// If the shifted constant is a power-of-2, test the shift amount directly:
// (ShiftValC >> X) >u C --> X <u (LZ(C) - LZ(ShiftValC))
- // TODO: Handle ult.
- if (!IsAShr && Pred == CmpInst::ICMP_UGT && ShiftValC->isPowerOf2()) {
+ // (ShiftValC >> X) <u C --> X >=u (LZ(C-1) - LZ(ShiftValC))
+ if (!IsAShr && ShiftValC->isPowerOf2() &&
+ (Pred == CmpInst::ICMP_UGT || Pred == CmpInst::ICMP_ULT)) {
+ bool IsUGT = Pred == CmpInst::ICMP_UGT;
assert(ShiftValC->ugt(C) && "Expected simplify of compare");
- unsigned CmpLZ = C.countLeadingZeros();
+ assert(IsUGT || !C.isZero() && "Expected X u< 0 to simplify");
+
+ unsigned CmpLZ =
+ IsUGT ? C.countLeadingZeros() : (C - 1).countLeadingZeros();
unsigned ShiftLZ = ShiftValC->countLeadingZeros();
Constant *NewC = ConstantInt::get(Shr->getType(), CmpLZ - ShiftLZ);
- return new ICmpInst(ICmpInst::ICMP_ULT, Shr->User::getOperand(1), NewC);
+ auto NewPred = IsUGT ? CmpInst::ICMP_ULT : CmpInst::ICMP_UGE;
+ return new ICmpInst(NewPred, Shr->getOperand(1), NewC);
}
}
define i1 @lshr_pow2_ult(i8 %x) {
; CHECK-LABEL: @lshr_pow2_ult(
-; CHECK-NEXT: [[S:%.*]] = lshr i8 4, [[X:%.*]]
-; CHECK-NEXT: [[R:%.*]] = icmp ult i8 [[S]], 2
+; CHECK-NEXT: [[R:%.*]] = icmp ugt i8 [[X:%.*]], 1
; CHECK-NEXT: ret i1 [[R]]
;
%s = lshr i8 4, %x
; CHECK-LABEL: @lshr_pow2_ult_use(
; CHECK-NEXT: [[S:%.*]] = lshr i8 -128, [[X:%.*]]
; CHECK-NEXT: call void @use(i8 [[S]])
-; CHECK-NEXT: [[R:%.*]] = icmp ult i8 [[S]], 5
+; CHECK-NEXT: [[R:%.*]] = icmp ugt i8 [[X]], 4
; CHECK-NEXT: ret i1 [[R]]
;
%s = lshr i8 128, %x
define <2 x i1> @lshr_pow2_ult_vec(<2 x i8> %x) {
; CHECK-LABEL: @lshr_pow2_ult_vec(
-; CHECK-NEXT: [[S:%.*]] = lshr <2 x i8> <i8 8, i8 8>, [[X:%.*]]
-; CHECK-NEXT: [[R:%.*]] = icmp ult <2 x i8> [[S]], <i8 6, i8 6>
+; CHECK-NEXT: [[R:%.*]] = icmp ne <2 x i8> [[X:%.*]], zeroinitializer
; CHECK-NEXT: ret <2 x i1> [[R]]
;
%s = lshr <2 x i8> <i8 8, i8 8>, %x
ret <2 x i1> %r
}
+; negative test - need power-of-2
+
define i1 @lshr_not_pow2_ult(i8 %x) {
; CHECK-LABEL: @lshr_not_pow2_ult(
; CHECK-NEXT: [[S:%.*]] = lshr i8 3, [[X:%.*]]
ret i1 %r
}
+; TODO: This should reduce to X != 0.
+
define i1 @lshr_pow2_ult_smin(i8 %x) {
; CHECK-LABEL: @lshr_pow2_ult_smin(
; CHECK-NEXT: [[S:%.*]] = lshr i8 -128, [[X:%.*]]
ret i1 %r
}
+; negative test - need logical shift
+
define i1 @ashr_pow2_ult(i8 %x) {
; CHECK-LABEL: @ashr_pow2_ult(
; CHECK-NEXT: [[S:%.*]] = ashr i8 -128, [[X:%.*]]
ret i1 %r
}
+; negative test - need unsigned pred
+
define i1 @lshr_pow2_slt(i8 %x) {
; CHECK-LABEL: @lshr_pow2_slt(
; CHECK-NEXT: [[S:%.*]] = lshr i8 -128, [[X:%.*]]