[llvm] [InstCombine] Generalize `foldAndOrOfICmpsUsingRanges` to handle more cases. (PR #158498)
via llvm-commits
llvm-commits at lists.llvm.org
Sun Sep 14 19:56:45 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-transforms
Author: Yingwei Zheng (dtcxzyw)
<details>
<summary>Changes</summary>
Closes https://github.com/llvm/llvm-project/issues/158326.
---
Full diff: https://github.com/llvm/llvm-project/pull/158498.diff
3 Files Affected:
- (modified) llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp (+38-63)
- (modified) llvm/test/Transforms/InstCombine/and-or-icmps.ll (+42-7)
- (modified) llvm/test/Transforms/InstCombine/icmp-range.ll (+1-4)
``````````diff
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index 2d7524e8018b2..7fd2d6a427396 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -1320,74 +1320,49 @@ static Value *foldAndOrOfICmpsWithConstEq(ICmpInst *Cmp0, ICmpInst *Cmp1,
Value *InstCombinerImpl::foldAndOrOfICmpsUsingRanges(ICmpInst *ICmp1,
ICmpInst *ICmp2,
bool IsAnd) {
- CmpPredicate Pred1, Pred2;
- Value *V1, *V2;
- const APInt *C1, *C2;
- if (!match(ICmp1, m_ICmp(Pred1, m_Value(V1), m_APInt(C1))) ||
- !match(ICmp2, m_ICmp(Pred2, m_Value(V2), m_APInt(C2))))
- return nullptr;
-
- // Look through add of a constant offset on V1, V2, or both operands. This
- // allows us to interpret the V + C' < C'' range idiom into a proper range.
- const APInt *Offset1 = nullptr, *Offset2 = nullptr;
- if (V1 != V2) {
- Value *X;
- if (match(V1, m_Add(m_Value(X), m_APInt(Offset1))))
- V1 = X;
- if (match(V2, m_Add(m_Value(X), m_APInt(Offset2))))
- V2 = X;
- }
-
- // Look through and with a negative power of 2 mask on V1 or V2. This
- // detects idioms of the form `(x == A) || ((x & Mask) == A + 1)` where A + 1
- // is aligned to the mask and A + 1 >= |Mask|. This pattern corresponds to a
- // contiguous range check, which can be folded into an addition and compare.
- // The same applies for `(x != A) && ((x & Mask) != A + 1)`.
- auto AreContiguousRangePredicates = [](CmpPredicate Pred1, CmpPredicate Pred2,
- bool IsAnd) {
- if (IsAnd)
- return Pred1 == ICmpInst::ICMP_NE && Pred2 == ICmpInst::ICMP_NE;
- return Pred1 == ICmpInst::ICMP_EQ && Pred2 == ICmpInst::ICMP_EQ;
- };
- const APInt *Mask1 = nullptr, *Mask2 = nullptr;
- bool MatchedAnd1 = false, MatchedAnd2 = false;
- if (V1 != V2 && AreContiguousRangePredicates(Pred1, Pred2, IsAnd)) {
+ auto MatchRangeCheck =
+ [](ICmpInst *ICmp) -> std::optional<std::pair<Value *, ConstantRange>> {
+ const APInt *C;
+ if (!match(ICmp->getOperand(1), m_APInt(C)))
+ return std::nullopt;
+ Value *LHS = ICmp->getOperand(0);
+ CmpPredicate Pred = ICmp->getPredicate();
Value *X;
- if (match(V1, m_OneUse(m_And(m_Value(X), m_NegatedPower2(Mask1)))) &&
- C1->getBitWidth() == C2->getBitWidth() && *C1 == *C2 + 1 &&
- C1->uge(Mask1->abs()) && C1->isPowerOf2()) {
- MatchedAnd1 = true;
- V1 = X;
- }
- if (match(V2, m_OneUse(m_And(m_Value(X), m_NegatedPower2(Mask2)))) &&
- C1->getBitWidth() == C2->getBitWidth() && *C2 == *C1 + 1 &&
- C2->uge(Mask2->abs()) && C2->isPowerOf2()) {
- MatchedAnd2 = true;
- V2 = X;
+ // Match (x & NegPow2) ==/!= C
+ const APInt *Mask;
+ if (ICmpInst::isEquality(Pred) &&
+ match(LHS, m_OneUse(m_And(m_Value(X), m_NegatedPower2(Mask)))) &&
+ C->countr_zero() >= Mask->countr_zero()) {
+ ConstantRange CR{*C, *C - *Mask};
+ if (Pred == ICmpInst::ICMP_NE)
+ CR = CR.inverse();
+ return std::make_pair(X, CR);
}
- }
+ ConstantRange CR = ConstantRange::makeExactICmpRegion(Pred, *C);
+ // Match (add X, C1) pred C
+ const APInt *C1;
+ if (match(LHS, m_AddLike(m_Value(X), m_APInt(C1))))
+ return std::make_pair(X, CR.subtract(*C1));
+ return std::make_pair(LHS, CR);
+ };
+
+ auto RC1 = MatchRangeCheck(ICmp1);
+ if (!RC1)
+ return nullptr;
- if (V1 != V2)
+ auto RC2 = MatchRangeCheck(ICmp2);
+ if (!RC2)
return nullptr;
- ConstantRange CR1 =
- MatchedAnd1
- ? ConstantRange(*C1, *C1 - *Mask1)
- : ConstantRange::makeExactICmpRegion(
- IsAnd ? ICmpInst::getInverseCmpPredicate(Pred1) : Pred1, *C1);
- if (Offset1)
- CR1 = CR1.subtract(*Offset1);
-
- ConstantRange CR2 =
- MatchedAnd2
- ? ConstantRange(*C2, *C2 - *Mask2)
- : ConstantRange::makeExactICmpRegion(
- IsAnd ? ICmpInst::getInverseCmpPredicate(Pred2) : Pred2, *C2);
- if (Offset2)
- CR2 = CR2.subtract(*Offset2);
-
- Type *Ty = V1->getType();
- Value *NewV = V1;
+ if (RC1->first != RC2->first)
+ return nullptr;
+
+ Value *V = RC1->first;
+ auto CR1 = IsAnd ? RC1->second.inverse() : RC1->second;
+ auto CR2 = IsAnd ? RC2->second.inverse() : RC2->second;
+
+ Type *Ty = V->getType();
+ Value *NewV = V;
std::optional<ConstantRange> CR = CR1.exactUnionWith(CR2);
if (!CR) {
if (!(ICmp1->hasOneUse() && ICmp2->hasOneUse()) || CR1.isWrappedSet() ||
diff --git a/llvm/test/Transforms/InstCombine/and-or-icmps.ll b/llvm/test/Transforms/InstCombine/and-or-icmps.ll
index 553c7ac5af0e9..290e344acb980 100644
--- a/llvm/test/Transforms/InstCombine/and-or-icmps.ll
+++ b/llvm/test/Transforms/InstCombine/and-or-icmps.ll
@@ -3672,13 +3672,11 @@ define i1 @neg_or_icmp_eq_double_and_pow2(i32 %x) {
ret i1 %ret
}
-define i1 @neg_select_icmp_eq_and_pow2(i32 %x) {
-; CHECK-LABEL: @neg_select_icmp_eq_and_pow2(
-; CHECK-NEXT: [[ICMP1:%.*]] = icmp sgt i32 [[X:%.*]], 127
-; CHECK-NEXT: [[AND:%.*]] = and i32 [[X]], -32
-; CHECK-NEXT: [[ICMP2:%.*]] = icmp eq i32 [[AND]], 128
-; CHECK-NEXT: [[TMP1:%.*]] = and i1 [[ICMP1]], [[ICMP2]]
-; CHECK-NEXT: ret i1 [[TMP1]]
+define i1 @implied_select_icmp_eq_and_pow2(i32 %x) {
+; CHECK-LABEL: @implied_select_icmp_eq_and_pow2(
+; CHECK-NEXT: [[TMP1:%.*]] = and i32 [[X:%.*]], -32
+; CHECK-NEXT: [[TMP2:%.*]] = icmp eq i32 [[TMP1]], 128
+; CHECK-NEXT: ret i1 [[TMP2]]
;
%icmp1 = icmp sgt i32 %x, 127
%and = and i32 %x, -32
@@ -3686,3 +3684,40 @@ define i1 @neg_select_icmp_eq_and_pow2(i32 %x) {
%1 = select i1 %icmp1, i1 %icmp2, i1 false
ret i1 %1
}
+
+define i1 @implied_range_check(i8 %a) {
+; CHECK-LABEL: @implied_range_check(
+; CHECK-NEXT: [[MASKED:%.*]] = and i8 [[A:%.*]], -2
+; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i8 [[MASKED]], 2
+; CHECK-NEXT: ret i1 [[CMP2]]
+;
+ %cmp1 = icmp ult i8 %a, 5
+ %masked = and i8 %a, -2
+ %cmp2 = icmp eq i8 %masked, 2
+ %and = and i1 %cmp1, %cmp2
+ ret i1 %and
+}
+
+define i1 @merge_range_check_and(i8 %a) {
+; CHECK-LABEL: @merge_range_check_and(
+; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i8 [[MASKED:%.*]], 2
+; CHECK-NEXT: ret i1 [[CMP2]]
+;
+ %cmp1 = icmp ult i8 %a, 3
+ %masked = and i8 %a, -2
+ %cmp2 = icmp eq i8 %masked, 2
+ %and = and i1 %cmp1, %cmp2
+ ret i1 %and
+}
+
+define i1 @merge_range_check_or(i8 %a) {
+; CHECK-LABEL: @merge_range_check_or(
+; CHECK-NEXT: [[AND:%.*]] = icmp ult i8 [[A:%.*]], 4
+; CHECK-NEXT: ret i1 [[AND]]
+;
+ %cmp1 = icmp ult i8 %a, 3
+ %masked = and i8 %a, -2
+ %cmp2 = icmp eq i8 %masked, 2
+ %and = or i1 %cmp1, %cmp2
+ ret i1 %and
+}
diff --git a/llvm/test/Transforms/InstCombine/icmp-range.ll b/llvm/test/Transforms/InstCombine/icmp-range.ll
index 97ed552b9a6da..1970694cf9c42 100644
--- a/llvm/test/Transforms/InstCombine/icmp-range.ll
+++ b/llvm/test/Transforms/InstCombine/icmp-range.ll
@@ -1678,10 +1678,7 @@ define i1 @icmp_slt_sext_ne_otherwise_nofold(i32 %a) {
; tests from PR59555
define i1 @isFloat(i64 %0) {
; CHECK-LABEL: @isFloat(
-; CHECK-NEXT: [[TMP2:%.*]] = icmp ugt i64 [[TMP0:%.*]], 281474976710655
-; CHECK-NEXT: [[TMP3:%.*]] = and i64 [[TMP0]], -281474976710656
-; CHECK-NEXT: [[TMP4:%.*]] = icmp ne i64 [[TMP3]], 281474976710656
-; CHECK-NEXT: [[TMP5:%.*]] = and i1 [[TMP2]], [[TMP4]]
+; CHECK-NEXT: [[TMP5:%.*]] = icmp ugt i64 [[TMP0:%.*]], 562949953421311
; CHECK-NEXT: ret i1 [[TMP5]]
;
%2 = icmp ugt i64 %0, 281474976710655
``````````
</details>
https://github.com/llvm/llvm-project/pull/158498
More information about the llvm-commits
mailing list