[ConstExpr] Don't create div/rem expressions

This removes creation of udiv/sdiv/urem/srem constant expressions,
in preparation for their removal. I've added a
ConstantExpr::isDesirableBinOp() predicate to determine whether
an expression should be created for a certain operator.

With this patch, div/rem expressions can still be created through
explicit IR/bitcode, forbidding them entirely will be the next step.

Differential Revision: https://reviews.llvm.org/D128820

1 files changed, 27 insertions, 0 deletions

diff --git a/llvm/lib/IR/Constants.cpp b/llvm/lib/IR/Constants.cpp
index 961e528..f6b745d 100644
--- a/llvm/lib/IR/Constants.cpp
+++ b/llvm/lib/IR/Constants.cpp
@@ -2365,6 +2365,33 @@ Constant *ConstantExpr::get(unsigned Opcode, Constant *C1, Constant *C2,
   return pImpl->ExprConstants.getOrCreate(C1->getType(), Key);
 }
 
+bool ConstantExpr::isDesirableBinOp(unsigned Opcode) {
+  switch (Opcode) {
+  case Instruction::UDiv:
+  case Instruction::SDiv:
+  case Instruction::URem:
+  case Instruction::SRem:
+    return false;
+  case Instruction::Add:
+  case Instruction::Sub:
+  case Instruction::Mul:
+  case Instruction::Shl:
+  case Instruction::LShr:
+  case Instruction::AShr:
+  case Instruction::And:
+  case Instruction::Or:
+  case Instruction::Xor:
+  case Instruction::FAdd:
+  case Instruction::FSub:
+  case Instruction::FMul:
+  case Instruction::FDiv:
+  case Instruction::FRem:
+    return true;
+  default:
+    llvm_unreachable("Argument must be binop opcode");
+  }
+}
+
 Constant *ConstantExpr::getSizeOf(Type* Ty) {
   // sizeof is implemented as: (i64) gep (Ty*)null, 1
   // Note that a non-inbounds gep is used, as null isn't within any object.