Index: llvm/trunk/lib/Transforms/Scalar/GVNHoist.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Scalar/GVNHoist.cpp
+++ llvm/trunk/lib/Transforms/Scalar/GVNHoist.cpp
@@ -201,15 +201,12 @@
 class GVNHoist {
 public:
   GVNHoist(DominatorTree *DT, AliasAnalysis *AA, MemoryDependenceResults *MD,
-           MemorySSA *MSSA, bool OptForMinSize)
+           MemorySSA *MSSA)
       : DT(DT), AA(AA), MD(MD), MSSA(MSSA),
         MSSAUpdater(make_unique<MemorySSAUpdater>(MSSA)),
-        OptForMinSize(OptForMinSize), HoistingGeps(OptForMinSize),
-        HoistedCtr(0) {
-    // Hoist as far as possible when optimizing for code-size.
-    if (OptForMinSize)
-      MaxNumberOfBBSInPath = -1;
-  }
+        HoistingGeps(false),
+        HoistedCtr(0)
+  { }
 
   bool run(Function &F) {
     VN.setDomTree(DT);
@@ -255,7 +252,6 @@
   MemoryDependenceResults *MD;
   MemorySSA *MSSA;
   std::unique_ptr<MemorySSAUpdater> MSSAUpdater;
-  const bool OptForMinSize;
   const bool HoistingGeps;
   DenseMap<const Value *, unsigned> DFSNumber;
   BBSideEffectsSet BBSideEffects;
@@ -509,11 +505,6 @@
   bool safeToHoistScalar(const BasicBlock *HoistBB,
                          SmallPtrSetImpl<const BasicBlock *> &WL,
                          int &NBBsOnAllPaths) {
-    // Enable scalar hoisting at -Oz as it is safe to hoist scalars to a place
-    // where they are partially needed.
-    if (OptForMinSize)
-      return true;
-
     // Check that the hoisted expression is needed on all paths.
     if (!hoistingFromAllPaths(HoistBB, WL))
       return false;
@@ -927,13 +918,8 @@
                 Intr->getIntrinsicID() == Intrinsic::assume)
               continue;
           }
-          if (Call->mayHaveSideEffects()) {
-            if (!OptForMinSize)
-              break;
-            // We may continue hoisting across calls which write to memory.
-            if (Call->mayThrow())
-              break;
-          }
+          if (Call->mayHaveSideEffects())
+            break;
 
           if (Call->isConvergent())
             break;
@@ -975,7 +961,7 @@
     auto &MD = getAnalysis<MemoryDependenceWrapperPass>().getMemDep();
     auto &MSSA = getAnalysis<MemorySSAWrapperPass>().getMSSA();
 
-    GVNHoist G(&DT, &AA, &MD, &MSSA, F.optForMinSize());
+    GVNHoist G(&DT, &AA, &MD, &MSSA);
     return G.run(F);
   }
 
@@ -995,7 +981,7 @@
   AliasAnalysis &AA = AM.getResult<AAManager>(F);
   MemoryDependenceResults &MD = AM.getResult<MemoryDependenceAnalysis>(F);
   MemorySSA &MSSA = AM.getResult<MemorySSAAnalysis>(F).getMSSA();
-  GVNHoist G(&DT, &AA, &MD, &MSSA, F.optForMinSize());
+  GVNHoist G(&DT, &AA, &MD, &MSSA);
   if (!G.run(F))
     return PreservedAnalyses::all();
 
Index: llvm/trunk/test/Transforms/GVNHoist/hoist-unsafe-pr31729.ll
===================================================================
--- llvm/trunk/test/Transforms/GVNHoist/hoist-unsafe-pr31729.ll
+++ llvm/trunk/test/Transforms/GVNHoist/hoist-unsafe-pr31729.ll
@@ -0,0 +1,81 @@
+; RUN: opt -gvn-hoist -S < %s | FileCheck %s
+
+; Check that urem is not hoisted.
+; CHECK-LABEL: @main
+; CHECK: urem
+; CHECK: urem
+; CHECK: urem
+
+@g_x_s = global i32 -470211272, align 4
+@g_z_s = global i32 2007237709, align 4
+@g_x_u = global i32 282475249, align 4
+@g_z_u = global i32 984943658, align 4
+@g_m = global i32 16807, align 4
+@res = common global i32 0, align 4
+
+; Function Attrs:
+define i64 @func() #0 {
+entry:
+  ret i64 1
+}
+
+; Function Attrs:
+define i32 @main() {
+entry:
+  %0 = load volatile i32, i32* @g_x_s, align 4
+  %1 = load volatile i32, i32* @g_z_s, align 4
+  %2 = load volatile i32, i32* @g_x_u, align 4
+  %3 = load volatile i32, i32* @g_z_u, align 4
+  %4 = load volatile i32, i32* @g_m, align 4
+  %call = call i64 @func() #4
+  %conv = sext i32 %1 to i64
+  %cmp = icmp ne i64 %call, %conv
+  br i1 %cmp, label %if.end, label %lor.lhs.false
+
+lor.lhs.false:
+  %div = udiv i32 %4, %1
+  %rem = urem i32 %0, %div
+  %cmp2 = icmp eq i32 %rem, 0
+  br i1 %cmp2, label %if.end, label %if.then
+
+if.then:
+  br label %cleanup
+
+if.end:
+  %call4 = call i64 @func() #4
+  %conv5 = zext i32 %3 to i64
+  %cmp6 = icmp ne i64 %call4, %conv5
+  br i1 %cmp6, label %if.end14, label %lor.lhs.false8
+
+lor.lhs.false8:
+  %div9 = udiv i32 %4, %3
+  %rem10 = urem i32 %0, %div9
+  %cmp11 = icmp eq i32 %rem10, 0
+  br i1 %cmp11, label %if.end14, label %if.then13
+
+if.then13:
+  br label %cleanup
+
+if.end14:
+  %call15 = call i64 @func() #4
+  %cmp17 = icmp ne i64 %call15, %conv
+  br i1 %cmp17, label %if.end25, label %lor.lhs.false19
+
+lor.lhs.false19:
+  %div20 = udiv i32 %4, %1
+  %rem21 = urem i32 %0, %div20
+  %cmp22 = icmp eq i32 %rem21, 0
+  br i1 %cmp22, label %if.end25, label %if.then24
+
+if.then24:
+  br label %cleanup
+
+if.end25:
+  br label %cleanup
+
+cleanup:
+  %retval.0 = phi i32 [ 0, %if.end25 ], [ 1, %if.then24 ], [ 1, %if.then13 ], [ 1, %if.then ]
+  ret i32 %retval.0
+}
+
+attributes #0 = { minsize noinline nounwind optsize uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }