[InstCombine] a && (a | b) is not simplified

[k-arrows]

https://alive2.llvm.org/ce/z/Z5Ly98

define i32 @src(i32 %0, i32 %1) {
%2:
  %3 = icmp ne i32 %0, 0
  %4 = or i32 %1, %0
  %5 = icmp ne i32 %4, 0
  %6 = and i1 %3, %5
  %7 = zext i1 %6 to i32
  ret i32 %7
}
=>
define i32 @tgt(i32 %0, i32 %1) {
%2:
  %3 = icmp ne i32 %0, 0
  %4 = zext i1 %3 to i32
  ret i32 %4
}
Transformation seems to be correct!

Reproducer:
https://godbolt.org/z/YEqW7sE6n

int foo(int a, int b)
{
   return a && (a | b);
}

[elhewaty]

I will Work on this.

[elhewaty]

@k-arrows Where is the function responsible for this optimization?
In InstCombmineAndOrXor.cpp the optimizations are about logical operators, not the logical ones.

[k-arrows]

@k-arrows Where is the function responsible for this optimization? In InstCombmineAndOrXor.cpp the optimizations are about logical operators, not the logical ones.

Thank you for the question, but I'm not a developer of LLVM, so it's not appropriate for me to answer this question.

@nikic @goldsteinn @dtcxzyw
Sorry to bother you, but do you have any suggestions for this question?

[dtcxzyw]

@k-arrows Where is the function responsible for this optimization? In InstCombmineAndOrXor.cpp the optimizations are about logical operators, not the logical ones.

@elhewaty I guess it has been fixed by #69840. I will update the regression tests soon.

[dtcxzyw]

@k-arrows Where is the function responsible for this optimization? In InstCombmineAndOrXor.cpp the optimizations are about logical operators, not the logical ones.

InstCombinerImpl::visitAnd calls simplifyAndInst. Then simplifyAndInst will simplify the and inst if LHS implies RHS/!RHS.

llvm-project/llvm/lib/Analysis/InstructionSimplify.cpp

Lines 2245 to 2262 in 00c8da6

	if (Op0->getType()->isIntOrIntVectorTy(1)) {
	if (std::optional<bool> Implied = isImpliedCondition(Op0, Op1, Q.DL)) {
	// If Op0 is true implies Op1 is true, then Op0 is a subset of Op1.
	if (*Implied == true)
	return Op0;
	// If Op0 is true implies Op1 is false, then they are not true together.
	if (*Implied == false)
	return ConstantInt::getFalse(Op0->getType());
	}
	if (std::optional<bool> Implied = isImpliedCondition(Op1, Op0, Q.DL)) {
	// If Op1 is true implies Op0 is true, then Op1 is a subset of Op0.
	if (*Implied)
	return Op1;
	// If Op1 is true implies Op0 is false, then they are not true together.
	if (!*Implied)
	return ConstantInt::getFalse(Op1->getType());
	}
	}

[elhewaty]

@dtcxzyw can you suggest an interesting issue for me to work on?

[dtcxzyw]

@elhewaty
Some missed-optimizations: #69803 #69050 #68227
Canonicalization of splat: #63868
Crash: #65107

Besides, there are many crashes reported by fuzzers. I guess you may not be interested in these issues since it is hard to reduce test cases and find bugs :(

[elhewaty]

@dtcxzyw Can you please assign them to me, except the crash one till I get familiar with the system more?

[dtcxzyw]

@dtcxzyw Can you please assign them to me, except the crash one till I get familiar with the system more?

I am sorry I cannot assign all these issues to you simultaneously. Someone may also be interested in these issues. You can pick one (or two) issues and leave comments on them :)