[LoopStrengthReduce] Don't rewrite PHIs with incoming values from CatchSwitches

Bail out if we have a PHI on an EHPad that gets a value from a
CatchSwitchInst.  Because the CatchSwitchInst cannot be split, there is
no good place to stick any instructions.

This fixes PR26373.

llvm-svn: 259702

3 files changed, 48 insertions, 0 deletions

diff --git a/llvm/include/llvm/IR/Instructions.h b/llvm/include/llvm/IR/Instructions.h
index cb7eeb4994a..efacf197acf 100644
--- a/llvm/include/llvm/IR/Instructions.h
+++ b/llvm/include/llvm/IR/Instructions.h
@@ -2512,6 +2512,14 @@ public:
     return block_begin() + getNumOperands();
   }
 
+  iterator_range<block_iterator> blocks() {
+    return make_range(block_begin(), block_end());
+  }
+
+  iterator_range<const_block_iterator> blocks() const {
+    return make_range(block_begin(), block_end());
+  }
+
   op_range incoming_values() { return operands(); }
 
   const_op_range incoming_values() const { return operands(); }
diff --git a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 2101225ed9f..acfdec43d21 100644
--- a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -4799,6 +4799,17 @@ LSRInstance::LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE,
       DEBUG(dbgs() << "LSR skipping loop, too many IV Users in " << U << "\n");
       return;
     }
+    // Bail out if we have a PHI on an EHPad that gets a value from a
+    // CatchSwitchInst.  Because the CatchSwitchInst cannot be split, there is
+    // no good place to stick any instructions.
+    if (auto *PN = dyn_cast<PHINode>(U.getUser())) {
+       auto *FirstNonPHI = PN->getParent()->getFirstNonPHI();
+       if (isa<FuncletPadInst>(FirstNonPHI) ||
+           isa<CatchSwitchInst>(FirstNonPHI))
+         for (BasicBlock *PredBB : PN->blocks())
+           if (isa<CatchSwitchInst>(PredBB->getFirstNonPHI()))
+             return;
+    }
   }
 
 #ifndef NDEBUG
diff --git a/llvm/test/Transforms/LoopStrengthReduce/funclet.ll b/llvm/test/Transforms/LoopStrengthReduce/funclet.ll
index 5d20646141c..1bee3706caf 100644
--- a/llvm/test/Transforms/LoopStrengthReduce/funclet.ll
+++ b/llvm/test/Transforms/LoopStrengthReduce/funclet.ll
@@ -214,3 +214,32 @@ try.cont.7:                                       ; preds = %try.cont
 
 ; CHECK: catch.dispatch.2:
 ; CHECK: %e.0 = phi i32* [ %c, %try.cont ], [ %b, %catch.dispatch ]
+
+define i32 @test2() personality i32 (...)* @_except_handler3 {
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %for.inc, %entry
+  %phi = phi i32 [ %inc, %for.inc ], [ 0, %entry ]
+  invoke void @reserve()
+          to label %for.inc unwind label %catch.dispatch
+
+catch.dispatch:                                   ; preds = %for.body
+  %tmp18 = catchswitch within none [label %catch.handler] unwind to caller
+
+catch.handler:                                    ; preds = %catch.dispatch
+  %phi.lcssa = phi i32 [ %phi, %catch.dispatch ]
+  %tmp19 = catchpad within %tmp18 [i8* null]
+  catchret from %tmp19 to label %done
+
+done:
+  ret i32 %phi.lcssa
+
+for.inc:                                          ; preds = %for.body
+  %inc = add i32 %phi, 1
+  br label %for.body
+}
+
+; CHECK-LABEL: define i32 @test2(
+; CHECK:      %phi.lcssa = phi i32 [ %phi, %catch.dispatch ]
+; CHECK-NEXT: catchpad within