[RelLookupTableConverter] Drop unnamed_addr to avoid generating GOTPCREL relocations #142304
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@llvm/pr-subscribers-llvm-transforms Author: dianqk (dianqk) ChangesFollow #72584 (comment), the patch will drop the 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) This is my concern. I'm not sure how unnamed_addr provides this guarantee, and I haven't found any test cases. Full diff: https://github.com/llvm/llvm-project/pull/142304.diff 2 Files Affected:
diff --git a/llvm/lib/Transforms/Utils/RelLookupTableConverter.cpp b/llvm/lib/Transforms/Utils/RelLookupTableConverter.cpp
index 2700b4307308c..8bad67044bea4 100644
--- a/llvm/lib/Transforms/Utils/RelLookupTableConverter.cpp
+++ b/llvm/lib/Transforms/Utils/RelLookupTableConverter.cpp
@@ -110,6 +110,11 @@ static GlobalVariable *createRelLookupTable(Function &Func,
for (Use &Operand : LookupTableArr->operands()) {
Constant *Element = cast<Constant>(Operand);
+ // Drop unnamed_addr to avoid matching pattern in
+ // `handleIndirectSymViaGOTPCRel`, which creates GOTPCREL relocations not
+ // supported by the GNU linker and LLD versions below 18 on aarch64.
+ 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..748d7522c1097
--- /dev/null
+++ b/llvm/test/Transforms/RelLookupTableConverter/unnamed_addr.ll
@@ -0,0 +1,88 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals all --version 5
+; RUN: opt < %s -passes=rel-lookup-table-converter -relocation-model=pic -mtriple=x86_64 -S | FileCheck -check-prefix=x86_64 %s
+; RUN: opt < %s -passes=rel-lookup-table-converter -relocation-model=pic -mtriple=aarch64 -S | FileCheck -check-prefix=aarch64 %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: @a0 = private constant i32 0
+; x86_64: @a1 = private constant i32 1
+; x86_64: @a2 = private 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 constant ptr @x3
+; x86_64: @y1 = internal constant ptr @x2
+; x86_64: @y2 = internal constant ptr @x1
+; x86_64: @y3 = internal 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
+;.
+; 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
+;.
+define ptr @load_relative_1(i64 %offset) {
+; 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]]
+;
+; 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]]
+;
+ %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-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]]
+;
+; 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]]
+;
+ %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: 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) }
+;.
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dianqk
changed the title
nikic
reviewed
Jun 1, 2025
| @@ -110,6 +110,11 @@ static GlobalVariable *createRelLookupTable(Function &Func, | |||
|
|
|||
| for (Use &Operand : LookupTableArr->operands()) { | |||
| Constant *Element = cast<Constant>(Operand); | |||
| // 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. | |||
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As we are working around problems with specific linkers on specific platforms, we should add triple checks like you originally had, for aarch64 and for x86-darwin (and list which linker versions are affected, so this can be removed in the future).
Does BFD not support GOTPCREL on aarch64 even in the newest version?
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Does BFD not support GOTPCREL on aarch64 even in the newest version?
Probably nobody noticed this.
/nix/...-binutils-aarch64-unknown-linux-gnu-2.44/bin/ld: /path/1.rcgu.o: unrecognized relocation type 0x13b in section `.rodata..Lswitch.table.bad.rel'
/nix/...-binutils-aarch64-unknown-linux-gnu-2.44/bin/ld: is this version of the linker - (GNU Binutils) 2.44 - out of date ?
/nix/...-binutils-aarch64-unknown-linux-gnu-2.44/bin/ld: final link failed: bad value
collect2: error: ld returned 1 exit status
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Huh. It would be good to file a bug for that...
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Huh. It would be good to file a bug for that...
I'm still in the process of creating an account. :\ (https://sourceware.org/bugzilla/createaccount.cgi)
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/144/builds/26573 Here is the relevant piece of the build log for the reference |
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/3/builds/16826 Here is the relevant piece of the build log for the reference |
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/27/builds/10902 Here is the relevant piece of the build log for the reference |
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nikic
reviewed
Jun 1, 2025
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Need REQUIRES: x86-registered-target and REQUIRES: aarch64-registered-target.
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/140/builds/24193 Here is the relevant piece of the build log for the reference |
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/133/builds/17092 Here is the relevant piece of the build log for the reference |
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/46/builds/17728 Here is the relevant piece of the build log for the reference |
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/190/builds/20928 Here is the relevant piece of the build log for the reference |
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dianqk
added a commit
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Jun 1, 2025
…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)
|
Backport PR: #142311. |
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/180/builds/18582 Here is the relevant piece of the build log for the reference |
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Rather than removing |
Does this sound like it will prevent the generation of all GOTPCRELs? This PR is to prevent "accidental" (we doesn't explicitly submit it) GOTPCREL generation. |
Oh yeah you're right. Disregard my last comment |
swift-ci
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Jun 3, 2025
…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)
DhruvSrivastavaX
pushed a commit
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that referenced
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Jun 12, 2025
…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.
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Follow #72584 (comment), the patch will drop the
unnamed_addrattribute 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.
This is my concern. I'm not sure how unnamed_addr provides this guarantee, and I haven't found any test cases.