[PATCH] D87107: [AMDGPU] Target hook to apply target specific split constraint

[Alexander via Phabricator via llvm-commits]

alex-t created this revision.
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The change introduce new target hook that allow target to apply split constraint to MBB.


https://reviews.llvm.org/D87107

Files:
  llvm/include/llvm/CodeGen/TargetInstrInfo.h
  llvm/lib/CodeGen/RegAllocGreedy.cpp
  llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
  llvm/lib/Target/AMDGPU/SIInstrInfo.h
  llvm/test/CodeGen/AMDGPU/spill-scavenge-offset.ll


Index: llvm/test/CodeGen/AMDGPU/spill-scavenge-offset.ll
===================================================================
--- llvm/test/CodeGen/AMDGPU/spill-scavenge-offset.ll
+++ llvm/test/CodeGen/AMDGPU/spill-scavenge-offset.ll
@@ -39,7 +39,7 @@
 ; GFX6-NEXT: buffer_load_dword v{{[0-9]+}}, off, s[{{[0-9:]+}}], s32
 ; GFX6-NEXT: s_sub_u32 s32, s32, 0x[[OFFSET:[0-9]+]]
 ; GFX6: NumSgprs: 48
-; GFX6: ScratchSize: 8624
+; GFX6: ScratchSize: 8656
 define amdgpu_kernel void @test_limited_sgpr(<64 x i32> addrspace(1)* %out, <64 x i32> addrspace(1)* %in) #0 {
 entry:
   %lo = call i32 @llvm.amdgcn.mbcnt.lo(i32 -1, i32 0)
Index: llvm/lib/Target/AMDGPU/SIInstrInfo.h
===================================================================
--- llvm/lib/Target/AMDGPU/SIInstrInfo.h
+++ llvm/lib/Target/AMDGPU/SIInstrInfo.h
@@ -981,6 +981,8 @@
 
   bool isBasicBlockPrologue(const MachineInstr &MI) const override;
 
+  bool IsValidForLISplit(MachineBasicBlock *MBB) const override;
+
   MachineInstr *createPHIDestinationCopy(MachineBasicBlock &MBB,
                                          MachineBasicBlock::iterator InsPt,
                                          const DebugLoc &DL, Register Src,
Index: llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
===================================================================
--- llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
+++ llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
@@ -6803,6 +6803,37 @@
          MI.modifiesRegister(AMDGPU::EXEC, &RI);
 }
 
+bool SIInstrInfo::IsValidForLISplit(MachineBasicBlock *MBB) const {
+  MachineFunction *MF = MBB->getParent();
+  const TargetRegisterInfo *TRI = MF->getRegInfo().getTargetRegisterInfo();
+  auto IsExecRestore = [TRI](MachineInstr *Instr) {
+    return (Instr->modifiesRegister(AMDGPU::EXEC, TRI) &&
+                (Instr->getOpcode() == AMDGPU::S_OR_B64) ||
+            (Instr->getOpcode() == AMDGPU::S_MOV_B64 &&
+             Instr->getOperand(0).getReg() == AMDGPU::EXEC));
+  };
+  for (auto Pred : MBB->predecessors()) {
+    MachineBasicBlock::iterator I = Pred->getFirstTerminator();
+    if (I != Pred->end() && I->modifiesRegister(AMDGPU::EXEC, TRI)) {
+      while (++I != Pred->end()) {
+        if (I->getOpcode() == AMDGPU::S_CBRANCH_EXECNZ) {
+          if ((++I)->getOpcode() == AMDGPU::S_BRANCH &&
+              I->getOperand(0).getMBB() == MBB) {
+            break;
+          }
+        } else if (I->getOpcode() == AMDGPU::S_CBRANCH_EXECZ &&
+                   I->getOperand(0).getMBB() == MBB) {
+          break;
+        }
+      }
+      if (I != MBB->end()) {
+        return false;
+      }
+    }
+  }
+  return true;
+}
+
 MachineInstrBuilder
 SIInstrInfo::getAddNoCarry(MachineBasicBlock &MBB,
                            MachineBasicBlock::iterator I,
Index: llvm/lib/CodeGen/RegAllocGreedy.cpp
===================================================================
--- llvm/lib/CodeGen/RegAllocGreedy.cpp
+++ llvm/lib/CodeGen/RegAllocGreedy.cpp
@@ -1259,7 +1259,8 @@
   for (unsigned i = 0; i != Blocks.size(); ++i) {
     unsigned Number = Blocks[i];
     Intf.moveToBlock(Number);
-
+    if (!TII->IsValidForLISplit(MF->getBlockNumbered(Number)))
+      return false;
     if (!Intf.hasInterference()) {
       assert(T < GroupSize && "Array overflow");
       TBS[T] = Number;
Index: llvm/include/llvm/CodeGen/TargetInstrInfo.h
===================================================================
--- llvm/include/llvm/CodeGen/TargetInstrInfo.h
+++ llvm/include/llvm/CodeGen/TargetInstrInfo.h
@@ -1749,6 +1749,8 @@
     return false;
   }
 
+  virtual bool IsValidForLISplit(MachineBasicBlock *MBB) const { return true; }
+
   /// During PHI eleimination lets target to make necessary checks and
   /// insert the copy to the PHI destination register in a target specific
   /// manner.


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