[AArch64] Remove unused ReverseCSRRestoreSeq option.

[sdesmalen-arm]

This patch removes the -reverse-csr-restore-seq option from AArch64FrameLowering, since this is no longer used.

[llvmbot]

@llvm/pr-subscribers-backend-aarch64

Author: Sander de Smalen (sdesmalen-arm)

Changes

This patch removes the -reverse-csr-restore-seq option from AArch64FrameLowering, since this is no longer used.

---

Full diff: https://github.com/llvm/llvm-project/pull/82326.diff

2 Files Affected:

• (modified) llvm/lib/Target/AArch64/AArch64FrameLowering.cpp (+21-45)
• (removed) llvm/test/CodeGen/AArch64/reverse-csr-restore-seq.mir (-101)

diff --git a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
index 0e9adde564b3e5..c013bbe9926fef 100644
--- a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
@@ -239,11 +239,6 @@ static cl::opt<bool> EnableRedZone("aarch64-redzone",
                                    cl::desc("enable use of redzone on AArch64"),
                                    cl::init(false), cl::Hidden);
 
-static cl::opt<bool>
-    ReverseCSRRestoreSeq("reverse-csr-restore-seq",
-                         cl::desc("reverse the CSR restore sequence"),
-                         cl::init(false), cl::Hidden);
-
 static cl::opt<bool> StackTaggingMergeSetTag(
     "stack-tagging-merge-settag",
     cl::desc("merge settag instruction in function epilog"), cl::init(true),
@@ -307,8 +302,6 @@ bool AArch64FrameLowering::homogeneousPrologEpilog(
     return false;
   if (!EnableHomogeneousPrologEpilog)
     return false;
-  if (ReverseCSRRestoreSeq)
-    return false;
   if (EnableRedZone)
     return false;
 
@@ -3111,7 +3104,27 @@ bool AArch64FrameLowering::restoreCalleeSavedRegisters(
 
   computeCalleeSaveRegisterPairs(MF, CSI, TRI, RegPairs, hasFP(MF));
 
-  auto EmitMI = [&](const RegPairInfo &RPI) -> MachineBasicBlock::iterator {
+  if (homogeneousPrologEpilog(MF, &MBB)) {
+    auto MIB = BuildMI(MBB, MBBI, DL, TII.get(AArch64::HOM_Epilog))
+                   .setMIFlag(MachineInstr::FrameDestroy);
+    for (auto &RPI : RegPairs) {
+      MIB.addReg(RPI.Reg1, RegState::Define);
+      MIB.addReg(RPI.Reg2, RegState::Define);
+    }
+    return true;
+  }
+
+  // For performance reasons restore SVE register in increasing order
+  auto IsPPR = [](const RegPairInfo &c) { return c.Type == RegPairInfo::PPR; };
+  auto PPRBegin = std::find_if(RegPairs.begin(), RegPairs.end(), IsPPR);
+  auto PPREnd = std::find_if(RegPairs.rbegin(), RegPairs.rend(), IsPPR);
+  std::reverse(PPRBegin, PPREnd.base());
+  auto IsZPR = [](const RegPairInfo &c) { return c.Type == RegPairInfo::ZPR; };
+  auto ZPRBegin = std::find_if(RegPairs.begin(), RegPairs.end(), IsZPR);
+  auto ZPREnd = std::find_if(RegPairs.rbegin(), RegPairs.rend(), IsZPR);
+  std::reverse(ZPRBegin, ZPREnd.base());
+
+  for (const RegPairInfo &RPI : RegPairs) {
     unsigned Reg1 = RPI.Reg1;
     unsigned Reg2 = RPI.Reg2;
 
@@ -3185,43 +3198,6 @@ bool AArch64FrameLowering::restoreCalleeSavedRegisters(
         MachineMemOperand::MOLoad, Size, Alignment));
     if (NeedsWinCFI)
       InsertSEH(MIB, TII, MachineInstr::FrameDestroy);
-
-    return MIB->getIterator();
-  };
-
-  if (homogeneousPrologEpilog(MF, &MBB)) {
-    auto MIB = BuildMI(MBB, MBBI, DL, TII.get(AArch64::HOM_Epilog))
-                   .setMIFlag(MachineInstr::FrameDestroy);
-    for (auto &RPI : RegPairs) {
-      MIB.addReg(RPI.Reg1, RegState::Define);
-      MIB.addReg(RPI.Reg2, RegState::Define);
-    }
-    return true;
-  }
-
-  // For performance reasons restore SVE register in increasing order
-  auto IsPPR = [](const RegPairInfo &c) { return c.Type == RegPairInfo::PPR; };
-  auto PPRBegin = std::find_if(RegPairs.begin(), RegPairs.end(), IsPPR);
-  auto PPREnd = std::find_if(RegPairs.rbegin(), RegPairs.rend(), IsPPR);
-  std::reverse(PPRBegin, PPREnd.base());
-  auto IsZPR = [](const RegPairInfo &c) { return c.Type == RegPairInfo::ZPR; };
-  auto ZPRBegin = std::find_if(RegPairs.begin(), RegPairs.end(), IsZPR);
-  auto ZPREnd = std::find_if(RegPairs.rbegin(), RegPairs.rend(), IsZPR);
-  std::reverse(ZPRBegin, ZPREnd.base());
-
-  if (ReverseCSRRestoreSeq) {
-    MachineBasicBlock::iterator First = MBB.end();
-    for (const RegPairInfo &RPI : reverse(RegPairs)) {
-      MachineBasicBlock::iterator It = EmitMI(RPI);
-      if (First == MBB.end())
-        First = It;
-    }
-    if (First != MBB.end())
-      MBB.splice(MBBI, &MBB, First);
-  } else {
-    for (const RegPairInfo &RPI : RegPairs) {
-      (void)EmitMI(RPI);
-    }
   }
 
   return true;
diff --git a/llvm/test/CodeGen/AArch64/reverse-csr-restore-seq.mir b/llvm/test/CodeGen/AArch64/reverse-csr-restore-seq.mir
deleted file mode 100644
index de4baec50e0c66..00000000000000
--- a/llvm/test/CodeGen/AArch64/reverse-csr-restore-seq.mir
+++ /dev/null
@@ -1,101 +0,0 @@
-# RUN: llc -run-pass=prologepilog -reverse-csr-restore-seq -o - -mtriple=aarch64-- %s | FileCheck %s --check-prefixes=CHECK
-# RUN: llc -start-before=prologepilog -stop-after=aarch64-ldst-opt -reverse-csr-restore-seq -o - -mtriple=aarch64-- %s | FileCheck %s --check-prefixes=CHECK
-#
---- |
-
-  define void @foo() nounwind { entry: unreachable }
-
-  define void @bar() nounwind { entry: unreachable }
-
-  define void @baz() nounwind { entry: unreachable }
-
-...
----
-name:            foo
-# CHECK-LABEL: name: foo
-tracksRegLiveness: true
-body:             |
-  bb.0:
-    $x19 = IMPLICIT_DEF
-    $x20 = IMPLICIT_DEF
-    $x21 = IMPLICIT_DEF
-    $x22 = IMPLICIT_DEF
-    $x23 = IMPLICIT_DEF
-    $x24 = IMPLICIT_DEF
-    $x25 = IMPLICIT_DEF
-    $x26 = IMPLICIT_DEF
-
-  ; The local stack size is 0, so the last ldp in the sequence will also
-  ; restore the stack.
-  ; CHECK: $x24, $x23 = frame-destroy LDPXi $sp, 2
-  ; CHECK-NEXT: $x22, $x21 = frame-destroy LDPXi $sp, 4
-  ; CHECK-NEXT: $x20, $x19 = frame-destroy LDPXi $sp, 6
-
-  ; The ldp and the stack increment get merged even before
-  ; the load-store optimizer.
-  ; CHECK-NEXT: early-clobber $sp, $x26, $x25 = frame-destroy LDPXpost $sp, 8
-
-    RET_ReallyLR
-...
----
-name:            bar
-# CHECK-LABEL: name: bar
-tracksRegLiveness: true
-stack:
-  - { id : 0, size: 8, alignment: 4,
-  stack-id: default, callee-saved-register: '', callee-saved-restored: true,
-  local-offset: -4, debug-info-variable: '', debug-info-expression: '',
-  debug-info-location: '' }
-
-body:             |
-  bb.0:
-    $x19 = IMPLICIT_DEF
-    $x20 = IMPLICIT_DEF
-    $x21 = IMPLICIT_DEF
-    $x22 = IMPLICIT_DEF
-    $x23 = IMPLICIT_DEF
-    $x24 = IMPLICIT_DEF
-    $x25 = IMPLICIT_DEF
-    $x26 = IMPLICIT_DEF
-
-  ; The local stack size is not 0, and we can combine the CSR stack size with
-  ; the local stack size. This results in rewriting the offsets for all the
-  ; save/restores and forbids us to merge the stack adjustment and the last pop.
-  ; In this case, there is no point of moving the first CSR pair at the end.
-  ; We do it anyway, as it's a small price to pay for the resulting
-  ; simplification in the epilogue emission code.
-  ; CHECK:      $x24, $x23 = frame-destroy LDPXi $sp, 4
-  ; CHECK-NEXT: $x22, $x21 = frame-destroy LDPXi $sp, 6
-  ; CHECK-NEXT: $x20, $x19 = frame-destroy LDPXi $sp, 8
-  ; CHECK-NEXT: $x26, $x25 = frame-destroy LDPXi $sp, 2
-  ; CHECK-NEXT: $sp = frame-destroy ADDXri $sp, 80, 0
-    RET_ReallyLR
-...
----
-# Check that the load from the offset 0 is moved at the end even when hasFP is
-# false.
-name:            baz
-# CHECK-LABEL: name: baz
-alignment:       4
-tracksRegLiveness: true
-frameInfo:
-  adjustsStack:    true
-  hasCalls:        true
-body:             |
-  bb.0:
-    successors: %bb.1
-
-    $x0 = IMPLICIT_DEF
-    $x20 = IMPLICIT_DEF
-    $x21 = IMPLICIT_DEF
-
-    ADJCALLSTACKDOWN 0, 0, implicit-def dead $sp, implicit $sp
-    BL @foo, csr_aarch64_aapcs, implicit-def dead $lr, implicit $sp, implicit $x0, implicit-def $sp, implicit-def $x0
-    ADJCALLSTACKUP 0, 0, implicit-def dead $sp, implicit $sp
-    B %bb.1
-
-  bb.1:
-   ; CHECK: $x21, $x20 = frame-destroy LDPXi $sp, 2
-   ; CHECK-NEXT: early-clobber $sp, $lr = frame-destroy LDRXpost $sp, 32
-    RET_ReallyLR
-...

[CarolineConcatto]

Thank you Sander!

[francisvm]

Thanks!