[llvm] [JITLink] Add support for R_X86_64_PC16 relocation type. (PR #109630)

[Xing Guo via llvm-commits]

https://github.com/higuoxing created https://github.com/llvm/llvm-project/pull/109630

This patch adds support for R_X86_64_PC16 relocation type and x86_64::Delta16 edge kind. This patch also adds missing test cases for R_X86_64_PC32, R_X86_64_PC64 relocation types.

>From 9edc73061765a9a580204aae7e322beb804a058c Mon Sep 17 00:00:00 2001
From: Xing Guo <higuoxing at gmail.com>
Date: Mon, 23 Sep 2024 15:57:42 +0800
Subject: [PATCH] [JITLink] Add support for R_X86_64_PC16 relocation type.

This patch adds support for R_X86_64_PC16 relocation type and
x86_64::Delta16 edge kind. This patch also adds missing test cases for
R_X86_64_PC32, R_X86_64_PC64 relocation types.
---
 .../llvm/ExecutionEngine/JITLink/x86_64.h     | 22 +++++++++++++++++++
 .../ExecutionEngine/JITLink/ELF_x86_64.cpp    |  3 +++
 llvm/lib/ExecutionEngine/JITLink/x86_64.cpp   |  2 ++
 .../{ELF_R_X86_64_PC8.s => ELF_R_X86_64_PC.s} |  5 ++++-
 4 files changed, 31 insertions(+), 1 deletion(-)
 rename llvm/test/ExecutionEngine/JITLink/x86-64/{ELF_R_X86_64_PC8.s => ELF_R_X86_64_PC.s} (61%)

diff --git a/llvm/include/llvm/ExecutionEngine/JITLink/x86_64.h b/llvm/include/llvm/ExecutionEngine/JITLink/x86_64.h
index 2f475ed884a7e2..24cf982fc3ab0f 100644
--- a/llvm/include/llvm/ExecutionEngine/JITLink/x86_64.h
+++ b/llvm/include/llvm/ExecutionEngine/JITLink/x86_64.h
@@ -95,6 +95,19 @@ enum EdgeKind_x86_64 : Edge::Kind {
   ///
   Delta32,
 
+  /// A 16-bit delta.
+  ///
+  /// Delta from the fixup to the target.
+  ///
+  /// Fixup expression:
+  ///   Fixup <- Target - Fixup + Addend : int16
+  ///
+  /// Errors:
+  ///   - The result of the fixup expression must fit into an int16, otherwise
+  ///     an out-of-range error will be returned.
+  ///
+  Delta16,
+
   /// An 8-bit delta.
   ///
   /// Delta from the fixup to the target.
@@ -486,6 +499,15 @@ inline Error applyFixup(LinkGraph &G, Block &B, const Edge &E,
     break;
   }
 
+  case Delta16: {
+    int64_t Value = E.getTarget().getAddress() - FixupAddress + E.getAddend();
+    if (LLVM_LIKELY(isInt<16>(Value)))
+      *(little16_t *)FixupPtr = Value;
+    else
+      return makeTargetOutOfRangeError(G, B, E);
+    break;
+  }
+
   case Delta8: {
     int64_t Value = E.getTarget().getAddress() - FixupAddress + E.getAddend();
     if (LLVM_LIKELY(isInt<8>(Value)))
diff --git a/llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp b/llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp
index b27a1a19acae0a..6a32ccc3776510 100644
--- a/llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp
@@ -156,6 +156,9 @@ class ELFLinkGraphBuilder_x86_64 : public ELFLinkGraphBuilder<object::ELF64LE> {
     case ELF::R_X86_64_PC8:
       Kind = x86_64::Delta8;
       break;
+    case ELF::R_X86_64_PC16:
+      Kind = x86_64::Delta16;
+      break;
     case ELF::R_X86_64_PC32:
     case ELF::R_X86_64_GOTPC32:
       Kind = x86_64::Delta32;
diff --git a/llvm/lib/ExecutionEngine/JITLink/x86_64.cpp b/llvm/lib/ExecutionEngine/JITLink/x86_64.cpp
index 9f7ece8ffbbb3f..cca4358a377660 100644
--- a/llvm/lib/ExecutionEngine/JITLink/x86_64.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/x86_64.cpp
@@ -34,6 +34,8 @@ const char *getEdgeKindName(Edge::Kind K) {
     return "Delta64";
   case Delta32:
     return "Delta32";
+  case Delta16:
+    return "Delta16";
   case Delta8:
     return "Delta8";
   case NegDelta64:
diff --git a/llvm/test/ExecutionEngine/JITLink/x86-64/ELF_R_X86_64_PC8.s b/llvm/test/ExecutionEngine/JITLink/x86-64/ELF_R_X86_64_PC.s
similarity index 61%
rename from llvm/test/ExecutionEngine/JITLink/x86-64/ELF_R_X86_64_PC8.s
rename to llvm/test/ExecutionEngine/JITLink/x86-64/ELF_R_X86_64_PC.s
index 46b851a836abb8..d88875e3855114 100644
--- a/llvm/test/ExecutionEngine/JITLink/x86-64/ELF_R_X86_64_PC8.s
+++ b/llvm/test/ExecutionEngine/JITLink/x86-64/ELF_R_X86_64_PC.s
@@ -2,7 +2,7 @@
 # RUN:     -filetype=obj -o %t.o %s
 # RUN: llvm-jitlink -noexec %t.o
 #
-# Check R_X86_64_PC8 handling.
+# Check R_X86_64_PC* handling.
 
 	.text
 	.globl	main
@@ -14,3 +14,6 @@ main:
 
 	.rodata
 	.byte	main-. # Generate R_X86_64_PC8 relocation.
+	.short	main-. # Generate R_X86_64_PC16 relocation.
+	.long	main-. # Generate R_X86_64_PC32 relocation.
+	.quad	main-. # Generate R_X86_64_PC64 relocation.