[PATCH] D97745: [AVR] Set R31R30 as clobbered after ADJCALLSTACKUP

[Ayke via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rG8544ce80f881: [AVR] Set R31R30 as clobbered after ADJCALLSTACKDOWN (authored by aykevl).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D97745/new/

https://reviews.llvm.org/D97745

Files:
  llvm/lib/Target/AVR/AVRInstrInfo.td


Index: llvm/lib/Target/AVR/AVRInstrInfo.td
===================================================================
--- llvm/lib/Target/AVR/AVRInstrInfo.td
+++ llvm/lib/Target/AVR/AVRInstrInfo.td
@@ -360,11 +360,13 @@
                                 "#ADJCALLSTACKDOWN",
                                 [(AVRcallseq_start timm:$amt, timm:$amt2)]>;
 
-  // R31R30 is used to update SP, since it is a scratch reg and this instruction
-  // is placed after the function call then R31R30 should be always free.
-  //let Defs = [R31R30],
-  //Uses = [R31R30] in
-  //:TODO: if we enable this, the pseudo is killed because it looks dead
+  // R31R30 is used to update SP. It is normally free because it is a
+  // call-clobbered register but it is necessary to set it as a def as the
+  // register allocator might use it in rare cases (for rematerialization, it
+  // seems). hasSideEffects needs to be set to true so this instruction isn't
+  // considered dead.
+  let Defs = [R31R30],
+  hasSideEffects=1 in
   def ADJCALLSTACKUP : Pseudo<(outs),
                               (ins i16imm:$amt1, i16imm:$amt2),
                               "#ADJCALLSTACKUP",


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