[llvm] 0ad6879 - [ConstraintElim] Try to use first cmp to prove second cmp for ANDs.
Florian Hahn via llvm-commits
llvm-commits at lists.llvm.org
Wed Jun 28 05:21:47 PDT 2023
Author: Florian Hahn
Date: 2023-06-28T13:19:41+01:00
New Revision: 0ad6879a626edc2947b4a513e1473febb47e8072
URL: https://github.com/llvm/llvm-project/commit/0ad6879a626edc2947b4a513e1473febb47e8072
DIFF: https://github.com/llvm/llvm-project/commit/0ad6879a626edc2947b4a513e1473febb47e8072.diff
LOG: [ConstraintElim] Try to use first cmp to prove second cmp for ANDs.
This patch extends the existing logic to handle cases where we have
branch conditions of the form (AND icmp, icmp) where the first icmp
implies the second. This can improve results in some cases, e.g. if
SimplifyCFG folded conditions from multiple branches to an AND.
The implementation handles this by adding a new type of check
(AndImpliedCheck), which are queued before conditional facts for the same
block.
When encountering AndImpliedChecks during solving, the first condition
is optimistically added to the constraint system, then we check if the
second icmp can be simplified, and finally the newly added entries are
removed.
The reason for doing things this way is to avoid clashes with signed
<-> unsigned condition transfer, which require us to re-order facts to
increase effectiveness.
Reviewed By: nikic, antoniofrighetto
Differential Revision: https://reviews.llvm.org/D151799
Added:
Modified:
llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
llvm/test/Transforms/ConstraintElimination/and-implied-by-operands.ll
llvm/test/Transforms/ConstraintElimination/and.ll
llvm/test/Transforms/ConstraintElimination/gep-arithmetic-signed-predicates.ll
llvm/test/Transforms/ConstraintElimination/geps-precondition-overflow-check.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
index aa8066c0661ac..afa554c62d2b0 100644
--- a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
@@ -1099,6 +1099,41 @@ 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) {
+ CmpInst::Predicate Pred;
+ Value *A, *B;
+ Instruction *And = CB.getContextInst();
+ if (!match(And->getOperand(0), m_ICmp(Pred, m_Value(A), m_Value(B))))
+ return false;
+
+ // Optimistically add fact from first condition.
+ unsigned OldSize = DFSInStack.size();
+ Info.addFact(Pred, A, B, CB.NumIn, CB.NumOut, DFSInStack);
+ if (OldSize == DFSInStack.size())
+ return false;
+
+ bool Changed = false;
+ // Check if the second condition can be simplified now.
+ if (auto ImpliedCondition =
+ checkCondition(cast<ICmpInst>(And->getOperand(1)), Info, CB.NumIn,
+ CB.NumOut, CB.getContextInst())) {
+ And->setOperand(1, ConstantInt::getBool(And->getType(), *ImpliedCondition));
+ Changed = true;
+ }
+
+ // Remove entries again.
+ while (OldSize < DFSInStack.size()) {
+ StackEntry E = DFSInStack.back();
+ removeEntryFromStack(E, Info, ReproducerModule, ReproducerCondStack,
+ DFSInStack);
+ }
+ return Changed;
+}
+
void ConstraintInfo::addFact(CmpInst::Predicate Pred, Value *A, Value *B,
unsigned NumIn, unsigned NumOut,
SmallVectorImpl<StackEntry> &DFSInStack) {
@@ -1300,9 +1335,16 @@ static bool eliminateConstraints(Function &F, DominatorTree &DT,
if (auto *II = dyn_cast<WithOverflowInst>(Inst)) {
Changed |= tryToSimplifyOverflowMath(II, Info, ToRemove);
} else if (auto *Cmp = dyn_cast<ICmpInst>(Inst)) {
- Changed |= checkAndReplaceCondition(
+ bool Simplified = checkAndReplaceCondition(
Cmp, Info, CB.NumIn, CB.NumOut, CB.getContextInst(),
ReproducerModule.get(), ReproducerCondStack, S.DT);
+ if (!Simplified && match(CB.getContextInst(),
+ m_LogicalAnd(m_Value(), m_Specific(Inst)))) {
+ Simplified =
+ checkAndSecondOpImpliedByFirst(CB, Info, ReproducerModule.get(),
+ ReproducerCondStack, DFSInStack);
+ }
+ Changed |= Simplified;
}
continue;
}
diff --git a/llvm/test/Transforms/ConstraintElimination/and-implied-by-operands.ll b/llvm/test/Transforms/ConstraintElimination/and-implied-by-operands.ll
index ab1ce772d88be..8796bdcf08677 100644
--- a/llvm/test/Transforms/ConstraintElimination/and-implied-by-operands.ll
+++ b/llvm/test/Transforms/ConstraintElimination/and-implied-by-operands.ll
@@ -6,7 +6,7 @@ define i1 @test_second_and_condition_implied_by_first(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 [[C_1]], [[T_1]]
+; CHECK-NEXT: [[AND:%.*]] = and i1 [[C_1]], true
; CHECK-NEXT: br i1 [[AND]], label [[THEN:%.*]], label [[ELSE:%.*]]
; CHECK: then:
; CHECK-NEXT: ret i1 false
@@ -31,7 +31,7 @@ define i1 @test_second_and_condition_implied_by_first_select_form(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:%.*]] = select i1 [[C_1]], i1 [[T_1]], i1 false
+; CHECK-NEXT: [[AND:%.*]] = select i1 [[C_1]], i1 true, i1 false
; CHECK-NEXT: br i1 [[AND]], label [[THEN:%.*]], label [[ELSE:%.*]]
; CHECK: then:
; CHECK-NEXT: ret i1 false
@@ -55,7 +55,7 @@ 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]], [[C_1]]
+; CHECK-NEXT: [[AND:%.*]] = and i1 [[C_1]], true
; CHECK-NEXT: br i1 [[AND]], label [[THEN:%.*]], label [[ELSE:%.*]]
; CHECK: then:
; CHECK-NEXT: ret i1 false
@@ -78,7 +78,7 @@ 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 [[C_1]], i1 false
+; CHECK-NEXT: [[AND:%.*]] = select i1 [[C_1]], i1 true, i1 false
; CHECK-NEXT: br i1 [[AND]], label [[THEN:%.*]], label [[ELSE:%.*]]
; CHECK: then:
; CHECK-NEXT: ret i1 false
@@ -325,7 +325,7 @@ define i1 @test_and_used_in_false_branch(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 [[C_1]], [[T_1]]
+; CHECK-NEXT: [[AND:%.*]] = and i1 [[C_1]], true
; CHECK-NEXT: br i1 [[AND]], label [[THEN:%.*]], label [[ELSE:%.*]]
; CHECK: then:
; CHECK-NEXT: ret i1 true
diff --git a/llvm/test/Transforms/ConstraintElimination/and.ll b/llvm/test/Transforms/ConstraintElimination/and.ll
index 594c3b6dc0dff..91bd01c97ef97 100644
--- a/llvm/test/Transforms/ConstraintElimination/and.ll
+++ b/llvm/test/Transforms/ConstraintElimination/and.ll
@@ -459,7 +459,7 @@ 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 [[C_1]], i1 false
+; CHECK-NEXT: [[AND_1:%.*]] = select i1 [[C_1]], i1 true, 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:%.*]]
@@ -546,7 +546,7 @@ 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 [[C_1]], i1 false
+; CHECK-NEXT: [[AND_1:%.*]] = select i1 [[C_1]], i1 true, 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 653fe44bdcd63..436b77fff688b 100644
--- a/llvm/test/Transforms/ConstraintElimination/gep-arithmetic-signed-predicates.ll
+++ b/llvm/test/Transforms/ConstraintElimination/gep-arithmetic-signed-predicates.ll
@@ -616,7 +616,7 @@ 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]], [[STEP_SLT_N]]
+; CHECK-NEXT: [[AND_STEP:%.*]] = and i1 [[STEP_POS]], false
; 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 d8441a5424a45..4792383618784 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]], [[DST_5_UGE]]
+; CHECK-NEXT: [[AND:%.*]] = and i1 [[DST_5_UGE]], true
; 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]], [[DST_5_UGE]]
+; CHECK-NEXT: [[AND:%.*]] = and i1 [[DST_5_UGE]], true
; 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]], [[DST_5_UGE]]
+; CHECK-NEXT: [[AND:%.*]] = and i1 [[DST_5_UGE]], true
; CHECK-NEXT: br i1 [[AND]], label [[THEN:%.*]], label [[ELSE:%.*]]
; CHECK: then:
; CHECK-NEXT: [[DST_4:%.*]] = getelementptr i32, ptr [[DST]], i64 4
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