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

[Matt Arsenault via llvm-commits]

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

>From e85c7ea38791a643693227729660dcfecb788720 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Sat, 3 May 2025 09:13:03 +0200
Subject: [PATCH 1/2] ARM: Add test which shows overriding shouldRewriteCopySrc
 does something

---
 llvm/test/CodeGen/ARM/shouldRewriteCopySrc.ll | 28 +++++++++++++++++++
 1 file changed, 28 insertions(+)
 create mode 100644 llvm/test/CodeGen/ARM/shouldRewriteCopySrc.ll

diff --git a/llvm/test/CodeGen/ARM/shouldRewriteCopySrc.ll b/llvm/test/CodeGen/ARM/shouldRewriteCopySrc.ll
new file mode 100644
index 0000000000000..e653aaa316fed
--- /dev/null
+++ b/llvm/test/CodeGen/ARM/shouldRewriteCopySrc.ll
@@ -0,0 +1,28 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc -mtriple=arm-none-eabihf -mcpu=cortex-a55 < %s | FileCheck %s
+
+; Test that the override of shouldRewriteCopySrc does something
+
+define float @shouldRewriteCopySrc(double %arg) #0 {
+; CHECK-LABEL: shouldRewriteCopySrc:
+; CHECK:       @ %bb.0: @ %bb
+; CHECK-NEXT:    .vsave {d8, d9, d10, d11, d12, d13, d14, d15}
+; CHECK-NEXT:    vpush {d8, d9, d10, d11, d12, d13, d14, d15}
+; CHECK-NEXT:    vadd.f64 d16, d0, d0
+; CHECK-NEXT:    @APP
+; CHECK-NEXT:    nop
+; CHECK-NEXT:    @NO_APP
+; CHECK-NEXT:    vmov r0, r1, d16
+; CHECK-NEXT:    vmov s0, r0
+; CHECK-NEXT:    vpop {d8, d9, d10, d11, d12, d13, d14, d15}
+; CHECK-NEXT:    bx lr
+bb:
+  %i = fadd double %arg, %arg
+  tail call void asm sideeffect "nop", "~{q0},~{q1},~{q2},~{q3},~{q4},~{q5},~{q6},~{q7}"() #0
+  %i1 = bitcast double %i to i64
+  %i2 = trunc i64 %i1 to i32
+  %i3 = bitcast i32 %i2 to float
+  ret float %i3
+}
+
+attributes #0 = { nounwind }

>From 0096a5d28395b183312cf7a43707bacdececfbf5 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 2/2] 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 -----
 llvm/test/CodeGen/ARM/shouldRewriteCopySrc.ll |  4 ++--
 3 files changed, 2 insertions(+), 21 deletions(-)

diff --git a/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp b/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp
index bc20daf0cfbbc..82941b5bcd4c7 100644
--- a/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp
+++ b/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp
@@ -961,17 +961,3 @@ 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 69e10ac2a54d2..71fe2d2b70828 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); }
 };
 
diff --git a/llvm/test/CodeGen/ARM/shouldRewriteCopySrc.ll b/llvm/test/CodeGen/ARM/shouldRewriteCopySrc.ll
index e653aaa316fed..2bf8f29eccb40 100644
--- a/llvm/test/CodeGen/ARM/shouldRewriteCopySrc.ll
+++ b/llvm/test/CodeGen/ARM/shouldRewriteCopySrc.ll
@@ -12,8 +12,8 @@ define float @shouldRewriteCopySrc(double %arg) #0 {
 ; CHECK-NEXT:    @APP
 ; CHECK-NEXT:    nop
 ; CHECK-NEXT:    @NO_APP
-; CHECK-NEXT:    vmov r0, r1, d16
-; CHECK-NEXT:    vmov s0, r0
+; CHECK-NEXT:    vmov.f64 d0, d16
+; CHECK-NEXT:    @ kill: def $s0 killed $s0 killed $d0
 ; CHECK-NEXT:    vpop {d8, d9, d10, d11, d12, d13, d14, d15}
 ; CHECK-NEXT:    bx lr
 bb: