[llvm-branch-commits] [llvm] release/18.x: [X86] Always use 64-bit relocations in no-PIC large code model (#89101) (PR #89124)

[via llvm-branch-commits]

https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/89124

Backport 6cea7c491f4c4c68aa0494a9b18f36ff40c22c81

Requested by: @aeubanks

>From 62da265640d070cb6c7e67de94202089a44b6e5c Mon Sep 17 00:00:00 2001
From: Arthur Eubanks <aeubanks at google.com>
Date: Wed, 17 Apr 2024 12:04:18 -0700
Subject: [PATCH] [X86] Always use 64-bit relocations in no-PIC large code
 model (#89101)

This matches other types of relocations, e.g. to constant pool. And
makes things more consistent with PIC large code model.

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.

So now functions in a section not marked large will use 64-bit
relocations to reference everything when using the large code model.

This also fixes some lldb tests broken by #88172
(https://lab.llvm.org/buildbot/#/builders/68/builds/72458).

(cherry picked from commit 6cea7c491f4c4c68aa0494a9b18f36ff40c22c81)
---
 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 833f058253d880..553d338b77904a 100644
--- a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -2923,11 +2923,10 @@ 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 afcffb3a7adeda..b6634403dc1d05 100644
--- a/llvm/test/CodeGen/X86/code-model-elf.ll
+++ b/llvm/test/CodeGen/X86/code-model-elf.ll
@@ -346,7 +346,7 @@ 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:
@@ -399,7 +399,7 @@ 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
 ;