[AArch64][AsmParser] Add MC support for %dtprel() relocation - #186599
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This patch adds support for the %dtprel relocation specifier in the AArch64 assembler. This specifier is used to generate the R_AARCH64_TLS_DTPREL64 relocation, which is particularly useful in .debug_info sections to describe the location of thread-local variables.
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@llvm/pr-subscribers-backend-aarch64 Author: Shivam Gupta (xgupta) ChangesThis patch adds support for the %dtprel relocation specifier in the AArch64 assembler. This specifier is used to generate the R_AARCH64_TLS_DTPREL64 relocation, which is particularly useful in .debug_info sections to describe the location of thread-local variables. Full diff: https://github.com/llvm/llvm-project/pull/186599.diff 4 Files Affected:
diff --git a/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp b/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
index 590da8f93873d..cdfb9ee46634a 100644
--- a/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
+++ b/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
@@ -4659,6 +4659,7 @@ bool AArch64AsmParser::parseSymbolicImmVal(const MCExpr *&ImmVal) {
.Case("prel_g1_nc", AArch64::S_PREL_G1_NC)
.Case("prel_g0", AArch64::S_PREL_G0)
.Case("prel_g0_nc", AArch64::S_PREL_G0_NC)
+ .Case("dtprel", AArch64::S_DTPREL)
.Case("dtprel_g2", AArch64::S_DTPREL_G2)
.Case("dtprel_g1", AArch64::S_DTPREL_G1)
.Case("dtprel_g1_nc", AArch64::S_DTPREL_G1_NC)
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFObjectWriter.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFObjectWriter.cpp
index e33196d4c0144..4ecf2ef268f91 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFObjectWriter.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFObjectWriter.cpp
@@ -249,6 +249,8 @@ unsigned AArch64ELFObjectWriter::getRelocType(const MCFixup &Fixup,
}
if (RefKind == AArch64::S_AUTH || RefKind == AArch64::S_AUTHADDR)
return ELF::R_AARCH64_AUTH_ABS64;
+ if (RefKind == AArch64::S_DTPREL)
+ return ELF::R_AARCH64_TLS_DTPREL64;
if (RefKind == AArch64::S_FUNCINIT)
return ELF::R_AARCH64_FUNCINIT64;
return ELF::R_AARCH64_ABS64;
@@ -465,6 +467,8 @@ unsigned AArch64ELFObjectWriter::getRelocType(const MCFixup &Fixup,
return R_CLS(MOVW_PREL_G0);
if (RefKind == AArch64::S_PREL_G0_NC)
return R_CLS(MOVW_PREL_G0_NC);
+ if (RefKind == AArch64::S_DTPREL)
+ return ELF::R_AARCH64_TLS_DTPREL64;
if (RefKind == AArch64::S_DTPREL_G2)
return ELF::R_AARCH64_TLSLD_MOVW_DTPREL_G2;
if (RefKind == AArch64::S_DTPREL_G1)
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCAsmInfo.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCAsmInfo.cpp
index 8c7336084c232..fb99523e81cd9 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCAsmInfo.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCAsmInfo.cpp
@@ -114,6 +114,7 @@ StringRef AArch64::getSpecifierName(AArch64::Specifier S) {
case AArch64::S_GOTPCREL: return "%gotpcrel";
case AArch64::S_PLT: return "%pltpcrel";
+ case AArch64::S_DTPREL: return "%dtprel";
case AArch64::S_FUNCINIT: return "%funcinit";
default:
llvm_unreachable("Invalid relocation specifier");
@@ -125,6 +126,7 @@ AArch64::Specifier AArch64::parsePercentSpecifierName(StringRef name) {
return StringSwitch<AArch64::Specifier>(name)
.Case("pltpcrel", AArch64::S_PLT)
.Case("gotpcrel", AArch64::S_GOTPCREL)
+ .Case("dtprel", AArch64::S_DTPREL)
.Case("funcinit", AArch64::S_FUNCINIT)
.Default(0);
}
diff --git a/llvm/test/MC/AArch64/tls-dtprel64.s b/llvm/test/MC/AArch64/tls-dtprel64.s
new file mode 100644
index 0000000000000..999b62fb84154
--- /dev/null
+++ b/llvm/test/MC/AArch64/tls-dtprel64.s
@@ -0,0 +1,41 @@
+// RUN: llvm-mc -triple=aarch64 -show-encoding < %s | FileCheck %s
+// RUN: llvm-mc -filetype=obj -triple=aarch64 %s | llvm-readobj -r - | FileCheck --check-prefix=CHECK-ELF %s
+
+# CHECK: .xword %dtprel(var)
+
+# CHECK-ELF: Relocations [
+# CHECK-ELF: Section {{.*}} .rela.debug_info {
+# CHECK-ELF: 0x{{[0-9A-F]+}} R_AARCH64_TLS_DTPREL64 var {{.*}}
+# CHECK-ELF: }
+
+.section .tdata,"awT",@progbits
+.globl var
+var:
+ .word 0
+
+.section .debug_abbrev,"",@progbits
+.byte 1 // Abbreviation Code
+.byte 17 // DW_TAG_compile_unit
+.byte 1 // DW_CHILDREN_yes
+.byte 0 // EOM(1)
+.byte 0 // EOM(2)
+
+.byte 2 // Abbreviation Code
+.byte 52 // DW_TAG_variable
+.byte 0 // DW_CHILDREN_no
+.byte 2; // DW_AT_location
+.byte 24 // DW_FORM_exprloc
+.byte 0 // EOM(1)
+.byte 0 // EOM(2)
+
+.section .debug_info,"",@progbits
+.Lcu_begin0:
+ .word .Lcu_end - .Lcu_body // Length of Unit
+.Lcu_body:
+ .hword 4 // DWARF version number
+ .word .debug_abbrev // Offset Into Abbrev. Section
+ .byte 8 // Address Size (in bytes)
+ .byte 1 // Abbrev [1] DW_TAG_compile_unit
+ .byte 2 // Abbrev [2] DW_TAG_variable
+ .xword %dtprel(var)
+.Lcu_end:
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MaskRay
reviewed
Mar 14, 2026
MaskRay
reviewed
Mar 14, 2026
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LGTM, if approved by an aarch64 reviewer. |
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gentle ping! |
smithp35
approved these changes
Mar 18, 2026
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LGTM. This matches the ABI recommended syntax in https://github.com/ARM-software/abi-aa/blob/main/sysvabi64/sysvabi64.rst#65assembler-language-addressing-mode-conventions-for-data
The R_AARCH64_DTPREL (AKA R_AARCH64_DTPREL64) relocation can be used statically and dynamically https://github.com/ARM-software/abi-aa/blob/main/aaelf64/aaelf64.rst#5712thread-local-storage-data-relocations
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Thanks @smithp35 for all the reviews and doing the ABI work. |
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/cherry-pick 60c1020 |
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Failed to cherry-pick: 60c1020 https://github.com/llvm/llvm-project/actions/runs/23794909740 Please manually backport the fix and push it to your github fork. Once this is done, please create a pull request |
xgupta
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Apr 8, 2026
…6599) This patch adds support for the %dtprel relocation specifier in the AArch64 assembler. This specifier is used to generate the R_AARCH64_TLS_DTPREL64 relocation, which is used in .debug_info sections to describe the location of thread-local variables. Prerequisite for llvm#146572 (cherry picked from commit 60c1020)
xgupta
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Apr 9, 2026
This patch adds support for the %dtprel relocation specifier in the AArch64 assembler. This specifier is used to generate the R_AARCH64_TLS_DTPREL64 relocation, which is used in .debug_info sections to describe the location of thread-local variables. Prerequisite for llvm#146572 (cherry picked from commit 60c1020)
xgupta
added a commit
to xgupta/llvm-project
that referenced
this pull request
Apr 9, 2026
…6599) This patch adds support for the %dtprel relocation specifier in the AArch64 assembler. This specifier is used to generate the R_AARCH64_TLS_DTPREL64 relocation, which is used in .debug_info sections to describe the location of thread-local variables. Prerequisite for llvm#146572 (cherry picked from commit 60c1020)
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This patch adds support for the %dtprel relocation specifier in the AArch64 assembler. This specifier is used to generate the R_AARCH64_TLS_DTPREL64 relocation, which is used in .debug_info sections to describe the location of thread-local variables.
Prerequisite for #146572