[X86] Refine X86DAGToDAGISel::isSExtAbsoluteSymbolRef()

[aeubanks]

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.

[llvmbot]

@llvm/pr-subscribers-backend-x86

Author: Arthur Eubanks (aeubanks)

Changes

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.

---

Full diff: https://github.com/llvm/llvm-project/pull/76191.diff

2 Files Affected:

• (modified) llvm/lib/Target/X86/X86ISelDAGToDAG.cpp (+10-6)
• (renamed) llvm/test/CodeGen/X86/relocimm-code-model.ll (+6-2)

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)

[aeubanks]

ping