[PATCH] D24680: Jump threading: avoid trying to split edge into landingpad block (PR27840)

[Hans Wennborg via llvm-commits]

hans created this revision.
hans added a reviewer: nlewycky.
hans added a subscriber: llvm-commits.

Splitting the edge is nontrivial because of the landing pad, and we would
currently assert trying to do it.

https://reviews.llvm.org/D24680

Files:
  lib/Transforms/Scalar/JumpThreading.cpp
  test/Transforms/JumpThreading/pr27840.ll

Index: test/Transforms/JumpThreading/pr27840.ll
===================================================================
--- /dev/null
+++ test/Transforms/JumpThreading/pr27840.ll
@@ -0,0 +1,33 @@
+; RUN: opt -jump-threading -S < %s | FileCheck %s
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.11.0"
+
+declare void @helper()
+declare i32 @__gxx_personality_v0(...)
+
+
+define void @pr27840(i8* %call, i1 %A) personality i32(...)* @__gxx_personality_v0 {
+entry:
+  invoke void @helper()
+          to label %invoke.cont unwind label %lpad
+
+; Don't jump threading; we can't split the critical edge from entry to lpad.
+; CHECK-LABEL: @pr27840
+; CHECK: invoke
+; CHECK-NEXT: to label %invoke.cont unwind label %lpad
+
+invoke.cont:
+  invoke void @helper()
+          to label %nowhere unwind label %lpad
+
+lpad:
+  %b = phi i1 [ true, %invoke.cont ], [ false, %entry ]
+  landingpad { i8*, i32 }
+          cleanup
+  %xor = xor i1 %b, %A
+  br i1 %xor, label %nowhere, label %invoke.cont
+
+nowhere:
+  unreachable
+}
Index: lib/Transforms/Scalar/JumpThreading.cpp
===================================================================
--- lib/Transforms/Scalar/JumpThreading.cpp
+++ lib/Transforms/Scalar/JumpThreading.cpp
@@ -1331,6 +1331,10 @@
   if (!isa<PHINode>(BB->front()))
     return false;
 
+  // If this BB is a landing pad, we won't be able to split the edge into it.
+  if (BB->isEHPad())
+    return false;
+
   // If we have a xor as the branch input to this block, and we know that the
   // LHS or RHS of the xor in any predecessor is true/false, then we can clone
   // the condition into the predecessor and fix that value to true, saving some


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