[llvm] [Hexagon] Support .reloc asm directive (PR #183849)

[Alexey Karyakin via llvm-commits]

https://github.com/quic-akaryaki updated https://github.com/llvm/llvm-project/pull/183849

>From a594deca1ad887e6215636574e3af9015a2f3681 Mon Sep 17 00:00:00 2001
From: Alexey Karyakin <akaryaki at qti.qualcomm.com>
Date: Fri, 27 Feb 2026 12:37:07 -0800
Subject: [PATCH] [Hexagon] Support .reloc asm directive

.reloc directive can be used in user assembly programs and created
internally by LLVM. In addition to Hexagon relocations, there are a few
generic names (BFD_RELOC_NONE, BFD_RELOC_8, BFD_RELOC_16,
and BFD_RELOC_32) that are mapped to Hexagon ones.
---
 .../MCTargetDesc/HexagonAsmBackend.cpp        | 16 +++++++
 llvm/test/MC/Hexagon/reloc-directive.s        | 45 +++++++++++++++++++
 2 files changed, 61 insertions(+)
 create mode 100644 llvm/test/MC/Hexagon/reloc-directive.s

diff --git a/llvm/lib/Target/Hexagon/MCTargetDesc/HexagonAsmBackend.cpp b/llvm/lib/Target/Hexagon/MCTargetDesc/HexagonAsmBackend.cpp
index ad00b9438c8a1..65fdc15cd1ac0 100644
--- a/llvm/lib/Target/Hexagon/MCTargetDesc/HexagonAsmBackend.cpp
+++ b/llvm/lib/Target/Hexagon/MCTargetDesc/HexagonAsmBackend.cpp
@@ -13,6 +13,7 @@
 #include "MCTargetDesc/HexagonMCInstrInfo.h"
 #include "MCTargetDesc/HexagonMCShuffler.h"
 #include "MCTargetDesc/HexagonMCTargetDesc.h"
+#include "llvm/ADT/StringSwitch.h"
 #include "llvm/MC/MCAsmBackend.h"
 #include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCContext.h"
@@ -81,6 +82,21 @@ class HexagonAsmBackend : public MCAsmBackend {
     return Result;
   }
 
+  std::optional<MCFixupKind> getFixupKind(StringRef Name) const override {
+    unsigned Type = llvm::StringSwitch<unsigned>(Name)
+#define ELF_RELOC(X, Y) .Case(#X, Y)
+#include "llvm/BinaryFormat/ELFRelocs/Hexagon.def"
+#undef ELF_RELOC
+                        .Case("BFD_RELOC_NONE", ELF::R_HEX_NONE)
+                        .Case("BFD_RELOC_8", ELF::R_HEX_8)
+                        .Case("BFD_RELOC_16", ELF::R_HEX_16)
+                        .Case("BFD_RELOC_32", ELF::R_HEX_32)
+                        .Default(-1u);
+    if (Type == -1u)
+      return std::nullopt;
+    return static_cast<MCFixupKind>(FirstLiteralRelocationKind + Type);
+  }
+
   MCFixupKindInfo getFixupKindInfo(MCFixupKind Kind) const override {
     // clang-format off
     const static MCFixupKindInfo Infos[Hexagon::NumTargetFixupKinds] = {
diff --git a/llvm/test/MC/Hexagon/reloc-directive.s b/llvm/test/MC/Hexagon/reloc-directive.s
new file mode 100644
index 0000000000000..9c6dd1edd40b0
--- /dev/null
+++ b/llvm/test/MC/Hexagon/reloc-directive.s
@@ -0,0 +1,45 @@
+# RUN: llvm-mc -triple=hexagon %s | FileCheck --check-prefix=PRINT %s
+# RUN: llvm-mc -triple=hexagon -filetype=obj %s | llvm-objdump -r - | FileCheck %s
+
+# PRINT: .reloc {{.*}}+8, R_HEX_NONE, .data
+# PRINT: .reloc {{.*}}+4, R_HEX_NONE, foo+4
+# PRINT: .reloc {{.*}}+0, R_HEX_NONE, 8
+# PRINT: .reloc {{.*}}+0, R_HEX_16, .data+2
+# PRINT: .reloc {{.*}}+0, R_HEX_32, foo+3
+# PRINT: .reloc {{.*}}+0, BFD_RELOC_NONE, 9
+# PRINT: .reloc {{.*}}+0, BFD_RELOC_16, 9
+# PRINT: .reloc {{.*}}+0, BFD_RELOC_32, 9
+.text
+  .reloc .+8, R_HEX_NONE, .data
+  .reloc .+4, R_HEX_NONE, foo+4
+  .reloc .+0, R_HEX_NONE, 8
+
+  .reloc .+0, R_HEX_8, .data+2
+  .reloc .+0, R_HEX_16, .data+2
+  .reloc .+0, R_HEX_32, foo+3
+
+  .reloc .+0, BFD_RELOC_NONE, 9
+  .reloc .+0, BFD_RELOC_8, 9
+  .reloc .+0, BFD_RELOC_16, 9
+  .reloc .+0, BFD_RELOC_32, 9
+  nop
+  nop
+  nop
+
+.data
+.globl foo
+foo:
+  .word 0
+  .word 0
+  .word 0
+
+# CHECK:      {{0+}}[[#%x,8]] R_HEX_NONE .data
+# CHECK-NEXT: {{0+}}[[#%x,4]] R_HEX_NONE foo+0x4
+# CHECK-NEXT: {{0+}} R_HEX_NONE *ABS*+0x8
+# CHECK-NEXT: {{0+}} R_HEX_8 .data+0x2
+# CHECK-NEXT: {{0+}} R_HEX_16 .data+0x2
+# CHECK-NEXT: {{0+}} R_HEX_32 foo+0x3
+# CHECK-NEXT: {{0+}} R_HEX_NONE *ABS*+0x9
+# CHECK-NEXT: {{0+}} R_HEX_8 *ABS*+0x9
+# CHECK-NEXT: {{0+}} R_HEX_16 *ABS*+0x9
+# CHECK-NEXT: {{0+}} R_HEX_32 *ABS*+0x9