[SimplifyCFG] fix accessing deleted PHINodes in switch-to-table conversion.

When we have a covered lookup table, make sure we don't delete PHINodes that
are cached in PHIs.

rdar://17887153

llvm-svn: 214642

diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 1c62559..63cb1c9 100644 (file)
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -3830,7 +3830,10 @@ static bool SwitchToLookupTable(SwitchInst *SI,
   const bool GeneratingCoveredLookupTable = MaxTableSize == TableSize;
   if (GeneratingCoveredLookupTable) {
     Builder.CreateBr(LookupBB);
-    SI->getDefaultDest()->removePredecessor(SI->getParent());
+    // We cached PHINodes in PHIs, to avoid accessing deleted PHINodes later,
+    // do not delete PHINodes here.
+    SI->getDefaultDest()->removePredecessor(SI->getParent(),
+                                            true/*DontDeleteUselessPHIs*/);
   } else {
     Value *Cmp = Builder.CreateICmpULT(TableIndex, ConstantInt::get(
                                        MinCaseVal->getType(), TableSize));

diff --git a/llvm/test/Transforms/SimplifyCFG/X86/switch-covered-bug.ll b/llvm/test/Transforms/SimplifyCFG/X86/switch-covered-bug.ll
new file mode 100644 (file)
index 0000000..22599b3
--- /dev/null
+++ b/llvm/test/Transforms/SimplifyCFG/X86/switch-covered-bug.ll
@@ -0,0 +1,50 @@
+; RUN: opt -S -simplifycfg < %s -mtriple=x86_64-apple-darwin12.0.0 | FileCheck %s
+; rdar://17887153
+target datalayout = "e-p:64:64:64-S128-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f16:16:16-f32:32:32-f64:64:64-f128:128:128-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
+target triple = "x86_64-apple-darwin12.0.0"
+
+; When we have a covered lookup table, make sure we don't delete PHINodes that
+; are cached in PHIs.
+; CHECK-LABEL: @test
+; CHECK: entry:
+; CHECK-NEXT: sub i3 %arg, -4
+; CHECK-NEXT: zext i3 %switch.tableidx to i4
+; CHECK-NEXT: getelementptr inbounds [8 x i64]* @switch.table, i32 0, i4 %switch.tableidx.zext
+; CHECK-NEXT: load i64* %switch.gep
+; CHECK-NEXT: add i64
+; CHECK-NEXT: ret i64
+define i64 @test(i3 %arg) {
+entry:
+  switch i3 %arg, label %Default [
+    i3 -2, label %Label6
+    i3 1, label %Label1
+    i3 2, label %Label2
+    i3 3, label %Label3
+    i3 -4, label %Label4
+    i3 -3, label %Label5
+  ]
+
+Default:
+  %v1 = phi i64 [ 7, %Label6 ], [ 11, %Label5 ], [ 6, %Label4 ], [ 13, %Label3 ], [ 9, %Label2 ], [ 15, %Label1 ], [ 8, %entry ]
+  %v2 = phi i64 [ 0, %Label6 ], [ 0, %Label5 ], [ 0, %Label4 ], [ 0, %Label3 ], [ 0, %Label2 ], [ 0, %Label1 ], [ 0, %entry ]
+  %v3 = add i64 %v1, %v2
+  ret i64 %v3
+
+Label1:
+  br label %Default
+
+Label2:
+  br label %Default
+
+Label3:
+  br label %Default
+
+Label4:
+  br label %Default
+
+Label5:
+  br label %Default
+
+Label6:
+  br label %Default
+}