[AMDGPU] Add TII::isIgnorableUse() to allow VOP rematerialization

Any def of EXEC prevents rematerialization of any VOP instruction
because of the physreg use. Create a callback to check if the
physreg use can be ingored to allow rematerialization.

Differential Revision: https://reviews.llvm.org/D105836

diff --git a/llvm/include/llvm/CodeGen/TargetInstrInfo.h b/llvm/include/llvm/CodeGen/TargetInstrInfo.h
index 21758e0..5c45cea 100644 (file)
--- a/llvm/include/llvm/CodeGen/TargetInstrInfo.h
+++ b/llvm/include/llvm/CodeGen/TargetInstrInfo.h
@@ -129,6 +129,12 @@ public:
              isReallyTriviallyReMaterializableGeneric(MI, AA)));
   }
 
+  /// Given \p MO is a PhysReg use return if it can be ignored for the purpose
+  /// of instruction rematerialization.
+  virtual bool isIgnorableUse(const MachineOperand &MO) const {
+    return false;
+  }
+
 protected:
   /// For instructions with opcodes for which the M_REMATERIALIZABLE flag is
   /// set, this hook lets the target specify whether the instruction is actually

diff --git a/llvm/lib/CodeGen/LiveRangeEdit.cpp b/llvm/lib/CodeGen/LiveRangeEdit.cpp
index c5d1734..64a2dd2 100644 (file)
--- a/llvm/lib/CodeGen/LiveRangeEdit.cpp
+++ b/llvm/lib/CodeGen/LiveRangeEdit.cpp
@@ -113,9 +113,10 @@ bool LiveRangeEdit::allUsesAvailableAt(const MachineInstr *OrigMI,
     if (!MO.isReg() || !MO.getReg() || !MO.readsReg())
       continue;
 
-    // We can't remat physreg uses, unless it is a constant.
+    // We can't remat physreg uses, unless it is a constant or target wants
+    // to ignore this use.
     if (Register::isPhysicalRegister(MO.getReg())) {
-      if (MRI.isConstantPhysReg(MO.getReg()))
+      if (MRI.isConstantPhysReg(MO.getReg()) || TII.isIgnorableUse(MO))
         continue;
       return false;
     }

diff --git a/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp b/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
index d0f5b2d..af276c6 100644 (file)
--- a/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
@@ -122,6 +122,12 @@ bool SIInstrInfo::isReallyTriviallyReMaterializable(const MachineInstr &MI,
   return false;
 }
 
+bool SIInstrInfo::isIgnorableUse(const MachineOperand &MO) const {
+  // Any implicit use of exec by VALU is not a real register read.
+  return MO.getReg() == AMDGPU::EXEC && MO.isImplicit() &&
+         isVALU(*MO.getParent());
+}
+
 bool SIInstrInfo::areLoadsFromSameBasePtr(SDNode *Load0, SDNode *Load1,
                                           int64_t &Offset0,
                                           int64_t &Offset1) const {

diff --git a/llvm/lib/Target/AMDGPU/SIInstrInfo.h b/llvm/lib/Target/AMDGPU/SIInstrInfo.h
index 768cfd8..e55774b 100644 (file)
--- a/llvm/lib/Target/AMDGPU/SIInstrInfo.h
+++ b/llvm/lib/Target/AMDGPU/SIInstrInfo.h
@@ -181,6 +181,8 @@ public:
   bool isReallyTriviallyReMaterializable(const MachineInstr &MI,
                                          AAResults *AA) const override;
 
+  bool isIgnorableUse(const MachineOperand &MO) const override;
+
   bool areLoadsFromSameBasePtr(SDNode *Load1, SDNode *Load2,
                                int64_t &Offset1,
                                int64_t &Offset2) const override;

diff --git a/llvm/test/CodeGen/AMDGPU/remat-sop.mir b/llvm/test/CodeGen/AMDGPU/remat-sop.mir
index 051f5ad..ed799bf 100644 (file)
--- a/llvm/test/CodeGen/AMDGPU/remat-sop.mir
+++ b/llvm/test/CodeGen/AMDGPU/remat-sop.mir
@@ -23,6 +23,35 @@ body:             |
     S_ENDPGM 0
 ...
 ---
+name:            test_no_remat_s_mov_b32_impuse_exec
+tracksRegLiveness: true
+machineFunctionInfo:
+  stackPtrOffsetReg:  $sgpr32
+body:             |
+  bb.0:
+    ; GCN-LABEL: name: test_no_remat_s_mov_b32_impuse_exec
+    ; GCN: $exec = IMPLICIT_DEF
+    ; GCN: renamable $sgpr0 = S_MOV_B32 1, implicit $exec
+    ; GCN: SI_SPILL_S32_SAVE killed renamable $sgpr0, %stack.1, implicit $exec, implicit $sgpr32 :: (store (s32) into %stack.1, addrspace 5)
+    ; GCN: renamable $sgpr1 = S_MOV_B32 2, implicit $exec
+    ; GCN: renamable $sgpr0 = S_MOV_B32 3, implicit $exec
+    ; GCN: SI_SPILL_S32_SAVE killed renamable $sgpr0, %stack.0, implicit $exec, implicit $sgpr32 :: (store (s32) into %stack.0, addrspace 5)
+    ; GCN: renamable $sgpr0 = SI_SPILL_S32_RESTORE %stack.1, implicit $exec, implicit $sgpr32 :: (load (s32) from %stack.1, addrspace 5)
+    ; GCN: S_NOP 0, implicit killed renamable $sgpr0
+    ; GCN: S_NOP 0, implicit killed renamable $sgpr1
+    ; GCN: renamable $sgpr0 = SI_SPILL_S32_RESTORE %stack.0, implicit $exec, implicit $sgpr32 :: (load (s32) from %stack.0, addrspace 5)
+    ; GCN: S_NOP 0, implicit killed renamable $sgpr0
+    ; GCN: S_ENDPGM 0
+    $exec = IMPLICIT_DEF
+    %0:sreg_32 = S_MOV_B32 1, implicit $exec
+    %1:sreg_32 = S_MOV_B32 2, implicit $exec
+    %2:sreg_32 = S_MOV_B32 3, implicit $exec
+    S_NOP 0, implicit %0
+    S_NOP 0, implicit %1
+    S_NOP 0, implicit %2
+    S_ENDPGM 0
+...
+---
 name:            test_remat_s_mov_b64
 tracksRegLiveness: true
 body:             |

diff --git a/llvm/test/CodeGen/AMDGPU/remat-vop.mir b/llvm/test/CodeGen/AMDGPU/remat-vop.mir
index 1de8efe..2be2705 100644 (file)
--- a/llvm/test/CodeGen/AMDGPU/remat-vop.mir
+++ b/llvm/test/CodeGen/AMDGPU/remat-vop.mir
@@ -52,6 +52,31 @@ body:             |
     S_ENDPGM 0
 ...
 ---
+name:            test_remat_v_mov_b32_e32_exec_def
+tracksRegLiveness: true
+machineFunctionInfo:
+  stackPtrOffsetReg:  $sgpr32
+body:             |
+  bb.0:
+    ; GCN-LABEL: name: test_remat_v_mov_b32_e32_exec_def
+    ; GCN: renamable $vgpr0 = V_MOV_B32_e32 1, implicit $exec
+    ; GCN: renamable $vgpr1 = V_MOV_B32_e32 2, implicit $exec
+    ; GCN: S_NOP 0, implicit killed renamable $vgpr0
+    ; GCN: S_NOP 0, implicit killed renamable $vgpr1
+    ; GCN: renamable $vgpr0 = V_MOV_B32_e32 3, implicit $exec
+    ; GCN: S_NOP 0, implicit killed renamable $vgpr0
+    ; GCN: $exec = S_ANDN2_B64_term $exec, undef renamable $sgpr0_sgpr1, implicit-def $scc
+    ; GCN: S_ENDPGM 0
+    %0:vgpr_32 = V_MOV_B32_e32 1, implicit $exec
+    %1:vgpr_32 = V_MOV_B32_e32 2, implicit $exec
+    %2:vgpr_32 = V_MOV_B32_e32 3, implicit $exec
+    S_NOP 0, implicit %0
+    S_NOP 0, implicit %1
+    S_NOP 0, implicit %2
+    $exec = S_ANDN2_B64_term $exec, undef %4:sreg_64, implicit-def $scc
+    S_ENDPGM 0
+...
+---
 name:            test_remat_v_mov_b32_e64
 tracksRegLiveness: true
 body:             |