[llvm] 7f54b38 - GlobalISel: Refactor unary FP op constant folding

[Matt Arsenault via llvm-commits]

Author: Matt Arsenault
Date: 2023-05-18T08:33:43+01:00
New Revision: 7f54b38e28b3b66195de672848f2b5366d0d51e3

URL: https://github.com/llvm/llvm-project/commit/7f54b38e28b3b66195de672848f2b5366d0d51e3
DIFF: https://github.com/llvm/llvm-project/commit/7f54b38e28b3b66195de672848f2b5366d0d51e3.diff

LOG: GlobalISel: Refactor unary FP op constant folding

Added: 
    

Modified: 
    llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h
    llvm/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h
    llvm/include/llvm/Target/GlobalISel/Combine.td
    llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h b/llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h
index ec3762094eacb..c22355ac0df41 100644
--- a/llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h
+++ b/llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h
@@ -29,6 +29,7 @@ namespace llvm {
 class GISelChangeObserver;
 class APFloat;
 class APInt;
+class ConstantFP;
 class GPtrAdd;
 class GStore;
 class GZExtLoad;
@@ -353,9 +354,8 @@ class CombinerHelper {
 
   /// Transform fp_instr(cst) to constant result of the fp operation.
   bool matchCombineConstantFoldFpUnary(MachineInstr &MI,
-                                       std::optional<APFloat> &Cst);
-  void applyCombineConstantFoldFpUnary(MachineInstr &MI,
-                                       std::optional<APFloat> &Cst);
+                                       const ConstantFP *&Cst);
+  void applyCombineConstantFoldFpUnary(MachineInstr &MI, const ConstantFP *Cst);
 
   /// Transform IntToPtr(PtrToInt(x)) to x if cast is in the same address space.
   bool matchCombineI2PToP2I(MachineInstr &MI, Register &Reg);

diff  --git a/llvm/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h b/llvm/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h
index a4168d924f7de..071fbe8044479 100644
--- a/llvm/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h
+++ b/llvm/include/llvm/CodeGen/GlobalISel/MachineIRBuilder.h
@@ -284,6 +284,10 @@ class MachineIRBuilder {
     return getMF().getFunction().getParent()->getDataLayout();
   }
 
+  LLVMContext &getContext() const {
+    return getMF().getFunction().getContext();
+  }
+
   /// Getter for DebugLoc
   const DebugLoc &getDL() { return State.DL; }
 

diff  --git a/llvm/include/llvm/Target/GlobalISel/Combine.td b/llvm/include/llvm/Target/GlobalISel/Combine.td
index 40ccfb084c0bf..f4f8d6b9fc852 100644
--- a/llvm/include/llvm/Target/GlobalISel/Combine.td
+++ b/llvm/include/llvm/Target/GlobalISel/Combine.td
@@ -469,7 +469,7 @@ def simplify_add_to_sub: GICombineRule <
 >;
 
 // Fold fp_op(cst) to the constant result of the floating point operation.
-def constant_fp_op_matchinfo: GIDefMatchData<"std::optional<APFloat>">;
+def constant_fp_op_matchinfo: GIDefMatchData<"const ConstantFP *">;
 def constant_fp_op: GICombineRule <
   (defs root:$root, constant_fp_op_matchinfo:$info),
   (match (wip_match_opcode G_FNEG, G_FABS, G_FPTRUNC, G_FSQRT, G_FLOG2):$root,

diff  --git a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
index 05d473e307127..0bbfdd4a1db76 100644
--- a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
@@ -1289,64 +1289,69 @@ bool CombinerHelper::tryCombineMemCpyFamily(MachineInstr &MI, unsigned MaxLen) {
 }
 
 static std::optional<APFloat>
-constantFoldFpUnary(unsigned Opcode, LLT DstTy, const Register Op,
-                    const MachineRegisterInfo &MRI) {
-  const ConstantFP *MaybeCst = getConstantFPVRegVal(Op, MRI);
-  if (!MaybeCst)
-    return std::nullopt;
-
-  APFloat V = MaybeCst->getValueAPF();
-  switch (Opcode) {
+constantFoldFpUnary(const MachineInstr &MI, const MachineRegisterInfo &MRI,
+                    const APFloat &Val) {
+  APFloat Result(Val);
+  switch (MI.getOpcode()) {
   default:
     llvm_unreachable("Unexpected opcode!");
   case TargetOpcode::G_FNEG: {
-    V.changeSign();
-    return V;
+    Result.changeSign();
+    return Result;
   }
   case TargetOpcode::G_FABS: {
-    V.clearSign();
-    return V;
+    Result.clearSign();
+    return Result;
+  }
+  case TargetOpcode::G_FPTRUNC: {
+    bool Unused;
+    LLT DstTy = MRI.getType(MI.getOperand(0).getReg());
+    Result.convert(getFltSemanticForLLT(DstTy), APFloat::rmNearestTiesToEven,
+                   &Unused);
+    return Result;
   }
-  case TargetOpcode::G_FPTRUNC:
-    break;
   case TargetOpcode::G_FSQRT: {
     bool Unused;
-    V.convert(APFloat::IEEEdouble(), APFloat::rmNearestTiesToEven, &Unused);
-    V = APFloat(sqrt(V.convertToDouble()));
+    Result.convert(APFloat::IEEEdouble(), APFloat::rmNearestTiesToEven,
+                   &Unused);
+    Result = APFloat(sqrt(Result.convertToDouble()));
     break;
   }
   case TargetOpcode::G_FLOG2: {
     bool Unused;
-    V.convert(APFloat::IEEEdouble(), APFloat::rmNearestTiesToEven, &Unused);
-    V = APFloat(log2(V.convertToDouble()));
+    Result.convert(APFloat::IEEEdouble(), APFloat::rmNearestTiesToEven,
+                   &Unused);
+    Result = APFloat(log2(Result.convertToDouble()));
     break;
   }
   }
   // Convert `APFloat` to appropriate IEEE type depending on `DstTy`. Otherwise,
-  // `buildFConstant` will assert on size mismatch. Only `G_FPTRUNC`, `G_FSQRT`,
-  // and `G_FLOG2` reach here.
+  // `buildFConstant` will assert on size mismatch. Only `G_FSQRT`, and
+  // `G_FLOG2` reach here.
   bool Unused;
-  V.convert(getFltSemanticForLLT(DstTy), APFloat::rmNearestTiesToEven, &Unused);
-  return V;
+  Result.convert(Val.getSemantics(), APFloat::rmNearestTiesToEven, &Unused);
+  return Result;
 }
 
-bool CombinerHelper::matchCombineConstantFoldFpUnary(
-    MachineInstr &MI, std::optional<APFloat> &Cst) {
-  Register DstReg = MI.getOperand(0).getReg();
+bool CombinerHelper::matchCombineConstantFoldFpUnary(MachineInstr &MI,
+                                                     const ConstantFP *&Cst) {
   Register SrcReg = MI.getOperand(1).getReg();
-  LLT DstTy = MRI.getType(DstReg);
-  Cst = constantFoldFpUnary(MI.getOpcode(), DstTy, SrcReg, MRI);
-  return Cst.has_value();
+  const ConstantFP *MaybeCst = getConstantFPVRegVal(SrcReg, MRI);
+  if (!MaybeCst)
+    return false;
+
+  if (auto Folded = constantFoldFpUnary(MI, MRI, MaybeCst->getValue())) {
+    Cst = ConstantFP::get(Builder.getContext(), *Folded);
+    return true;
+  }
+
+  return false;
 }
 
-void CombinerHelper::applyCombineConstantFoldFpUnary(
-    MachineInstr &MI, std::optional<APFloat> &Cst) {
-  assert(Cst && "Optional is unexpectedly empty!");
+void CombinerHelper::applyCombineConstantFoldFpUnary(MachineInstr &MI,
+                                                     const ConstantFP *Cst) {
   Builder.setInstrAndDebugLoc(MI);
-  MachineFunction &MF = Builder.getMF();
-  auto *FPVal = ConstantFP::get(MF.getFunction().getContext(), *Cst);
-  Register DstReg = MI.getOperand(0).getReg();
-  Builder.buildFConstant(DstReg, *FPVal);
+  Builder.buildFConstant(MI.getOperand(0), *Cst);
   MI.eraseFromParent();
 }