[llvm] [ConstraintElim] Add facts implied by llvm.abs (PR #73189)
Alexander Shaposhnikov via llvm-commits
llvm-commits at lists.llvm.org
Fri Dec 29 22:08:38 PST 2023
https://github.com/alexander-shaposhnikov updated https://github.com/llvm/llvm-project/pull/73189
>From eefaeb0b27f6548ce3b06ccd38b0264a5170fb95 Mon Sep 17 00:00:00 2001
From: Alexander Shaposhnikov <ashaposhnikov at google.com>
Date: Sun, 3 Dec 2023 13:42:45 +0000
Subject: [PATCH] [ConstraintElim] Add facts implied by llvm.abs
---
.../Scalar/ConstraintElimination.cpp | 48 ++++++++++++-------
.../Transforms/ConstraintElimination/abs.ll | 21 +++-----
2 files changed, 38 insertions(+), 31 deletions(-)
diff --git a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
index 899d7e0a11e6f4..710336f2108a3c 100644
--- a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
@@ -1010,22 +1010,14 @@ void State::addInfoFor(BasicBlock &BB) {
continue;
}
- if (match(&I, m_Intrinsic<Intrinsic::ssub_with_overflow>())) {
- WorkList.push_back(
- FactOrCheck::getCheck(DT.getNode(&BB), cast<CallInst>(&I)));
- continue;
- }
-
- if (isa<MinMaxIntrinsic>(&I)) {
- WorkList.push_back(FactOrCheck::getInstFact(DT.getNode(&BB), &I));
- continue;
- }
-
- Value *A, *B;
- CmpInst::Predicate Pred;
- // For now, just handle assumes with a single compare as condition.
- if (match(&I, m_Intrinsic<Intrinsic::assume>(
- m_ICmp(Pred, m_Value(A), m_Value(B))))) {
+ auto *II = dyn_cast<IntrinsicInst>(&I);
+ Intrinsic::ID ID = II ? II->getIntrinsicID() : Intrinsic::not_intrinsic;
+ switch (ID) {
+ case Intrinsic::assume: {
+ Value *A, *B;
+ CmpInst::Predicate Pred;
+ if (!match(I.getOperand(0), m_ICmp(Pred, m_Value(A), m_Value(B))))
+ break;
if (GuaranteedToExecute) {
// The assume is guaranteed to execute when BB is entered, hence Cond
// holds on entry to BB.
@@ -1035,7 +1027,23 @@ void State::addInfoFor(BasicBlock &BB) {
WorkList.emplace_back(
FactOrCheck::getInstFact(DT.getNode(I.getParent()), &I));
}
+ break;
}
+ // Enqueue ssub_with_overflow for simplification.
+ case Intrinsic::ssub_with_overflow:
+ WorkList.push_back(
+ FactOrCheck::getCheck(DT.getNode(&BB), cast<CallInst>(&I)));
+ break;
+ // Enqueue the intrinsics to add extra info.
+ case Intrinsic::abs:
+ case Intrinsic::umin:
+ case Intrinsic::umax:
+ case Intrinsic::smin:
+ case Intrinsic::smax:
+ WorkList.push_back(FactOrCheck::getInstFact(DT.getNode(&BB), &I));
+ break;
+ }
+
GuaranteedToExecute &= isGuaranteedToTransferExecutionToSuccessor(&I);
}
@@ -1286,7 +1294,7 @@ static std::optional<bool> checkCondition(CmpInst::Predicate Pred, Value *A,
LLVM_DEBUG(dbgs() << "Checking " << *CheckInst << "\n");
auto R = Info.getConstraintForSolving(Pred, A, B);
- if (R.empty() || !R.isValid(Info)){
+ if (R.empty() || !R.isValid(Info)) {
LLVM_DEBUG(dbgs() << " failed to decompose condition\n");
return std::nullopt;
}
@@ -1693,6 +1701,12 @@ static bool eliminateConstraints(Function &F, DominatorTree &DT, LoopInfo &LI,
ICmpInst::Predicate Pred;
if (!CB.isConditionFact()) {
+ if (Value *X; match(CB.Inst, m_Intrinsic<Intrinsic::abs>(m_Value(X)))) {
+ // TODO: Add CB.Inst >= 0 fact.
+ AddFact(CmpInst::ICMP_SGE, CB.Inst, X);
+ continue;
+ }
+
if (auto *MinMax = dyn_cast<MinMaxIntrinsic>(CB.Inst)) {
Pred = ICmpInst::getNonStrictPredicate(MinMax->getPredicate());
AddFact(Pred, MinMax, MinMax->getLHS());
diff --git a/llvm/test/Transforms/ConstraintElimination/abs.ll b/llvm/test/Transforms/ConstraintElimination/abs.ll
index b6d5e203029961..c3162ba48c2e4a 100644
--- a/llvm/test/Transforms/ConstraintElimination/abs.ll
+++ b/llvm/test/Transforms/ConstraintElimination/abs.ll
@@ -5,8 +5,7 @@ define i1 @abs_int_min_is_not_poison(i32 %arg) {
; CHECK-LABEL: define i1 @abs_int_min_is_not_poison(
; CHECK-SAME: i32 [[ARG:%.*]]) {
; CHECK-NEXT: [[ABS:%.*]] = tail call i32 @llvm.abs.i32(i32 [[ARG]], i1 false)
-; CHECK-NEXT: [[CMP:%.*]] = icmp sge i32 [[ABS]], [[ARG]]
-; CHECK-NEXT: ret i1 [[CMP]]
+; CHECK-NEXT: ret i1 true
;
%abs = tail call i32 @llvm.abs.i32(i32 %arg, i1 false)
%cmp = icmp sge i32 %abs, %arg
@@ -17,8 +16,7 @@ define i1 @abs_int_min_is_poison(i32 %arg) {
; CHECK-LABEL: define i1 @abs_int_min_is_poison(
; CHECK-SAME: i32 [[ARG:%.*]]) {
; CHECK-NEXT: [[ABS:%.*]] = tail call i32 @llvm.abs.i32(i32 [[ARG]], i1 true)
-; CHECK-NEXT: [[CMP:%.*]] = icmp sge i32 [[ABS]], [[ARG]]
-; CHECK-NEXT: ret i1 [[CMP]]
+; CHECK-NEXT: ret i1 true
;
%abs = tail call i32 @llvm.abs.i32(i32 %arg, i1 true)
%cmp = icmp sge i32 %abs, %arg
@@ -30,8 +28,7 @@ define i1 @abs_plus_one(i32 %arg) {
; CHECK-SAME: i32 [[ARG:%.*]]) {
; CHECK-NEXT: [[ABS:%.*]] = tail call i32 @llvm.abs.i32(i32 [[ARG]], i1 true)
; CHECK-NEXT: [[ABS_PLUS_ONE:%.*]] = add nsw i32 [[ABS]], 1
-; CHECK-NEXT: [[CMP:%.*]] = icmp sge i32 [[ABS_PLUS_ONE]], [[ARG]]
-; CHECK-NEXT: ret i1 [[CMP]]
+; CHECK-NEXT: ret i1 true
;
%abs = tail call i32 @llvm.abs.i32(i32 %arg, i1 true)
%abs_plus_one = add nsw i32 %abs, 1
@@ -44,8 +41,7 @@ define i1 @arg_minus_one_strict_less(i32 %arg) {
; CHECK-SAME: i32 [[ARG:%.*]]) {
; CHECK-NEXT: [[ABS:%.*]] = tail call i32 @llvm.abs.i32(i32 [[ARG]], i1 true)
; CHECK-NEXT: [[ARG_MINUS_ONE:%.*]] = add nsw i32 [[ARG]], -1
-; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[ARG_MINUS_ONE]], [[ABS]]
-; CHECK-NEXT: ret i1 [[CMP]]
+; CHECK-NEXT: ret i1 true
;
%abs = tail call i32 @llvm.abs.i32(i32 %arg, i1 true)
%arg_minus_one = add nsw i32 %arg, -1
@@ -58,8 +54,7 @@ define i1 @arg_minus_one_strict_greater(i32 %arg) {
; CHECK-SAME: i32 [[ARG:%.*]]) {
; CHECK-NEXT: [[ABS:%.*]] = tail call i32 @llvm.abs.i32(i32 [[ARG]], i1 true)
; CHECK-NEXT: [[ARG_MINUS_ONE:%.*]] = add nsw i32 [[ARG]], -1
-; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i32 [[ARG_MINUS_ONE]], [[ABS]]
-; CHECK-NEXT: ret i1 [[CMP]]
+; CHECK-NEXT: ret i1 false
;
%abs = tail call i32 @llvm.abs.i32(i32 %arg, i1 true)
%arg_minus_one = add nsw i32 %arg, -1
@@ -74,8 +69,7 @@ define i1 @abs_plus_one_unsigned_greater_or_equal_nonnegative_arg(i32 %arg) {
; CHECK-NEXT: call void @llvm.assume(i1 [[CMP_ARG_NONNEGATIVE]])
; CHECK-NEXT: [[ABS:%.*]] = tail call i32 @llvm.abs.i32(i32 [[ARG]], i1 true)
; CHECK-NEXT: [[ABS_PLUS_ONE:%.*]] = add nuw i32 [[ABS]], 1
-; CHECK-NEXT: [[CMP:%.*]] = icmp uge i32 [[ABS_PLUS_ONE]], [[ARG]]
-; CHECK-NEXT: ret i1 [[CMP]]
+; CHECK-NEXT: ret i1 true
;
%cmp_arg_nonnegative = icmp sge i32 %arg, 0
call void @llvm.assume(i1 %cmp_arg_nonnegative)
@@ -113,8 +107,7 @@ define i1 @abs_constant_negative_arg() {
define i1 @abs_constant_positive_arg() {
; CHECK-LABEL: define i1 @abs_constant_positive_arg() {
; CHECK-NEXT: [[ABS:%.*]] = tail call i32 @llvm.abs.i32(i32 3, i1 false)
-; CHECK-NEXT: [[CMP:%.*]] = icmp sge i32 [[ABS]], 3
-; CHECK-NEXT: ret i1 [[CMP]]
+; CHECK-NEXT: ret i1 true
;
%abs = tail call i32 @llvm.abs.i32(i32 3, i1 false)
%cmp = icmp sge i32 %abs, 3
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