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[WebAssembly] Enable nontrapping-fptoint and bulk-memory by default. #112049

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Oct 25, 2024
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[WebAssembly] Enable nontrapping-fptoint and bulk-memory by default. #112049

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c4327c9
[WebAssembly] Enable nontrapping-fptoint and bulk-memory by default.
sunfishcode Oct 11, 2024
8a655be
Update tests.
sunfishcode Oct 11, 2024
229888f
Update tests.
sunfishcode Oct 14, 2024
d757a4d
Update tests.
sunfishcode Oct 14, 2024
6f4d40e
Move `-bulk-memory` flags from wasm-ld flags to a function attributes.
sunfishcode Oct 15, 2024
d3e79ec
Delete redundant features.
sunfishcode Oct 16, 2024
04b0211
Sort the feature macros alphabetically.
sunfishcode Oct 16, 2024
543ee22
Fix subtarget feature coalescing to allow default features to be disa…
sunfishcode Oct 25, 2024
a119df5
code formatting
sunfishcode Oct 25, 2024
548564b
formatting
sunfishcode Oct 25, 2024
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9 changes: 9 additions & 0 deletions clang/docs/ReleaseNotes.rst
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Expand Up @@ -671,6 +671,15 @@ NetBSD Support
WebAssembly Support
^^^^^^^^^^^^^^^^^^^

The default target CPU, "generic", now enables the `-mnontrapping-fptoint`
and `-mbulk-memory` flags, which correspond to the [Bulk Memory Operations]
and [Non-trapping float-to-int Conversions] language features, which are
[widely implemented in engines].

[Bulk Memory Operations]: https://github.com/WebAssembly/bulk-memory-operations/blob/master/proposals/bulk-memory-operations/Overview.md
[Non-trapping float-to-int Conversions]: https://github.com/WebAssembly/spec/blob/master/proposals/nontrapping-float-to-int-conversion/Overview.md
[widely implemented in engines]: https://webassembly.org/features/

AVR Support
^^^^^^^^^^^

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4 changes: 2 additions & 2 deletions clang/lib/Basic/Targets/WebAssembly.cpp
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Expand Up @@ -154,20 +154,20 @@ bool WebAssemblyTargetInfo::initFeatureMap(
llvm::StringMap<bool> &Features, DiagnosticsEngine &Diags, StringRef CPU,
const std::vector<std::string> &FeaturesVec) const {
auto addGenericFeatures = [&]() {
Features["bulk-memory"] = true;
Features["multivalue"] = true;
Features["mutable-globals"] = true;
Features["nontrapping-fptoint"] = true;
Features["reference-types"] = true;
Features["sign-ext"] = true;
};
auto addBleedingEdgeFeatures = [&]() {
addGenericFeatures();
Features["atomics"] = true;
Features["bulk-memory"] = true;
Features["exception-handling"] = true;
Features["extended-const"] = true;
Features["fp16"] = true;
Features["multimemory"] = true;
Features["nontrapping-fptoint"] = true;
Features["tail-call"] = true;
Features["wide-arithmetic"] = true;
setSIMDLevel(Features, RelaxedSIMD, true);
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4 changes: 2 additions & 2 deletions clang/test/Preprocessor/wasm-target-features.c
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Expand Up @@ -163,8 +163,10 @@
// RUN: -target wasm64-unknown-unknown -mcpu=generic \
// RUN: | FileCheck %s -check-prefix=GENERIC-INCLUDE
//
// GENERIC-INCLUDE-DAG: #define __wasm_bulk_memory__ 1{{$}}
// GENERIC-INCLUDE-DAG: #define __wasm_multivalue__ 1{{$}}
// GENERIC-INCLUDE-DAG: #define __wasm_mutable_globals__ 1{{$}}
// GENERIC-INCLUDE-DAG: #define __wasm_nontrapping_fptoint__ 1{{$}}
// GENERIC-INCLUDE-DAG: #define __wasm_reference_types__ 1{{$}}
// GENERIC-INCLUDE-DAG: #define __wasm_sign_ext__ 1{{$}}
//
Expand All @@ -176,12 +178,10 @@
// RUN: | FileCheck %s -check-prefix=GENERIC
//
// GENERIC-NOT: #define __wasm_atomics__ 1{{$}}
// GENERIC-NOT: #define __wasm_bulk_memory__ 1{{$}}
// GENERIC-NOT: #define __wasm_exception_handling__ 1{{$}}
// GENERIC-NOT: #define __wasm_extended_const__ 1{{$}}
// GENERIC-NOT: #define __wasm__fp16__ 1{{$}}
// GENERIC-NOT: #define __wasm_multimemory__ 1{{$}}
// GENERIC-NOT: #define __wasm_nontrapping_fptoint__ 1{{$}}
// GENERIC-NOT: #define __wasm_relaxed_simd__ 1{{$}}
// GENERIC-NOT: #define __wasm_simd128__ 1{{$}}
// GENERIC-NOT: #define __wasm_tail_call__ 1{{$}}
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2 changes: 1 addition & 1 deletion lld/test/wasm/custom-section-name.ll
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@@ -1,4 +1,4 @@
; RUN: llc -filetype=obj %s -o %t.o
; RUN: llc -filetype=obj -mattr=-bulk-memory %s -o %t.o
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Why do we need to disable bulk memory here and in many other files?

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@sunfishcode sunfishcode Oct 16, 2024 •
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In lld/test/wasm/custom-section-name.ll, it's because bulk-memory makes the target_features section bigger and thus changes some of the section offsets and it was easier to just disable bulk-memory than to figure out the new section offsets. I can update the section offsets if you prefer though. See my comment below.

In lld/test/wasm/data-segments.ll, it's because the test is written to test both bulk-memory and non-bulk-memory, and to keep it doing that, it's now necessary to explicitly disable bulk-memory for the non-bulk-memory case.

In lld/test/wasm/lto/stub-library-libcall.s it's because the test is testing the use of a memcpy stub function, and with bulk-memory it gets inlined.

llvm/test/MC/WebAssembly/extern-functype-intrinsic.ll is similarly testing memset calls.

llvm/test/MC/WebAssembly/libcall.ll is similarly testing memcpy calls.

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Thanks for the explanation!

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I've now investigated custom-section-name.ll more.

With bulk-memory, we get a __wasm_init_memory function:

(module $custom-section-name.bss.wasm
  (type (;0;) (func))
  (import "env" "memory" (memory (;0;) 2))
  (func $__wasm_call_ctors (;0;) (type 0))
  (func $__wasm_init_memory (;1;) (type 0)
    i32.const 1036
    i32.const 0
    i32.const 4
    memory.fill
  )
  (global $__stack_pointer (;0;) (mut i32) i32.const 66576)
  (start $__wasm_init_memory)
  (data $WowZero! (;0;) (i32.const 1024) "\00\00\00\00")
  (data $MyAwesomeSection (;1;) (i32.const 1028) "*\00\00\00")
  (data $AnotherGreatSection (;2;) (i32.const 1032) "\07\00\00\00")
  (@custom "target_features" (after data) "\06+\0bbulk-memory+\16call-indirect-overlong+\0amultivalue+\0fmutable-globals+\0freference-types+\08sign-ext")
)

Without bulk-memory we get a .bss section:

(module $custom-section-name.bss.wasm
  (type (;0;) (func))
  (import "env" "memory" (memory (;0;) 2))
  (func $__wasm_call_ctors (;0;) (type 0))
  (global $__stack_pointer (;0;) (mut i32) i32.const 66576)
  (data $WowZero! (;0;) (i32.const 1024) "\00\00\00\00")
  (data $MyAwesomeSection (;1;) (i32.const 1028) "*\00\00\00")
  (data $AnotherGreatSection (;2;) (i32.const 1032) "\07\00\00\00")
  (data $.bss (;3;) (i32.const 1036) "\00\00\00\00")
  (@custom "target_features" (after data) "\05+\16call-indirect-overlong+\0amultivalue+\0fmutable-globals+\0freference-types+\08sign-ext")
)

The test is intended to test the use of the .bss section, and we only get a .bss section in this test if we disable bulk-memory.

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Hm, interesting, so we are using passive segments anytime bulk memory is enabled. That makes sense since this was all meant for threads, but is this actually an improvement in the non-threads case? i.e. maybe we don't want the extra explicit initialization code if we can help it?

edit: i just checked this out but I'll leave it here FTR: it looks like after linking we actually don't use passive segments unless threads is also enabled. so this seems like not a problem.

; RUN: wasm-ld -no-gc-sections --no-entry -o %t.wasm %t.o
; RUN: obj2yaml %t.wasm | FileCheck %s --check-prefixes=CHECK,NO-BSS
; RUN: wasm-ld -no-gc-sections --no-entry --import-memory -o %t.bss.wasm %t.o
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2 changes: 1 addition & 1 deletion lld/test/wasm/data-segments.ll
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@@ -1,4 +1,4 @@
; RUN: llc --mtriple=wasm32-unknown-unknown -filetype=obj %s -o %t.atomics.o -mattr=+atomics
; RUN: llc --mtriple=wasm32-unknown-unknown -filetype=obj %s -o %t.atomics.o -mattr=+atomics,-bulk-memory
; RUN: llc --mtriple=wasm32-unknown-unknown -filetype=obj %s -o %t.bulk-mem.o -mattr=+bulk-memory
; RUN: llc --mtriple=wasm64-unknown-unknown -filetype=obj %s -o %t.bulk-mem64.o -mattr=+bulk-memory
; RUN: llc --mtriple=wasm32-unknown-unknown -filetype=obj %s -o %t.atomics.bulk-mem.o -mattr=+atomics,+bulk-memory
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4 changes: 3 additions & 1 deletion lld/test/wasm/lto/Inputs/libcall-archive.ll
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@@ -1,6 +1,8 @@
target datalayout = "e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-n32:64-S128"
target triple = "wasm32-unknown-unknown"

define void @memcpy() {
define void @memcpy() #0 {
ret void
}

attributes #0 = { "target-features"="-bulk-memory" }
4 changes: 3 additions & 1 deletion lld/test/wasm/lto/libcall-archive.ll
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Expand Up @@ -8,14 +8,16 @@
target datalayout = "e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-n32:64-S128"
target triple = "wasm32-unknown-unknown"

define void @_start(ptr %a, ptr %b) {
define void @_start(ptr %a, ptr %b) #0 {
entry:
call void @llvm.memcpy.p0.p0.i64(ptr %a, ptr %b, i64 1024, i1 false)
ret void
}

declare void @llvm.memcpy.p0.p0.i64(ptr nocapture, ptr nocapture, i64, i1)

attributes #0 = { "target-features"="-bulk-memory" }

; CHECK: - Type: CUSTOM
; CHECK-NEXT: Name: name
; CHECK-NEXT: FunctionNames:
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4 changes: 2 additions & 2 deletions lld/test/wasm/lto/stub-library-libcall.s
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Expand Up @@ -2,7 +2,7 @@
# RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown -o %t_main.o %t/main.s
# RUN: llvm-as %S/Inputs/foo.ll -o %t_foo.o
# RUN: llvm-as %S/Inputs/libcall.ll -o %t_libcall.o
# RUN: wasm-ld %t_main.o %t_libcall.o %t_foo.o %p/Inputs/stub.so -o %t.wasm
# RUN: wasm-ld -mllvm -mattr=-bulk-memory %t_main.o %t_libcall.o %t_foo.o %p/Inputs/stub.so -o %t.wasm
# RUN: obj2yaml %t.wasm | FileCheck %s

# The function `func_with_libcall` will generate an undefined reference to
Expand All @@ -12,7 +12,7 @@
# If %t_foo.o is not included in the link we get an undefined symbol reported
# to the dependency of memcpy on the foo export:

# RUN: not wasm-ld %t_main.o %t_libcall.o %p/Inputs/stub.so -o %t.wasm 2>&1 | FileCheck --check-prefix=MISSING %s
# RUN: not wasm-ld -mllvm -mattr=-bulk-memory %t_main.o %t_libcall.o %p/Inputs/stub.so -o %t.wasm 2>&1 | FileCheck --check-prefix=MISSING %s
# MISSING: stub.so: undefined symbol: foo. Required by memcpy

#--- main.s
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9 changes: 9 additions & 0 deletions llvm/docs/ReleaseNotes.md
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Expand Up @@ -175,6 +175,15 @@ Changes to the RISC-V Backend
Changes to the WebAssembly Backend
----------------------------------

The default target CPU, "generic", now enables the `-mnontrapping-fptoint`
and `-mbulk-memory` flags, which correspond to the [Bulk Memory Operations]
and [Non-trapping float-to-int Conversions] language features, which are
[widely implemented in engines].

[Bulk Memory Operations]: https://github.com/WebAssembly/bulk-memory-operations/blob/master/proposals/bulk-memory-operations/Overview.md
[Non-trapping float-to-int Conversions]: https://github.com/WebAssembly/spec/blob/master/proposals/nontrapping-float-to-int-conversion/Overview.md
[widely implemented in engines]: https://webassembly.org/features/

Changes to the Windows Target
-----------------------------

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3 changes: 2 additions & 1 deletion llvm/lib/Target/WebAssembly/WebAssembly.td
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Expand Up @@ -114,7 +114,8 @@ def : ProcessorModel<"mvp", NoSchedModel, []>;
// consideration given to available support in relevant engines and tools, and
// the importance of the features.
def : ProcessorModel<"generic", NoSchedModel,
[FeatureMultivalue, FeatureMutableGlobals,
[FeatureBulkMemory, FeatureMultivalue,
FeatureMutableGlobals, FeatureNontrappingFPToInt,
FeatureReferenceTypes, FeatureSignExt]>;

// Latest and greatest experimental version of WebAssembly. Bugs included!
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2 changes: 2 additions & 0 deletions llvm/lib/Target/WebAssembly/WebAssemblyFixFunctionBitcasts.cpp
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Expand Up @@ -111,6 +111,7 @@ static Function *createWrapper(Function *F, FunctionType *Ty) {

Function *Wrapper = Function::Create(Ty, Function::PrivateLinkage,
F->getName() + "_bitcast", M);
Wrapper->setAttributes(F->getAttributes());
BasicBlock *BB = BasicBlock::Create(M->getContext(), "body", Wrapper);
const DataLayout &DL = BB->getDataLayout();

Expand Down Expand Up @@ -201,6 +202,7 @@ static Function *createWrapper(Function *F, FunctionType *Ty) {
Wrapper->eraseFromParent();
Wrapper = Function::Create(Ty, Function::PrivateLinkage,
F->getName() + "_bitcast_invalid", M);
Wrapper->setAttributes(F->getAttributes());
BasicBlock *BB = BasicBlock::Create(M->getContext(), "body", Wrapper);
new UnreachableInst(M->getContext(), BB);
Wrapper->setName(F->getName() + "_bitcast_invalid");
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29 changes: 23 additions & 6 deletions llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
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Expand Up @@ -233,13 +233,30 @@ class CoalesceFeaturesAndStripAtomics final : public ModulePass {

private:
FeatureBitset coalesceFeatures(const Module &M) {
FeatureBitset Features =
WasmTM
->getSubtargetImpl(std::string(WasmTM->getTargetCPU()),
std::string(WasmTM->getTargetFeatureString()))
->getFeatureBits();
for (auto &F : M)
// Union the features of all defined functions. Start with an empty set, so
// that if a feature is disabled in every function, we'll compute it as
// disabled. If any function lacks a target-features attribute, it'll
// default to the target CPU from the `TargetMachine`.
FeatureBitset Features;
bool AnyDefinedFuncs = false;
for (auto &F : M) {
if (F.isDeclaration())
continue;

Features |= WasmTM->getSubtargetImpl(F)->getFeatureBits();
AnyDefinedFuncs = true;
}

// If we have no defined functions, use the target CPU from the
// `TargetMachine`.
if (!AnyDefinedFuncs) {
Features =
WasmTM
->getSubtargetImpl(std::string(WasmTM->getTargetCPU()),
std::string(WasmTM->getTargetFeatureString()))
->getFeatureBits();
}

return Features;
}

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10 changes: 5 additions & 5 deletions llvm/test/CodeGen/WebAssembly/cfg-stackify-eh-legacy.ll
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@@ -1,9 +1,9 @@
; REQUIRES: asserts
; RUN: llc < %s -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -disable-block-placement -verify-machineinstrs -fast-isel=false -machine-sink-split-probability-threshold=0 -cgp-freq-ratio-to-skip-merge=1000 -wasm-enable-eh -exception-model=wasm -mattr=+exception-handling | FileCheck %s
; RUN: llc < %s -disable-wasm-fallthrough-return-opt -disable-block-placement -verify-machineinstrs -fast-isel=false -machine-sink-split-probability-threshold=0 -cgp-freq-ratio-to-skip-merge=1000 -wasm-enable-eh -exception-model=wasm -mattr=+exception-handling
; RUN: llc < %s -O0 -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -verify-machineinstrs -wasm-enable-eh -exception-model=wasm -mattr=+exception-handling | FileCheck %s --check-prefix=NOOPT
; RUN: llc < %s -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -disable-block-placement -verify-machineinstrs -fast-isel=false -machine-sink-split-probability-threshold=0 -cgp-freq-ratio-to-skip-merge=1000 -wasm-enable-eh -exception-model=wasm -mattr=+exception-handling -wasm-disable-ehpad-sort -stats 2>&1 | FileCheck %s --check-prefix=NOSORT
; RUN: llc < %s -disable-wasm-fallthrough-return-opt -disable-block-placement -verify-machineinstrs -fast-isel=false -machine-sink-split-probability-threshold=0 -cgp-freq-ratio-to-skip-merge=1000 -wasm-enable-eh -exception-model=wasm -mattr=+exception-handling -wasm-disable-ehpad-sort | FileCheck %s --check-prefix=NOSORT-LOCALS
; RUN: llc < %s -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -disable-block-placement -verify-machineinstrs -fast-isel=false -machine-sink-split-probability-threshold=0 -cgp-freq-ratio-to-skip-merge=1000 -wasm-enable-eh -exception-model=wasm -mattr=+exception-handling,bulk-memory | FileCheck %s
; RUN: llc < %s -disable-wasm-fallthrough-return-opt -disable-block-placement -verify-machineinstrs -fast-isel=false -machine-sink-split-probability-threshold=0 -cgp-freq-ratio-to-skip-merge=1000 -wasm-enable-eh -exception-model=wasm -mattr=+exception-handling,bulk-memory
; RUN: llc < %s -O0 -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -verify-machineinstrs -wasm-enable-eh -exception-model=wasm -mattr=+exception-handling,-bulk-memory | FileCheck %s --check-prefix=NOOPT
; RUN: llc < %s -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -disable-block-placement -verify-machineinstrs -fast-isel=false -machine-sink-split-probability-threshold=0 -cgp-freq-ratio-to-skip-merge=1000 -wasm-enable-eh -exception-model=wasm -mattr=+exception-handling,-bulk-memory -wasm-disable-ehpad-sort -stats 2>&1 | FileCheck %s --check-prefix=NOSORT
; RUN: llc < %s -disable-wasm-fallthrough-return-opt -disable-block-placement -verify-machineinstrs -fast-isel=false -machine-sink-split-probability-threshold=0 -cgp-freq-ratio-to-skip-merge=1000 -wasm-enable-eh -exception-model=wasm -mattr=+exception-handling,-bulk-memory -wasm-disable-ehpad-sort | FileCheck %s --check-prefix=NOSORT-LOCALS

target triple = "wasm32-unknown-unknown"

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8 changes: 7 additions & 1 deletion llvm/test/CodeGen/WebAssembly/target-features-cpus.ll
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Expand Up @@ -13,14 +13,20 @@ target triple = "wasm32-unknown-unknown"

; generic: +multivalue, +mutable-globals, +reference-types, +sign-ext
; GENERIC-LABEL: .custom_section.target_features,"",@
; GENERIC-NEXT: .int8 4
; GENERIC-NEXT: .int8 6
; GENERIC-NEXT: .int8 43
; GENERIC-NEXT: .int8 11
; GENERIC-NEXT: .ascii "bulk-memory"
; GENERIC-NEXT: .int8 43
; GENERIC-NEXT: .int8 10
; GENERIC-NEXT: .ascii "multivalue"
; GENERIC-NEXT: .int8 43
; GENERIC-NEXT: .int8 15
; GENERIC-NEXT: .ascii "mutable-globals"
; GENERIC-NEXT: .int8 43
; GENERIC-NEXT: .int8 19
; GENERIC-NEXT: .ascii "nontrapping-fptoint"
; GENERIC-NEXT: .int8 43
; GENERIC-NEXT: .int8 15
; GENERIC-NEXT: .ascii "reference-types"
; GENERIC-NEXT: .int8 43
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4 changes: 2 additions & 2 deletions llvm/test/MC/WebAssembly/extern-functype-intrinsic.ll
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@@ -1,5 +1,5 @@
; RUN: llc %s -o - | FileCheck %s
; RUN: llc %s -o - | llvm-mc -triple=wasm32-unknown-unknown | FileCheck %s
; RUN: llc %s -mattr=-bulk-memory -o - | FileCheck %s
; RUN: llc %s -mattr=-bulk-memory -o - | llvm-mc -triple=wasm32-unknown-unknown | FileCheck %s

; ModuleID = 'test.c'
source_filename = "test.c"
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2 changes: 1 addition & 1 deletion llvm/test/MC/WebAssembly/libcall.ll
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@@ -1,4 +1,4 @@
; RUN: llc -filetype=obj %s -o - | obj2yaml | FileCheck %s
; RUN: llc -filetype=obj -mattr=-bulk-memory %s -o - | obj2yaml | FileCheck %s

target triple = "wasm32-unknown-unknown"

Expand Down