[WIP][X86] Remove LOW32_ADDR_ACCESS_RBP RegisterClass

[jiang1997]

WIP

Fixes #155430

[llvmbot]

@llvm/pr-subscribers-backend-x86

Author: None (jiang1997)

Changes

The FIXME comment appears to be outdated. Deleting the register class has no observable impact on code generation in the current codebase.

Fixes #155430

---

Full diff: https://github.com/llvm/llvm-project/pull/164850.diff

2 Files Affected:

• (modified) llvm/lib/Target/X86/X86ISelLowering.cpp (+1-2)
• (modified) llvm/lib/Target/X86/X86RegisterInfo.td (-4)

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index d49f25a950e3a..4bd26a2216ba1 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -61643,8 +61643,7 @@ static bool isGRClass(const TargetRegisterClass &RC) {
   return RC.hasSuperClassEq(&X86::GR8RegClass) ||
          RC.hasSuperClassEq(&X86::GR16RegClass) ||
          RC.hasSuperClassEq(&X86::GR32RegClass) ||
-         RC.hasSuperClassEq(&X86::GR64RegClass) ||
-         RC.hasSuperClassEq(&X86::LOW32_ADDR_ACCESS_RBPRegClass);
+         RC.hasSuperClassEq(&X86::GR64RegClass);
 }
 
 /// Check if \p RC is a vector register class.
diff --git a/llvm/lib/Target/X86/X86RegisterInfo.td b/llvm/lib/Target/X86/X86RegisterInfo.td
index 99b7910131dc5..1c58b31700b75 100644
--- a/llvm/lib/Target/X86/X86RegisterInfo.td
+++ b/llvm/lib/Target/X86/X86RegisterInfo.td
@@ -716,10 +716,6 @@ def GR64_NOREX2_NOSP : RegisterClass<"X86", [i64], 64,
 // which we do not have right now.
 def LOW32_ADDR_ACCESS : RegisterClass<"X86", [i32], 32, (add GR32, RIP)>;
 
-// FIXME: This is unused, but deleting it results in codegen changes
-def LOW32_ADDR_ACCESS_RBP : RegisterClass<"X86", [i32], 32,
-                                          (add LOW32_ADDR_ACCESS, RBP)>;
-
 // A class to support the 'A' assembler constraint: [ER]AX then [ER]DX.
 def GR32_AD : RegisterClass<"X86", [i32], 32, (add EAX, EDX)>;
 def GR64_AD : RegisterClass<"X86", [i64], 64, (add RAX, RDX)>;