From b30591ec646b5f53c1163bf9bd74091248598589 Mon Sep 17 00:00:00 2001
From: Nick Lewycky <nicholas@mxc.ca>
Date: Wed, 6 Aug 2008 04:54:03 +0000
Subject: [PATCH] Reinstate this optimization, but without the miscompile.
 Thanks to Bill for tracking down that this was breaking llvm-gcc bootstrap on
 Linux.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@54394 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/InstructionCombining.cpp    | 15 +++++++++++++++
 test/Transforms/InstCombine/2008-07-08-AndICmp.ll | 10 ++++++++++
 2 files changed, 25 insertions(+)
 create mode 100644 test/Transforms/InstCombine/2008-07-08-AndICmp.ll

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index d15b6cf18bd..fbd0d200717 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -3586,6 +3586,21 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
     }
   }
   
+  { // (icmp ult A, C) & (icmp ult B, C) --> (icmp ult (A|B), C)
+    // where C is a power of 2
+    Value *A, *B;
+    ConstantInt *C1, *C2;
+    ICmpInst::Predicate LHSCC, RHSCC;
+    if (match(&I, m_And(m_ICmp(LHSCC, m_Value(A), m_ConstantInt(C1)),
+                        m_ICmp(RHSCC, m_Value(B), m_ConstantInt(C2)))))
+      if (C1 == C2 && LHSCC == RHSCC && LHSCC == ICmpInst::ICMP_ULT &&
+          C1->getValue().isPowerOf2()) {
+        Instruction *NewOr = BinaryOperator::CreateOr(A, B);
+        InsertNewInstBefore(NewOr, I);
+        return new ICmpInst(LHSCC, NewOr, C1);
+      }
+  }
+  
   if (ICmpInst *RHS = dyn_cast<ICmpInst>(Op1)) {
     // (icmp1 A, B) & (icmp2 A, B) --> (icmp3 A, B)
     if (Instruction *R = AssociativeOpt(I, FoldICmpLogical(*this, RHS)))
diff --git a/test/Transforms/InstCombine/2008-07-08-AndICmp.ll b/test/Transforms/InstCombine/2008-07-08-AndICmp.ll
new file mode 100644
index 00000000000..c6002413147
--- /dev/null
+++ b/test/Transforms/InstCombine/2008-07-08-AndICmp.ll
@@ -0,0 +1,10 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep icmp | count 1
+; PR2330
+
+define i1 @foo(i32 %a, i32 %b) nounwind {
+entry:
+	icmp ult i32 %a, 8		; <i1>:0 [#uses=1]
+	icmp ult i32 %b, 8		; <i1>:1 [#uses=1]
+	and i1 %1, %0		; <i1>:2 [#uses=1]
+	ret i1 %2
+}