From 162f046004b302fd1aa2d3c27df43ee163c4c6b6 Mon Sep 17 00:00:00 2001
From: Sanjoy Das <sanjoy@playingwithpointers.com>
Date: Tue, 11 Aug 2015 21:33:55 +0000
Subject: [PATCH] Fix PR24354.

`InstCombiner::OptimizeOverflowCheck` was asserting an
invariant (operands to binary operations are ordered by decreasing
complexity) that wasn't really an invariant.  Fix this by instead having
`InstCombiner::OptimizeOverflowCheck` establish the invariant if it does
not hold.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@244676 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/InstCombine/InstCombineCompares.cpp |  5 ++--
 test/Transforms/InstCombine/pr24354.ll             | 33 ++++++++++++++++++++++
 2 files changed, 35 insertions(+), 3 deletions(-)
 create mode 100644 test/Transforms/InstCombine/pr24354.ll

diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 0bd6fd2f226..95bba3c7af7 100644
--- a/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -2112,9 +2112,8 @@ static Instruction *ProcessUGT_ADDCST_ADD(ICmpInst &I, Value *A, Value *B,
 bool InstCombiner::OptimizeOverflowCheck(OverflowCheckFlavor OCF, Value *LHS,
                                          Value *RHS, Instruction &OrigI,
                                          Value *&Result, Constant *&Overflow) {
-  assert((!OrigI.isCommutative() ||
-          !(isa<Constant>(LHS) && !isa<Constant>(RHS))) &&
-         "call with a constant RHS if possible!");
+  if (OrigI.isCommutative() && isa<Constant>(LHS) && !isa<Constant>(RHS))
+    std::swap(LHS, RHS);
 
   auto SetResult = [&](Value *OpResult, Constant *OverflowVal, bool ReuseName) {
     Result = OpResult;
diff --git a/test/Transforms/InstCombine/pr24354.ll b/test/Transforms/InstCombine/pr24354.ll
new file mode 100644
index 00000000000..3b36fd1b74e
--- /dev/null
+++ b/test/Transforms/InstCombine/pr24354.ll
@@ -0,0 +1,33 @@
+; RUN: opt -instcombine -S < %s | FileCheck %s
+
+; This used to crash opt
+
+@c = common global i32 0, align 4
+@b = common global i32 0, align 4
+@a = common global i16 0, align 2
+@d = common global i32 0, align 4
+
+define void @fn3() {
+; CHECK: @fn3
+bb:
+  %tmp = load i32, i32* @c, align 4
+  %tmp1 = icmp eq i32 %tmp, 0
+  br i1 %tmp1, label %bb2, label %bb6
+
+bb2:                                              ; preds = %bb
+  %tmp3 = load i32, i32* @b, align 4
+  %tmp.i = add nsw i32 255, %tmp3
+  %tmp5 = icmp ugt i32 %tmp.i, 254
+  br label %bb6
+
+bb6:                                              ; preds = %bb, %bb2
+  %tmp7 = phi i1 [ true, %bb ], [ %tmp5, %bb2 ]
+  %tmp8 = zext i1 %tmp7 to i32
+  %tmp10 = icmp eq i32 %tmp8, 0
+  %tmp12 = load i16, i16* @a, align 2
+  %tmp14 = icmp ne i16 %tmp12, 0
+  %tmp16 = select i1 %tmp10, i1 false, i1 %tmp14
+  %tmp17 = zext i1 %tmp16 to i32
+  store i32 %tmp17, i32* @d, align 4
+  ret void
+}
-- 
2.11.0