[llvm] 91fb9ea - [ARM] Remove dead instructions before creating VPT block bundles

[David Green via llvm-commits]

Author: David Green
Date: 2020-12-08T14:05:07Z
New Revision: 91fb9eac0b562cdfdc6b677f8ab2ee67f1ae1a77

URL: https://github.com/llvm/llvm-project/commit/91fb9eac0b562cdfdc6b677f8ab2ee67f1ae1a77
DIFF: https://github.com/llvm/llvm-project/commit/91fb9eac0b562cdfdc6b677f8ab2ee67f1ae1a77.diff

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

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.

Differential Revision: https://reviews.llvm.org/D92227

Added: 
    

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

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/ARM/MVEVPTBlockPass.cpp b/llvm/lib/Target/ARM/MVEVPTBlockPass.cpp
index 7b8a33d046fa..9a710b784fd1 100644
--- a/llvm/lib/Target/ARM/MVEVPTBlockPass.cpp
+++ b/llvm/lib/Target/ARM/MVEVPTBlockPass.cpp
@@ -285,20 +285,18 @@ bool MVEVPTBlock::InsertVPTBlocks(MachineBasicBlock &Block) {
       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;
 }
 

diff  --git a/llvm/test/CodeGen/Thumb2/mve-vpt-3-blocks-kill-vpr.mir b/llvm/test/CodeGen/Thumb2/mve-vpt-3-blocks-kill-vpr.mir
index a60c217404be..03cd4ee690bf 100644
--- a/llvm/test/CodeGen/Thumb2/mve-vpt-3-blocks-kill-vpr.mir
+++ b/llvm/test/CodeGen/Thumb2/mve-vpt-3-blocks-kill-vpr.mir
@@ -68,10 +68,10 @@ body:             |
     ; 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 {