[PATCH] D127712: Prevent crash when TurnSwitchRangeIntoICmp receives default unreachable destination

[Hans Wennborg via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rGbf02ed240dfa: Prevent crash when TurnSwitchRangeIntoICmp receives default unreachable… (authored by swamulism, committed by hans).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D127712/new/

https://reviews.llvm.org/D127712

Files:
  llvm/lib/Transforms/Utils/SimplifyCFG.cpp
  llvm/test/Transforms/SimplifyCFG/switch-range-to-icmp.ll


Index: llvm/test/Transforms/SimplifyCFG/switch-range-to-icmp.ll
===================================================================
--- llvm/test/Transforms/SimplifyCFG/switch-range-to-icmp.ll
+++ llvm/test/Transforms/SimplifyCFG/switch-range-to-icmp.ll
@@ -145,3 +145,47 @@
 unreach2:
   unreachable
 }
+
+
+define void @pr53208_single_reachable_dest(i8 %sw, i32* %p0) {
+; CHECK-LABEL: @pr53208_single_reachable_dest(
+; CHECK-NEXT:  group2:
+; CHECK-NEXT:    call void @bar(i32* [[P0:%.*]])
+; CHECK-NEXT:    ret void
+;
+  switch i8 %sw, label %group3 [
+  i8 0, label %group1
+  i8 1, label %group1
+  i8 2, label %group1
+  i8 3, label %group1
+  i8 11, label %group1
+  i8 12, label %group1
+  i8 13, label %group1
+  i8 7, label %group1
+  i8 17, label %group1
+  i8 14, label %group1
+  i8 15, label %group1
+  i8 4, label %group2
+  i8 5, label %group2
+  i8 6, label %group2
+  i8 8, label %group2
+  i8 9, label %group2
+  i8 10, label %group2
+  ]
+
+group1:
+  br label %exit
+
+group2:
+  br label %exit
+
+group3:
+  br label %exit
+
+exit:
+  %phi = phi i32* [ null, %group3 ], [ %p0, %group2 ], [ null, %group1 ]
+  call void @bar(i32* %phi)
+  ret void
+}
+
+declare void @bar(i32* nonnull dereferenceable(4))
Index: llvm/lib/Transforms/Utils/SimplifyCFG.cpp
===================================================================
--- llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -5184,8 +5184,9 @@
   }
 }
 
-/// Turn a switch with two reachable destinations into an integer range
-/// comparison and branch.
+/// Turn a switch into an integer range comparison and branch.
+/// Switches with more than 2 destinations are ignored.
+/// Switches with 1 destination are also ignored.
 bool SimplifyCFGOpt::TurnSwitchRangeIntoICmp(SwitchInst *SI,
                                              IRBuilder<> &Builder) {
   assert(SI->getNumCases() > 1 && "Degenerate switch?");
@@ -5217,6 +5218,8 @@
     }
     return false; // More than two destinations.
   }
+  if (!DestB)
+    return false; // All destinations are the same and the default is unreachable
 
   assert(DestA && DestB &&
          "Single-destination switch should have been folded.");


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