https://bugs.llvm.org/show_bug.cgi?id=39660
Bug ID: 39660
Summary: Incorrect use-list order is generated due to stale
user created when attempting to constant fold
Product: new-bugs
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: new bugs
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected]
Created attachment 21119
--> https://bugs.llvm.org/attachment.cgi?id=21119&action=edit
IR reproducer.
Seen on trunk (r346809).
A run of verify-uselistorder on the attached IR reproducer fails, due to the
use-list order for i64 ptrtoint (i64 ()* @foo to i64) being incorrect.
$ verify-uselistorder reduced.ll -debug 2>&1 | grep -A11 fail:
- fail: user mismatch: ID = 5
- LHS value = i64 ptrtoint (i64 ()* @foo to i64)
=> use: op = 0, user-id = 7, user = i64 add (i64 ptrtoint (i64 ()* @foo to
i64), i64 ptrtoint (i64 ()* @foo to i64))
=> use: op = 1, user-id = 7, user = i64 add (i64 ptrtoint (i64 ()* @foo to
i64), i64 ptrtoint (i64 ()* @foo to i64))
=> use: op = 0, user-id = 9, user = i64 add (i64 ptrtoint (i64 ()* @foo to
i64), i64 1)
=> use: op = 0, user-id = 0, user = i64 add (i64 ptrtoint (i64 ()* @foo to
i64), i64 zext (i1 icmp eq (i64 add (i64 ptrtoint (i64 ()* @foo to i64), i64
1), i64 0) to i64))
- RHS value = i64 ptrtoint (i64 ()* @foo to i64)
=> use: op = 0, user-id = 0, user = i64 add (i64 ptrtoint (i64 ()* @foo to
i64), i64 zext (i1 icmp eq (i64 add (i64 ptrtoint (i64 ()* @foo to i64), i64
1), i64 0) to i64))
=> use: op = 0, user-id = 9, user = i64 add (i64 ptrtoint (i64 ()* @foo to
i64), i64 1)
=> use: op = 1, user-id = 7, user = i64 add (i64 ptrtoint (i64 ()* @foo to
i64), i64 ptrtoint (i64 ()* @foo to i64))
=> use: op = 0, user-id = 7, user = i64 add (i64 ptrtoint (i64 ()* @foo to
i64), i64 ptrtoint (i64 ()* @foo to i64))
If you look in the file, you can see that the following user does not exist:
user = i64 add (i64 ptrtoint (i64 ()* @foo to i64), i64 zext (i1 icmp eq (i64
add (i64 ptrtoint (i64 ()* @foo to i64), i64 1), i64 0) to i64))
That constant expression is created when parsing:
i64 add (i64 add (i64 ptrtoint (i64 () * @foo to i64), i64 ptrtoint (i64 () *
@foo to i64)), i64 zext (i1 icmp eq (i64 add (i64 ptrtoint (i64 () * @foo to
i64), i64 1), i64 0) to i64))
That constant expression is attempted to be constant folded by
ConstantFoldBinaryInstruction(), and the new constant expression is created
when attempting to rewrite the outermost add:
// Given ((a + b) + c), if (b + c) folds to something interesting, return
// (a + (b + c)).
if (Instruction::isAssociative(Opcode) && CE1->getOpcode() == Opcode) {
Constant *T = ConstantExpr::get(Opcode, CE1->getOperand(1), C2);
if (!isa<ConstantExpr>(T) || cast<ConstantExpr>(T)->getOpcode() != Opcode)
return ConstantExpr::get(Opcode, CE1->getOperand(0), T);
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