[PATCH] D62819: [SCCP] Add UnaryOperator visitor to SCCP

[Cameron McInally via Phabricator via llvm-commits]

cameron.mcinally created this revision.
cameron.mcinally added reviewers: spatel, craig.topper, arsenm, kpn, andrew.w.kaylor, majnemer, davide.
Herald added subscribers: llvm-commits, hiraditya, wdng.
Herald added a project: LLVM.

I don't know this pass at all, so would appreciate a thorough review.

I did notice that FP BinaryOperators are handled conservatively. FNeg is more an XOR than an FP operation, so I think I handled it appropriately. Please advise...


Repository:
  rL LLVM

https://reviews.llvm.org/D62819

Files:
  llvm/lib/Transforms/Scalar/SCCP.cpp
  llvm/test/Transforms/SCCP/undef-resolve.ll


Index: llvm/test/Transforms/SCCP/undef-resolve.ll
===================================================================
--- llvm/test/Transforms/SCCP/undef-resolve.ll
+++ llvm/test/Transforms/SCCP/undef-resolve.ll
@@ -180,3 +180,11 @@
 ; CHECK-LABEL: @test11(
 ; CHECK: ret i32 0
 }
+
+; Test unary ops
+define double @test12(double %x) {
+  %t = fneg double undef
+  ret double %t
+; CHECK-LABEL: @test12(
+; CHECK: double undef
+}
Index: llvm/lib/Transforms/Scalar/SCCP.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/SCCP.cpp
+++ llvm/lib/Transforms/Scalar/SCCP.cpp
@@ -613,6 +613,7 @@
 
   void visitCastInst(CastInst &I);
   void visitSelectInst(SelectInst &I);
+  void visitUnaryOperator(Instruction &I);
   void visitBinaryOperator(Instruction &I);
   void visitCmpInst(CmpInst &I);
   void visitExtractValueInst(ExtractValueInst &EVI);
@@ -970,6 +971,29 @@
 }
 
 // Handle Binary Operators.
+void SCCPSolver::visitUnaryOperator(Instruction &I) {
+  LatticeVal VState = getValueState(I.getOperand(0));
+
+  LatticeVal &IV = ValueState[&I];
+  if (IV.isOverdefined()) return;
+
+  if (VState.isConstant()) {
+    Constant *C = ConstantExpr::get(I.getOpcode(), VState.getConstant());
+
+    // op Y -> undef.
+    if (isa<UndefValue>(C))
+      return;
+    return (void)markConstant(IV, &I, C);
+  }
+
+  // If something is undef, wait for it to resolve.
+  if (!VState.isOverdefined())
+    return;
+
+  markOverdefined(&I);
+}
+
+// Handle Binary Operators.
 void SCCPSolver::visitBinaryOperator(Instruction &I) {
   LatticeVal V1State = getValueState(I.getOperand(0));
   LatticeVal V2State = getValueState(I.getOperand(1));
@@ -1484,6 +1508,8 @@
         else
           markOverdefined(&I);
         return true;
+      case Instruction::FNeg:
+        break; // fneg undef -> undef
       case Instruction::ZExt:
       case Instruction::SExt:
       case Instruction::FPToUI:


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