[PATCH] D52307: [LoopRotate] Fix lifetime handling.

[Florian Hahn via Phabricator via llvm-commits]

fhahn updated this revision to Diff 166310.
fhahn added a comment.

Move the lifetime handling before cloning the instruction. The cases where we delete the clone do not apply to lifetime intrinsics anyways, so there is no need to clone it in that case.


https://reviews.llvm.org/D52307

Files:
  lib/Transforms/Utils/LoopRotationUtils.cpp
  test/Transforms/LoopRotate/lifetimes.ll


Index: test/Transforms/LoopRotate/lifetimes.ll
===================================================================
--- /dev/null
+++ test/Transforms/LoopRotate/lifetimes.ll
@@ -0,0 +1,52 @@
+; RUN: opt -S -loop-rotate < %s -verify-loop-info -verify-dom-info | FileCheck %s
+
+; Make sure we extend lifetimes properly.
+
+; CHECK-LABEL: @test(
+; CHECK-LABEL: entry:
+; CHECK:         call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull %tmp)
+
+; CHECK-LABEL: for.body.lr.ph:
+; CHECK-NOT:     call void @llvm.lifetime.start.p0i8
+; CHECK-NOT:     call void @llvm.lifetime.end.p0i8
+
+; CHECK-LABEL: return.loopexit:
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull %tmp)
+
+define void @test(i32 %x) nounwind {
+entry:
+  %m = alloca i32, align 4
+  br label %for.cond
+
+for.cond:                                         ; preds = %if.end, %entry
+  %i.0 = phi i32 [ 0, %entry ], [ %inc, %if.end ]
+  %cmp = icmp eq i32 %i.0, %x
+  %tmp = bitcast i32* %m to i8*
+  call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull %tmp)
+  store i32 1, i32* %m
+  call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull %tmp)
+  br i1 %cmp, label %return.loopexit, label %for.body
+
+for.body:                                         ; preds = %for.cond
+  %call = tail call i32 @foo(i32 %i.0)
+  %tobool = icmp eq i32 %call, 0
+  br i1 %tobool, label %if.end, label %a
+
+if.end:                                           ; preds = %for.body
+  %inc = add i32 %i.0, 1
+  br label %for.cond
+
+a:                                                ; preds = %for.body
+  br label %return
+
+return.loopexit:                                  ; preds = %for.cond
+  br label %return
+
+return:                                           ; preds = %return.loopexit, %a
+  ret void
+}
+
+declare  void @llvm.lifetime.start.p0i8(i64, i8*)
+declare  void @llvm.lifetime.end.p0i8(i64, i8*)
+
+declare i32 @foo(i32)
Index: lib/Transforms/Utils/LoopRotationUtils.cpp
===================================================================
--- lib/Transforms/Utils/LoopRotationUtils.cpp
+++ lib/Transforms/Utils/LoopRotationUtils.cpp
@@ -332,6 +332,19 @@
       continue;
     }
 
+    // Duplicating lifetimes will create invalid lifetimes. Instead we can
+    // extend the lifetime of the memory location by hoisting the start to
+    // the loop entry and sinking ends to the loop exit.
+    if (auto *IntrInst = dyn_cast<IntrinsicInst>(Inst)) {
+      if (IntrInst->getIntrinsicID() == Intrinsic::lifetime_start) {
+        Inst->moveBefore(LoopEntryBranch);
+        continue;
+      } else if (IntrInst->getIntrinsicID() == Intrinsic::lifetime_end) {
+        Inst->moveBefore(Exit->getFirstNonPHI());
+        continue;
+      }
+    }
+
     // Otherwise, create a duplicate of the instruction.
     Instruction *C = Inst->clone();
 


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