[PATCH] D140302: [GlobalISel] [AArch64] Fold G_PTRTOINT(G_CONSTANT)

[Andreu Carminati via Phabricator via llvm-commits]

andcarminati updated this revision to Diff 526967.
andcarminati added a comment.

The patch was updated to the main branch.

Some background: we are upstreaming this pattern through the AArch64 because the target backend that we are developing in our company was not upstreamed yet. About usability, we observed that this pattern is being matched and can impact the final code.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D140302/new/

https://reviews.llvm.org/D140302

Files:
  llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h
  llvm/include/llvm/Target/GlobalISel/Combine.td
  llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
  llvm/test/CodeGen/AArch64/GlobalISel/combine-ptradd-int2ptr.mir


Index: llvm/test/CodeGen/AArch64/GlobalISel/combine-ptradd-int2ptr.mir
===================================================================
--- llvm/test/CodeGen/AArch64/GlobalISel/combine-ptradd-int2ptr.mir
+++ llvm/test/CodeGen/AArch64/GlobalISel/combine-ptradd-int2ptr.mir
@@ -8,9 +8,8 @@
   bb.1:
     liveins: $x0
     ; CHECK-LABEL: name: agc.test_combine_ptradd_constants_intres
-    ; CHECK: [[C:%[0-9]+]]:_(p64) = G_CONSTANT i64 44
-    ; CHECK: [[PTRTOINT:%[0-9]+]]:_(s64) = G_PTRTOINT [[C]](p64)
-    ; CHECK: $x0 = COPY [[PTRTOINT]](s64)
+    ; CHECK: [[C:%[0-9]+]]:_(s64) =  G_CONSTANT i64 44
+    ; CHECK: $x0 = COPY [[C]](s64)
     %1:_(s32) = G_CONSTANT i32 42
     %2:_(s32) = G_CONSTANT i32 2
     %3:_(p64) = G_INTTOPTR %2
Index: llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
===================================================================
--- llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
+++ llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
@@ -2091,6 +2091,24 @@
   MI.eraseFromParent();
 }
 
+bool CombinerHelper::matchCombineP2IToC(MachineInstr &MI, Register &Reg) {
+  assert(MI.getOpcode() == TargetOpcode::G_PTRTOINT && "Expected a G_PTRTOINT");
+  const Register SrcReg = MI.getOperand(1).getReg();
+  const MachineInstr *SrcInstr = MRI.getVRegDef(SrcReg);
+  return SrcInstr->getOpcode() == TargetOpcode::G_CONSTANT;
+}
+
+void CombinerHelper::applyCombineP2IToC(MachineInstr &MI, Register &Reg) {
+  assert(MI.getOpcode() == TargetOpcode::G_PTRTOINT && "Expected a G_PTRTOINT");
+  Register DstReg = MI.getOperand(0).getReg();
+  Register SrcReg = MI.getOperand(1).getReg();
+  MachineInstr *SrcMI = MRI.getVRegDef(SrcReg);
+  const MachineOperand &CstVal = SrcMI->getOperand(1);
+  Builder.setInstr(MI);
+  Builder.buildConstant(DstReg, CstVal.getCImm()->getValue());
+  MI.eraseFromParent();
+}
+
 bool CombinerHelper::matchCombineAddP2IToPtrAdd(
     MachineInstr &MI, std::pair<Register, bool> &PtrReg) {
   assert(MI.getOpcode() == TargetOpcode::G_ADD);
Index: llvm/include/llvm/Target/GlobalISel/Combine.td
===================================================================
--- llvm/include/llvm/Target/GlobalISel/Combine.td
+++ llvm/include/llvm/Target/GlobalISel/Combine.td
@@ -506,6 +506,14 @@
   (apply [{ Helper.applyCombineP2IToI2P(*${mi}, ${info}); }])
 >;
 
+// Fold ptr2int(cst) -> cst
+def i2p_to_c: GICombineRule<
+  (defs root:$root, register_matchinfo:$info),
+  (match (wip_match_opcode G_PTRTOINT):$root,
+    [{ return Helper.matchCombineP2IToC(*${root}, ${info}); }]),
+  (apply [{ Helper.applyCombineP2IToC(*${root}, ${info}); }])
+>;
+
 // Fold add ptrtoint(x), y -> ptrtoint (ptr_add x), y
 def add_p2i_to_ptradd_matchinfo : GIDefMatchData<"std::pair<Register, bool>">;
 def add_p2i_to_ptradd : GICombineRule<
@@ -1083,7 +1091,8 @@
                                         add_sub_reg, buildvector_identity_fold,
                                         trunc_buildvector_fold,
                                         trunc_lshr_buildvector_fold,
-                                        bitcast_bitcast_fold, fptrunc_fpext_fold]>;
+                                        bitcast_bitcast_fold, fptrunc_fpext_fold,
+                                        i2p_to_c]>;
 
 def const_combines : GICombineGroup<[constant_fold_fp_ops, const_ptradd_to_i2p,
                                      overlapping_and, mulo_by_2, mulo_by_0,
Index: llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h
===================================================================
--- llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h
+++ llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h
@@ -362,6 +362,10 @@
   /// Transform PtrToInt(IntToPtr(x)) to x.
   void applyCombineP2IToI2P(MachineInstr &MI, Register &Reg);
 
+  /// Transform Fold G_PTRTOINT(G_CONSTANT(x)) to x.
+  bool matchCombineP2IToC(MachineInstr &MI, Register &Reg);
+  void applyCombineP2IToC(MachineInstr &MI, Register &Reg);
+
   /// Transform G_ADD (G_PTRTOINT x), y -> G_PTRTOINT (G_PTR_ADD x, y)
   /// Transform G_ADD y, (G_PTRTOINT x) -> G_PTRTOINT (G_PTR_ADD x, y)
   bool matchCombineAddP2IToPtrAdd(MachineInstr &MI,


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