[llvm] [X86] Always use 64-bit relocations in no-PIC large code model (PR #89101)

[Arthur Eubanks via llvm-commits]

https://github.com/aeubanks created https://github.com/llvm/llvm-project/pull/89101

This matches other types of relocations, e.g. to constant pool.

Some users of the large code model may not place small data in the lower 2GB of the address space (e.g. https://github.com/ClangBuiltLinux/linux/issues/2016), so just unconditionally use 64-bit relocations in the large code model.

>From bc9982c8b0a76411a3bc4af5489e71f27763a258 Mon Sep 17 00:00:00 2001
From: Arthur Eubanks <aeubanks at google.com>
Date: Wed, 17 Apr 2024 17:09:43 +0000
Subject: [PATCH] [X86] Always use 64-bit relocations in no-PIC large code
 model

This matches other types of relocations, e.g. to constant pool.

Some users of the large code model may not place small data in the lower 2GB of the address space (e.g. https://github.com/ClangBuiltLinux/linux/issues/2016), so just unconditionally use 64-bit relocations in the large code model.
---
 llvm/lib/Target/X86/X86ISelDAGToDAG.cpp | 7 +++----
 llvm/test/CodeGen/X86/code-model-elf.ll | 4 ++--
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
index 4e4241efd63d6b..7dcde2a508949d 100644
--- a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -2927,11 +2927,10 @@ bool X86DAGToDAGISel::selectAddr(SDNode *Parent, SDValue N, SDValue &Base,
 }
 
 bool X86DAGToDAGISel::selectMOV64Imm32(SDValue N, SDValue &Imm) {
-  // Cannot use 32 bit constants to reference objects in kernel code model.
-  // Cannot use 32 bit constants to reference objects in large PIC mode since
-  // GOTOFF is 64 bits.
+  // Cannot use 32 bit constants to reference objects in kernel/large code
+  // model.
   if (TM.getCodeModel() == CodeModel::Kernel ||
-      (TM.getCodeModel() == CodeModel::Large && TM.isPositionIndependent()))
+      TM.getCodeModel() == CodeModel::Large)
     return false;
 
   // In static codegen with small code model, we can get the address of a label
diff --git a/llvm/test/CodeGen/X86/code-model-elf.ll b/llvm/test/CodeGen/X86/code-model-elf.ll
index 0da62e3e7a6519..f60f75bc26911e 100644
--- a/llvm/test/CodeGen/X86/code-model-elf.ll
+++ b/llvm/test/CodeGen/X86/code-model-elf.ll
@@ -350,7 +350,7 @@ define dso_local ptr @lea_forced_small_data() #0 {
 ;
 ; LARGE-STATIC-LABEL: lea_forced_small_data:
 ; LARGE-STATIC:       # %bb.0:
-; LARGE-STATIC-NEXT:    movl $forced_small_data, %eax
+; LARGE-STATIC-NEXT:    movabsq $forced_small_data, %rax
 ; LARGE-STATIC-NEXT:    retq
 ;
 ; SMALL-PIC-LABEL: lea_forced_small_data:
@@ -403,7 +403,7 @@ define dso_local i32 @load_forced_small_data() #0 {
 ;
 ; LARGE-STATIC-LABEL: load_forced_small_data:
 ; LARGE-STATIC:       # %bb.0:
-; LARGE-STATIC-NEXT:    movl $forced_small_data+8, %eax
+; LARGE-STATIC-NEXT:    movabsq $forced_small_data+8, %rax
 ; LARGE-STATIC-NEXT:    movl (%rax), %eax
 ; LARGE-STATIC-NEXT:    retq
 ;