObjects(V, Pointers, DL);
+      GetUnderlyingObjects(getStoredPointerOperand(BBI), Pointers, DL);
 
       // Stores to stack values are valid candidates for removal.
       bool AllDead = true;
@@ -862,15 +844,6 @@ bool DSE::handleEndBlock(BasicBlock &BB)
       continue;
     }
 
-    if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(BBI))
-      if (II->getIntrinsicID() == Intrinsic::lifetime_start) {
-        // We found a lifetime start for a live object, which we could not
-        // remove. So we must stop removing lifetime intrinsics from this block
-        // because they're useful for stack coloring again
-        canRemoveLifetimeIntrinsics = false;
-        continue;
-      }
-
     if (auto CS = CallSite(BBI)) {
       // Remove allocation function calls from the list of dead stack objects; 
       // there can't be any references before the definition.

Modified: llvm/trunk/test/Transforms/DeadStoreElimination/lifetime.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/DeadStoreElimination/lifetime.ll?rev=245543&r1=245542&r2=245543&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/DeadStoreElimination/lifetime.ll (original)
+++ llvm/trunk/test/Transforms/DeadStoreElimination/lifetime.ll Thu Aug 20 03:58:47 2015
@@ -5,16 +5,14 @@ target datalayout = "E-p:64:64:64-a0:0:8
 declare void @llvm.lifetime.start(i64, i8* nocapture) nounwind
 declare void @llvm.lifetime.end(i64, i8* nocapture) nounwind
 declare void @llvm.memset.p0i8.i8(i8* nocapture, i8, i8, i32, i1) nounwind
-declare void @callee(i8*)
 
 define void @test1() {
 ; CHECK-LABEL: @test1(
   %A = alloca i8
 
   store i8 0, i8* %A  ;; Written to by memset
-; CHECK-NOT: store
   call void @llvm.lifetime.end(i64 1, i8* %A)
-; CHECK-NOT: lifetime.end
+; CHECK: lifetime.end
 
   call void @llvm.memset.p0i8.i8(i8* %A, i8 0, i8 -1, i32 0, i1 false)
 ; CHECK-NOT: memset
@@ -24,7 +22,7 @@ define void @test1() {
 }
 
 define void @test2(i32* %P) {
-; CHECK-LABEL: test2
+; CHECK: test2
   %Q = getelementptr i32, i32* %P, i32 1
   %R = bitcast i32* %Q to i8*
   call void @llvm.lifetime.start(i64 4, i8* %R)
@@ -36,51 +34,4 @@ define void @test2(i32* %P) {
   ret void
 }
 
-define void @test3(i8*) {
-; CHECK-LABEL: test3
-  %a = alloca i8
-  call void @llvm.lifetime.start(i64 1, i8* %a)
-; CHECK-NOT: lifetime.start
-  call void @llvm.lifetime.end(i64 1, i8* %a)
-; CHECK-NOT: lifetime.end
-  call void @llvm.lifetime.start(i64 1, i8* undef)
-; CHECK-NOT: lifetime.start
-  call void @llvm.lifetime.end(i64 1, i8* undef)
-; CHECK-NOT: lifetime.end
-  ret void
-}
-
-define void @test4(i8*) {
-; CHECK-LABEL: test4
-  %a = alloca i8
-  call void @llvm.lifetime.start(i64 1, i8* %a)
-; CHECK: lifetime.start
-  call void @llvm.lifetime.end(i64 1, i8* %a)
-; CHECK: lifetime.end
-  call void @llvm.lifetime.start(i64 1, i8* %0)
-; CHECK: lifetime.start
-  call void @llvm.lifetime.end(i64 1, i8* %0)
-; CHECK: lifetime.end
-  call void @llvm.lifetime.start(i64 1, i8* %a)
-; CHECK-NOT: lifetime.start
-  call void @llvm.lifetime.end(i64 1, i8* %a)
-; CHECK-NOT: lifetime.end
-  ret void
-}
 
-define void @test5() {
-; CHECK-LABEL: test5
-  %a = alloca i8
-  %b = alloca i8
-  call void @llvm.lifetime.start(i64 1, i8* %a)
-; CHECK: lifetime.start
-  call void @llvm.lifetime.end(i64 1, i8* %a)
-; CHECK: lifetime.end
-  call void @llvm.lifetime.start(i64 1, i8* %b)
-; CHECK: lifetime.start
-  call void @callee(i8* %b)
-; CHECK: call void @callee
-  call void @llvm.lifetime.end(i64 1, i8* %b)
-; CHECK-NOT: lifetime.end
-  ret void
-}