[llvm] ARM: Remove override of shouldRewriteCopySrc (PR #125219)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm created https://github.com/llvm/llvm-project/pull/125219

All of the overrides of shouldRewriteCopySrc appear to be hacks
for bugs in the base implementation, so I'm trying to delete
all of the overrides. I was expecting this to find an example
issue like the x86 version, but no tests change with this.

>From a3195b22cb361f27e678cfcef9249aa4b6df910a Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Fri, 31 Jan 2025 20:47:32 +0700
Subject: [PATCH] ARM: Remove override of shouldRewriteCopySrc

All of the overrides of shouldRewriteCopySrc appear to be hacks
for bugs in the base implementation, so I'm trying to delete
all of the overrides. I was expecting this to find an example
issue like the x86 version, but no tests change with this.
---
 llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp | 14 --------------
 llvm/lib/Target/ARM/ARMBaseRegisterInfo.h   |  5 -----
 2 files changed, 19 deletions(-)

diff --git a/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp b/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp
index 22ebe175ff62fcf..d52903eb906b983 100644
--- a/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp
+++ b/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp
@@ -942,17 +942,3 @@ bool ARMBaseRegisterInfo::shouldCoalesce(MachineInstr *MI,
   }
   return false;
 }
-
-bool ARMBaseRegisterInfo::shouldRewriteCopySrc(const TargetRegisterClass *DefRC,
-                                               unsigned DefSubReg,
-                                               const TargetRegisterClass *SrcRC,
-                                               unsigned SrcSubReg) const {
-  // We can't extract an SPR from an arbitary DPR (as opposed to a DPR_VFP2).
-  if (DefRC == &ARM::SPRRegClass && DefSubReg == 0 &&
-      SrcRC == &ARM::DPRRegClass &&
-      (SrcSubReg == ARM::ssub_0 || SrcSubReg == ARM::ssub_1))
-    return false;
-
-  return TargetRegisterInfo::shouldRewriteCopySrc(DefRC, DefSubReg,
-                                                  SrcRC, SrcSubReg);
-}
diff --git a/llvm/lib/Target/ARM/ARMBaseRegisterInfo.h b/llvm/lib/Target/ARM/ARMBaseRegisterInfo.h
index 68a28043fd32ec7..37c27f26eb04a18 100644
--- a/llvm/lib/Target/ARM/ARMBaseRegisterInfo.h
+++ b/llvm/lib/Target/ARM/ARMBaseRegisterInfo.h
@@ -159,11 +159,6 @@ class ARMBaseRegisterInfo : public ARMGenRegisterInfo {
                       const TargetRegisterClass *NewRC,
                       LiveIntervals &LIS) const override;
 
-  bool shouldRewriteCopySrc(const TargetRegisterClass *DefRC,
-                            unsigned DefSubReg,
-                            const TargetRegisterClass *SrcRC,
-                            unsigned SrcSubReg) const override;
-
   int getSEHRegNum(unsigned i) const { return getEncodingValue(i); }
 };