[PATCH] D75185: [RDA] Track implicit-defs

[Sam Parker via Phabricator via llvm-commits]

samparker created this revision.
samparker added reviewers: SjoerdMeijer, dmgreen.
Herald added subscribers: hiraditya, kristof.beyls.
Herald added a project: LLVM.

Ensure that we're recording implicit defs, as well as visiting implicit uses and implicit defs when we're walking through operands. This requires a change to ARMLowOverheadLoops because RDA now knows that t2LoopEnd is set to define the CPSR.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D75185

Files:
  llvm/lib/CodeGen/ReachingDefAnalysis.cpp
  llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp
  llvm/test/CodeGen/Thumb2/LowOverheadLoops/dont-ignore-vctp.mir


Index: llvm/test/CodeGen/Thumb2/LowOverheadLoops/dont-ignore-vctp.mir
===================================================================
--- llvm/test/CodeGen/Thumb2/LowOverheadLoops/dont-ignore-vctp.mir
+++ llvm/test/CodeGen/Thumb2/LowOverheadLoops/dont-ignore-vctp.mir
@@ -95,12 +95,12 @@
   ; CHECK-LABEL: name: dont_ignore_vctp
   ; CHECK: bb.0.entry:
   ; CHECK:   successors: %bb.1(0x80000000)
-  ; CHECK:   liveins: $lr, $r0, $r1, $r3, $r7
+  ; CHECK:   liveins: $lr, $r0, $r1, $r2, $r7
   ; CHECK:   frame-setup tPUSH 14 /* CC::al */, $noreg, killed $r7, killed $lr, implicit-def $sp, implicit $sp
   ; CHECK:   frame-setup CFI_INSTRUCTION def_cfa_offset 8
   ; CHECK:   frame-setup CFI_INSTRUCTION offset $lr, -4
   ; CHECK:   frame-setup CFI_INSTRUCTION offset $r7, -8
-  ; CHECK:   tCMPi8 renamable $r3, 4, 14 /* CC::al */, $noreg, implicit-def dead $cpsr
+  ; CHECK:   renamable $r3, dead $cpsr = tLSLri killed renamable $r2, 1, 14 /* CC::al */, $noreg
   ; CHECK:   renamable $r2 = tLEApcrel %const.0, 14 /* CC::al */, $noreg
   ; CHECK:   renamable $q0 = MVE_VLDRWU32 killed renamable $r2, 0, 0, $noreg :: (load 16 from constant-pool)
   ; CHECK:   $lr = MVE_DLSTP_32 killed renamable $r3
Index: llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp
===================================================================
--- llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp
+++ llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp
@@ -817,8 +817,12 @@
   MachineBasicBlock *MBB = MI->getParent();
   MachineInstr *Last = &MBB->back();
   SmallPtrSet<MachineInstr*, 1> Ignore;
-  if (Last->getOpcode() == ARM::t2LoopEnd)
-    Ignore.insert(Last);
+  for (auto I = MachineBasicBlock::iterator(MI), E = MBB->end(); I != E; ++I) {
+    if (I->getOpcode() == ARM::t2LoopEnd) {
+      Ignore.insert(&*I);
+      break;
+    }
+  }
 
   // If nothing defines CPSR between LoopDec and LoopEnd, use a t2SUBS.
   bool SetFlags = RDA->isSafeToDefRegAt(MI, ARM::CPSR, Ignore);
Index: llvm/lib/CodeGen/ReachingDefAnalysis.cpp
===================================================================
--- llvm/lib/CodeGen/ReachingDefAnalysis.cpp
+++ llvm/lib/CodeGen/ReachingDefAnalysis.cpp
@@ -100,14 +100,9 @@
   unsigned MBBNumber = MI->getParent()->getNumber();
   assert(MBBNumber < MBBReachingDefs.size() &&
          "Unexpected basic block number.");
-  const MCInstrDesc &MCID = MI->getDesc();
-  for (unsigned i = 0,
-                e = MI->isVariadic() ? MI->getNumOperands() : MCID.getNumDefs();
-       i != e; ++i) {
-    MachineOperand &MO = MI->getOperand(i);
-    if (!MO.isReg() || !MO.getReg())
-      continue;
-    if (MO.isUse())
+
+  for (auto &MO : MI->operands()) {
+    if (!MO.isReg() || !MO.getReg() || MO.isUse())
       continue;
     for (MCRegUnitIterator Unit(MO.getReg(), TRI); Unit.isValid(); ++Unit) {
       // This instruction explicitly defines the current reg unit.
@@ -530,9 +525,12 @@
   Dead.insert(MI);
   auto IsDead = [this](MachineInstr *Def, int PhysReg) {
     unsigned LiveDefs = 0;
-    for (auto &MO : Def->defs())
+    for (auto &MO : Def->operands()) {
+      if (!MO.isReg() || !MO.getReg() || MO.isUse())
+        continue;
       if (!MO.isDead())
         ++LiveDefs;
+    }
 
     if (LiveDefs > 1)
       return false;
@@ -542,8 +540,8 @@
     return Uses.size() == 1;
   };
 
-  for (auto &MO : MI->uses()) {
-    if (!MO.isReg() || MO.getReg() == 0 || !MO.isKill())
+  for (auto &MO : MI->operands()) {
+    if (!MO.isReg() || !MO.getReg() || !MO.isUse() || !MO.isKill())
       continue;
     if (MachineInstr *Def = getReachingLocalMIDef(MI, MO.getReg()))
       if (IsDead(Def, MO.getReg()))


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