InstCombine miscompilation

[bongjunj]

The following lines are executed:

llvm-project/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

Lines 1184 to 1195 in 3de5dbb

	auto SQDistributive = SQ.getWithInstruction(&I).getWithoutUndef();
	Value *L = simplifyBinOp(TopLevelOpcode, A, B, SQDistributive);
	Value *R = simplifyBinOp(TopLevelOpcode, A, C, SQDistributive);
	// Do "A op B" and "A op C" both simplify?
	if (L && R) {
	// They do! Return "L op' R".
	++NumExpand;
	A = Builder.CreateBinOp(InnerOpcode, L, R);
	A->takeName(&I);
	return A;
	}

Alive2 report: https://alive2.llvm.org/ce/z/4Ht3eF

----------------------------------------
define i8 @or_not_and_and_not_and_xor_commute2.2(i8 %a0, i8 %b, i8 %c) {
#0:
  %#1 = sdiv i8 %a0, 10
  %and1 = and i8 %b, %b
  %not1 = xor i8 %and1, 255
  %or1 = or i8 %#1, %not1
  %#2 = sdiv i8 %b, %not1
  %and2 = and i8 %#2, %#1
  %not2 = xor i8 %and2, 255
  %and3 = and i8 %or1, %not2
  ret i8 %and3
}
=>
define i8 @or_not_and_and_not_and_xor_commute2.2(i8 %a0, i8 %b, i8 %c) {
#0:
  %#1 = sdiv i8 %a0, 10
  %not1 = xor i8 %b, 255
  %or1 = or i8 %#1, %not1
  %#2 = sdiv i8 %b, %not1
  %and2 = and i8 %#2, %#1
  %and3 = xor i8 %and2, %or1
  ret i8 %and3
}
Transformation doesn't verify!

ERROR: Value mismatch

Example:
i8 %a0 = undef
i8 %b = #xbb (187, -69)
i8 %c = #x00 (0)	[based on undef value]

Source:
i8 %#1 = #x00 (0)	[based on undef value]
i8 %and1 = #xbb (187, -69)
i8 %not1 = #x44 (68)
i8 %or1 = #x44 (68)
i8 %#2 = #xff (255, -1)
i8 %and2 = #x00 (0)	[based on undef value]
i8 %not2 = #xff (255, -1)
i8 %and3 = #x44 (68)

Target:
i8 %#1 = #x00 (0)
i8 %not1 = #x44 (68)
i8 %or1 = #x44 (68)
i8 %#2 = #xff (255, -1)
i8 %and2 = #xfb (251, -5)
i8 %and3 = #xbf (191, -65)
Source value: #x44 (68)
Target value: #xbf (191, -65)

Summary:
  0 correct transformations
  1 incorrect transformations
  0 failed-to-prove transformations
  0 Alive2 errors