return false;
// Don't bother to break this up unless either the LHS is an associable add or
- // if this is only used by one.
- if (isReassociableOp(Sub->getOperand(0), Instruction::Add))
+ // subtract or if this is only used by one.
+ if (isReassociableOp(Sub->getOperand(0), Instruction::Add) ||
+ isReassociableOp(Sub->getOperand(0), Instruction::Sub))
return true;
- if (isReassociableOp(Sub->getOperand(1), Instruction::Add))
+ if (isReassociableOp(Sub->getOperand(1), Instruction::Add) ||
+ isReassociableOp(Sub->getOperand(0), Instruction::Sub))
return true;
-
- if (Sub->hasOneUse() && isReassociableOp(Sub->use_back(), Instruction::Add))
+ if (Sub->hasOneUse() &&
+ (isReassociableOp(Sub->use_back(), Instruction::Add) ||
+ isReassociableOp(Sub->use_back(), Instruction::Sub)))
return true;
return false;
--- /dev/null
+; With sub reassociation, constant folding can eliminate the uses of %a.
+;
+; RUN: llvm-as < %s | opt -reassociate -instcombine | llvm-dis | grep %a | count 1
+; PR2047
+
+define i32 @test(i32 %a, i32 %b, i32 %c) nounwind {
+entry:
+ %tmp3 = sub i32 %a, %b ; <i32> [#uses=1]
+ %tmp5 = sub i32 %tmp3, %c ; <i32> [#uses=1]
+ %tmp7 = sub i32 %tmp5, %a ; <i32> [#uses=1]
+ ret i32 %tmp7
+}
+