Index: llvm/include/llvm/Transforms/Scalar/JumpThreading.h
===================================================================
--- llvm/include/llvm/Transforms/Scalar/JumpThreading.h
+++ llvm/include/llvm/Transforms/Scalar/JumpThreading.h
@@ -90,6 +90,7 @@
 #endif
 
   unsigned BBDupThreshold;
+  unsigned DefaultBBDupThreshold;
 
 public:
   JumpThreadingPass(int T = -1);
Index: llvm/lib/Transforms/Scalar/JumpThreading.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -170,7 +170,7 @@
 }
 
 JumpThreadingPass::JumpThreadingPass(int T) {
-  BBDupThreshold = (T == -1) ? BBDuplicateThreshold : unsigned(T);
+  DefaultBBDupThreshold = (T == -1) ? BBDuplicateThreshold : unsigned(T);
 }
 
 // Update branch probability information according to conditional
@@ -374,6 +374,15 @@
     BFI = std::move(BFI_);
   }
 
+  // Reduce the number of instructions duplicated when optimizing strictly for
+  // size.
+  if (BBDuplicateThreshold.getNumOccurrences())
+    BBDupThreshold = BBDuplicateThreshold;
+  else if (F.hasFnAttribute(Attribute::MinSize))
+    BBDupThreshold = 3;
+  else
+    BBDupThreshold = DefaultBBDupThreshold;
+
   // JumpThreading must not processes blocks unreachable from entry. It's a
   // waste of compute time and can potentially lead to hangs.
   SmallPtrSet<BasicBlock *, 16> Unreachable;
Index: llvm/test/Transforms/JumpThreading/codesize-loop.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/JumpThreading/codesize-loop.ll
@@ -0,0 +1,152 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -jump-threading -S %s -o - | FileCheck %s --check-prefix=DEFAULT
+; RUN: opt -jump-threading -S -jump-threading-threshold=6 %s -o - | FileCheck %s --check-prefix=OVERIDE
+
+@.str = private unnamed_addr constant [4 x i8] c"%d\0A\00", align 1
+define i32 @test_minsize(i32 %argc, i8** nocapture readonly %argv) local_unnamed_addr #0 {
+; DEFAULT-LABEL: @test_minsize(
+; DEFAULT-NEXT:  entry:
+; DEFAULT-NEXT:    [[CMP:%.*]] = icmp eq i32 [[ARGC:%.*]], 2
+; DEFAULT-NEXT:    br i1 [[CMP]], label [[COND_TRUE:%.*]], label [[COND_END:%.*]]
+; DEFAULT:       cond.true:
+; DEFAULT-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds i8*, i8** [[ARGV:%.*]], i32 1
+; DEFAULT-NEXT:    [[TMP0:%.*]] = load i8*, i8** [[ARRAYIDX]], align 4
+; DEFAULT-NEXT:    [[CALL:%.*]] = tail call i32 @atoi(i8* [[TMP0]])
+; DEFAULT-NEXT:    br label [[COND_END]]
+; DEFAULT:       cond.end:
+; DEFAULT-NEXT:    [[COND:%.*]] = phi i32 [ [[CALL]], [[COND_TRUE]] ], [ 46, [[ENTRY:%.*]] ]
+; DEFAULT-NEXT:    [[TMP1:%.*]] = mul i32 [[COND]], [[COND]]
+; DEFAULT-NEXT:    [[TMP2:%.*]] = mul i32 [[TMP1]], [[TMP1]]
+; DEFAULT-NEXT:    [[TMP3:%.*]] = mul i32 [[COND]], [[TMP2]]
+; DEFAULT-NEXT:    [[TMP4:%.*]] = icmp sgt i32 [[COND]], 0
+; DEFAULT-NEXT:    br i1 [[TMP4]], label [[TMP5:%.*]], label [[TMP6:%.*]]
+; DEFAULT:       5:
+; DEFAULT-NEXT:    br label [[TMP6]]
+; DEFAULT:       6:
+; DEFAULT-NEXT:    [[TMP7:%.*]] = phi i32 [ [[COND]], [[TMP5]] ], [ 0, [[COND_END]] ]
+; DEFAULT-NEXT:    [[TMP8:%.*]] = mul i32 [[TMP3]], [[TMP7]]
+; DEFAULT-NEXT:    [[CALL33:%.*]] = tail call i32 (i8*, ...) @printf(i8* nonnull dereferenceable(1) getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i32 0, i32 0), i32 [[TMP8]])
+; DEFAULT-NEXT:    ret i32 0
+;
+; OVERIDE-LABEL: @test_minsize(
+; OVERIDE-NEXT:  entry:
+; OVERIDE-NEXT:    [[CMP:%.*]] = icmp eq i32 [[ARGC:%.*]], 2
+; OVERIDE-NEXT:    br i1 [[CMP]], label [[COND_END:%.*]], label [[COND_END_THREAD:%.*]]
+; OVERIDE:       cond.end:
+; OVERIDE-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds i8*, i8** [[ARGV:%.*]], i32 1
+; OVERIDE-NEXT:    [[TMP0:%.*]] = load i8*, i8** [[ARRAYIDX]], align 4
+; OVERIDE-NEXT:    [[CALL:%.*]] = tail call i32 @atoi(i8* [[TMP0]])
+; OVERIDE-NEXT:    [[TMP1:%.*]] = mul i32 [[CALL]], [[CALL]]
+; OVERIDE-NEXT:    [[TMP2:%.*]] = mul i32 [[TMP1]], [[TMP1]]
+; OVERIDE-NEXT:    [[TMP3:%.*]] = mul i32 [[CALL]], [[TMP2]]
+; OVERIDE-NEXT:    [[TMP4:%.*]] = icmp sgt i32 [[CALL]], 0
+; OVERIDE-NEXT:    br i1 [[TMP4]], label [[COND_END_THREAD]], label [[TMP6:%.*]]
+; OVERIDE:       cond.end.thread:
+; OVERIDE-NEXT:    [[TMP5:%.*]] = phi i32 [ [[TMP3]], [[COND_END]] ], [ 205962976, [[ENTRY:%.*]] ]
+; OVERIDE-NEXT:    [[COND2:%.*]] = phi i32 [ [[CALL]], [[COND_END]] ], [ 46, [[ENTRY]] ]
+; OVERIDE-NEXT:    br label [[TMP6]]
+; OVERIDE:       6:
+; OVERIDE-NEXT:    [[TMP7:%.*]] = phi i32 [ [[TMP5]], [[COND_END_THREAD]] ], [ [[TMP3]], [[COND_END]] ]
+; OVERIDE-NEXT:    [[TMP8:%.*]] = phi i32 [ [[COND2]], [[COND_END_THREAD]] ], [ 0, [[COND_END]] ]
+; OVERIDE-NEXT:    [[TMP9:%.*]] = mul i32 [[TMP7]], [[TMP8]]
+; OVERIDE-NEXT:    [[CALL33:%.*]] = tail call i32 (i8*, ...) @printf(i8* nonnull dereferenceable(1) getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i32 0, i32 0), i32 [[TMP9]])
+; OVERIDE-NEXT:    ret i32 0
+;
+entry:
+  %cmp = icmp eq i32 %argc, 2
+  br i1 %cmp, label %cond.true, label %cond.end
+
+cond.true:                                        ; preds = %entry
+  %arrayidx = getelementptr inbounds i8*, i8** %argv, i32 1
+  %0 = load i8*, i8** %arrayidx, align 4
+  %call = tail call i32 @atoi(i8* %0)
+  br label %cond.end
+
+cond.end:                                         ; preds = %entry, %cond.true
+  %cond = phi i32 [ %call, %cond.true ], [ 46, %entry ]
+  %1 = mul i32 %cond, %cond
+  %2 = mul i32 %1, %1
+  %3 = mul i32 %cond, %2
+  %4 = icmp sgt i32 %cond, 0
+  %spec.select = select i1 %4, i32 %cond, i32 0
+  %5 = mul i32 %3, %spec.select
+  %call33 = tail call i32 (i8*, ...) @printf(i8* nonnull dereferenceable(1) getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i32 0, i32 0), i32 %5) #4
+  ret i32 0
+}
+
+define i32 @test_optsize(i32 %argc, i8** nocapture readonly %argv) local_unnamed_addr #1 {
+; DEFAULT-LABEL: @test_optsize(
+; DEFAULT-NEXT:  entry:
+; DEFAULT-NEXT:    [[CMP:%.*]] = icmp eq i32 [[ARGC:%.*]], 2
+; DEFAULT-NEXT:    br i1 [[CMP]], label [[COND_END:%.*]], label [[COND_END_THREAD:%.*]]
+; DEFAULT:       cond.end:
+; DEFAULT-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds i8*, i8** [[ARGV:%.*]], i32 1
+; DEFAULT-NEXT:    [[TMP0:%.*]] = load i8*, i8** [[ARRAYIDX]], align 4
+; DEFAULT-NEXT:    [[CALL:%.*]] = tail call i32 @atoi(i8* [[TMP0]])
+; DEFAULT-NEXT:    [[TMP1:%.*]] = mul i32 [[CALL]], [[CALL]]
+; DEFAULT-NEXT:    [[TMP2:%.*]] = mul i32 [[TMP1]], [[TMP1]]
+; DEFAULT-NEXT:    [[TMP3:%.*]] = mul i32 [[CALL]], [[TMP2]]
+; DEFAULT-NEXT:    [[TMP4:%.*]] = icmp sgt i32 [[CALL]], 0
+; DEFAULT-NEXT:    br i1 [[TMP4]], label [[COND_END_THREAD]], label [[TMP6:%.*]]
+; DEFAULT:       cond.end.thread:
+; DEFAULT-NEXT:    [[TMP5:%.*]] = phi i32 [ [[TMP3]], [[COND_END]] ], [ 205962976, [[ENTRY:%.*]] ]
+; DEFAULT-NEXT:    [[COND2:%.*]] = phi i32 [ [[CALL]], [[COND_END]] ], [ 46, [[ENTRY]] ]
+; DEFAULT-NEXT:    br label [[TMP6]]
+; DEFAULT:       6:
+; DEFAULT-NEXT:    [[TMP7:%.*]] = phi i32 [ [[TMP5]], [[COND_END_THREAD]] ], [ [[TMP3]], [[COND_END]] ]
+; DEFAULT-NEXT:    [[TMP8:%.*]] = phi i32 [ [[COND2]], [[COND_END_THREAD]] ], [ 0, [[COND_END]] ]
+; DEFAULT-NEXT:    [[TMP9:%.*]] = mul i32 [[TMP7]], [[TMP8]]
+; DEFAULT-NEXT:    [[CALL33:%.*]] = tail call i32 (i8*, ...) @printf(i8* nonnull dereferenceable(1) getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i32 0, i32 0), i32 [[TMP9]])
+; DEFAULT-NEXT:    ret i32 0
+;
+; OVERIDE-LABEL: @test_optsize(
+; OVERIDE-NEXT:  entry:
+; OVERIDE-NEXT:    [[CMP:%.*]] = icmp eq i32 [[ARGC:%.*]], 2
+; OVERIDE-NEXT:    br i1 [[CMP]], label [[COND_END:%.*]], label [[COND_END_THREAD:%.*]]
+; OVERIDE:       cond.end:
+; OVERIDE-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds i8*, i8** [[ARGV:%.*]], i32 1
+; OVERIDE-NEXT:    [[TMP0:%.*]] = load i8*, i8** [[ARRAYIDX]], align 4
+; OVERIDE-NEXT:    [[CALL:%.*]] = tail call i32 @atoi(i8* [[TMP0]])
+; OVERIDE-NEXT:    [[TMP1:%.*]] = mul i32 [[CALL]], [[CALL]]
+; OVERIDE-NEXT:    [[TMP2:%.*]] = mul i32 [[TMP1]], [[TMP1]]
+; OVERIDE-NEXT:    [[TMP3:%.*]] = mul i32 [[CALL]], [[TMP2]]
+; OVERIDE-NEXT:    [[TMP4:%.*]] = icmp sgt i32 [[CALL]], 0
+; OVERIDE-NEXT:    br i1 [[TMP4]], label [[COND_END_THREAD]], label [[TMP6:%.*]]
+; OVERIDE:       cond.end.thread:
+; OVERIDE-NEXT:    [[TMP5:%.*]] = phi i32 [ [[TMP3]], [[COND_END]] ], [ 205962976, [[ENTRY:%.*]] ]
+; OVERIDE-NEXT:    [[COND2:%.*]] = phi i32 [ [[CALL]], [[COND_END]] ], [ 46, [[ENTRY]] ]
+; OVERIDE-NEXT:    br label [[TMP6]]
+; OVERIDE:       6:
+; OVERIDE-NEXT:    [[TMP7:%.*]] = phi i32 [ [[TMP5]], [[COND_END_THREAD]] ], [ [[TMP3]], [[COND_END]] ]
+; OVERIDE-NEXT:    [[TMP8:%.*]] = phi i32 [ [[COND2]], [[COND_END_THREAD]] ], [ 0, [[COND_END]] ]
+; OVERIDE-NEXT:    [[TMP9:%.*]] = mul i32 [[TMP7]], [[TMP8]]
+; OVERIDE-NEXT:    [[CALL33:%.*]] = tail call i32 (i8*, ...) @printf(i8* nonnull dereferenceable(1) getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i32 0, i32 0), i32 [[TMP9]])
+; OVERIDE-NEXT:    ret i32 0
+;
+entry:
+  %cmp = icmp eq i32 %argc, 2
+  br i1 %cmp, label %cond.true, label %cond.end
+
+cond.true:                                        ; preds = %entry
+  %arrayidx = getelementptr inbounds i8*, i8** %argv, i32 1
+  %0 = load i8*, i8** %arrayidx, align 4
+  %call = tail call i32 @atoi(i8* %0)
+  br label %cond.end
+
+cond.end:                                         ; preds = %entry, %cond.true
+  %cond = phi i32 [ %call, %cond.true ], [ 46, %entry ]
+  %1 = mul i32 %cond, %cond
+  %2 = mul i32 %1, %1
+  %3 = mul i32 %cond, %2
+  %4 = icmp sgt i32 %cond, 0
+  %spec.select = select i1 %4, i32 %cond, i32 0
+  %5 = mul i32 %3, %spec.select
+  %call33 = tail call i32 (i8*, ...) @printf(i8* nonnull dereferenceable(1) getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i32 0, i32 0), i32 %5) #4
+  ret i32 0
+}
+declare i32 @atoi(i8* nocapture) local_unnamed_addr
+declare i32 @printf(i8* nocapture readonly, ...) local_unnamed_addr
+
+attributes #0 = { minsize optsize }
+attributes #1 = { optsize }
+