[PATCH] D86099: [AArch64][SVE] Fix calculation restore point for SVE callee saves.

[Sander de Smalen via Phabricator via llvm-commits]

sdesmalen created this revision.
sdesmalen added reviewers: paulwalker-arm, efriedma, david-arm.
Herald added subscribers: danielkiss, psnobl, hiraditya, kristof.beyls, tschuett.
Herald added a project: LLVM.
sdesmalen requested review of this revision.

This fixes an issue where the restore point of callee-saves in the
function epilogues was incorrectly calculated when the basic block
consisted of only a RET instruction. This caused dealloc instructions
to be inserted in between the block of callee-save restore instructions,
rather than before it.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D86099

Files:
  llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
  llvm/test/CodeGen/AArch64/framelayout-sve-calleesaves-fix.mir


Index: llvm/test/CodeGen/AArch64/framelayout-sve-calleesaves-fix.mir
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AArch64/framelayout-sve-calleesaves-fix.mir
@@ -0,0 +1,36 @@
+# NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+# RUN: llc -mattr=+sve -mtriple=aarch64-none-linux-gnu -start-before=prologepilog %s -o - | FileCheck %s
+
+--- |
+  define aarch64_sve_vector_pcs void @fix_restorepoint_p4() { entry: unreachable }
+  ; CHECK-LABEL: fix_restorepoint_p4:
+  ; CHECK:       // %bb.0: // %entry
+  ; CHECK-NEXT:    str x29, [sp, #-16]! // 8-byte Folded Spill
+  ; CHECK-NEXT:    addvl sp, sp, #-2
+  ; CHECK-NEXT:    str p4, [sp, #7, mul vl] // 2-byte Folded Spill
+  ; CHECK-NEXT:    str z8, [sp, #1, mul vl] // 16-byte Folded Spill
+  ; CHECK-NEXT:    addvl sp, sp, #-1
+  ; CHECK-NEXT:    .cfi_escape 0x0f, 0x0c, 0x8f, 0x00, 0x11, 0x10, 0x22, 0x11, 0x18, 0x92, 0x2e, 0x00, 0x1e, 0x22 // sp + 16 + 24 * VG
+  ; CHECK-NEXT:    .cfi_escape 0x10, 0x48, 0x0a, 0x11, 0x70, 0x22, 0x11, 0x78, 0x92, 0x2e, 0x00, 0x1e, 0x22 // $d8 @ cfa - 16 - 8 * VG
+  ; CHECK-NEXT:    .cfi_offset w29, -16
+  ; CHECK-NEXT:    // implicit-def: $z8
+  ; CHECK-NEXT:    // implicit-def: $p4
+  ; CHECK-NEXT:    addvl sp, sp, #1
+  ; CHECK-NEXT:    ldr p4, [sp, #7, mul vl] // 2-byte Folded Reload
+  ; CHECK-NEXT:    ldr z8, [sp, #1, mul vl] // 16-byte Folded Reload
+  ; CHECK-NEXT:    addvl sp, sp, #2
+  ; CHECK-NEXT:    ldr x29, [sp], #16 // 8-byte Folded Reload
+  ; CHECK-NEXT:    ret
+...
+name: fix_restorepoint_p4
+stack:
+  - { id: 0, stack-id: sve-vec, size: 16, alignment: 16 }
+body:             |
+  bb.0.entry:
+    $z8 = IMPLICIT_DEF
+    $p4 = IMPLICIT_DEF
+    B %bb.1
+
+  bb.1.entry:
+    RET_ReallyLR
+---
Index: llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
===================================================================
--- llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
+++ llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
@@ -1698,7 +1698,9 @@
     while (IsSVECalleeSave(RestoreBegin) &&
            RestoreBegin != MBB.begin())
       --RestoreBegin;
-    ++RestoreBegin;
+
+    if (!IsSVECalleeSave(RestoreBegin))
+      ++RestoreBegin;
 
     assert(IsSVECalleeSave(RestoreBegin) &&
            IsSVECalleeSave(std::prev(RestoreEnd)) && "Unexpected instruction");


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