[RelLookupTableConverter] Drop unnamed_addr for GVs in entries to avoid generating GOTPCREL relocations #146068

dianqk · 2025-06-27T12:45:01Z

The entry in a relative lookup table is a global variable with a constant offset, such as @gv, GEP @gv, 1, and so on.

We cannot only consider the case of a trivial global variable. This PR handles all cases using the existing IsConstantOffsetFromGlobal function.

…oid generating GOTPCREL relocations

…oid generating GOTPCREL relocations (Style 2)

llvmbot · 2025-06-27T12:45:34Z

@llvm/pr-subscribers-llvm-transforms

Author: dianqk (dianqk)

Changes

A more robust approach than #142304.

Full diff: https://github.com/llvm/llvm-project/pull/146068.diff

2 Files Affected:

(modified) llvm/lib/Transforms/Utils/RelLookupTableConverter.cpp (+21-16)
(modified) llvm/test/Transforms/RelLookupTableConverter/unnamed_addr.ll (+45)

diff --git a/llvm/lib/Transforms/Utils/RelLookupTableConverter.cpp b/llvm/lib/Transforms/Utils/RelLookupTableConverter.cpp
index af0f516f7b002..d53a3144bf57d 100644
--- a/llvm/lib/Transforms/Utils/RelLookupTableConverter.cpp
+++ b/llvm/lib/Transforms/Utils/RelLookupTableConverter.cpp
@@ -66,6 +66,20 @@ static bool shouldConvertToRelLookupTable(Module &M, GlobalVariable &GV) {
   if (!ElemType->isPointerTy() || DL.getPointerTypeSizeInBits(ElemType) != 64)
     return false;
 
+  SmallVector<GlobalVariable *, 4> GVOps;
+  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 (const Use &Op : Array->operands()) {
     Constant *ConstOp = cast<Constant>(&Op);
     GlobalValue *GVOp;
@@ -85,8 +99,15 @@ static bool shouldConvertToRelLookupTable(Module &M, GlobalVariable &GV) {
         !GlovalVarOp->isDSOLocal() ||
         !GlovalVarOp->isImplicitDSOLocal())
       return false;
+
+    if (ShouldDropUnnamedAddr)
+      GVOps.push_back(GlovalVarOp);
   }
 
+  if (ShouldDropUnnamedAddr)
+    for (auto *GVOp : GVOps)
+      GVOp->setUnnamedAddr(GlobalValue::UnnamedAddr::None);
+
   return true;
 }
 
@@ -108,24 +129,8 @@ 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
index 78b8a4aa126c9..322c38d090fe1 100644
--- a/llvm/test/Transforms/RelLookupTableConverter/unnamed_addr.ll
+++ b/llvm/test/Transforms/RelLookupTableConverter/unnamed_addr.ll
@@ -20,6 +20,14 @@
 @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]
 
+@b0 = private unnamed_addr constant [8 x i8] c"00000000"
+@b1 = private unnamed_addr constant [8 x i8] c"11111111"
+@b2 = private unnamed_addr constant [8 x i8] c"22222222"
+@load_relative_3.table = private unnamed_addr constant [3 x ptr] [
+  ptr getelementptr inbounds (i8, ptr @b0, i64 8),
+  ptr getelementptr inbounds (i8, ptr @b1, i64 8),
+  ptr getelementptr inbounds (i8, ptr @b2, i64 8)]
+
 ;.
 ; x86_64-apple-darwin: @a0 = private constant i32 0
 ; x86_64-apple-darwin: @a1 = private constant i32 1
@@ -34,6 +42,10 @@
 ; 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
+; x86_64-apple-darwin: @b0 = private constant [8 x i8] c"00000000"
+; x86_64-apple-darwin: @b1 = private constant [8 x i8] c"11111111"
+; x86_64-apple-darwin: @b2 = private constant [8 x i8] c"22222222"
+; x86_64-apple-darwin: @load_relative_3.table.rel = private unnamed_addr constant [3 x i32] [i32 trunc (i64 sub (i64 ptrtoint (ptr getelementptr inbounds (i8, ptr @b0, i64 8) to i64), i64 ptrtoint (ptr @load_relative_3.table.rel to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr getelementptr inbounds (i8, ptr @b1, i64 8) to i64), i64 ptrtoint (ptr @load_relative_3.table.rel to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr getelementptr inbounds (i8, ptr @b2, i64 8) to i64), i64 ptrtoint (ptr @load_relative_3.table.rel to i64)) to i32)], align 4
 ;.
 ; aarch64: @a0 = private constant i32 0
 ; aarch64: @a1 = private constant i32 1
@@ -48,6 +60,10 @@
 ; 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
+; aarch64: @b0 = private constant [8 x i8] c"00000000"
+; aarch64: @b1 = private constant [8 x i8] c"11111111"
+; aarch64: @b2 = private constant [8 x i8] c"22222222"
+; aarch64: @load_relative_3.table.rel = private unnamed_addr constant [3 x i32] [i32 trunc (i64 sub (i64 ptrtoint (ptr getelementptr inbounds (i8, ptr @b0, i64 8) to i64), i64 ptrtoint (ptr @load_relative_3.table.rel to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr getelementptr inbounds (i8, ptr @b1, i64 8) to i64), i64 ptrtoint (ptr @load_relative_3.table.rel to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr getelementptr inbounds (i8, ptr @b2, i64 8) to i64), i64 ptrtoint (ptr @load_relative_3.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
@@ -62,6 +78,10 @@
 ; 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
+; x86_64: @b0 = private unnamed_addr constant [8 x i8] c"00000000"
+; x86_64: @b1 = private unnamed_addr constant [8 x i8] c"11111111"
+; x86_64: @b2 = private unnamed_addr constant [8 x i8] c"22222222"
+; x86_64: @load_relative_3.table.rel = private unnamed_addr constant [3 x i32] [i32 trunc (i64 sub (i64 ptrtoint (ptr getelementptr inbounds (i8, ptr @b0, i64 8) to i64), i64 ptrtoint (ptr @load_relative_3.table.rel to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr getelementptr inbounds (i8, ptr @b1, i64 8) to i64), i64 ptrtoint (ptr @load_relative_3.table.rel to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr getelementptr inbounds (i8, ptr @b2, i64 8) to i64), i64 ptrtoint (ptr @load_relative_3.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(
@@ -110,6 +130,31 @@ define ptr @load_relative_2(i64 %offset) {
   %load = load ptr, ptr %gep
   ret ptr %load
 }
+
+define ptr @load_relative_3(i64 %offset) {
+; x86_64-apple-darwin-LABEL: define ptr @load_relative_3(
+; 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_3.table.rel, i64 [[RELTABLE_SHIFT]])
+; x86_64-apple-darwin-NEXT:    ret ptr [[RELTABLE_INTRINSIC]]
+;
+; aarch64-LABEL: define ptr @load_relative_3(
+; 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_3.table.rel, i64 [[RELTABLE_SHIFT]])
+; aarch64-NEXT:    ret ptr [[RELTABLE_INTRINSIC]]
+;
+; x86_64-LABEL: define ptr @load_relative_3(
+; 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_3.table.rel, i64 [[RELTABLE_SHIFT]])
+; x86_64-NEXT:    ret ptr [[RELTABLE_INTRINSIC]]
+;
+  %gep = getelementptr inbounds [3 x ptr], ptr @load_relative_3.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) }
 ;.

nikic · 2025-06-27T12:49:53Z

Please write a proper PR description. This handles table entries that are GEPs?

dianqk · 2025-06-27T13:07:42Z

Please write a proper PR description. This handles table entries that are GEPs?

Yes. I have updated.

nikic

LGTM

@gv

…id generating GOTPCREL relocations (llvm#146068) The entry in a relative lookup table is a global variable with a constant offset, such as `@gv`, `GEP @gv, 1`, and so on. We cannot only consider the case of a trivial global variable. This PR handles all cases using the existing `IsConstantOffsetFromGlobal` function. (cherry picked from commit c43282a)

dianqk · 2025-06-28T02:11:48Z

Backport PR: #146191

@gv

…id generating GOTPCREL relocations (llvm#146068) The entry in a relative lookup table is a global variable with a constant offset, such as `@gv`, `GEP @gv, 1`, and so on. We cannot only consider the case of a trivial global variable. This PR handles all cases using the existing `IsConstantOffsetFromGlobal` function. (cherry picked from commit c43282a)

@gv

…id generating GOTPCREL relocations (llvm#146068) The entry in a relative lookup table is a global variable with a constant offset, such as `@gv`, `GEP @gv, 1`, and so on. We cannot only consider the case of a trivial global variable. This PR handles all cases using the existing `IsConstantOffsetFromGlobal` function.

dianqk added 3 commits June 27, 2025 19:50

Pre-commit test cases

1b81769

[RelLookupTableConverter] Drop unnamed_addr for GVs in operands to av…

cdb91ff

…oid generating GOTPCREL relocations

[RelLookupTableConverter] Drop unnamed_addr for GVs in operands to av…

9920aab

…oid generating GOTPCREL relocations (Style 2)

dianqk requested review from nikic and MaskRay June 27, 2025 12:45

llvmbot added the llvm:transforms label Jun 27, 2025

dianqk mentioned this pull request Jun 27, 2025

release builds using rustc 1.86.0 on macOS Ventura (intel) SDK exhibit incorrect behaviour rust-lang/rust#140686

Open

dianqk changed the title ~~[RelLookupTableConverter] Drop unnamed_addr for GVs in operands to avoid generating GOTPCREL relocations~~ [RelLookupTableConverter] Drop unnamed_addr for GVs in entries to avoid generating GOTPCREL relocations Jun 27, 2025

nikic approved these changes Jun 27, 2025

View reviewed changes

dianqk merged commit c43282a into llvm:main Jun 27, 2025
9 checks passed

dianqk deleted the rel-got-2 branch June 27, 2025 22:42

dianqk added this to the LLVM 20.X Release milestone Jun 28, 2025

github-project-automation bot moved this to Needs Triage in LLVM Release Status Jun 28, 2025

github-project-automation bot added this to LLVM Release Status Jun 28, 2025

nikic moved this from Needs Triage to Done in LLVM Release Status Jun 30, 2025

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[RelLookupTableConverter] Drop unnamed_addr for GVs in entries to avoid generating GOTPCREL relocations #146068

[RelLookupTableConverter] Drop unnamed_addr for GVs in entries to avoid generating GOTPCREL relocations #146068

dianqk commented Jun 27, 2025 •

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[RelLookupTableConverter] Drop unnamed_addr for GVs in entries to avoid generating GOTPCREL relocations #146068

[RelLookupTableConverter] Drop unnamed_addr for GVs in entries to avoid generating GOTPCREL relocations #146068

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