[llvm] dd86235 - AsmPrinter: Remove ELF's special lowerRelativeReference for unnamed_addr function
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Mon Mar 31 20:44:32 PDT 2025
Author: Fangrui Song
Date: 2025-03-31T20:44:29-07:00
New Revision: dd862356e20d2d7e0d0356dff5bd80623c14febc
URL: https://github.com/llvm/llvm-project/commit/dd862356e20d2d7e0d0356dff5bd80623c14febc
DIFF: https://github.com/llvm/llvm-project/commit/dd862356e20d2d7e0d0356dff5bd80623c14febc.diff
LOG: AsmPrinter: Remove ELF's special lowerRelativeReference for unnamed_addr function
https://reviews.llvm.org/D17938 introduced lowerRelativeReference to
give ConstantExpr sub (A-B) special semantics in ELF: when `A` is an
`unnamed_addr` function, create a PLT-generating relocation. This was
intended for C++ relative vtables, but C++ relative vtable ended up
using DSOLocalEquivalent (lowerDSOLocalEquivalent).
This special treatment of `unnamed_addr` seems unusual.
Let's remove it. Only COFF needs an overload to generate a @IMGREL32
relocation specifier (llvm/test/MC/COFF/cross-section-relative.ll).
Pull Request: https://github.com/llvm/llvm-project/pull/132684
Added:
llvm/test/CodeGen/ARM/relative-reloc.ll
llvm/test/CodeGen/RISCV/relative-reloc.ll
llvm/test/CodeGen/X86/relative-reloc-32.ll
llvm/test/CodeGen/X86/relative-reloc-64.ll
Modified:
llvm/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
Removed:
llvm/test/CodeGen/ARM/plt-relative-reloc.ll
llvm/test/CodeGen/RISCV/plt-relative-reloc.ll
llvm/test/CodeGen/X86/x86-64-plt-relative-reloc.ll
llvm/test/CodeGen/X86/x86-plt-relative-reloc.ll
################################################################################
diff --git a/llvm/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h b/llvm/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
index 8b0e5798d1b61..f035d81e85ddb 100644
--- a/llvm/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
+++ b/llvm/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
@@ -125,10 +125,6 @@ class TargetLoweringObjectFileELF : public TargetLoweringObjectFile {
lowerSymbolDifference(const MCSymbol *LHS, const MCSymbol *RHS,
int64_t Addend,
std::optional<int64_t> PCRelativeOffset) const;
- const MCExpr *lowerRelativeReference(const GlobalValue *LHS,
- const GlobalValue *RHS, int64_t Addend,
- std::optional<int64_t> PCRelativeOffset,
- const TargetMachine &TM) const override;
const MCExpr *lowerDSOLocalEquivalent(const MCSymbol *LHS,
const MCSymbol *RHS, int64_t Addend,
diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index 4c20c5dc74d9a..c9415292e88f7 100644
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -1233,24 +1233,6 @@ const MCExpr *TargetLoweringObjectFileELF::lowerSymbolDifference(
return Res;
}
-const MCExpr *TargetLoweringObjectFileELF::lowerRelativeReference(
- const GlobalValue *LHS, const GlobalValue *RHS, int64_t Addend,
- std::optional<int64_t> PCRelativeOffset, const TargetMachine &TM) const {
- // We may only use a PLT-relative relocation to refer to unnamed_addr
- // functions.
- if (!LHS->hasGlobalUnnamedAddr() || !LHS->getValueType()->isFunctionTy())
- return nullptr;
-
- // Basic correctness checks.
- if (LHS->getType()->getPointerAddressSpace() != 0 ||
- RHS->getType()->getPointerAddressSpace() != 0 || LHS->isThreadLocal() ||
- RHS->isThreadLocal())
- return nullptr;
-
- return lowerSymbolDifference(TM.getSymbol(LHS), TM.getSymbol(RHS), Addend,
- PCRelativeOffset);
-}
-
// Reference the PLT entry of a function, optionally with a subtrahend (`RHS`).
const MCExpr *TargetLoweringObjectFileELF::lowerDSOLocalEquivalent(
const MCSymbol *LHS, const MCSymbol *RHS, int64_t Addend,
diff --git a/llvm/test/CodeGen/ARM/plt-relative-reloc.ll b/llvm/test/CodeGen/ARM/relative-reloc.ll
similarity index 78%
rename from llvm/test/CodeGen/ARM/plt-relative-reloc.ll
rename to llvm/test/CodeGen/ARM/relative-reloc.ll
index ede891900e6d0..65053726e66bf 100644
--- a/llvm/test/CodeGen/ARM/plt-relative-reloc.ll
+++ b/llvm/test/CodeGen/ARM/relative-reloc.ll
@@ -10,7 +10,8 @@ declare void @fn1() unnamed_addr
declare void @fn2() unnamed_addr
declare void @fn3()
+;; Create a PC-relative relocation that the linker might decline if the addend symbol is preemptible.
; CHECK: .long 0
-; CHECK-NEXT: .long fn1(prel31)-vtable-4
-; CHECK-NEXT: .long fn2(prel31)-vtable-4
+; CHECK-NEXT: .long fn1-vtable-4
+; CHECK-NEXT: .long fn2-vtable-4
; CHECK-NEXT: .long fn3-vtable-4
diff --git a/llvm/test/CodeGen/RISCV/plt-relative-reloc.ll b/llvm/test/CodeGen/RISCV/relative-reloc.ll
similarity index 84%
rename from llvm/test/CodeGen/RISCV/plt-relative-reloc.ll
rename to llvm/test/CodeGen/RISCV/relative-reloc.ll
index d2dceb773b2e9..6c94b9fce9308 100644
--- a/llvm/test/CodeGen/RISCV/plt-relative-reloc.ll
+++ b/llvm/test/CodeGen/RISCV/relative-reloc.ll
@@ -12,10 +12,11 @@ declare void @fn2() unnamed_addr
declare void @fn3()
@global4 = external unnamed_addr global i8
+;; Create a PC-relative relocation that the linker might decline if the addend symbol is preemptible.
; CHECK: vtable:
; CHECK-NEXT: .word 0 # 0x0
-; CHECK-NEXT: .word %pltpcrel(fn1)
-; CHECK-NEXT: .word %pltpcrel(fn2+4)
+; CHECK-NEXT: .word fn1-vtable-4
+; CHECK-NEXT: .word fn2-vtable-4
; CHECK-NEXT: .word fn3-vtable-4
; CHECK-NEXT: .word global4-vtable-4
; CHECK-NEXT: .size vtable, 20
diff --git a/llvm/test/CodeGen/X86/x86-plt-relative-reloc.ll b/llvm/test/CodeGen/X86/relative-reloc-32.ll
similarity index 89%
rename from llvm/test/CodeGen/X86/x86-plt-relative-reloc.ll
rename to llvm/test/CodeGen/X86/relative-reloc-32.ll
index d5e80285b160d..7d0b1fd546a00 100644
--- a/llvm/test/CodeGen/X86/x86-plt-relative-reloc.ll
+++ b/llvm/test/CodeGen/X86/relative-reloc-32.ll
@@ -11,6 +11,6 @@ declare void @fn2() unnamed_addr
declare void @fn3()
; CHECK: .long 0
-; CHECK-NEXT: .long fn1 at PLT-vtable-4
-; CHECK-NEXT: .long fn2 at PLT-vtable-4
+; CHECK-NEXT: .long fn1-vtable-4
+; CHECK-NEXT: .long fn2-vtable-4
; CHECK-NEXT: .long fn3-vtable-4
diff --git a/llvm/test/CodeGen/X86/x86-64-plt-relative-reloc.ll b/llvm/test/CodeGen/X86/relative-reloc-64.ll
similarity index 84%
rename from llvm/test/CodeGen/X86/x86-64-plt-relative-reloc.ll
rename to llvm/test/CodeGen/X86/relative-reloc-64.ll
index 54736c94af248..6f88edfa075b8 100644
--- a/llvm/test/CodeGen/X86/x86-64-plt-relative-reloc.ll
+++ b/llvm/test/CodeGen/X86/relative-reloc-64.ll
@@ -12,8 +12,9 @@ declare void @fn2() unnamed_addr
declare void @fn3()
@global4 = external unnamed_addr global i8
+;; Create a PC-relative relocation that the linker might decline if the addend symbol is preemptible.
; CHECK: .long 0
-; CHECK-NEXT: .long fn1 at PLT-vtable-4
-; CHECK-NEXT: .long fn2 at PLT-vtable-4
+; CHECK-NEXT: .long fn1-vtable-4
+; CHECK-NEXT: .long fn2-vtable-4
; CHECK-NEXT: .long fn3-vtable-4
; CHECK-NEXT: .long global4-vtable-4
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