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ValueTracking: teach implied-cond about samesign #116614

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7 changes: 5 additions & 2 deletions llvm/lib/Analysis/ValueTracking.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -9268,6 +9268,7 @@ static std::optional<bool> isImpliedCondICmps(const ICmpInst *LHS,
// case, invert the predicate to make it so.
CmpInst::Predicate LPred =
LHSIsTrue ? LHS->getPredicate() : LHS->getInversePredicate();
bool LHasSameSign = LHS->hasSameSign();

// We can have non-canonical operands, so try to normalize any common operand
// to L0/R0.
Expand Down Expand Up @@ -9321,7 +9322,8 @@ static std::optional<bool> isImpliedCondICmps(const ICmpInst *LHS,
// must be positive if X >= Y and no overflow".
// Take SGT as an example: L0:x > L1:y and C >= 0
// ==> R0:(x -nsw y) < R1:(-C) is false
if ((LPred == ICmpInst::ICMP_SGT || LPred == ICmpInst::ICMP_SGE) &&
if ((ICmpInst::isSigned(LPred) || LHasSameSign) &&
(ICmpInst::isGE(LPred) || ICmpInst::isGT(LPred)) &&
match(R0, m_NSWSub(m_Specific(L0), m_Specific(L1)))) {
if (match(R1, m_NonPositive()) &&
isImpliedCondMatchingOperands(LPred, RPred) == false)
Expand All @@ -9330,7 +9332,8 @@ static std::optional<bool> isImpliedCondICmps(const ICmpInst *LHS,

// Take SLT as an example: L0:x < L1:y and C <= 0
// ==> R0:(x -nsw y) < R1:(-C) is true
if ((LPred == ICmpInst::ICMP_SLT || LPred == ICmpInst::ICMP_SLE) &&
if ((ICmpInst::isSigned(LPred) || LHasSameSign) &&
(ICmpInst::isLE(LPred) || ICmpInst::isLT(LPred)) &&
match(R0, m_NSWSub(m_Specific(L0), m_Specific(L1)))) {
if (match(R1, m_NonNegative()) &&
isImpliedCondMatchingOperands(LPred, RPred) == true)
Expand Down
215 changes: 215 additions & 0 deletions llvm/test/Analysis/ValueTracking/implied-condition-samesign.ll
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@@ -0,0 +1,215 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
; RUN: opt -passes=instsimplify -S %s | FileCheck %s

define i32 @gt_sub_nsw(i32 %x, i32 %y) {
; CHECK-LABEL: define i32 @gt_sub_nsw(
; CHECK-SAME: i32 [[X:%.*]], i32 [[Y:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[CMP:%.*]] = icmp samesign ugt i32 [[X]], [[Y]]
; CHECK-NEXT: br i1 [[CMP]], label %[[COND_TRUE:.*]], label %[[COND_END:.*]]
; CHECK: [[COND_TRUE]]:
; CHECK-NEXT: [[SUB:%.*]] = sub nsw i32 [[X]], [[Y]]
; CHECK-NEXT: [[ADD:%.*]] = add nsw i32 [[SUB]], 1
; CHECK-NEXT: ret i32 [[ADD]]
; CHECK: [[COND_END]]:
; CHECK-NEXT: ret i32 0
;
entry:
%cmp = icmp samesign ugt i32 %x, %y ; x>y ? abs (x-y+1): 0
br i1 %cmp, label %cond.true, label %cond.end

cond.true: ; preds = %entry
%sub = sub nsw i32 %x, %y
%add = add nsw i32 %sub, 1
%neg = xor i32 %sub, -1 ; sub nsw i32 0, %add
%abscond = icmp samesign ult i32 %sub, -1
%abs = select i1 %abscond, i32 %neg, i32 %add
ret i32 %abs

cond.end: ; preds = %entry, %cond.true
ret i32 0
}

define i32 @ge_sub_nsw(i32 %x, i32 %y) {
; CHECK-LABEL: define i32 @ge_sub_nsw(
; CHECK-SAME: i32 [[X:%.*]], i32 [[Y:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[CMP:%.*]] = icmp samesign uge i32 [[X]], [[Y]]
; CHECK-NEXT: br i1 [[CMP]], label %[[COND_TRUE:.*]], label %[[COND_END:.*]]
; CHECK: [[COND_TRUE]]:
; CHECK-NEXT: [[SUB:%.*]] = sub nsw i32 [[X]], [[Y]]
; CHECK-NEXT: [[ADD:%.*]] = add nsw i32 [[SUB]], 1
; CHECK-NEXT: ret i32 [[ADD]]
; CHECK: [[COND_END]]:
; CHECK-NEXT: ret i32 0
;
entry:
%cmp = icmp samesign uge i32 %x, %y ; x>=y ? abs (x-y+1): 0
br i1 %cmp, label %cond.true, label %cond.end

cond.true: ; preds = %entry
%sub = sub nsw i32 %x, %y
%add = add nsw i32 %sub, 1
%neg = xor i32 %sub, -1 ; sub nsw i32 0, %add
%abscond = icmp samesign ult i32 %sub, -1
%abs = select i1 %abscond, i32 %neg, i32 %add
ret i32 %abs

cond.end: ; preds = %entry, %cond.true
ret i32 0
}

define i8 @gt_sub_no_nsw(i8 %x, i8 %y) {
; CHECK-LABEL: define i8 @gt_sub_no_nsw(
; CHECK-SAME: i8 [[X:%.*]], i8 [[Y:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[CMP:%.*]] = icmp samesign ugt i8 [[X]], [[Y]]
; CHECK-NEXT: br i1 [[CMP]], label %[[COND_TRUE:.*]], label %[[COND_END:.*]]
; CHECK: [[COND_TRUE]]:
; CHECK-NEXT: [[SUB:%.*]] = sub i8 [[X]], [[Y]]
; CHECK-NEXT: [[ADD:%.*]] = add i8 [[SUB]], 1
; CHECK-NEXT: [[NEG:%.*]] = xor i8 [[SUB]], -1
; CHECK-NEXT: [[ABSCOND:%.*]] = icmp samesign ult i8 [[SUB]], -1
; CHECK-NEXT: [[ABS:%.*]] = select i1 [[ABSCOND]], i8 [[NEG]], i8 [[ADD]]
; CHECK-NEXT: ret i8 [[ABS]]
; CHECK: [[COND_END]]:
; CHECK-NEXT: ret i8 0
;
entry:
%cmp = icmp samesign ugt i8 %x, %y
br i1 %cmp, label %cond.true, label %cond.end

cond.true: ; preds = %entry
%sub = sub i8 %x, %y
%add = add i8 %sub, 1
%neg = xor i8 %sub, -1
%abscond = icmp samesign ult i8 %sub, -1
%abs = select i1 %abscond, i8 %neg, i8 %add
ret i8 %abs

cond.end: ; preds = %entry, %cond.true
ret i8 0
}

define i8 @ugt_sub_nsw(i8 %x, i8 %y) {
; CHECK-LABEL: define i8 @ugt_sub_nsw(
; CHECK-SAME: i8 [[X:%.*]], i8 [[Y:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[CMP:%.*]] = icmp ugt i8 [[X]], [[Y]]
; CHECK-NEXT: br i1 [[CMP]], label %[[COND_TRUE:.*]], label %[[COND_END:.*]]
; CHECK: [[COND_TRUE]]:
; CHECK-NEXT: [[SUB:%.*]] = sub i8 [[X]], [[Y]]
; CHECK-NEXT: [[ADD:%.*]] = add i8 [[SUB]], 1
; CHECK-NEXT: [[NEG:%.*]] = xor i8 [[SUB]], -1
; CHECK-NEXT: [[ABSCOND:%.*]] = icmp ult i8 [[SUB]], -1
; CHECK-NEXT: [[ABS:%.*]] = select i1 [[ABSCOND]], i8 [[NEG]], i8 [[ADD]]
; CHECK-NEXT: ret i8 [[ABS]]
; CHECK: [[COND_END]]:
; CHECK-NEXT: ret i8 0
;
entry:
%cmp = icmp ugt i8 %x, %y
br i1 %cmp, label %cond.true, label %cond.end

cond.true: ; preds = %entry
%sub = sub i8 %x, %y
%add = add i8 %sub, 1
%neg = xor i8 %sub, -1
%abscond = icmp ult i8 %sub, -1
%abs = select i1 %abscond, i8 %neg, i8 %add
ret i8 %abs

cond.end: ; preds = %entry, %cond.true
ret i8 0
}

define i32 @lt_sub_nsw(i32 %x, i32 %y) {
; CHECK-LABEL: define i32 @lt_sub_nsw(
; CHECK-SAME: i32 [[X:%.*]], i32 [[Y:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[CMP:%.*]] = icmp samesign ult i32 [[X]], [[Y]]
; CHECK-NEXT: br i1 [[CMP]], label %[[COND_TRUE:.*]], label %[[COND_END:.*]]
; CHECK: [[COND_TRUE]]:
; CHECK-NEXT: [[SUB:%.*]] = sub nsw i32 [[X]], [[Y]]
; CHECK-NEXT: [[NEG:%.*]] = add nsw i32 [[SUB]], 1
; CHECK-NEXT: ret i32 [[NEG]]
; CHECK: [[COND_END]]:
; CHECK-NEXT: ret i32 0
;
entry:
%cmp = icmp samesign ult i32 %x, %y ; x<y ? abs (x-y+1): 0
br i1 %cmp, label %cond.true, label %cond.end

cond.true: ; preds = %entry
%sub = sub nsw i32 %x, %y
%add = add nsw i32 %sub, 1
%neg = xor i32 %sub, -1 ; sub nsw i32 0, %add
%abscond = icmp samesign ugt i32 %sub, -1
%abs = select i1 %abscond, i32 %neg, i32 %add
ret i32 %abs

cond.end: ; preds = %entry, %cond.true
ret i32 0
}

define i32 @le_sub_nsw(i32 %x, i32 %y) {
; CHECK-LABEL: define i32 @le_sub_nsw(
; CHECK-SAME: i32 [[X:%.*]], i32 [[Y:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[CMP:%.*]] = icmp samesign ule i32 [[X]], [[Y]]
; CHECK-NEXT: br i1 [[CMP]], label %[[COND_TRUE:.*]], label %[[COND_END:.*]]
; CHECK: [[COND_TRUE]]:
; CHECK-NEXT: [[SUB:%.*]] = sub nsw i32 [[X]], [[Y]]
; CHECK-NEXT: [[ADD:%.*]] = add nsw i32 [[SUB]], 1
; CHECK-NEXT: ret i32 [[ADD]]
; CHECK: [[COND_END]]:
; CHECK-NEXT: ret i32 0
;
entry:
%cmp = icmp samesign ule i32 %x, %y ; x<=y ? abs (x-y+1): 0
br i1 %cmp, label %cond.true, label %cond.end

cond.true: ; preds = %entry
%sub = sub nsw i32 %x, %y
%add = add nsw i32 %sub, 1
%neg = xor i32 %sub, -1 ; sub nsw i32 0, %add
%abscond = icmp samesign ugt i32 %sub, -1
%abs = select i1 %abscond, i32 %neg, i32 %add
ret i32 %abs

cond.end: ; preds = %entry, %cond.true
ret i32 0
}

define i8 @gt_sub_nsw_wrong_const(i8 %x, i8 %y) {
; CHECK-LABEL: define i8 @gt_sub_nsw_wrong_const(
; CHECK-SAME: i8 [[X:%.*]], i8 [[Y:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[CMP:%.*]] = icmp samesign ugt i8 [[X]], [[Y]]
; CHECK-NEXT: br i1 [[CMP]], label %[[COND_TRUE:.*]], label %[[COND_END:.*]]
; CHECK: [[COND_TRUE]]:
; CHECK-NEXT: [[SUB:%.*]] = sub i8 [[X]], [[Y]]
; CHECK-NEXT: [[ADD:%.*]] = add i8 [[SUB]], 2
; CHECK-NEXT: [[NEG:%.*]] = xor i8 [[SUB]], -1
; CHECK-NEXT: [[ABSCOND:%.*]] = icmp samesign ult i8 [[SUB]], -2
; CHECK-NEXT: [[ABS:%.*]] = select i1 [[ABSCOND]], i8 [[NEG]], i8 [[ADD]]
; CHECK-NEXT: ret i8 [[ABS]]
; CHECK: [[COND_END]]:
; CHECK-NEXT: ret i8 0
;
entry:
%cmp = icmp samesign ugt i8 %x, %y ; x>y ? abs (x-y+2): 0
br i1 %cmp, label %cond.true, label %cond.end

cond.true: ; preds = %entry
%sub = sub i8 %x, %y
%add = add i8 %sub, 2 ; x-y+2
%neg = xor i8 %sub, -1 ; y-x-1
%neg1 = sub i8 %neg, 1 ; y-x-2
%abscond = icmp samesign ult i8 %sub, -2
%abs = select i1 %abscond, i8 %neg, i8 %add
ret i8 %abs

cond.end: ; preds = %entry, %cond.true
ret i8 0
}
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