release/20.x: [RelLookupTableConverter] Drop unnamed_addr to avoid generating GOTPCREL relocations (#142304) #142311

dianqk · 2025-06-01T14:49:05Z

Backport aa09dbb

Requested by: @dianqk

llvmbot · 2025-06-01T14:49:43Z

@llvm/pr-subscribers-llvm-transforms

Author: dianqk (dianqk)

Changes

Backport aa09dbb

Requested by: @dianqk

Full diff: https://github.com/llvm/llvm-project/pull/142311.diff

2 Files Affected:

(modified) llvm/lib/Transforms/Utils/RelLookupTableConverter.cpp (+17)
(added) llvm/test/Transforms/RelLookupTableConverter/unnamed_addr.ll (+119)

diff --git a/llvm/lib/Transforms/Utils/RelLookupTableConverter.cpp b/llvm/lib/Transforms/Utils/RelLookupTableConverter.cpp
index 2700b4307308c..4486cba2bf6c0 100644
--- a/llvm/lib/Transforms/Utils/RelLookupTableConverter.cpp
+++ b/llvm/lib/Transforms/Utils/RelLookupTableConverter.cpp
@@ -18,6 +18,7 @@
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Module.h"
+#include "llvm/TargetParser/Triple.h"
 
 using namespace llvm;
 
@@ -108,8 +109,24 @@ static GlobalVariable *createRelLookupTable(Function &Func,
   uint64_t Idx = 0;
   SmallVector<Constant *, 64> RelLookupTableContents(NumElts);
 
+  Triple TT(M.getTargetTriple());
+  // FIXME: This should be removed in the future.
+  bool ShouldDropUnnamedAddr =
+      // Drop unnamed_addr to avoid matching pattern in
+      // `handleIndirectSymViaGOTPCRel`, which generates GOTPCREL relocations
+      // not supported by the GNU linker and LLD versions below 18 on aarch64.
+      TT.isAArch64()
+      // Apple's ld64 (and ld-prime on Xcode 15.2) miscompile something on
+      // x86_64-apple-darwin. See
+      // https://github.com/rust-lang/rust/issues/140686 and
+      // https://github.com/rust-lang/rust/issues/141306.
+      || (TT.isX86() && TT.isOSDarwin());
+
   for (Use &Operand : LookupTableArr->operands()) {
     Constant *Element = cast<Constant>(Operand);
+    if (ShouldDropUnnamedAddr)
+      if (auto *GlobalElement = dyn_cast<GlobalValue>(Element))
+        GlobalElement->setUnnamedAddr(GlobalValue::UnnamedAddr::None);
     Type *IntPtrTy = M.getDataLayout().getIntPtrType(M.getContext());
     Constant *Base = llvm::ConstantExpr::getPtrToInt(RelLookupTable, IntPtrTy);
     Constant *Target = llvm::ConstantExpr::getPtrToInt(Element, IntPtrTy);
diff --git a/llvm/test/Transforms/RelLookupTableConverter/unnamed_addr.ll b/llvm/test/Transforms/RelLookupTableConverter/unnamed_addr.ll
new file mode 100644
index 0000000000000..78b8a4aa126c9
--- /dev/null
+++ b/llvm/test/Transforms/RelLookupTableConverter/unnamed_addr.ll
@@ -0,0 +1,119 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals all --version 5
+; REQUIRES: x86-registered-target
+; REQUIRES: aarch64-registered-target
+; 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
+; RUN: opt < %s -passes=rel-lookup-table-converter -relocation-model=pic -mtriple=aarch64 -S | FileCheck -check-prefix=aarch64 %s
+; RUN: opt < %s -passes=rel-lookup-table-converter -relocation-model=pic -mtriple=x86_64 -S | FileCheck -check-prefix=x86_64 %s
+
+@a0 = private unnamed_addr constant i32 0
+@a1 = private unnamed_addr constant i32 1
+@a2 = private unnamed_addr constant i32 2
+@load_relative_1.table = private unnamed_addr constant [3 x ptr] [ptr @a0, ptr @a1, ptr @a2]
+
+@x0 = internal unnamed_addr constant i64 0
+@x1 = internal unnamed_addr constant i64 1
+@x2 = internal unnamed_addr constant i64 2
+@x3 = internal unnamed_addr constant i64 3
+@y0 = internal unnamed_addr constant ptr @x3
+@y1 = internal unnamed_addr constant ptr @x2
+@y2 = internal unnamed_addr constant ptr @x1
+@y3 = internal unnamed_addr constant ptr @x0
+@load_relative_2.table = private unnamed_addr constant [4 x ptr] [ptr @y3, ptr @y2, ptr @y1, ptr @y0]
+
+;.
+; x86_64-apple-darwin: @a0 = private constant i32 0
+; x86_64-apple-darwin: @a1 = private constant i32 1
+; x86_64-apple-darwin: @a2 = private constant i32 2
+; 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
+; x86_64-apple-darwin: @x0 = internal unnamed_addr constant i64 0
+; x86_64-apple-darwin: @x1 = internal unnamed_addr constant i64 1
+; x86_64-apple-darwin: @x2 = internal unnamed_addr constant i64 2
+; x86_64-apple-darwin: @x3 = internal unnamed_addr constant i64 3
+; x86_64-apple-darwin: @y0 = internal constant ptr @x3
+; x86_64-apple-darwin: @y1 = internal constant ptr @x2
+; x86_64-apple-darwin: @y2 = internal constant ptr @x1
+; x86_64-apple-darwin: @y3 = internal constant ptr @x0
+; 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
+;.
+; aarch64: @a0 = private constant i32 0
+; aarch64: @a1 = private constant i32 1
+; aarch64: @a2 = private constant i32 2
+; 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
+; aarch64: @x0 = internal unnamed_addr constant i64 0
+; aarch64: @x1 = internal unnamed_addr constant i64 1
+; aarch64: @x2 = internal unnamed_addr constant i64 2
+; aarch64: @x3 = internal unnamed_addr constant i64 3
+; aarch64: @y0 = internal constant ptr @x3
+; aarch64: @y1 = internal constant ptr @x2
+; aarch64: @y2 = internal constant ptr @x1
+; aarch64: @y3 = internal constant ptr @x0
+; 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
+;.
+; x86_64: @a0 = private unnamed_addr constant i32 0
+; x86_64: @a1 = private unnamed_addr constant i32 1
+; x86_64: @a2 = private unnamed_addr constant i32 2
+; 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
+; x86_64: @x0 = internal unnamed_addr constant i64 0
+; x86_64: @x1 = internal unnamed_addr constant i64 1
+; x86_64: @x2 = internal unnamed_addr constant i64 2
+; x86_64: @x3 = internal unnamed_addr constant i64 3
+; x86_64: @y0 = internal unnamed_addr constant ptr @x3
+; x86_64: @y1 = internal unnamed_addr constant ptr @x2
+; x86_64: @y2 = internal unnamed_addr constant ptr @x1
+; x86_64: @y3 = internal unnamed_addr constant ptr @x0
+; 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
+;.
+define ptr @load_relative_1(i64 %offset) {
+; x86_64-apple-darwin-LABEL: define ptr @load_relative_1(
+; x86_64-apple-darwin-SAME: i64 [[OFFSET:%.*]]) {
+; x86_64-apple-darwin-NEXT:    [[RELTABLE_SHIFT:%.*]] = shl i64 [[OFFSET]], 2
+; x86_64-apple-darwin-NEXT:    [[RELTABLE_INTRINSIC:%.*]] = call ptr @llvm.load.relative.i64(ptr @load_relative_1.table.rel, i64 [[RELTABLE_SHIFT]])
+; x86_64-apple-darwin-NEXT:    ret ptr [[RELTABLE_INTRINSIC]]
+;
+; aarch64-LABEL: define ptr @load_relative_1(
+; aarch64-SAME: i64 [[OFFSET:%.*]]) {
+; aarch64-NEXT:    [[RELTABLE_SHIFT:%.*]] = shl i64 [[OFFSET]], 2
+; aarch64-NEXT:    [[RELTABLE_INTRINSIC:%.*]] = call ptr @llvm.load.relative.i64(ptr @load_relative_1.table.rel, i64 [[RELTABLE_SHIFT]])
+; aarch64-NEXT:    ret ptr [[RELTABLE_INTRINSIC]]
+;
+; x86_64-LABEL: define ptr @load_relative_1(
+; x86_64-SAME: i64 [[OFFSET:%.*]]) {
+; x86_64-NEXT:    [[RELTABLE_SHIFT:%.*]] = shl i64 [[OFFSET]], 2
+; x86_64-NEXT:    [[RELTABLE_INTRINSIC:%.*]] = call ptr @llvm.load.relative.i64(ptr @load_relative_1.table.rel, i64 [[RELTABLE_SHIFT]])
+; x86_64-NEXT:    ret ptr [[RELTABLE_INTRINSIC]]
+;
+  %gep = getelementptr inbounds [3 x ptr], ptr @load_relative_1.table, i64 0, i64 %offset
+  %load = load ptr, ptr %gep
+  ret ptr %load
+}
+
+define ptr @load_relative_2(i64 %offset) {
+; x86_64-apple-darwin-LABEL: define ptr @load_relative_2(
+; x86_64-apple-darwin-SAME: i64 [[OFFSET:%.*]]) {
+; x86_64-apple-darwin-NEXT:    [[RELTABLE_SHIFT:%.*]] = shl i64 [[OFFSET]], 2
+; x86_64-apple-darwin-NEXT:    [[RELTABLE_INTRINSIC:%.*]] = call ptr @llvm.load.relative.i64(ptr @load_relative_2.table.rel, i64 [[RELTABLE_SHIFT]])
+; x86_64-apple-darwin-NEXT:    ret ptr [[RELTABLE_INTRINSIC]]
+;
+; aarch64-LABEL: define ptr @load_relative_2(
+; aarch64-SAME: i64 [[OFFSET:%.*]]) {
+; aarch64-NEXT:    [[RELTABLE_SHIFT:%.*]] = shl i64 [[OFFSET]], 2
+; aarch64-NEXT:    [[RELTABLE_INTRINSIC:%.*]] = call ptr @llvm.load.relative.i64(ptr @load_relative_2.table.rel, i64 [[RELTABLE_SHIFT]])
+; aarch64-NEXT:    ret ptr [[RELTABLE_INTRINSIC]]
+;
+; x86_64-LABEL: define ptr @load_relative_2(
+; x86_64-SAME: i64 [[OFFSET:%.*]]) {
+; x86_64-NEXT:    [[RELTABLE_SHIFT:%.*]] = shl i64 [[OFFSET]], 2
+; x86_64-NEXT:    [[RELTABLE_INTRINSIC:%.*]] = call ptr @llvm.load.relative.i64(ptr @load_relative_2.table.rel, i64 [[RELTABLE_SHIFT]])
+; x86_64-NEXT:    ret ptr [[RELTABLE_INTRINSIC]]
+;
+  %gep = getelementptr inbounds [4 x ptr], ptr @load_relative_2.table, i64 0, i64 %offset
+  %load = load ptr, ptr %gep
+  ret ptr %load
+}
+;.
+; x86_64-apple-darwin: attributes #[[ATTR0:[0-9]+]] = { nocallback nofree nosync nounwind willreturn memory(argmem: read) }
+;.
+; aarch64: attributes #[[ATTR0:[0-9]+]] = { nocallback nofree nosync nounwind willreturn memory(argmem: read) }
+;.
+; x86_64: attributes #[[ATTR0:[0-9]+]] = { nocallback nofree nosync nounwind willreturn memory(argmem: read) }
+;.

…REL 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. (cherry picked from commit aa09dbb)

github-actions · 2025-06-03T21:50:24Z

@dianqk (or anyone else). If you would like to add a note about this fix in the release notes (completely optional). Please reply to this comment with a one or two sentence description of the fix. When you are done, please add the release:note label to this PR.

dianqk · 2025-06-03T23:55:27Z

@dianqk (or anyone else). If you would like to add a note about this fix in the release notes (completely optional). Please reply to this comment with a one or two sentence description of the fix. When you are done, please add the release:note label to this PR.

Add a workaround for relocations in the data sections for Apple's ld64, ld-prime, and GNU linker, which will be removed in the future.

dianqk · 2025-06-03T23:56:41Z

Note to me: I propose to keep a major version around until the gnu linker release supports it and GitHub Actions defaults to Xcode 15.3+.

dianqk requested review from nikic and MaskRay June 1, 2025 14:49

llvmbot added the llvm:transforms label Jun 1, 2025

dianqk mentioned this pull request Jun 1, 2025

[RelLookupTableConverter] Drop unnamed_addr to avoid generating GOTPCREL relocations #142304

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nikic added this to the LLVM 20.X Release milestone Jun 1, 2025

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github-project-automation bot moved this to Needs Triage in LLVM Release Status Jun 1, 2025

nikic approved these changes Jun 2, 2025

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github-project-automation bot moved this from Needs Triage to Needs Merge in LLVM Release Status Jun 2, 2025

tstellar force-pushed the backport-142304 branch from 7b2f3a9 to e0586e2 Compare June 3, 2025 21:49

tstellar merged commit e0586e2 into llvm:release/20.x Jun 3, 2025
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github-project-automation bot moved this from Needs Merge to Done in LLVM Release Status Jun 3, 2025

dianqk deleted the backport-142304 branch June 3, 2025 23:55

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release/20.x: [RelLookupTableConverter] Drop unnamed_addr to avoid generating GOTPCREL relocations (#142304) #142311

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release/20.x: [RelLookupTableConverter] Drop unnamed_addr to avoid generating GOTPCREL relocations (#142304) #142311

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