[ConstantFold][RFC] Add AllowLHSConstant parameter in getBinOpAbsorber (#109736)

Add a AllowLHSConstant parameter in getBinOpAbsorber function for
supporting more binary operators.

1 files changed, 8 insertions, 24 deletions

diff --git a/llvm/lib/IR/ConstantFold.cpp b/llvm/lib/IR/ConstantFold.cpp
index 05ab096..a6f46da 100644
--- a/llvm/lib/IR/ConstantFold.cpp
+++ b/llvm/lib/IR/ConstantFold.cpp
@@ -731,11 +731,11 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, Constant *C1,
 
   // Handle simplifications when the RHS is a constant int.
   if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
+    if (C2 == ConstantExpr::getBinOpAbsorber(Opcode, C2->getType(),
+                                             /*AllowLHSConstant*/ false))
+      return C2;
+
     switch (Opcode) {
-    case Instruction::Mul:
-      if (CI2->isZero())
-        return C2; // X * 0 == 0
-      break;
     case Instruction::UDiv:
     case Instruction::SDiv:
       if (CI2->isZero())
@@ -749,9 +749,7 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, Constant *C1,
         return PoisonValue::get(CI2->getType());              // X % 0 == poison
       break;
     case Instruction::And:
-      if (CI2->isZero())
-        return C2; // X & 0 == 0
-
+      assert(!CI2->isZero() && "And zero handled above");
       if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) {
         // If and'ing the address of a global with a constant, fold it.
         if (CE1->getOpcode() == Instruction::PtrToInt &&
@@ -791,10 +789,6 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, Constant *C1,
         }
       }
       break;
-    case Instruction::Or:
-      if (CI2->isMinusOne())
-        return C2; // X | -1 == -1
-      break;
     }
   } else if (isa<ConstantInt>(C1)) {
     // If C1 is a ConstantInt and C2 is not, swap the operands.
@@ -854,19 +848,9 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, Constant *C1,
       }
     }
 
-    switch (Opcode) {
-    case Instruction::SDiv:
-    case Instruction::UDiv:
-    case Instruction::URem:
-    case Instruction::SRem:
-    case Instruction::LShr:
-    case Instruction::AShr:
-    case Instruction::Shl:
-      if (CI1->isZero()) return C1;
-      break;
-    default:
-      break;
-    }
+    if (C1 == ConstantExpr::getBinOpAbsorber(Opcode, C1->getType(),
+                                             /*AllowLHSConstant*/ true))
+      return C1;
   } else if (ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) {
     if (ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) {
       const APFloat &C1V = CFP1->getValueAPF();