Index: llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
+++ llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
@@ -353,9 +353,9 @@
   LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
   OptSize = F.optForSize();
 
+  ProfileSummaryInfo *PSI =
+      getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
   if (ProfileGuidedSectionPrefix) {
-    ProfileSummaryInfo *PSI =
-        getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
     if (PSI->isFunctionHotInCallGraph(&F))
       F.setSectionPrefix(".hot");
     else if (PSI->isFunctionColdInCallGraph(&F))
@@ -364,7 +364,8 @@
 
   /// This optimization identifies DIV instructions that can be
   /// profitably bypassed and carried out with a shorter, faster divide.
-  if (!OptSize && TLI && TLI->isSlowDivBypassed()) {
+  if (!OptSize && !PSI->hasHugeWorkingSetSize() && TLI &&
+      TLI->isSlowDivBypassed()) {
     const DenseMap<unsigned int, unsigned int> &BypassWidths =
        TLI->getBypassSlowDivWidths();
     BasicBlock* BB = &*F.begin();
Index: llvm/trunk/test/CodeGen/X86/bypass-slow-division-tune.ll
===================================================================
--- llvm/trunk/test/CodeGen/X86/bypass-slow-division-tune.ll
+++ llvm/trunk/test/CodeGen/X86/bypass-slow-division-tune.ll
@@ -2,6 +2,7 @@
 ; RUN: llc -mtriple=x86_64-unknown-linux-gnu -mcpu=atom       < %s | FileCheck -check-prefixes=ATOM,CHECK %s
 ; RUN: llc -mtriple=x86_64-unknown-linux-gnu -mcpu=silvermont < %s | FileCheck -check-prefixes=REST,CHECK %s
 ; RUN: llc -mtriple=x86_64-unknown-linux-gnu -mcpu=skylake    < %s | FileCheck -check-prefixes=REST,CHECK %s
+; RUN: llc -profile-summary-huge-working-set-size-threshold=1 -mtriple=x86_64-unknown-linux-gnu -mcpu=skylake    < %s | FileCheck -check-prefixes=HUGEWS %s
 
 ; Verify that div32 is bypassed only for Atoms.
 define i32 @div32(i32 %a, i32 %b) {
@@ -36,6 +37,15 @@
 define i64 @div64_optsize(i64 %a, i64 %b) optsize {
 ; CHECK-LABEL: div64_optsize:
 ; CHECK-NOT: divl
+; CHECK: ret
+  %div = sdiv i64 %a, %b
+  ret i64 %div
+}
+
+define i64 @div64_hugews(i64 %a, i64 %b) {
+; HUGEWS-LABEL: div64_hugews:
+; HUGEWS-NOT: divl
+; HUGEWS: ret
   %div = sdiv i64 %a, %b
   ret i64 %div
 }
@@ -43,6 +53,7 @@
 define i32 @div32_optsize(i32 %a, i32 %b) optsize {
 ; CHECK-LABEL: div32_optsize:
 ; CHECK-NOT: divb
+; CHECK: ret
   %div = sdiv i32 %a, %b
   ret i32 %div
 }
@@ -50,6 +61,23 @@
 define i32 @div32_minsize(i32 %a, i32 %b) minsize {
 ; CHECK-LABEL: div32_minsize:
 ; CHECK-NOT: divb
+; CHECK: ret
   %div = sdiv i32 %a, %b
   ret i32 %div
 }
+
+!llvm.module.flags = !{!1}
+!1 = !{i32 1, !"ProfileSummary", !2}
+!2 = !{!3, !4, !5, !6, !7, !8, !9, !10}
+!3 = !{!"ProfileFormat", !"InstrProf"}
+!4 = !{!"TotalCount", i64 10000}
+!5 = !{!"MaxCount", i64 1000}
+!6 = !{!"MaxInternalCount", i64 1}
+!7 = !{!"MaxFunctionCount", i64 1000}
+!8 = !{!"NumCounts", i64 3}
+!9 = !{!"NumFunctions", i64 3}
+!10 = !{!"DetailedSummary", !11}
+!11 = !{!12, !13, !14}
+!12 = !{i32 10000, i64 1000, i32 1}
+!13 = !{i32 999000, i64 1000, i32 3}
+!14 = !{i32 999999, i64 5, i32 3}