diff --git a/llvm/lib/ExecutionEngine/Orc/Core.cpp b/llvm/lib/ExecutionEngine/Orc/Core.cpp
index 6a9ebb41e79f6..978057237e531 100644
--- a/llvm/lib/ExecutionEngine/Orc/Core.cpp
+++ b/llvm/lib/ExecutionEngine/Orc/Core.cpp
@@ -1821,17 +1821,10 @@ ExecutionSession::lookup(const JITDylibSearchOrder &SearchOrder,
                          RegisterDependenciesFunction RegisterDependencies) {
 #if LLVM_ENABLE_THREADS
   // In the threaded case we use promises to return the results.
-  std::promise<SymbolMap> PromisedResult;
-  Error ResolutionError = Error::success();
+  std::promise<MSVCPExpected<SymbolMap>> PromisedResult;
 
   auto NotifyComplete = [&](Expected<SymbolMap> R) {
-    if (R)
-      PromisedResult.set_value(std::move(*R));
-    else {
-      ErrorAsOutParameter _(ResolutionError);
-      ResolutionError = R.takeError();
-      PromisedResult.set_value(SymbolMap());
-    }
+    PromisedResult.set_value(std::move(R));
   };
 
 #else
@@ -1848,18 +1841,11 @@ ExecutionSession::lookup(const JITDylibSearchOrder &SearchOrder,
 #endif
 
   // Perform the asynchronous lookup.
-  lookup(K, SearchOrder, std::move(Symbols), RequiredState, NotifyComplete,
-         RegisterDependencies);
+  lookup(K, SearchOrder, std::move(Symbols), RequiredState,
+         std::move(NotifyComplete), RegisterDependencies);
 
 #if LLVM_ENABLE_THREADS
-  auto ResultFuture = PromisedResult.get_future();
-  auto Result = ResultFuture.get();
-
-  if (ResolutionError)
-    return std::move(ResolutionError);
-
-  return std::move(Result);
-
+  return PromisedResult.get_future().get();
 #else
   if (ResolutionError)
     return std::move(ResolutionError);
diff --git a/llvm/test/ExecutionEngine/JITLink/AArch32/ELF_data_alignment.s b/llvm/test/ExecutionEngine/JITLink/AArch32/ELF_data_alignment.s
index b4f6e04d4eb4a..9296f048e51ed 100644
--- a/llvm/test/ExecutionEngine/JITLink/AArch32/ELF_data_alignment.s
+++ b/llvm/test/ExecutionEngine/JITLink/AArch32/ELF_data_alignment.s
@@ -1,16 +1,18 @@
 # REQUIRES: asserts
 # RUN: llvm-mc -triple=armv7-linux-gnueabi -arm-add-build-attributes -filetype=obj -o %t_armv7.o %s
 # RUN: llvm-objdump -s --section=.rodata %t_armv7.o | FileCheck --check-prefix=CHECK-OBJ %s
-# RUN: llvm-jitlink -noexec -slab-address 0x76ff0000 -slab-allocate 10Kb \
-# RUN:              -slab-page-size 4096 %t_armv7.o -debug-only=jitlink 2>&1 \
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
+# RUN:              -slab-address 0x76ff0000 -slab-allocate 10Kb \
+# RUN:              -slab-page-size 4096 %t_armv7.o 2>&1 \
 # RUN:              | FileCheck --check-prefix=CHECK-LG %s
 # RUN: llvm-jitlink -noexec -slab-address 0x76ff0000 -slab-allocate 10Kb \
 # RUN:              -slab-page-size 4096 %t_armv7.o -check %s
 
 # RUN: llvm-mc -triple=thumbv7-linux-gnueabi -arm-add-build-attributes -filetype=obj -o %t_thumbv7.o %s
 # RUN: llvm-objdump -s --section=.rodata %t_thumbv7.o | FileCheck --check-prefix=CHECK-OBJ %s
-# RUN: llvm-jitlink -noexec -slab-address 0x76ff0000 -slab-allocate 10Kb \
-# RUN:              -slab-page-size 4096 %t_thumbv7.o -debug-only=jitlink 2>&1 \
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
+# RUN:              -slab-address 0x76ff0000 -slab-allocate 10Kb \
+# RUN:              -slab-page-size 4096 %t_thumbv7.o 2>&1 \
 # RUN:              | FileCheck --check-prefix=CHECK-LG %s
 # RUN: llvm-jitlink -noexec -slab-address 0x76ff0000 -slab-allocate 10Kb \
 # RUN:              -slab-page-size 4096 %t_thumbv7.o -check %s
diff --git a/llvm/test/ExecutionEngine/JITLink/AArch64/ELF_ehframe.s b/llvm/test/ExecutionEngine/JITLink/AArch64/ELF_ehframe.s
index 151a041e7bcda..b25ffee270c45 100644
--- a/llvm/test/ExecutionEngine/JITLink/AArch64/ELF_ehframe.s
+++ b/llvm/test/ExecutionEngine/JITLink/AArch64/ELF_ehframe.s
@@ -1,7 +1,7 @@
 # REQUIRES: asserts
 # RUN: llvm-mc -triple=aarch64-linux-gnu -filetype=obj -o %t %s
-# RUN: llvm-jitlink -noexec -phony-externals -debug-only=jitlink %t 2>&1 | \
-# RUN:   FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
+# RUN:              -phony-externals %t 2>&1 | FileCheck %s
 #
 # Check that splitting of eh-frame sections works.
 #
diff --git a/llvm/test/ExecutionEngine/JITLink/AArch64/MachO_compact_unwind.s b/llvm/test/ExecutionEngine/JITLink/AArch64/MachO_compact_unwind.s
index 20534d5a48656..b2adb8566e7c1 100644
--- a/llvm/test/ExecutionEngine/JITLink/AArch64/MachO_compact_unwind.s
+++ b/llvm/test/ExecutionEngine/JITLink/AArch64/MachO_compact_unwind.s
@@ -1,6 +1,7 @@
 # REQUIRES: asserts
 # RUN: llvm-mc -triple=arm64-apple-ios -filetype=obj -o %t %s
-# RUN: llvm-jitlink -noexec -debug-only=jitlink %t 2>&1 | FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec %t 2>&1 \
+# RUN:              | FileCheck %s
 #
 # Check that splitting of compact-unwind sections works.
 #
diff --git a/llvm/test/ExecutionEngine/JITLink/AArch64/MachO_ehframe.s b/llvm/test/ExecutionEngine/JITLink/AArch64/MachO_ehframe.s
index 8d43b0f975f69..4e84518f86a0a 100644
--- a/llvm/test/ExecutionEngine/JITLink/AArch64/MachO_ehframe.s
+++ b/llvm/test/ExecutionEngine/JITLink/AArch64/MachO_ehframe.s
@@ -1,7 +1,7 @@
 # REQUIRES: asserts
 # RUN: llvm-mc -triple=arm64-apple-darwin11 -filetype=obj -o %t %s
-# RUN: llvm-jitlink -noexec -phony-externals -debug-only=jitlink %t 2>&1 | \
-# RUN:   FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
+# RUN:              -phony-externals %t 2>&1 | FileCheck %s
 #
 # Check that splitting of eh-frame sections works.
 #
diff --git a/llvm/test/ExecutionEngine/JITLink/LoongArch/ELF_loongarch64_ehframe.s b/llvm/test/ExecutionEngine/JITLink/LoongArch/ELF_loongarch64_ehframe.s
index cc545853f3278..806cdcf392f29 100644
--- a/llvm/test/ExecutionEngine/JITLink/LoongArch/ELF_loongarch64_ehframe.s
+++ b/llvm/test/ExecutionEngine/JITLink/LoongArch/ELF_loongarch64_ehframe.s
@@ -1,7 +1,7 @@
 # REQUIRES: asserts
-# RUN: llvm-mc --triple=loongarch64-linux-gnu --filetype=obj -o %t %s
-# RUN: llvm-jitlink --noexec --phony-externals --debug-only=jitlink %t 2>&1 | \
-# RUN:   FileCheck %s
+# RUN: llvm-mc -triple=loongarch64-linux-gnu -filetype=obj -o %t %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
+# RUN:              -phony-externals %t 2>&1 | FileCheck %s
 
 ## Check that splitting of eh-frame sections works.
 
diff --git a/llvm/test/ExecutionEngine/JITLink/RISCV/ELF_relax_call.s b/llvm/test/ExecutionEngine/JITLink/RISCV/ELF_relax_call.s
index 480fbb8613107..2b5c9e383c04f 100644
--- a/llvm/test/ExecutionEngine/JITLink/RISCV/ELF_relax_call.s
+++ b/llvm/test/ExecutionEngine/JITLink/RISCV/ELF_relax_call.s
@@ -1,15 +1,15 @@
 # REQUIRES: asserts
 # RUN: llvm-mc -triple=riscv32 -mattr=+relax -filetype=obj -o %t.rv32 %s
-# RUN: llvm-jitlink -noexec \
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
 # RUN:     -slab-allocate 100Kb -slab-address 0x1000 -slab-page-size 4096 \
-# RUN:     -debug-only=jitlink -check %s %t.rv32 \
-# RUN:    2>&1 | FileCheck %s
+# RUN:     -check %s %t.rv32 2>&1 \
+# RUN:     | FileCheck %s
 
 # RUN: llvm-mc -triple=riscv64 -mattr=+relax -filetype=obj -o %t.rv64 %s
-# RUN: llvm-jitlink -noexec \
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
 # RUN:     -slab-allocate 100Kb -slab-address 0x1000 -slab-page-size 4096 \
-# RUN:     -debug-only=jitlink -check %s %t.rv64 \
-# RUN:    2>&1 | FileCheck %s
+# RUN:     -check %s %t.rv64 2>&1 \
+# RUN:     | FileCheck %s
 
         .text
 
diff --git a/llvm/test/ExecutionEngine/JITLink/RISCV/ELF_relax_call_rvc.s b/llvm/test/ExecutionEngine/JITLink/RISCV/ELF_relax_call_rvc.s
index e8a2928999f4a..3bbfd557a0a6c 100644
--- a/llvm/test/ExecutionEngine/JITLink/RISCV/ELF_relax_call_rvc.s
+++ b/llvm/test/ExecutionEngine/JITLink/RISCV/ELF_relax_call_rvc.s
@@ -1,43 +1,43 @@
 # REQUIRES: asserts
 # RUN: llvm-mc -triple=riscv32 -mattr=+relax,+c -filetype=obj -o %t.rv32 %s
-# RUN: llvm-jitlink -noexec \
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
 # RUN:     -slab-allocate 100Kb -slab-address 0x1000 -slab-page-size 4096 \
-# RUN:     -debug-only=jitlink -check %s %t.rv32 \
-# RUN:    2>&1 | FileCheck %s
-# RUN: llvm-jitlink -noexec \
+# RUN:     -check %s %t.rv32 2>&1 \
+# RUN:     | FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
 # RUN:     -slab-allocate 100Kb -slab-address 0x1000 -slab-page-size 4096 \
-# RUN:     -debug-only=jitlink -check %s -check-name=jitlink-check-rv32 %t.rv32 \
-# RUN:     2>&1 | FileCheck -check-prefix=CHECK-RV32 %s
+# RUN:     -check %s -check-name=jitlink-check-rv32 %t.rv32 2>&1 \
+# RUN:     | FileCheck -check-prefix=CHECK-RV32 %s
 
 # RUN: llvm-mc -triple=riscv64 -mattr=+relax,+c -filetype=obj -o %t.rv64 %s
-# RUN: llvm-jitlink -noexec \
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
 # RUN:     -slab-allocate 100Kb -slab-address 0x1000 -slab-page-size 4096 \
-# RUN:     -debug-only=jitlink -check %s %t.rv64 \
-# RUN:     2>&1 | FileCheck %s
-# RUN: llvm-jitlink -noexec \
+# RUN:     -check %s %t.rv64 2>&1 \
+# RUN:     | FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
 # RUN:     -slab-allocate 100Kb -slab-address 0x1000 -slab-page-size 4096 \
-# RUN:     -debug-only=jitlink -check %s -check-name=jitlink-check-rv64 %t.rv64 \
-# RUN:     2>&1 | FileCheck -check-prefix=CHECK-RV64 %s
+# RUN:     -check %s -check-name=jitlink-check-rv64 %t.rv64 2>&1 \
+# RUN:     | FileCheck -check-prefix=CHECK-RV64 %s
 
 # RUN: llvm-mc -triple=riscv32 -mattr=+relax,+zca -filetype=obj -o %t.rv32zca %s
-# RUN: llvm-jitlink -noexec \
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
 # RUN:     -slab-allocate 100Kb -slab-address 0x1000 -slab-page-size 4096 \
-# RUN:     -debug-only=jitlink -check %s %t.rv32zca \
-# RUN:    2>&1 | FileCheck %s
-# RUN: llvm-jitlink -noexec \
+# RUN:     -check %s %t.rv32zca 2>&1 \
+# RUN:     | FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
 # RUN:     -slab-allocate 100Kb -slab-address 0x1000 -slab-page-size 4096 \
-# RUN:     -debug-only=jitlink -check %s -check-name=jitlink-check-rv32 %t.rv32zca \
-# RUN:     2>&1 | FileCheck -check-prefix=CHECK-RV32 %s
+# RUN:     -check %s -check-name=jitlink-check-rv32 %t.rv32zca 2>&1 \
+# RUN:     | FileCheck -check-prefix=CHECK-RV32 %s
 
 # RUN: llvm-mc -triple=riscv64 -mattr=+relax,+c -filetype=obj -o %t.rv64 %s
-# RUN: llvm-jitlink -noexec \
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
 # RUN:     -slab-allocate 100Kb -slab-address 0x1000 -slab-page-size 4096 \
-# RUN:     -debug-only=jitlink -check %s %t.rv64 \
-# RUN:     2>&1 | FileCheck %s
-# RUN: llvm-jitlink -noexec \
+# RUN:     -check %s %t.rv64 2>&1 \
+# RUN:     | FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
 # RUN:     -slab-allocate 100Kb -slab-address 0x1000 -slab-page-size 4096 \
-# RUN:     -debug-only=jitlink -check %s -check-name=jitlink-check-rv64 %t.rv64 \
-# RUN:     2>&1 | FileCheck -check-prefix=CHECK-RV64 %s
+# RUN:     -check %s -check-name=jitlink-check-rv64 %t.rv64 2>&1 \
+# RUN:     | FileCheck -check-prefix=CHECK-RV64 %s
 
         .text
 
diff --git a/llvm/test/ExecutionEngine/JITLink/RISCV/anonymous_symbol.s b/llvm/test/ExecutionEngine/JITLink/RISCV/anonymous_symbol.s
index e7114e4d643c6..a1badfd0ee3dc 100644
--- a/llvm/test/ExecutionEngine/JITLink/RISCV/anonymous_symbol.s
+++ b/llvm/test/ExecutionEngine/JITLink/RISCV/anonymous_symbol.s
@@ -1,6 +1,7 @@
 # REQUIRES: asserts
 # RUN: llvm-mc -triple=riscv64 -filetype=obj -o %t %s
-# RUN: llvm-jitlink -debug-only=jitlink -noexec %t 2>&1 | FileCheck %s
+# RUN: llvm-jitlink -debug-only=jitlink -num-threads=0 -noexec %t 2>&1 \
+# RUN:              | FileCheck %s
 #
 # Because of the exist of cfi directive, sections like eh_frame section will be emitted
 # in llvm's object code emission phase. Anonymous symbols will also be emitted to indicate
diff --git a/llvm/test/ExecutionEngine/JITLink/ppc64/ELF_ppc64_ehframe.s b/llvm/test/ExecutionEngine/JITLink/ppc64/ELF_ppc64_ehframe.s
index 9e9b340c5d8d2..75f09ff402ad9 100644
--- a/llvm/test/ExecutionEngine/JITLink/ppc64/ELF_ppc64_ehframe.s
+++ b/llvm/test/ExecutionEngine/JITLink/ppc64/ELF_ppc64_ehframe.s
@@ -1,10 +1,12 @@
 # REQUIRES: asserts
 # RUN: llvm-mc -triple=powerpc64le-unknown-linux-gnu -filetype=obj -o %t %s
-# RUN: llvm-jitlink -noexec -phony-externals -debug-only=jitlink %t 2>&1 | \
-# RUN:   FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec -phony-externals \
+# RUN:              %t 2>&1 \
+# RUN:              | FileCheck %s
 # RUN: llvm-mc -triple=powerpc64-unknown-linux-gnu -filetype=obj -o %t %s
-# RUN: llvm-jitlink -noexec -phony-externals -debug-only=jitlink %t 2>&1 | \
-# RUN:   FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec -phony-externals \
+# RUN:              %t 2>&1 \
+# RUN:              | FileCheck %s
 #
 # Check that splitting of eh-frame sections works.
 #
diff --git a/llvm/test/ExecutionEngine/JITLink/ppc64/external_weak.s b/llvm/test/ExecutionEngine/JITLink/ppc64/external_weak.s
index 0bc90903caf97..7021a27294c93 100644
--- a/llvm/test/ExecutionEngine/JITLink/ppc64/external_weak.s
+++ b/llvm/test/ExecutionEngine/JITLink/ppc64/external_weak.s
@@ -4,8 +4,9 @@
 # RUN:   %t/external_weak.o %S/Inputs/external_weak.s
 # RUN: llvm-mc -triple=powerpc64le-unknown-linux-gnu -filetype=obj -o \
 # RUN:   %t/external_weak_main.o %S/Inputs/external_weak_main.s
-# RUN: llvm-jitlink -noexec -debug-only=jitlink %t/external_weak.o \
-# RUN:   %t/external_weak_main.o 2>&1 | FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
+# RUN:              %t/external_weak.o %t/external_weak_main.o 2>&1 \
+# RUN:              | FileCheck %s
 # CHECK: Created ELFLinkGraphBuilder for "{{.*}}external_weak_main.o"
 # CHECK: Creating defined graph symbol for ELF symbol "foo"
 # CHECK: External symbols:
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_abs.s b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_abs.s
index 830a2e00f4872..d69dbbdd70404 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_abs.s
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_abs.s
@@ -1,6 +1,7 @@
 # REQUIRES: asserts
 # RUN: llvm-mc -filetype=obj -triple=x86_64-windows-msvc %s -o %t
-# RUN: llvm-jitlink --debug-only=jitlink -noexec %t 2>&1 | FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec %t 2>&1 \
+# RUN:              | FileCheck %s
 #
 # Check absolute symbol is created with a correct value.
 #
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_any.test b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_any.test
index 10f118280b1d8..b1176744b9a46 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_any.test
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_any.test
@@ -1,7 +1,8 @@
 # REQUIRES: asserts
 # RUN: yaml2obj %s -o %t
-# RUN: llvm-jitlink -noexec --debug-only=jitlink -noexec %t 2>&1 | FileCheck %s
-# 
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec %t 2>&1 \
+# RUN:              | FileCheck %s
+#
 # Check a weak symbol is created for a COMDAT symbol with IMAGE_COMDAT_SELECT_ANY selection type.
 #
 # CHECK: Creating graph symbols...
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_associative.test b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_associative.test
index 7dfb4c7ec8eaa..8915d04d7cbf9 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_associative.test
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_associative.test
@@ -1,16 +1,19 @@
 # REQUIRES: asserts
 # RUN: yaml2obj %s -o %t
-# RUN: llvm-jitlink -noexec --debug-only=jitlink -noexec %t 2>&1
-# 
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec %t 2>&1 \
+# RUN:              | FileCheck %s
+#
 # Check COMDAT associative symbol is emitted as local symbol.
 #
-# CHECK: Creating graph symbols...
-# CHECK:      2: Creating defined graph symbol for COFF symbol ".text" in .text (index: 2)
-# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000001, linkage: strong, scope: local, dead  -   <anonymous symbol>
-# CHECK-NEXT: 4: Exporting COMDAT graph symbol for COFF symbol "func" in section 2
-# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000001, linkage: weak, scope: default, dead  -   func
-# CHECK-NEXT: 5: Creating defined graph symbol for COFF symbol ".xdata" in .xdata (index: 3)
-# CHECK-NEXT:   0x0 (block + 0x00000000): size: 0x00000000, linkage: strong, scope: local, dead  -   .xdata
+# CHECK:       Creating graph symbols...
+# CHECK:         0: Creating defined graph symbol for COFF symbol ".text" in .text (index: 1)
+# CHECK-NEXT:      0x0 (block + 0x00000000): size: 0x00000000, linkage: strong, scope: local, dead  -   .text
+# CHECK-NEXT:    4: Exporting COMDAT graph symbol for COFF symbol "func" in section 2
+# CHECK-NEXT:      0x0 (block + 0x00000000): size: 0x00000000, linkage: weak, scope: default, dead  -   func
+# CHECK-NEXT:    4: Creating defined graph symbol for COFF symbol "func" in .text (index: 2)
+# CHECK-NEXT:      0x0 (block + 0x00000000): size: 0x00000000, linkage: weak, scope: default, dead  -   func
+# CHECK-NEXT:    5: Creating defined graph symbol for COFF symbol ".xdata" in .xdata (index: 3)
+# CHECK-NEXT:      0x0 (block + 0x00000000): size: 0x00000000, linkage: strong, scope: local, dead  -   .xdata
 
 --- !COFF
 header:
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_exact_match.test b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_exact_match.test
index f7572714bae16..76a0ac4813b86 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_exact_match.test
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_exact_match.test
@@ -1,7 +1,8 @@
 # REQUIRES: asserts
 # RUN: yaml2obj %s -o %t
-# RUN: llvm-jitlink -noexec --debug-only=jitlink -noexec %t 2>&1 | FileCheck %s
-# 
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec %t 2>&1 \
+# RUN:              | FileCheck %s
+#
 # Check a weak symbol is created for a COMDAT symbol with IMAGE_COMDAT_SELECT_EXACT_MATCH selection type.
 # Doesn't check the content validation.
 #
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_intervene.test b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_intervene.test
index 11a1825783797..79f4b15bd53b5 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_intervene.test
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_intervene.test
@@ -1,7 +1,8 @@
 # REQUIRES: asserts
 # RUN: yaml2obj %s -o %t
-# RUN: llvm-jitlink -noexec --debug-only=jitlink -noexec %t 2>&1 | FileCheck %s
-# 
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec %t 2>&1 \
+# RUN:              | FileCheck %s
+#
 # Check a comdat export is done correctly even if second symbol of comdat sequences appear out of order
 #
 # CHECK: Creating graph symbols...
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_largest.test b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_largest.test
index 86d809d63ed2b..dc0529780f6a5 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_largest.test
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_largest.test
@@ -1,7 +1,8 @@
 # REQUIRES: asserts
 # RUN: yaml2obj %s -o %t
-# RUN: llvm-jitlink -noexec --debug-only=jitlink -noexec %t 2>&1
-# 
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec %t 2>&1 \
+# RUN:              | FileCheck %s
+#
 # Check jitlink handles largest selection type as plain weak symbol.
 #
 # CHECK: Creating graph symbols...
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_noduplicate.test b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_noduplicate.test
index 53b2c81b5ec7f..0c5313eb7d61b 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_noduplicate.test
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_noduplicate.test
@@ -1,7 +1,8 @@
 # REQUIRES: asserts
 # RUN: yaml2obj %s -o %t
-# RUN: llvm-jitlink -noexec --debug-only=jitlink -noexec %t 2>&1 | FileCheck %s
-# 
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec -noexec %t 2>&1 \
+# RUN:              | FileCheck %s
+#
 # Check a strong symbol is created for a COMDAT symbol with IMAGE_COMDAT_SELECT_NODUPLICATES selection type.
 #
 # CHECK: Creating graph symbols...
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_offset.test b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_offset.test
index 97467fdb5ee9a..6cd8ff9b1e5ae 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_offset.test
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_offset.test
@@ -1,7 +1,8 @@
 # REQUIRES: asserts
 # RUN: yaml2obj %s -o %t
-# RUN: llvm-jitlink -noexec --debug-only=jitlink -noexec %t 2>&1 | FileCheck %s
-# 
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec %t 2>&1 \
+# RUN:              | FileCheck %s
+#
 # Check a COMDAT symbol with an offset is handled correctly.
 #
 # CHECK: Creating graph symbols...
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_same_size.test b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_same_size.test
index ef0f84a584c3c..e1d955f54ffb1 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_same_size.test
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_same_size.test
@@ -1,7 +1,8 @@
 # REQUIRES: asserts
 # RUN: yaml2obj %s -o %t
-# RUN: llvm-jitlink -noexec --debug-only=jitlink -noexec %t 2>&1 | FileCheck %s
-# 
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec %t 2>&1 \
+# RUN:              | FileCheck %s
+#
 # Check a weak symbol is created for a COMDAT symbol with IMAGE_COMDAT_SELECT_SAME_SIZE selection type.
 # Doesn't check the size validation.
 #
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_weak.s b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_weak.s
index 79ac75ffe441f..8fa8ba0d8c950 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_weak.s
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_comdat_weak.s
@@ -1,6 +1,7 @@
 # REQUIRES: asserts
 # RUN: llvm-mc -filetype=obj -triple=x86_64-windows-msvc %s -o %t
-# RUN: llvm-jitlink --debug-only=jitlink -noexec %t 2>&1 | FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec %t 2>&1 \
+# RUN:              | FileCheck %s
 #
 # Check a COMDAT any symbol is exported as a weak symbol.
 #
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_common_symbol.s b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_common_symbol.s
index 2d4ad30f94d8d..2788a9b0ae142 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_common_symbol.s
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_common_symbol.s
@@ -1,6 +1,7 @@
 # REQUIRES: asserts
 # RUN: llvm-mc -filetype=obj -triple=x86_64-windows-msvc %s -o %t
-# RUN: llvm-jitlink --debug-only=jitlink -noexec %t 2>&1 | FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec %t 2>&1 \
+# RUN:              | FileCheck %s
 #
 # Check a common symbol is created.
 #
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_duplicate_externals.test b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_duplicate_externals.test
index e929c01316860..ebce7958442cd 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_duplicate_externals.test
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_duplicate_externals.test
@@ -1,10 +1,10 @@
 # REQUIRES: asserts
 # RUN: yaml2obj %s -o %t
-# RUN: llvm-jitlink -noexec -abs __ImageBase=0xfff00000 \
-# RUN: --debug-only=jitlink \
-# RUN: -slab-allocate 100Kb -slab-address 0xfff00000 -slab-page-size 4096 \
-# RUN: %t 2>&1 | FileCheck %s
-# 
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
+# RUN:              -abs __ImageBase=0xfff00000 -slab-allocate 100Kb \
+# RUN:              -slab-address 0xfff00000 -slab-page-size 4096 %t 2>&1 \
+# RUN:              | FileCheck %s
+#
 # Check duplicate undefined external symbols are handled correctly.
 #
 # CHECK: Creating graph symbols...
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_file_debug.s b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_file_debug.s
index 3980f81801ac2..ac1ef2dc962bf 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_file_debug.s
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_file_debug.s
@@ -1,6 +1,8 @@
 # REQUIRES: asserts
 # RUN: llvm-mc -filetype=obj -triple=x86_64-windows-msvc %s -o %t
-# RUN: llvm-jitlink -abs func=0xcafef00d --debug-only=jitlink -noexec %t 2>&1 | FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
+# RUN:              -abs func=0xcafef00d %t 2>&1 \
+# RUN:              | FileCheck %s
 #
 # Check a file debug symbol is skipped.
 #
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_static_var.s b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_static_var.s
index 5275c7d81766e..dce0c1eaa77ca 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_static_var.s
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_static_var.s
@@ -1,6 +1,8 @@
 # REQUIRES: asserts
 # RUN: llvm-mc -filetype=obj -triple=x86_64-windows-msvc %s -o %t
-# RUN: llvm-jitlink -abs var=0xcafef00d --debug-only=jitlink -noexec %t 2>&1 | FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
+# RUN:              -abs var=0xcafef00d  %t 2>&1 \
+# RUN:              | FileCheck %s
 #
 # Check a local symbol is created for a static variable.
 #
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_weak_external.s b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_weak_external.s
index c750d75b82f2d..d49d56150017b 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_weak_external.s
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/COFF_weak_external.s
@@ -1,6 +1,8 @@
 # REQUIRES: asserts
 # RUN: llvm-mc -filetype=obj -triple=x86_64-windows-msvc %s -o %t
-# RUN: llvm-jitlink -abs var=0xcafef00d --debug-only=jitlink -noexec %t 2>&1 | FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
+# RUN:              -abs var=0xcafef00d %t 2>&1 | \
+# RUN:              FileCheck %s
 #
 # Check a default symbol is aliased as a weak external symbol.
 #
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/ELF_debug_section_lifetime_is_NoAlloc.yaml b/llvm/test/ExecutionEngine/JITLink/x86-64/ELF_debug_section_lifetime_is_NoAlloc.yaml
index 0afcda467c326..09dda47392253 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/ELF_debug_section_lifetime_is_NoAlloc.yaml
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/ELF_debug_section_lifetime_is_NoAlloc.yaml
@@ -1,6 +1,7 @@
 # REQUIRES: asserts
 # RUN: yaml2obj -o %t.o %s
-# RUN: llvm-jitlink -debug-only=jitlink -noexec %t.o 2>&1 | FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec %t.o 2>&1 \
+# RUN:              | FileCheck %s
 #
 # Check that debug sections get NoAlloc lifetimes.
 #
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/ELF_ehframe_basic.s b/llvm/test/ExecutionEngine/JITLink/x86-64/ELF_ehframe_basic.s
index c01ced5d0523b..9339f076c67f8 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/ELF_ehframe_basic.s
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/ELF_ehframe_basic.s
@@ -2,8 +2,9 @@
 # UNSUPPORTED: system-windows
 # RUN: llvm-mc -triple=x86_64-unknown-linux -position-independent \
 # RUN:     -filetype=obj -o %t %s
-# RUN: llvm-jitlink -debug-only=jitlink -abs bar=0x01 \
-# RUN:     -abs _ZTIi=0x02 -noexec %t 2>&1 | FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
+# RUN:              -abs bar=0x01 -abs _ZTIi=0x02 %t 2>&1 \
+# RUN:              | FileCheck %s
 #
 # FIXME: This test should run on windows. Investigate spurious
 # 'note: command had no output on stdout or stderr' errors, then re-enable.
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/ELF_ehframe_large_static_personality_encodings.s b/llvm/test/ExecutionEngine/JITLink/x86-64/ELF_ehframe_large_static_personality_encodings.s
index 64990b5d38f07..98fc5f4e3acc4 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/ELF_ehframe_large_static_personality_encodings.s
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/ELF_ehframe_large_static_personality_encodings.s
@@ -2,8 +2,9 @@
 # UNSUPPORTED: system-windows
 # RUN: llvm-mc -triple=x86_64-pc-linux-gnu -large-code-model \
 # RUN:   -filetype=obj -o %t %s
-# RUN: llvm-jitlink -debug-only=jitlink -noexec -phony-externals %t 2>&1 | \
-# RUN:   FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
+# RUN:              -phony-externals %t 2>&1 \
+# RUN:              | FileCheck %s
 #
 # Check handling of pointer encodings for personality functions when compiling
 # with `-mcmodel=large -static`.
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/LocalDependencyPropagation.s b/llvm/test/ExecutionEngine/JITLink/x86-64/LocalDependencyPropagation.s
index 0898ad8b18230..83d71cdf6fc83 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/LocalDependencyPropagation.s
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/LocalDependencyPropagation.s
@@ -1,7 +1,8 @@
 # REQUIRES: asserts
 # RUN: llvm-mc -triple=x86_64-apple-macosx10.9 -filetype=obj -o %t %s
-# RUN: llvm-jitlink -debug-only=orc -num-threads=0 -noexec \
-# RUN:     -abs _external_func=0x1 -entry=_foo %t 2>&1 | FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=orc -noexec \
+# RUN:              -abs _external_func=0x1 -entry=_foo %t 2>&1 \
+# RUN:              | FileCheck %s
 #
 # Check that simplification eliminates dependencies on symbols in this unit,
 # and correctly propagates dependencies on symbols outside the unit (including
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/MachO-check-dwarf-filename.s b/llvm/test/ExecutionEngine/JITLink/x86-64/MachO-check-dwarf-filename.s
index df44ce996ecad..81ea18f249340 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/MachO-check-dwarf-filename.s
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/MachO-check-dwarf-filename.s
@@ -1,6 +1,7 @@
 # RUN: llvm-mc -triple=x86_64-apple-macosx10.9 -filetype=obj -o %t.o %s
-# RUN: llvm-jitlink -debug-only=orc -noexec -debugger-support %t.o 2>&1 | \
-# RUN:     FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=orc -noexec -debugger-support \
+# RUN:              %t.o 2>&1 \
+# RUN:              | FileCheck %s
 #
 # REQUIRES: asserts && system-darwin
 #
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/MachO_compact_unwind.s b/llvm/test/ExecutionEngine/JITLink/x86-64/MachO_compact_unwind.s
index e57831418304c..38522078f4ce9 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/MachO_compact_unwind.s
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/MachO_compact_unwind.s
@@ -1,6 +1,7 @@
 # REQUIRES: asserts
 # RUN: llvm-mc -triple=x86_64-apple-darwin11 -filetype=obj -o %t %s
-# RUN: llvm-jitlink -noexec -debug-only=jitlink %t 2>&1 | FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec %t 2>&1 \
+# RUN:              | FileCheck %s
 #
 # Check that splitting of compact-unwind sections works.
 #
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/MachO_cstring_section_alignment.s b/llvm/test/ExecutionEngine/JITLink/x86-64/MachO_cstring_section_alignment.s
index 5a8cef5749f0a..3859a35ce2214 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/MachO_cstring_section_alignment.s
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/MachO_cstring_section_alignment.s
@@ -1,6 +1,7 @@
 # REQUIRES: asserts
 # RUN: llvm-mc -triple=x86_64-apple-macos10.9 -filetype=obj -o %t %s
-# RUN: llvm-jitlink -debug-only=jitlink -noexec %t 2>&1 | FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec %t 2>&1 \
+# RUN:              | FileCheck %s
 #
 # Verify that PC-begin candidate symbols have been sorted correctly when adding
 # PC-begin edges for FDEs. In this test both _main and _X are at address zero,
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/MachO_cstring_section_splitting.s b/llvm/test/ExecutionEngine/JITLink/x86-64/MachO_cstring_section_splitting.s
index a5baf5611cc29..0d68a10c59d19 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/MachO_cstring_section_splitting.s
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/MachO_cstring_section_splitting.s
@@ -1,7 +1,8 @@
 # REQUIRES: asserts
 # RUN: llvm-mc -triple=x86_64-apple-macosx10.9 -filetype=obj -o %t %s
-# RUN: llvm-jitlink -debug-only=jitlink -noexec -entry hook %t 2>&1 | \
-# RUN:   FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec \
+# RUN:              -entry hook %t 2>&1 \
+# RUN:              | FileCheck %s
 #
 # Verify that we split C string literals on null-terminators, rather than on
 # symbol boundaries. We expect four dead-stripped symbols: l_str.0, l_str.2,
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/MachO_non_subsections_via_symbols.s b/llvm/test/ExecutionEngine/JITLink/x86-64/MachO_non_subsections_via_symbols.s
index e1adb3bc75a1f..66fcb47fc7abf 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/MachO_non_subsections_via_symbols.s
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/MachO_non_subsections_via_symbols.s
@@ -4,7 +4,8 @@
 #
 # REQUIRES: asserts
 # RUN: llvm-mc -triple=x86_64-apple-macosx10.9 -filetype=obj -o %t %s
-# RUN: llvm-jitlink -debug-only=jitlink -noexec %t 2>&1 | FileCheck %s
+# RUN: llvm-jitlink -num-threads=0 -debug-only=jitlink -noexec %t 2>&1 \
+# RUN:              | FileCheck %s
 
 # CHECK:        Creating graph symbols...
 # CHECK:          Graphifying regular section __DATA,__data...
diff --git a/llvm/tools/llvm-jitlink/llvm-jitlink.cpp b/llvm/tools/llvm-jitlink/llvm-jitlink.cpp
index 646d4cef01a57..431b86a27e16b 100644
--- a/llvm/tools/llvm-jitlink/llvm-jitlink.cpp
+++ b/llvm/tools/llvm-jitlink/llvm-jitlink.cpp
@@ -1667,6 +1667,12 @@ static Error sanitizeArguments(const Triple &TT, const char *ArgV0) {
                                      inconvertibleErrorCode());
   }
 
+#ifndef NDEBUG
+  if (DebugFlag && MaterializationThreads != 0)
+    errs() << "Warning: debugging output is not thread safe. "
+              "Use -num-threads=0 to stabilize output.\n";
+#endif // NDEBUG
+
   // Only one of -oop-executor and -oop-executor-connect can be used.
   if (!!OutOfProcessExecutor.getNumOccurrences() &&
       !!OutOfProcessExecutorConnect.getNumOccurrences())