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

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-x86

Author: Arthur Eubanks (aeubanks)

<details>
<summary>Changes</summary>

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
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)

``````````

</details>


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