[llvm] r370376 - [SimplifyCFG] Skip sinking common lifetime markers of `alloca`.

[Michael Liao via llvm-commits]

Author: hliao
Date: Thu Aug 29 09:12:05 2019
New Revision: 370376

URL: http://llvm.org/viewvc/llvm-project?rev=370376&view=rev
Log:
[SimplifyCFG] Skip sinking common lifetime markers of `alloca`.

Summary:
- Similar to the workaround in fix of PR30188, skip sinking common
  lifetime markers of `alloca`. They are mostly left there after
  inlining functions in branches.

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66950

Modified:
    llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
    llvm/trunk/test/Transforms/SimplifyCFG/sink-common-code.ll

Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=370376&r1=370375&r2=370376&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Thu Aug 29 09:12:05 2019
@@ -1421,6 +1421,20 @@ HoistTerminator:
   return true;
 }
 
+// Check lifetime markers.
+static bool isLifeTimeMarker(const Instruction *I) {
+  if (auto II = dyn_cast<IntrinsicInst>(I)) {
+    switch (II->getIntrinsicID()) {
+    default:
+      break;
+    case Intrinsic::lifetime_start:
+    case Intrinsic::lifetime_end:
+      return true;
+    }
+  }
+  return false;
+}
+
 // All instructions in Insts belong to different blocks that all unconditionally
 // branch to a common successor. Analyze each instruction and return true if it
 // would be possible to sink them into their successor, creating one common
@@ -1475,20 +1489,25 @@ static bool canSinkInstructions(
       return false;
   }
 
-  // Because SROA can't handle speculating stores of selects, try not
-  // to sink loads or stores of allocas when we'd have to create a PHI for
-  // the address operand. Also, because it is likely that loads or stores
-  // of allocas will disappear when Mem2Reg/SROA is run, don't sink them.
+  // Because SROA can't handle speculating stores of selects, try not to sink
+  // loads, stores or lifetime markers of allocas when we'd have to create a
+  // PHI for the address operand. Also, because it is likely that loads or
+  // stores of allocas will disappear when Mem2Reg/SROA is run, don't sink
+  // them.
   // This can cause code churn which can have unintended consequences down
   // the line - see https://llvm.org/bugs/show_bug.cgi?id=30244.
   // FIXME: This is a workaround for a deficiency in SROA - see
   // https://llvm.org/bugs/show_bug.cgi?id=30188
   if (isa<StoreInst>(I0) && any_of(Insts, [](const Instruction *I) {
-        return isa<AllocaInst>(I->getOperand(1));
+        return isa<AllocaInst>(I->getOperand(1)->stripPointerCasts());
       }))
     return false;
   if (isa<LoadInst>(I0) && any_of(Insts, [](const Instruction *I) {
-        return isa<AllocaInst>(I->getOperand(0));
+        return isa<AllocaInst>(I->getOperand(0)->stripPointerCasts());
+      }))
+    return false;
+  if (isLifeTimeMarker(I0) && any_of(Insts, [](const Instruction *I) {
+        return isa<AllocaInst>(I->getOperand(1)->stripPointerCasts());
       }))
     return false;
 

Modified: llvm/trunk/test/Transforms/SimplifyCFG/sink-common-code.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/sink-common-code.ll?rev=370376&r1=370375&r2=370376&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/sink-common-code.ll (original)
+++ llvm/trunk/test/Transforms/SimplifyCFG/sink-common-code.ll Thu Aug 29 09:12:05 2019
@@ -886,6 +886,33 @@ return:
 ; CHECK: ret
 }
 
+; CHECK-LABEL: @test_not_sink_lifetime_marker
+; CHECK-NOT: select
+; CHECK: call void @llvm.lifetime.end
+; CHECK: call void @llvm.lifetime.end
+define i32 @test_not_sink_lifetime_marker(i1 zeroext %flag, i32 %x) {
+entry:
+  %y = alloca i32
+  %z = alloca i32
+  br i1 %flag, label %if.then, label %if.else
+
+if.then:
+  %y.cast = bitcast i32* %y to i8*
+  call void @llvm.lifetime.end.p0i8(i64 4, i8* %y.cast)
+  br label %if.end
+
+if.else:
+  %z.cast = bitcast i32* %z to i8*
+  call void @llvm.lifetime.end.p0i8(i64 4, i8* %z.cast)
+  br label %if.end
+
+if.end:
+  ret i32 1
+}
+
+declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture)
+declare void @llvm.lifetime.end.p0i8(i64, i8* nocapture)
+
 
 ; CHECK: ![[$TBAA]] = !{![[TYPE:[0-9]]], ![[TYPE]], i64 0}
 ; CHECK: ![[TYPE]] = !{!"float", ![[TEXT:[0-9]]]}