[ConstraintElim] Check if second op implies first for And. #75750
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Generalize checkAndSecondOpImpliedByFirst to also check if the second operand implies the first.
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@llvm/pr-subscribers-llvm-transforms Author: Florian Hahn (fhahn) ChangesGeneralize checkAndSecondOpImpliedByFirst to also check if the second operand implies the first. Full diff: https://github.com/llvm/llvm-project/pull/75750.diff 5 Files Affected:
diff --git a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
index 18266ba0789897..da019ecbc7c429 100644
--- a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
@@ -1365,16 +1365,24 @@ removeEntryFromStack(const StackEntry &E, ConstraintInfo &Info,
ReproducerCondStack.pop_back();
}
-/// Check if the first condition for an AND implies the second.
-static bool checkAndSecondOpImpliedByFirst(
- FactOrCheck &CB, ConstraintInfo &Info, Module *ReproducerModule,
- SmallVectorImpl<ReproducerEntry> &ReproducerCondStack,
- SmallVectorImpl<StackEntry> &DFSInStack) {
+/// Check if either the first condition of an AND is implied by the second or
+/// vice versa.
+static bool
+checkAndOpImpliedByOther(FactOrCheck &CB, ConstraintInfo &Info,
+ Module *ReproducerModule,
+ SmallVectorImpl<ReproducerEntry> &ReproducerCondStack,
+ SmallVectorImpl<StackEntry> &DFSInStack) {
CmpInst::Predicate Pred;
Value *A, *B;
Instruction *And = CB.getContextInst();
- if (!match(And->getOperand(0), m_ICmp(Pred, m_Value(A), m_Value(B))))
+ CmpInst *CmpToCheck = cast<CmpInst>(CB.getInstructionToSimplify());
+ unsigned OtherOpIdx = And->getOperand(0) == CmpToCheck ? 1 : 0;
+
+ if (OtherOpIdx != 0 && isa<SelectInst>(And))
+ return false;
+
+ if (!match(And->getOperand(OtherOpIdx), m_ICmp(Pred, m_Value(A), m_Value(B))))
return false;
// Optimistically add fact from first condition.
@@ -1385,11 +1393,12 @@ static bool checkAndSecondOpImpliedByFirst(
bool Changed = false;
// Check if the second condition can be simplified now.
- ICmpInst *Cmp = cast<ICmpInst>(And->getOperand(1));
- if (auto ImpliedCondition = checkCondition(
- Cmp->getPredicate(), Cmp->getOperand(0), Cmp->getOperand(1), Cmp,
- Info, CB.NumIn, CB.NumOut, CB.getContextInst())) {
- And->setOperand(1, ConstantInt::getBool(And->getType(), *ImpliedCondition));
+ if (auto ImpliedCondition =
+ checkCondition(CmpToCheck->getPredicate(), CmpToCheck->getOperand(0),
+ CmpToCheck->getOperand(1), CmpToCheck, Info, CB.NumIn,
+ CB.NumOut, CB.getContextInst())) {
+ And->setOperand(1 - OtherOpIdx,
+ ConstantInt::getBool(And->getType(), *ImpliedCondition));
Changed = true;
}
@@ -1609,11 +1618,11 @@ static bool eliminateConstraints(Function &F, DominatorTree &DT, LoopInfo &LI,
bool Simplified = checkAndReplaceCondition(
Cmp, Info, CB.NumIn, CB.NumOut, CB.getContextInst(),
ReproducerModule.get(), ReproducerCondStack, S.DT, ToRemove);
- if (!Simplified && match(CB.getContextInst(),
- m_LogicalAnd(m_Value(), m_Specific(Inst)))) {
+ if (!Simplified &&
+ match(CB.getContextInst(), m_LogicalAnd(m_Value(), m_Value()))) {
Simplified =
- checkAndSecondOpImpliedByFirst(CB, Info, ReproducerModule.get(),
- ReproducerCondStack, DFSInStack);
+ checkAndOpImpliedByByOther(CB, Info, ReproducerModule.get(),
+ ReproducerCondStack, DFSInStack);
}
Changed |= Simplified;
}
diff --git a/llvm/test/Transforms/ConstraintElimination/and-implied-by-operands.ll b/llvm/test/Transforms/ConstraintElimination/and-implied-by-operands.ll
index dc3b0f17c79602..3d2a480195abc3 100644
--- a/llvm/test/Transforms/ConstraintElimination/and-implied-by-operands.ll
+++ b/llvm/test/Transforms/ConstraintElimination/and-implied-by-operands.ll
@@ -31,7 +31,7 @@ define i1 @test_first_and_condition_implied_by_second_ops(i8 %x) {
; CHECK-NEXT: entry:
; CHECK-NEXT: [[C_1:%.*]] = icmp ugt i8 [[X:%.*]], 10
; CHECK-NEXT: [[T_1:%.*]] = icmp ugt i8 [[X]], 5
-; CHECK-NEXT: [[AND:%.*]] = and i1 [[T_1]], [[C_1]]
+; CHECK-NEXT: [[AND:%.*]] = and i1 true, [[C_1]]
; CHECK-NEXT: br i1 [[AND]], label [[THEN:%.*]], label [[ELSE:%.*]]
; CHECK: then:
; CHECK-NEXT: ret i1 false
@@ -105,7 +105,7 @@ define i1 @test_same_cond_for_and(i8 %x) {
; CHECK-LABEL: @test_same_cond_for_and(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[C_1:%.*]] = icmp ugt i8 [[X:%.*]], 10
-; CHECK-NEXT: [[AND:%.*]] = and i1 [[C_1]], true
+; CHECK-NEXT: [[AND:%.*]] = and i1 true, [[C_1]]
; CHECK-NEXT: br i1 [[AND]], label [[THEN:%.*]], label [[ELSE:%.*]]
; CHECK: then:
; CHECK-NEXT: ret i1 false
@@ -128,7 +128,7 @@ define i1 @test_same_cond_for_and_select_form(i8 %x) {
; CHECK-LABEL: @test_same_cond_for_and_select_form(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[C_1:%.*]] = icmp ugt i8 [[X:%.*]], 10
-; CHECK-NEXT: [[AND:%.*]] = select i1 [[C_1]], i1 true, i1 false
+; CHECK-NEXT: [[AND:%.*]] = select i1 [[C_1]], i1 [[C_1]], i1 false
; CHECK-NEXT: br i1 [[AND]], label [[THEN:%.*]], label [[ELSE:%.*]]
; CHECK: then:
; CHECK-NEXT: ret i1 false
@@ -152,7 +152,7 @@ define i1 @test_second_and_condition_not_implied_by_first(i8 %x) {
; CHECK-NEXT: entry:
; CHECK-NEXT: [[C_1:%.*]] = icmp ugt i8 [[X:%.*]], 10
; CHECK-NEXT: [[C_2:%.*]] = icmp ugt i8 [[X]], 5
-; CHECK-NEXT: [[AND:%.*]] = and i1 [[C_2]], [[C_1]]
+; CHECK-NEXT: [[AND:%.*]] = and i1 true, [[C_1]]
; CHECK-NEXT: br i1 [[AND]], label [[THEN:%.*]], label [[ELSE:%.*]]
; CHECK: then:
; CHECK-NEXT: ret i1 false
diff --git a/llvm/test/Transforms/ConstraintElimination/and.ll b/llvm/test/Transforms/ConstraintElimination/and.ll
index 389a676651a428..f9824df3975e97 100644
--- a/llvm/test/Transforms/ConstraintElimination/and.ll
+++ b/llvm/test/Transforms/ConstraintElimination/and.ll
@@ -438,7 +438,7 @@ define i1 @test_and_chain_select_ule(i4 %x, i4 %y, i4 %z, i4 %a) {
; CHECK-NEXT: [[C_2:%.*]] = icmp ule i4 [[Y]], [[Z:%.*]]
; CHECK-NEXT: [[C_3:%.*]] = icmp ule i4 3, [[X]]
; CHECK-NEXT: [[C_4:%.*]] = icmp ule i4 3, [[A:%.*]]
-; CHECK-NEXT: [[AND_1:%.*]] = select i1 [[C_1]], i1 true, i1 false
+; CHECK-NEXT: [[AND_1:%.*]] = select i1 [[C_1]], i1 [[C_1]], i1 false
; CHECK-NEXT: [[AND_2:%.*]] = select i1 [[AND_1]], i1 [[C_3]], i1 false
; CHECK-NEXT: [[AND_3:%.*]] = select i1 [[C_4]], i1 [[AND_2]], i1 false
; CHECK-NEXT: br i1 [[AND_3]], label [[BB1:%.*]], label [[EXIT:%.*]]
@@ -522,7 +522,7 @@ define i1 @test_and_chain_select_ule_logical_or(i4 %x, i4 %y, i4 %z, i4 %a) {
; CHECK-NEXT: [[C_2:%.*]] = icmp ule i4 [[Y]], [[Z:%.*]]
; CHECK-NEXT: [[C_3:%.*]] = icmp ule i4 3, [[X]]
; CHECK-NEXT: [[C_4:%.*]] = icmp ule i4 3, [[A:%.*]]
-; CHECK-NEXT: [[AND_1:%.*]] = select i1 [[C_1]], i1 true, i1 false
+; CHECK-NEXT: [[AND_1:%.*]] = select i1 [[C_1]], i1 [[C_1]], i1 false
; CHECK-NEXT: [[AND_2:%.*]] = select i1 [[AND_1]], i1 [[C_3]], i1 false
; CHECK-NEXT: [[AND_3:%.*]] = select i1 [[C_4]], i1 [[AND_2]], i1 false
; CHECK-NEXT: [[AND_4:%.*]] = select i1 [[AND_3]], i1 true, i1 false
diff --git a/llvm/test/Transforms/ConstraintElimination/gep-arithmetic-signed-predicates.ll b/llvm/test/Transforms/ConstraintElimination/gep-arithmetic-signed-predicates.ll
index d8ed479f3ee671..96ff98b00538ef 100644
--- a/llvm/test/Transforms/ConstraintElimination/gep-arithmetic-signed-predicates.ll
+++ b/llvm/test/Transforms/ConstraintElimination/gep-arithmetic-signed-predicates.ll
@@ -611,7 +611,7 @@ define i4 @ptr_N_signed_positive_assume(ptr %src, ptr %lower, ptr %upper, i16 %N
; CHECK: step.check:
; CHECK-NEXT: [[STEP_POS:%.*]] = icmp sge i16 [[STEP:%.*]], 0
; CHECK-NEXT: [[STEP_SLT_N:%.*]] = icmp slt i16 [[STEP]], [[N]]
-; CHECK-NEXT: [[AND_STEP:%.*]] = and i1 [[STEP_POS]], false
+; CHECK-NEXT: [[AND_STEP:%.*]] = and i1 false, [[STEP_SLT_N]]
; CHECK-NEXT: br i1 [[AND_STEP]], label [[PTR_CHECK:%.*]], label [[EXIT:%.*]]
; CHECK: ptr.check:
; CHECK-NEXT: [[SRC_STEP:%.*]] = getelementptr inbounds i8, ptr [[SRC]], i16 [[STEP]]
diff --git a/llvm/test/Transforms/ConstraintElimination/geps-precondition-overflow-check.ll b/llvm/test/Transforms/ConstraintElimination/geps-precondition-overflow-check.ll
index 47923836187845..834db0418b4d46 100644
--- a/llvm/test/Transforms/ConstraintElimination/geps-precondition-overflow-check.ll
+++ b/llvm/test/Transforms/ConstraintElimination/geps-precondition-overflow-check.ll
@@ -36,7 +36,7 @@ define i1 @overflow_check_2_and(ptr %dst) {
; CHECK-NEXT: entry:
; CHECK-NEXT: [[DST_5:%.*]] = getelementptr i32, ptr [[DST:%.*]], i64 5
; CHECK-NEXT: [[DST_5_UGE:%.*]] = icmp uge ptr [[DST_5]], [[DST]]
-; CHECK-NEXT: [[AND:%.*]] = and i1 [[DST_5_UGE]], true
+; CHECK-NEXT: [[AND:%.*]] = and i1 true, [[DST_5_UGE]]
; CHECK-NEXT: br i1 [[AND]], label [[THEN:%.*]], label [[ELSE:%.*]]
; CHECK: then:
; CHECK-NEXT: [[DST_4:%.*]] = getelementptr i32, ptr [[DST]], i64 4
@@ -65,7 +65,7 @@ define i1 @overflow_check_3_and(ptr %dst) {
; CHECK-NEXT: entry:
; CHECK-NEXT: [[DST_5:%.*]] = getelementptr i32, ptr [[DST:%.*]], i64 5
; CHECK-NEXT: [[DST_5_UGE:%.*]] = icmp uge ptr [[DST_5]], [[DST]]
-; CHECK-NEXT: [[AND:%.*]] = and i1 [[DST_5_UGE]], true
+; CHECK-NEXT: [[AND:%.*]] = and i1 true, [[DST_5_UGE]]
; CHECK-NEXT: br i1 [[AND]], label [[THEN:%.*]], label [[ELSE:%.*]]
; CHECK: then:
; CHECK-NEXT: [[DST_4:%.*]] = getelementptr i32, ptr [[DST]], i64 4
@@ -98,7 +98,7 @@ define i1 @overflow_check_4_and(ptr %dst) {
; CHECK-NEXT: entry:
; CHECK-NEXT: [[DST_5:%.*]] = getelementptr i32, ptr [[DST:%.*]], i64 5
; CHECK-NEXT: [[DST_5_UGE:%.*]] = icmp uge ptr [[DST_5]], [[DST]]
-; CHECK-NEXT: [[AND:%.*]] = and i1 [[DST_5_UGE]], true
+; CHECK-NEXT: [[AND:%.*]] = and i1 true, [[DST_5_UGE]]
; CHECK-NEXT: br i1 [[AND]], label [[THEN:%.*]], label [[ELSE:%.*]]
; CHECK: then:
; CHECK-NEXT: [[DST_4:%.*]] = getelementptr i32, ptr [[DST]], i64 4
|
nikic
reviewed
Dec 17, 2023
| CmpInst *CmpToCheck = cast<CmpInst>(CB.getInstructionToSimplify()); | ||
| unsigned OtherOpIdx = And->getOperand(0) == CmpToCheck ? 1 : 0; | ||
|
|
||
| if (OtherOpIdx != 0 && isa<SelectInst>(And)) |
There was a problem hiding this comment.
Is this due to a poison-propagation issue?
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Yep, added a comment plus a TODO to check if the first op may be poison, thanks!
nikic
reviewed
Dec 17, 2023
| @@ -128,7 +128,7 @@ define i1 @test_same_cond_for_and_select_form(i8 %x) { | |||
| ; CHECK-LABEL: @test_same_cond_for_and_select_form( | |||
| ; CHECK-NEXT: entry: | |||
| ; CHECK-NEXT: [[C_1:%.*]] = icmp ugt i8 [[X:%.*]], 10 | |||
| ; CHECK-NEXT: [[AND:%.*]] = select i1 [[C_1]], i1 true, i1 false | |||
| ; CHECK-NEXT: [[AND:%.*]] = select i1 [[C_1]], i1 [[C_1]], i1 false | |||
There was a problem hiding this comment.
In this case, both conds are the same, and in the new code we will try OtherOpIdx = 1 first, which then hits the early-exit condition for selects; Not sure if it is worth avoiding that and complicating the conditions.
fhahn
added a commit
that referenced
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Dec 21, 2023
…son. Extra test for TODO from #75750.
fhahn
added a commit
to fhahn/llvm-project
that referenced
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Dec 21, 2023
Address the TODO from llvm#75750 by checking if the second operand may be poison. We can simplify the first operand if it is implied by the other operand, if the other operand is guaranteed to not be undef/poison. If it may be poison, it would mean the select would be unconditionally poison after the transform. Note that the original TODO incorrectly said that the first operand would need checking, but it is the other one that needs checking.
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Generalize checkAndSecondOpImpliedByFirst to also check if the second operand implies the first.