[PATCH] D92227: [ARM] Remove dead instructions before creating VPT block bundles

[Dave Green via Phabricator via llvm-commits]

dmgreen created this revision.
dmgreen added reviewers: SjoerdMeijer, samtebbs, efriedma, simon_tatham, ostannard.
Herald added subscribers: danielkiss, hiraditya, kristof.beyls.
Herald added a project: LLVM.
dmgreen requested review of this revision.

We remove VPNOT instructions in VPT blocks as we create them, turning them into else predicates. We don't remove the dead instructions until after the block has been created though. Because the VPNOT will have killed the vpr register it used, this makes finalizeBundle add "internal" flags to the vpr uses of any instructions after the VPNOT. These incorrect flags can then confuse what is alive and what is not, leading to machine verifier problems.

This patch removes them earlier instead, before the bundle is finalized so that kill flags remain valid.


https://reviews.llvm.org/D92227

Files:
  llvm/lib/Target/ARM/MVEVPTBlockPass.cpp
  llvm/test/CodeGen/Thumb2/mve-vpt-3-blocks-kill-vpr.mir


Index: llvm/test/CodeGen/Thumb2/mve-vpt-3-blocks-kill-vpr.mir
===================================================================
--- llvm/test/CodeGen/Thumb2/mve-vpt-3-blocks-kill-vpr.mir
+++ llvm/test/CodeGen/Thumb2/mve-vpt-3-blocks-kill-vpr.mir
@@ -68,10 +68,10 @@
     ; CHECK: liveins: $q0, $q1, $q2, $r0
     ; CHECK: $vpr = VMSR_P0 killed $r0, 14 /* CC::al */, $noreg
     ; CHECK: $q3 = MVE_VORR $q0, $q0, 0, $noreg, undef $q3
-    ; CHECK: BUNDLE implicit-def dead $q3, implicit-def $d6, implicit-def $s12, implicit-def $s13, implicit-def $d7, implicit-def $s14, implicit-def $s15, implicit-def $vpr, implicit-def $q1, implicit-def $d2, implicit-def $s4, implicit-def $s5, implicit-def $d3, implicit-def $s6, implicit-def $s7, implicit killed $vpr, implicit killed $q1, implicit $q2, implicit killed $q3 {
+    ; CHECK: BUNDLE implicit-def dead $q3, implicit-def $d6, implicit-def $s12, implicit-def $s13, implicit-def $d7, implicit-def $s14, implicit-def $s15, implicit-def $q1, implicit-def $d2, implicit-def $s4, implicit-def $s5, implicit-def $d3, implicit-def $s6, implicit-def $s7, implicit $vpr, implicit killed $q1, implicit $q2, implicit killed $q3 {
     ; CHECK:   MVE_VPST 12, implicit $vpr
     ; CHECK:   renamable $q3 = nnan ninf nsz MVE_VMINNMf32 killed renamable $q1, renamable $q2, 1, renamable $vpr, killed renamable $q3
-    ; CHECK:   renamable $q1 = nnan ninf nsz MVE_VMINNMf32 internal killed renamable $q3, internal renamable $q3, 2, internal renamable $vpr, undef renamable $q1
+    ; CHECK:   renamable $q1 = nnan ninf nsz MVE_VMINNMf32 internal killed renamable $q3, internal renamable $q3, 2, renamable $vpr, undef renamable $q1
     ; CHECK: }
     ; CHECK: $q3 = MVE_VORR $q0, $q0, 0, $noreg, undef $q3
     ; CHECK: BUNDLE implicit-def dead $q3, implicit-def $d6, implicit-def $s12, implicit-def $s13, implicit-def $d7, implicit-def $s14, implicit-def $s15, implicit-def $q0, implicit-def $d0, implicit-def $s0, implicit-def $s1, implicit-def $d1, implicit-def $s2, implicit-def $s3, implicit killed $vpr, implicit killed $q1, implicit killed $q2, implicit killed $q3, implicit killed $q0 {
Index: llvm/lib/Target/ARM/MVEVPTBlockPass.cpp
===================================================================
--- llvm/lib/Target/ARM/MVEVPTBlockPass.cpp
+++ llvm/lib/Target/ARM/MVEVPTBlockPass.cpp
@@ -285,20 +285,18 @@
       MIBuilder.addImm((uint64_t)BlockMask);
     }
 
+    // Erase all dead instructions (VPNOT's). Do that now so that they do not
+    // mess with the bundle creation.
+    for (MachineInstr *DeadMI : DeadInstructions)
+      DeadMI->eraseFromParent();
+    DeadInstructions.clear();
+
     finalizeBundle(
         Block, MachineBasicBlock::instr_iterator(MIBuilder.getInstr()), MBIter);
 
     Modified = true;
   }
 
-  // Erase all dead instructions
-  for (MachineInstr *DeadMI : DeadInstructions) {
-    if (DeadMI->isInsideBundle())
-      DeadMI->eraseFromBundle();
-    else
-      DeadMI->eraseFromParent();
-  }
-
   return Modified;
 }
 


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