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[RelLookupTableConverter] Drop unnamed_addr to avoid generating GOTPCREL relocations (llvm#142304)
Follow llvm#72584 (comment), the patch will drop the `unnamed_addr` attribute when generating relative lookup tables. I'm not very confident about this patch, but it does resolve rust-lang/rust#140686, rust-lang/rust#141306 and rust-lang/rust#141737. But I don't think this will result in worse problems. > LLVM provides that the calculation of such a constant initializer will not overflow at link time under the medium code model if x is an unnamed_addr function. However, it does not provide this guarantee for a constant initializer folded into a function body. This intrinsic can be used to avoid the possibility of overflows when loading from such a constant. ([‘llvm.load.relative’ Intrinsic](https://llvm.org/docs/LangRef.html#id2592)) This is my concern. I'm not sure how unnamed_addr provides this guarantee, and I haven't found any test cases.
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‎llvm/lib/Transforms/Utils/RelLookupTableConverter.cpp

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@@ -108,8 +108,24 @@ static GlobalVariable *createRelLookupTable(Function &Func,
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uint64_t Idx = 0;
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SmallVector<Constant *, 64> RelLookupTableContents(NumElts);
110110

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Triple TT = M.getTargetTriple();
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// FIXME: This should be removed in the future.
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bool ShouldDropUnnamedAddr =
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// Drop unnamed_addr to avoid matching pattern in
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// `handleIndirectSymViaGOTPCRel`, which generates GOTPCREL relocations
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// not supported by the GNU linker and LLD versions below 18 on aarch64.
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TT.isAArch64()
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// Apple's ld64 (and ld-prime on Xcode 15.2) miscompile something on
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// x86_64-apple-darwin. See
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// https://github.com/rust-lang/rust/issues/140686 and
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// https://github.com/rust-lang/rust/issues/141306.
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|| (TT.isX86() && TT.isOSDarwin());
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for (Use &Operand : LookupTableArr->operands()) {
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Constant *Element = cast<Constant>(Operand);
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if (ShouldDropUnnamedAddr)
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if (auto *GlobalElement = dyn_cast<GlobalValue>(Element))
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GlobalElement->setUnnamedAddr(GlobalValue::UnnamedAddr::None);
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Type *IntPtrTy = M.getDataLayout().getIntPtrType(M.getContext());
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Constant *Base = llvm::ConstantExpr::getPtrToInt(RelLookupTable, IntPtrTy);
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Constant *Target = llvm::ConstantExpr::getPtrToInt(Element, IntPtrTy);

‎llvm/test/Transforms/RelLookupTableConverter/unnamed_addr.ll

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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals all --version 5
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; RUN: opt < %s -passes=rel-lookup-table-converter -relocation-model=pic -mtriple=x86_64-apple-darwin -S | FileCheck -check-prefix=x86_64-apple-darwin %s
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; RUN: opt < %s -passes=rel-lookup-table-converter -relocation-model=pic -mtriple=aarch64 -S | FileCheck -check-prefix=aarch64 %s
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; RUN: opt < %s -passes=rel-lookup-table-converter -relocation-model=pic -mtriple=x86_64 -S | FileCheck -check-prefix=x86_64 %s
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@a0 = private unnamed_addr constant i32 0
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@a1 = private unnamed_addr constant i32 1
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@a2 = private unnamed_addr constant i32 2
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@load_relative_1.table = private unnamed_addr constant [3 x ptr] [ptr @a0, ptr @a1, ptr @a2]
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@x0 = internal unnamed_addr constant i64 0
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@x1 = internal unnamed_addr constant i64 1
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@x2 = internal unnamed_addr constant i64 2
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@x3 = internal unnamed_addr constant i64 3
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@y0 = internal unnamed_addr constant ptr @x3
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@y1 = internal unnamed_addr constant ptr @x2
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@y2 = internal unnamed_addr constant ptr @x1
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@y3 = internal unnamed_addr constant ptr @x0
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@load_relative_2.table = private unnamed_addr constant [4 x ptr] [ptr @y3, ptr @y2, ptr @y1, ptr @y0]
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;.
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; x86_64-apple-darwin: @a0 = private constant i32 0
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; x86_64-apple-darwin: @a1 = private constant i32 1
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; x86_64-apple-darwin: @a2 = private constant i32 2
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; x86_64-apple-darwin: @load_relative_1.table.rel = private unnamed_addr constant [3 x i32] [i32 trunc (i64 sub (i64 ptrtoint (ptr @a0 to i64), i64 ptrtoint (ptr @load_relative_1.table.rel to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr @a1 to i64), i64 ptrtoint (ptr @load_relative_1.table.rel to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr @a2 to i64), i64 ptrtoint (ptr @load_relative_1.table.rel to i64)) to i32)], align 4
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; x86_64-apple-darwin: @x0 = internal unnamed_addr constant i64 0
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; x86_64-apple-darwin: @x1 = internal unnamed_addr constant i64 1
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; x86_64-apple-darwin: @x2 = internal unnamed_addr constant i64 2
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; x86_64-apple-darwin: @x3 = internal unnamed_addr constant i64 3
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; x86_64-apple-darwin: @y0 = internal constant ptr @x3
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; x86_64-apple-darwin: @y1 = internal constant ptr @x2
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; x86_64-apple-darwin: @y2 = internal constant ptr @x1
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; x86_64-apple-darwin: @y3 = internal constant ptr @x0
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; x86_64-apple-darwin: @load_relative_2.table.rel = private unnamed_addr constant [4 x i32] [i32 trunc (i64 sub (i64 ptrtoint (ptr @y3 to i64), i64 ptrtoint (ptr @load_relative_2.table.rel to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr @y2 to i64), i64 ptrtoint (ptr @load_relative_2.table.rel to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr @y1 to i64), i64 ptrtoint (ptr @load_relative_2.table.rel to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr @y0 to i64), i64 ptrtoint (ptr @load_relative_2.table.rel to i64)) to i32)], align 4
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;.
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; aarch64: @a0 = private constant i32 0
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; aarch64: @a1 = private constant i32 1
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; aarch64: @a2 = private constant i32 2
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; aarch64: @load_relative_1.table.rel = private unnamed_addr constant [3 x i32] [i32 trunc (i64 sub (i64 ptrtoint (ptr @a0 to i64), i64 ptrtoint (ptr @load_relative_1.table.rel to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr @a1 to i64), i64 ptrtoint (ptr @load_relative_1.table.rel to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr @a2 to i64), i64 ptrtoint (ptr @load_relative_1.table.rel to i64)) to i32)], align 4
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; aarch64: @x0 = internal unnamed_addr constant i64 0
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; aarch64: @x1 = internal unnamed_addr constant i64 1
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; aarch64: @x2 = internal unnamed_addr constant i64 2
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; aarch64: @x3 = internal unnamed_addr constant i64 3
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; aarch64: @y0 = internal constant ptr @x3
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; aarch64: @y1 = internal constant ptr @x2
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; aarch64: @y2 = internal constant ptr @x1
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; aarch64: @y3 = internal constant ptr @x0
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; aarch64: @load_relative_2.table.rel = private unnamed_addr constant [4 x i32] [i32 trunc (i64 sub (i64 ptrtoint (ptr @y3 to i64), i64 ptrtoint (ptr @load_relative_2.table.rel to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr @y2 to i64), i64 ptrtoint (ptr @load_relative_2.table.rel to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr @y1 to i64), i64 ptrtoint (ptr @load_relative_2.table.rel to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr @y0 to i64), i64 ptrtoint (ptr @load_relative_2.table.rel to i64)) to i32)], align 4
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;.
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; x86_64: @a0 = private unnamed_addr constant i32 0
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; x86_64: @a1 = private unnamed_addr constant i32 1
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; x86_64: @a2 = private unnamed_addr constant i32 2
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; x86_64: @load_relative_1.table.rel = private unnamed_addr constant [3 x i32] [i32 trunc (i64 sub (i64 ptrtoint (ptr @a0 to i64), i64 ptrtoint (ptr @load_relative_1.table.rel to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr @a1 to i64), i64 ptrtoint (ptr @load_relative_1.table.rel to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr @a2 to i64), i64 ptrtoint (ptr @load_relative_1.table.rel to i64)) to i32)], align 4
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; x86_64: @x0 = internal unnamed_addr constant i64 0
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; x86_64: @x1 = internal unnamed_addr constant i64 1
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; x86_64: @x2 = internal unnamed_addr constant i64 2
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; x86_64: @x3 = internal unnamed_addr constant i64 3
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; x86_64: @y0 = internal unnamed_addr constant ptr @x3
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; x86_64: @y1 = internal unnamed_addr constant ptr @x2
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; x86_64: @y2 = internal unnamed_addr constant ptr @x1
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; x86_64: @y3 = internal unnamed_addr constant ptr @x0
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; x86_64: @load_relative_2.table.rel = private unnamed_addr constant [4 x i32] [i32 trunc (i64 sub (i64 ptrtoint (ptr @y3 to i64), i64 ptrtoint (ptr @load_relative_2.table.rel to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr @y2 to i64), i64 ptrtoint (ptr @load_relative_2.table.rel to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr @y1 to i64), i64 ptrtoint (ptr @load_relative_2.table.rel to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr @y0 to i64), i64 ptrtoint (ptr @load_relative_2.table.rel to i64)) to i32)], align 4
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;.
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define ptr @load_relative_1(i64 %offset) {
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; x86_64-apple-darwin-LABEL: define ptr @load_relative_1(
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; x86_64-apple-darwin-SAME: i64 [[OFFSET:%.*]]) {
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; x86_64-apple-darwin-NEXT: [[RELTABLE_SHIFT:%.*]] = shl i64 [[OFFSET]], 2
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; x86_64-apple-darwin-NEXT: [[RELTABLE_INTRINSIC:%.*]] = call ptr @llvm.load.relative.i64(ptr @load_relative_1.table.rel, i64 [[RELTABLE_SHIFT]])
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; x86_64-apple-darwin-NEXT: ret ptr [[RELTABLE_INTRINSIC]]
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;
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; aarch64-LABEL: define ptr @load_relative_1(
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; aarch64-SAME: i64 [[OFFSET:%.*]]) {
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; aarch64-NEXT: [[RELTABLE_SHIFT:%.*]] = shl i64 [[OFFSET]], 2
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; aarch64-NEXT: [[RELTABLE_INTRINSIC:%.*]] = call ptr @llvm.load.relative.i64(ptr @load_relative_1.table.rel, i64 [[RELTABLE_SHIFT]])
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; aarch64-NEXT: ret ptr [[RELTABLE_INTRINSIC]]
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;
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; x86_64-LABEL: define ptr @load_relative_1(
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; x86_64-SAME: i64 [[OFFSET:%.*]]) {
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; x86_64-NEXT: [[RELTABLE_SHIFT:%.*]] = shl i64 [[OFFSET]], 2
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; x86_64-NEXT: [[RELTABLE_INTRINSIC:%.*]] = call ptr @llvm.load.relative.i64(ptr @load_relative_1.table.rel, i64 [[RELTABLE_SHIFT]])
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; x86_64-NEXT: ret ptr [[RELTABLE_INTRINSIC]]
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;
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%gep = getelementptr inbounds [3 x ptr], ptr @load_relative_1.table, i64 0, i64 %offset
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%load = load ptr, ptr %gep
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ret ptr %load
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}
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define ptr @load_relative_2(i64 %offset) {
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; x86_64-apple-darwin-LABEL: define ptr @load_relative_2(
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; x86_64-apple-darwin-SAME: i64 [[OFFSET:%.*]]) {
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; x86_64-apple-darwin-NEXT: [[RELTABLE_SHIFT:%.*]] = shl i64 [[OFFSET]], 2
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; x86_64-apple-darwin-NEXT: [[RELTABLE_INTRINSIC:%.*]] = call ptr @llvm.load.relative.i64(ptr @load_relative_2.table.rel, i64 [[RELTABLE_SHIFT]])
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; x86_64-apple-darwin-NEXT: ret ptr [[RELTABLE_INTRINSIC]]
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;
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; aarch64-LABEL: define ptr @load_relative_2(
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; aarch64-SAME: i64 [[OFFSET:%.*]]) {
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; aarch64-NEXT: [[RELTABLE_SHIFT:%.*]] = shl i64 [[OFFSET]], 2
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; aarch64-NEXT: [[RELTABLE_INTRINSIC:%.*]] = call ptr @llvm.load.relative.i64(ptr @load_relative_2.table.rel, i64 [[RELTABLE_SHIFT]])
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; aarch64-NEXT: ret ptr [[RELTABLE_INTRINSIC]]
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;
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; x86_64-LABEL: define ptr @load_relative_2(
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; x86_64-SAME: i64 [[OFFSET:%.*]]) {
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; x86_64-NEXT: [[RELTABLE_SHIFT:%.*]] = shl i64 [[OFFSET]], 2
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; x86_64-NEXT: [[RELTABLE_INTRINSIC:%.*]] = call ptr @llvm.load.relative.i64(ptr @load_relative_2.table.rel, i64 [[RELTABLE_SHIFT]])
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; x86_64-NEXT: ret ptr [[RELTABLE_INTRINSIC]]
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;
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%gep = getelementptr inbounds [4 x ptr], ptr @load_relative_2.table, i64 0, i64 %offset
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%load = load ptr, ptr %gep
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ret ptr %load
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}
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;.
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; x86_64-apple-darwin: attributes #[[ATTR0:[0-9]+]] = { nocallback nofree nosync nounwind willreturn memory(argmem: read) }
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;.
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; aarch64: attributes #[[ATTR0:[0-9]+]] = { nocallback nofree nosync nounwind willreturn memory(argmem: read) }
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;.
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; x86_64: attributes #[[ATTR0:[0-9]+]] = { nocallback nofree nosync nounwind willreturn memory(argmem: read) }
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;.

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