Index: include/llvm/CodeGen/StackMaps.h
===================================================================
--- include/llvm/CodeGen/StackMaps.h
+++ include/llvm/CodeGen/StackMaps.h
@@ -142,7 +142,7 @@
 
   typedef SmallVector<Location, 8> LocationVec;
   typedef SmallVector<LiveOutReg, 8> LiveOutVec;
-  typedef MapVector<int64_t, int64_t> ConstantPool;
+  typedef MapVector<uint64_t, uint64_t> ConstantPool;
   typedef MapVector<const MCSymbol *, uint64_t> FnStackSizeMap;
 
   struct CallsiteInfo {
Index: lib/CodeGen/StackMaps.cpp
===================================================================
--- lib/CodeGen/StackMaps.cpp
+++ lib/CodeGen/StackMaps.cpp
@@ -222,6 +222,12 @@
     // -1 is directly encoded as .long 0xFFFFFFFF with no constant pool.
     if (I->LocType == Location::Constant && !isInt<32>(I->Offset)) {
       I->LocType = Location::ConstantIndex;
+      // ConstPool is intentionally a MapVector of uint64_ts (as
+      // opposed to int64_ts).  We should never be in a situation
+      // where we have to insert either the tombstone or the empty
+      // keys into a map, and for a DenseMap<uint64_t, T> these are
+      // (uint64_t)0 and (uint64_t)-1.  They can be and are
+      // represented using 32 bit integers.
       auto Result = ConstPool.insert(std::make_pair(I->Offset, I->Offset));
       I->Offset = Result.first - ConstPool.begin();
     }
Index: test/CodeGen/X86/stackmap-large-constants.ll
===================================================================
--- /dev/null
+++ test/CodeGen/X86/stackmap-large-constants.ll
@@ -0,0 +1,83 @@
+; RUN: llc < %s -mtriple=x86_64-apple-darwin | FileCheck %s
+
+; CHECK-LABEL:	.section	__LLVM_STACKMAPS,__llvm_stackmaps
+; CHECK-NEXT: __LLVM_StackMaps:
+; version
+; CHECK-NEXT: 	.byte	1
+; reserved
+; CHECK-NEXT: 	.byte	0
+; reserved
+; CHECK-NEXT: 	.short	0
+; # functions
+; CHECK-NEXT: 	.long	2
+; # constants
+; CHECK-NEXT: 	.long	2
+; # records
+; CHECK-NEXT: 	.long	2
+; function address & stack size
+; CHECK-NEXT: 	.quad	_foo
+; CHECK-NEXT: 	.quad	8
+; function address & stack size
+; CHECK-NEXT: 	.quad	_bar
+; CHECK-NEXT: 	.quad	8
+
+; Constants Array:
+; CHECK-NEXT: 	.quad	9223372036854775807
+; CHECK-NEXT: 	.quad	-9223372036854775808
+
+; Patchpoint ID
+; CHECK-NEXT: 	.quad	0
+; Instruction offset
+; CHECK-NEXT: 	.long	Ltmp3-_foo
+; reserved
+; CHECK-NEXT: 	.short	0
+; # locations
+; CHECK-NEXT: 	.short	1
+; ConstantIndex
+; CHECK-NEXT: 	.byte	5
+; reserved
+; CHECK-NEXT: 	.byte	8
+; Dwarf RegNum
+; CHECK-NEXT: 	.short	0
+; Offset
+; CHECK-NEXT: 	.long	0
+; padding
+; CHECK-NEXT: 	.short	0
+; NumLiveOuts
+; CHECK-NEXT: 	.short	0
+
+; CHECK-NEXT: 	.align	3
+
+declare void @llvm.experimental.stackmap(i64, i32, ...)
+
+define void @foo() {
+  tail call void (i64, i32, ...)* @llvm.experimental.stackmap(i64 0, i32 0, i64 9223372036854775807)
+  ret void
+}
+
+; Patchpoint ID
+; CHECK-NEXT: 	.quad	0
+; Instruction Offset
+; CHECK-NEXT: 	.long	Ltmp7-_bar
+; reserved
+; CHECK-NEXT: 	.short	0
+; # locations
+; CHECK-NEXT: 	.short	1
+; ConstantIndex
+; CHECK-NEXT: 	.byte	5
+; reserved
+; CHECK-NEXT: 	.byte	8
+; Dwarf RegNum
+; CHECK-NEXT: 	.short	0
+; Offset
+; CHECK-NEXT: 	.long	1
+; padding
+; CHECK-NEXT: 	.short	0
+; NumLiveOuts
+; CHECK-NEXT: 	.short	0
+
+
+define void @bar() {
+  tail call void (i64, i32, ...)* @llvm.experimental.stackmap(i64 0, i32 0, i64 -9223372036854775808)
+  ret void
+}