[ValueTracking] Add logic for `isKnownNonZero(sshl.sat/ushl.sat X, Y)`

[goldstein.w.n]

Summary

(sshl/ushl X, Y) != 0 -> X != 0

Alive2 Links

https://alive2.llvm.org/ce/z/4WLM2p
https://alive2.llvm.org/ce/z/BHFng4

[nikic]

LGTM

[goldstein.w.n]

Rebase

[goldstein.w.n]

Rebase

[goldstein.w.n]

Rebase

llvm/lib/Analysis/ValueTracking.cpp

case Instruction::ExtractElement:
     break;
   case Instruction::Freeze:
     return isKnownNonZero(I->getOperand(0), Depth, Q) &&
            isGuaranteedNotToBePoison(I->getOperand(0), Q.AC, Q.CxtI, Q.DT,
                                      Depth);
   case Instruction::Call:
     if (auto *II = dyn_cast<IntrinsicInst>(I)) {
       switch (II->getIntrinsicID()) {
+      case Intrinsic::sshl_sat:
+      case Intrinsic::ushl_sat:
       case Intrinsic::abs:
       case Intrinsic::bitreverse:
       case Intrinsic::bswap:
       case Intrinsic::ctpop:
         if (isKnownNonZero(II->getArgOperand(0), DemandedElts, Depth, Q))
           return true;
         break;
       case Intrinsic::uadd_sat:

llvm/test/Analysis/ValueTracking/known-non-zero.ll

;
   %r = icmp eq i8 %z, 0
   ret i1 %r
 }
 
 define i1 @sshl_nonzero(i8 %xx, i8 %y, i8 %ind) {
 ; CHECK-LABEL: @sshl_nonzero(
 ; CHECK-NEXT:    [[X_NZ:%.*]] = icmp ne i8 [[XX:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[X_NZ]])
-; CHECK-NEXT:    [[X:%.*]] = call i8 @llvm.sshl.sat.i8(i8 [[XX]], i8 [[Y:%.*]])
-; CHECK-NEXT:    [[Z:%.*]] = or i8 [[X]], [[IND:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[Z]], 0
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
 ;
   %x_nz = icmp ne i8 %xx, 0
   call void @llvm.assume(i1 %x_nz)
   %x = call i8 @llvm.sshl.sat.i8(i8 %xx, i8 %y)
   %z = or i8 %x, %ind
   %r = icmp eq i8 %z, 0
   ret i1 %r
 }
;
   %r = icmp eq i8 %z, 0
   ret i1 %r
 }
 
 define i1 @ushl_nonzero(i8 %xx, i8 %y, i8 %ind) {
 ; CHECK-LABEL: @ushl_nonzero(
 ; CHECK-NEXT:    [[X_NZ:%.*]] = icmp ne i8 [[XX:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[X_NZ]])
-; CHECK-NEXT:    [[X:%.*]] = call i8 @llvm.ushl.sat.i8(i8 [[XX]], i8 [[Y:%.*]])
-; CHECK-NEXT:    [[Z:%.*]] = or i8 [[X]], [[IND:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[Z]], 0
-; CHECK-NEXT:    ret i1 [[R]]
+; CHECK-NEXT:    ret i1 false
 ;
   %x_nz = icmp ne i8 %xx, 0
   call void @llvm.assume(i1 %x_nz)
   %x = call i8 @llvm.ushl.sat.i8(i8 %xx, i8 %y)
   %z = or i8 %x, %ind
   %r = icmp eq i8 %z, 0
   ret i1 %r
 }