[llvm] r222927 - [LICM] Store sink and indirectbr instructions

[Bruno Cardoso Lopes]

Author: bruno
Date: Fri Nov 28 13:47:46 2014
New Revision: 222927

URL: http://llvm.org/viewvc/llvm-project?rev=222927&view=rev
Log:
[LICM] Store sink and indirectbr instructions

Loop simplify skips exit-block insertion when exits contain indirectbr
instructions. This leads to an assertion in LICM when trying to sink
stores out of non-dedicated loop exits containing indirectbr
instructions. This patch fix this issue by re-checking for dedicated
exits in LICM prior to store sink attempts.

Differential Revision: http://reviews.llvm.org/D6414

rdar://problem/18943047

Modified:
    llvm/trunk/lib/Transforms/Scalar/LICM.cpp
    llvm/trunk/test/Transforms/LICM/sinking.ll

Modified: llvm/trunk/lib/Transforms/Scalar/LICM.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LICM.cpp?rev=222927&r1=222926&r2=222927&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LICM.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LICM.cpp Fri Nov 28 13:47:46 2014
@@ -810,6 +810,7 @@ void LICM::PromoteAliasSet(AliasSet &AS,
   // us to prove better alignment.
   unsigned Alignment = 1;
   AAMDNodes AATags;
+  bool HasDedicatedExits = CurLoop->hasDedicatedExits();
 
   // Check that all of the pointers in the alias set have the same type.  We
   // cannot (yet) promote a memory location that is loaded and stored in
@@ -844,6 +845,11 @@ void LICM::PromoteAliasSet(AliasSet &AS,
         assert(!store->isVolatile() && "AST broken");
         if (!store->isSimple())
           return;
+        // Don't sink stores from loops without dedicated block exits. Exits
+        // containing indirect branches are not transformed by loop simplify,
+        // make sure we catch that.
+        if (!HasDedicatedExits)
+          return;
 
         // Note that we only check GuaranteedToExecute inside the store case
         // so that we do not introduce stores where they did not exist before

Modified: llvm/trunk/test/Transforms/LICM/sinking.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LICM/sinking.ll?rev=222927&r1=222926&r2=222927&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/LICM/sinking.ll (original)
+++ llvm/trunk/test/Transforms/LICM/sinking.ll Fri Nov 28 13:47:46 2014
@@ -314,6 +314,51 @@ exit:
   ret i32 %lcssa
 }
 
+; Can't sink stores out of exit blocks containing indirectbr instructions
+; because loop simplify does not create dedicated exits for such blocks. Test
+; that by sinking the store from lab21 to lab22, but not further.
+define void @test12() {
+; CHECK-LABEL: @test12
+  br label %lab4
+
+lab4:
+  br label %lab20
+
+lab5:
+  br label %lab20
+
+lab6:
+  br label %lab4
+
+lab7:
+  br i1 undef, label %lab8, label %lab13
+
+lab8:
+  br i1 undef, label %lab13, label %lab10
+
+lab10:
+  br label %lab7
+
+lab13:
+  ret void
+
+lab20:
+  br label %lab21
+
+lab21:
+; CHECK: lab21:
+; CHECK-NOT: store
+; CHECK: br i1 false, label %lab21, label %lab22
+  store i32 36127957, i32* undef, align 4
+  br i1 undef, label %lab21, label %lab22
+
+lab22:
+; CHECK: lab22:
+; CHECK: store
+; CHECK-NEXT: indirectbr i8* undef
+  indirectbr i8* undef, [label %lab5, label %lab6, label %lab7]
+}
+
 declare void @f(i32*)
 
 declare void @g()