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[ValueTracking] Compute knownbits from (icmp upred (add/sub nuw X, Y), C) #87180

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[ValueTracking] Compute knownbits from (icmp upred (add/sub nuw X, Y), C) #87180

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1690b9a
[ValueTracking] Add tests for computing knownbits from `(icmp upred (…
goldsteinn Mar 31, 2024
1adbd10
[ValueTracking] Compute knownbits from `(icmp upred (add/sub nuw X, Y…
goldsteinn Mar 31, 2024
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47 changes: 29 additions & 18 deletions llvm/lib/Analysis/ValueTracking.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -706,17 +706,22 @@ static void computeKnownBitsFromCmp(const Value *V, CmpInst::Predicate Pred,
LHSRange = LHSRange.sub(*Offset);
Known = Known.unionWith(LHSRange.toKnownBits());
}
// X & Y u> C -> X u> C && Y u> C
if ((Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE) &&
match(LHS, m_c_And(m_V, m_Value()))) {
Known.One.setHighBits(
(*C + (Pred == ICmpInst::ICMP_UGT)).countLeadingOnes());
if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE) {
// X & Y u> C -> X u> C && Y u> C
// X nuw- Y u> C -> X u> C
if (match(LHS, m_c_And(m_V, m_Value())) ||
match(LHS, m_NUWSub(m_V, m_Value())))
Known.One.setHighBits(
(*C + (Pred == ICmpInst::ICMP_UGT)).countLeadingOnes());
}
// X | Y u< C -> X u< C && Y u< C
if ((Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) &&
match(LHS, m_c_Or(m_V, m_Value()))) {
Known.Zero.setHighBits(
(*C - (Pred == ICmpInst::ICMP_ULT)).countLeadingZeros());
if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) {
// X | Y u< C -> X u< C && Y u< C
// X nuw+ Y u< C -> X u< C && Y u< C
if (match(LHS, m_c_Or(m_V, m_Value())) ||
match(LHS, m_c_NUWAdd(m_V, m_Value()))) {
Known.Zero.setHighBits(
(*C - (Pred == ICmpInst::ICMP_ULT)).countLeadingZeros());
}
}
}
break;
Expand Down Expand Up @@ -9576,14 +9581,20 @@ void llvm::findValuesAffectedByCondition(
if (match(A, m_AddLike(m_Value(X), m_ConstantInt())))
AddAffected(X);

Value *Y;
// X & Y u> C -> X >u C && Y >u C
// X | Y u< C -> X u< C && Y u< C
if (ICmpInst::isUnsigned(Pred) &&
(match(A, m_And(m_Value(X), m_Value(Y))) ||
match(A, m_Or(m_Value(X), m_Value(Y))))) {
AddAffected(X);
AddAffected(Y);
if (ICmpInst::isUnsigned(Pred)) {
Value *Y;
// X & Y u> C -> X >u C && Y >u C
// X | Y u< C -> X u< C && Y u< C
// X nuw+ Y u< C -> X u< C && Y u< C
if (match(A, m_And(m_Value(X), m_Value(Y))) ||
match(A, m_Or(m_Value(X), m_Value(Y))) ||
match(A, m_NUWAdd(m_Value(X), m_Value(Y)))) {
AddAffected(X);
AddAffected(Y);
}
// X nuw- Y u> C -> X u> C
if (match(A, m_NUWSub(m_Value(X), m_Value())))
AddAffected(X);
}
}

Expand Down
272 changes: 272 additions & 0 deletions llvm/test/Transforms/InstCombine/known-bits.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -1698,5 +1698,277 @@ define i32 @test_none(float nofpclass(all) %x) {
ret i32 %and
}

define i8 @test_icmp_add(i8 %n, i8 %n2, i8 %other) {
; CHECK-LABEL: @test_icmp_add(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[N_ADD:%.*]] = add nuw i8 [[N:%.*]], [[N2:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i8 [[N_ADD]], 32
; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
; CHECK: if.then:
; CHECK-NEXT: ret i8 0
; CHECK: if.else:
; CHECK-NEXT: ret i8 [[OTHER:%.*]]
;
entry:
%n_add = add nuw i8 %n, %n2
%cmp = icmp ult i8 %n_add, 32
br i1 %cmp, label %if.then, label %if.else

if.then:
%r = and i8 %n, 32
ret i8 %r

if.else:
ret i8 %other
}

define i8 @test_icmp_add_fail_nsw(i8 %n, i8 %n2, i8 %other) {
; CHECK-LABEL: @test_icmp_add_fail_nsw(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[N_ADD:%.*]] = add nsw i8 [[N:%.*]], [[N2:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i8 [[N_ADD]], 32
; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
; CHECK: if.then:
; CHECK-NEXT: [[R:%.*]] = and i8 [[N]], 32
; CHECK-NEXT: ret i8 [[R]]
; CHECK: if.else:
; CHECK-NEXT: ret i8 [[OTHER:%.*]]
;
entry:
%n_add = add nsw i8 %n, %n2
%cmp = icmp ult i8 %n_add, 32
br i1 %cmp, label %if.then, label %if.else

if.then:
%r = and i8 %n, 32
ret i8 %r

if.else:
ret i8 %other
}

define i8 @test_icmp_add2(i8 %n, i8 %n2, i8 %other) {
; CHECK-LABEL: @test_icmp_add2(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[N_ADD:%.*]] = add nuw nsw i8 [[N:%.*]], [[N2:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i8 [[N_ADD]], 14
; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
; CHECK: if.then:
; CHECK-NEXT: ret i8 [[OTHER:%.*]]
; CHECK: if.else:
; CHECK-NEXT: ret i8 0
;
entry:
%n_add = add nsw nuw i8 %n, %n2
%cmp = icmp uge i8 %n_add, 15
br i1 %cmp, label %if.then, label %if.else

if.then:
ret i8 %other
if.else:
%r = and i8 %n, 32
ret i8 %r

}

define i8 @test_icmp_add_fail_bad_range(i8 %n, i8 %n2, i8 %other) {
; CHECK-LABEL: @test_icmp_add_fail_bad_range(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[N_ADD:%.*]] = add nuw i8 [[N:%.*]], [[N2:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i8 [[N_ADD]], 33
; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
; CHECK: if.then:
; CHECK-NEXT: [[R:%.*]] = and i8 [[N]], 32
; CHECK-NEXT: ret i8 [[R]]
; CHECK: if.else:
; CHECK-NEXT: ret i8 [[OTHER:%.*]]
;
entry:
%n_add = add nuw i8 %n, %n2
%cmp = icmp ule i8 %n_add, 32
br i1 %cmp, label %if.then, label %if.else

if.then:
%r = and i8 %n, 32
ret i8 %r

if.else:
ret i8 %other
}

define i8 @test_icmp_add_fail_bad_pred(i8 %n, i8 %n2, i8 %other) {
; CHECK-LABEL: @test_icmp_add_fail_bad_pred(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[N_ADD:%.*]] = add nuw i8 [[N:%.*]], [[N2:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i8 [[N_ADD]], 32
; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
; CHECK: if.then:
; CHECK-NEXT: [[R:%.*]] = and i8 [[N]], 32
; CHECK-NEXT: ret i8 [[R]]
; CHECK: if.else:
; CHECK-NEXT: ret i8 [[OTHER:%.*]]
;
entry:
%n_add = add nuw i8 %n, %n2
%cmp = icmp ugt i8 %n_add, 32
br i1 %cmp, label %if.then, label %if.else

if.then:
%r = and i8 %n, 32
ret i8 %r

if.else:
ret i8 %other
}

define i8 @test_icmp_sub(i8 %n, i8 %n2, i8 %other) {
; CHECK-LABEL: @test_icmp_sub(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[N_SUB:%.*]] = sub nuw i8 [[N:%.*]], [[N2:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i8 [[N_SUB]], -33
; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
; CHECK: if.then:
; CHECK-NEXT: ret i8 32
; CHECK: if.else:
; CHECK-NEXT: ret i8 [[OTHER:%.*]]
;
entry:
%n_sub = sub nuw i8 %n, %n2
%cmp = icmp ugt i8 %n_sub, 223
br i1 %cmp, label %if.then, label %if.else

if.then:
%r = and i8 %n, 32
ret i8 %r

if.else:
ret i8 %other
}

define i8 @test_icmp_sub_fail_wrong_arg(i8 %n, i8 %n2, i8 %other) {
; CHECK-LABEL: @test_icmp_sub_fail_wrong_arg(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[N_SUB:%.*]] = sub nuw i8 [[N:%.*]], [[N2:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i8 [[N_SUB]], -33
; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
; CHECK: if.then:
; CHECK-NEXT: [[R:%.*]] = and i8 [[N2]], 32
; CHECK-NEXT: ret i8 [[R]]
; CHECK: if.else:
; CHECK-NEXT: ret i8 [[OTHER:%.*]]
;
entry:
%n_sub = sub nuw i8 %n, %n2
%cmp = icmp ugt i8 %n_sub, 223
br i1 %cmp, label %if.then, label %if.else

if.then:
%r = and i8 %n2, 32
ret i8 %r

if.else:
ret i8 %other
}

define i8 @test_icmp_sub2(i8 %n, i8 %n2, i8 %other) {
; CHECK-LABEL: @test_icmp_sub2(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[N_SUB:%.*]] = sub nuw i8 [[N:%.*]], [[N2:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i8 [[N_SUB]], -31
; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
; CHECK: if.then:
; CHECK-NEXT: ret i8 [[OTHER:%.*]]
; CHECK: if.else:
; CHECK-NEXT: ret i8 32
;
entry:
%n_sub = sub nuw i8 %n, %n2
%cmp = icmp ule i8 %n_sub, 224
br i1 %cmp, label %if.then, label %if.else

if.then:
ret i8 %other
if.else:
%r = and i8 %n, 32
ret i8 %r

}

define i8 @test_icmp_sub2_fail_nsw(i8 %n, i8 %n2, i8 %other) {
; CHECK-LABEL: @test_icmp_sub2_fail_nsw(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[N_SUB:%.*]] = sub nsw i8 [[N:%.*]], [[N2:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i8 [[N_SUB]], -31
; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
; CHECK: if.then:
; CHECK-NEXT: ret i8 [[OTHER:%.*]]
; CHECK: if.else:
; CHECK-NEXT: [[R:%.*]] = and i8 [[N]], 32
; CHECK-NEXT: ret i8 [[R]]
;
entry:
%n_sub = sub nsw i8 %n, %n2
%cmp = icmp ule i8 %n_sub, 224
br i1 %cmp, label %if.then, label %if.else

if.then:
ret i8 %other
if.else:
%r = and i8 %n, 32
ret i8 %r

}


define i8 @test_icmp_sub_fail_bad_range(i8 %n, i8 %n2, i8 %other) {
; CHECK-LABEL: @test_icmp_sub_fail_bad_range(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[N_SUB:%.*]] = sub nuw i8 [[N:%.*]], [[N2:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i8 [[N_SUB]], -34
; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
; CHECK: if.then:
; CHECK-NEXT: [[R:%.*]] = and i8 [[N]], 32
; CHECK-NEXT: ret i8 [[R]]
; CHECK: if.else:
; CHECK-NEXT: ret i8 [[OTHER:%.*]]
;
entry:
%n_sub = sub nuw i8 %n, %n2
%cmp = icmp uge i8 %n_sub, 223
br i1 %cmp, label %if.then, label %if.else

if.then:
%r = and i8 %n, 32
ret i8 %r

if.else:
ret i8 %other
}

define i8 @test_icmp_sub_fail_bad_pred(i8 %n, i8 %n2, i8 %other) {
; CHECK-LABEL: @test_icmp_sub_fail_bad_pred(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[N_SUB:%.*]] = sub nuw i8 [[N:%.*]], [[N2:%.*]]
; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i8 [[N_SUB]], 31
; CHECK-NEXT: br i1 [[CMP]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
; CHECK: if.then:
; CHECK-NEXT: [[R:%.*]] = and i8 [[N]], 32
; CHECK-NEXT: ret i8 [[R]]
; CHECK: if.else:
; CHECK-NEXT: ret i8 [[OTHER:%.*]]
;
entry:
%n_sub = sub nuw i8 %n, %n2
%cmp = icmp sge i8 %n_sub, 32
br i1 %cmp, label %if.then, label %if.else

if.then:
%r = and i8 %n, 32
ret i8 %r

if.else:
ret i8 %other
}

declare void @use(i1)
declare void @sink(i8)
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