[llvm] [X86] Refine X86DAGToDAGISel::isSExtAbsoluteSymbolRef() (PR #76191)

[Arthur Eubanks via llvm-commits]

https://github.com/aeubanks created https://github.com/llvm/llvm-project/pull/76191

We just need to check if the global is large or not.

In the kernel code model, globals are in the negative 2GB of the address
space, so globals can be a sign extended 32-bit immediate.

In other code models, small globals are in the low 2GB of the address
space, so sign extending them is equivalent to zero extending them.


>From 2b30c006476330bf6eaf364bc136489757f66dfa Mon Sep 17 00:00:00 2001
From: Arthur Eubanks <aeubanks at google.com>
Date: Thu, 21 Dec 2023 14:15:11 -0800
Subject: [PATCH] [X86] Refine X86DAGToDAGISel::isSExtAbsoluteSymbolRef()

We just need to check if the global is large or not.

In the kernel code model, globals are in the negative 2GB of the address
space, so globals can be a sign extended 32-bit immediate.

In other code models, small globals are in the low 2GB of the address
space, so sign extending them is equivalent to zero extending them.
---
 llvm/lib/Target/X86/X86ISelDAGToDAG.cpp          | 16 ++++++++++------
 ...imm-small-model.ll => relocimm-code-model.ll} |  8 ++++++--
 2 files changed, 16 insertions(+), 8 deletions(-)
 rename llvm/test/CodeGen/X86/{relocimm-small-model.ll => relocimm-code-model.ll} (62%)

diff --git a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
index 77a997588c4fee..cbaabe521002a6 100644
--- a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -3189,12 +3189,16 @@ bool X86DAGToDAGISel::isSExtAbsoluteSymbolRef(unsigned Width, SDNode *N) const {
   if (!GA)
     return false;
 
-  std::optional<ConstantRange> CR = GA->getGlobal()->getAbsoluteSymbolRange();
-  if (!CR)
-    return Width == 32 && TM.getCodeModel() == CodeModel::Small;
-
-  return CR->getSignedMin().sge(-1ull << Width) &&
-         CR->getSignedMax().slt(1ull << Width);
+  auto *GV = GA->getGlobal();
+  std::optional<ConstantRange> CR = GV->getAbsoluteSymbolRange();
+  if (CR)
+    return CR->getSignedMin().sge(-1ull << Width) &&
+           CR->getSignedMax().slt(1ull << Width);
+  // In the kernel code model, globals are in the negative 2GB of the address
+  // space, so globals can be a sign extended 32-bit immediate.
+  // In other code models, small globals are in the low 2GB of the address
+  // space, so sign extending them is equivalent to zero extending them.
+  return Width == 32 && !TM.isLargeGlobalValue(GV);
 }
 
 X86::CondCode X86DAGToDAGISel::getCondFromNode(SDNode *N) const {
diff --git a/llvm/test/CodeGen/X86/relocimm-small-model.ll b/llvm/test/CodeGen/X86/relocimm-code-model.ll
similarity index 62%
rename from llvm/test/CodeGen/X86/relocimm-small-model.ll
rename to llvm/test/CodeGen/X86/relocimm-code-model.ll
index 5c128e15c1e26c..82483abc1ed0a5 100644
--- a/llvm/test/CodeGen/X86/relocimm-small-model.ll
+++ b/llvm/test/CodeGen/X86/relocimm-code-model.ll
@@ -1,5 +1,9 @@
 ; RUN: llc < %s | FileCheck %s --check-prefix=CHECK-SMALL
-; RUN: llc --code-model=medium < %s | FileCheck %s --check-prefix=CHECK-MEDIUM
+; RUN: llc --code-model=medium -large-data-threshold=100 < %s | FileCheck %s --check-prefix=CHECK-SMALL
+; RUN: llc --code-model=medium < %s | FileCheck %s --check-prefix=CHECK-LARGE
+; RUN: llc --code-model=large -large-data-threshold=100 < %s | FileCheck %s --check-prefix=CHECK-SMALL
+; RUN: llc --code-model=large < %s | FileCheck %s --check-prefix=CHECK-LARGE
+; RUN: llc --code-model=kernel < %s | FileCheck %s --check-prefix=CHECK-SMALL
 
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
@@ -9,7 +13,7 @@ target triple = "x86_64-unknown-linux-gnu"
 declare void @f()
 
 define void @foo(i64 %b) {
-; CHECK-MEDIUM: cmpq  %rax, %rdi
+; CHECK-LARGE: cmpq %rax, %rdi
 ; CHECK-SMALL: cmpq $a, %rdi
 entry:
   %cmp = icmp eq i64 %b, ptrtoint (ptr @a to i64)