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[ValueTracking] Improve tracking for constant range of {s|u}rem C #82303

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[ValueTracking] Improve tracking for constant range of {s|u}rem C #82303

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c6b9007
[ValueTracking] Add tests for constant range of `{s|u}rem C, x`; NFC
goldsteinn Feb 20, 2024
ac430ea
[ValueTracking] Improve tracking for constant range of `{s|u}rem C, x`
goldsteinn Feb 20, 2024
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13 changes: 13 additions & 0 deletions llvm/lib/Analysis/ValueTracking.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -8776,13 +8776,26 @@ static void setLimitsForBinOp(const BinaryOperator &BO, APInt &Lower,
// 'srem x, C' produces (-|C|, |C|).
Upper = C->abs();
Lower = (-Upper) + 1;
} else if (match(BO.getOperand(0), m_APInt(C))) {
if (C->isNegative()) {
// 'srem -|C|, x' produces [-|C|, 0].
Upper = 1;
Lower = *C;
} else {
// 'srem |C|, x' produces [0, |C|].
Upper = *C + 1;
Lower = 0;
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Suggested change
Lower = 0;

}
}
break;

case Instruction::URem:
if (match(BO.getOperand(1), m_APInt(C)))
// 'urem x, C' produces [0, C).
Upper = *C;
else if (match(BO.getOperand(0), m_APInt(C)))
// 'urem C, x' produces [0, C].
Upper = *C + 1;
break;

default:
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100 changes: 100 additions & 0 deletions llvm/test/Analysis/ValueTracking/constant-ranges.ll
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Expand Up @@ -130,3 +130,103 @@ define i1 @and_ugt_fail(i8 %xx) {
%r = icmp ugt i8 %x_p2, 127
ret i1 %r
}

define i1 @urem_okay(i8 %x) {
; CHECK-LABEL: @urem_okay(
; CHECK-NEXT: ret i1 true
;
%val = urem i8 34, %x
%r = icmp ule i8 %val, 35
ret i1 %r
}

define i1 @urem_fail(i8 %x) {
; CHECK-LABEL: @urem_fail(
; CHECK-NEXT: [[VAL:%.*]] = urem i8 34, [[X:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp ule i8 [[VAL]], 33
; CHECK-NEXT: ret i1 [[R]]
;
%val = urem i8 34, %x
%r = icmp ule i8 %val, 33
ret i1 %r
}

define i1 @srem_posC_okay0(i8 %x) {
; CHECK-LABEL: @srem_posC_okay0(
; CHECK-NEXT: ret i1 true
;
%val = srem i8 34, %x
%r = icmp sle i8 %val, 34
ret i1 %r
}

define i1 @srem_posC_okay1(i8 %x) {
; CHECK-LABEL: @srem_posC_okay1(
; CHECK-NEXT: ret i1 true
;
%val = srem i8 34, %x
%r = icmp sge i8 %val, -3
ret i1 %r
}

define i1 @srem_negC_okay0(i8 %x) {
; CHECK-LABEL: @srem_negC_okay0(
; CHECK-NEXT: ret i1 true
;
%val = srem i8 -34, %x
%r = icmp sle i8 %val, 0
ret i1 %r
}

define i1 @srem_negC_okay1(i8 %x) {
; CHECK-LABEL: @srem_negC_okay1(
; CHECK-NEXT: ret i1 true
;
%val = srem i8 -34, %x
%r = icmp sge i8 %val, -34
ret i1 %r
}

define i1 @srem_posC_fail0(i8 %x) {
; CHECK-LABEL: @srem_posC_fail0(
; CHECK-NEXT: [[VAL:%.*]] = srem i8 34, [[X:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp sle i8 [[VAL]], 32
; CHECK-NEXT: ret i1 [[R]]
;
%val = srem i8 34, %x
%r = icmp sle i8 %val, 32
ret i1 %r
}

define i1 @srem_posC_fail1(i8 %x) {
; CHECK-LABEL: @srem_posC_fail1(
; CHECK-NEXT: [[VAL:%.*]] = srem i8 34, [[X:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp sge i8 [[VAL]], 1
; CHECK-NEXT: ret i1 [[R]]
;
%val = srem i8 34, %x
%r = icmp sge i8 %val, 1
ret i1 %r
}

define i1 @srem_negC_fail0(i8 %x) {
; CHECK-LABEL: @srem_negC_fail0(
; CHECK-NEXT: [[VAL:%.*]] = srem i8 -34, [[X:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp sle i8 [[VAL]], -1
; CHECK-NEXT: ret i1 [[R]]
;
%val = srem i8 -34, %x
%r = icmp sle i8 %val, -1
ret i1 %r
}

define i1 @srem_negC_fail1(i8 %x) {
; CHECK-LABEL: @srem_negC_fail1(
; CHECK-NEXT: [[VAL:%.*]] = srem i8 -34, [[X:%.*]]
; CHECK-NEXT: [[R:%.*]] = icmp sge i8 [[VAL]], -33
; CHECK-NEXT: ret i1 [[R]]
;
%val = srem i8 -34, %x
%r = icmp sge i8 %val, -33
ret i1 %r
}