From 63da0c238bfb90a1d04e94ab92fe122cff72dc0d Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Fri, 6 Jan 2017 22:58:02 +0000
Subject: [InstSimplify] Optimize away udivs in the presence of range metadata

We know that udiv %V, C can be optimized away to 0 if %V is ult C.

llvm-svn: 291296
---
 llvm/lib/Analysis/InstructionSimplify.cpp | 10 ++++++++++
 1 file changed, 10 insertions(+)

(limited to 'llvm/lib/Analysis')

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 7ae7c4ef939..8da2f0981d0 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -1106,6 +1106,16 @@ static Value *SimplifyUDivInst(Value *Op0, Value *Op1, const Query &Q,
   if (Value *V = SimplifyDiv(Instruction::UDiv, Op0, Op1, Q, MaxRecurse))
     return V;
 
+  // udiv %V, C -> 0 if %V < C
+  if (MaxRecurse) {
+    if (Constant *C = dyn_cast_or_null<Constant>(SimplifyICmpInst(
+            ICmpInst::ICMP_ULT, Op0, Op1, Q, MaxRecurse - 1))) {
+      if (C->isAllOnesValue()) {
+        return Constant::getNullValue(Op0->getType());
+      }
+    }
+  }
+
   return nullptr;
 }
 
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