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[LVI] Infer non-zero from equality icmp (#112838)
This following pattern is common in loop headers: ``` %101 = sub nuw i64 %78, %98 %103 = icmp eq i64 %78, %98 br i1 %103, label %.thread.i.i, label %.preheader.preheader.i.i .preheader.preheader.i.i: %invariant.umin.i.i = call i64 @llvm.umin.i64(i64 %101, i64 9) %umax.i = call i64 @llvm.umax.i64(i64 %invariant.umin.i.i, i64 1) br label %.preheader.i.i .preheader.i.i: ... %116 = add nuw nsw i64 %.011.i.i, 1 %exitcond.not.i = icmp eq i64 %116, %umax.i br i1 %exitcond.not.i, label %.critedge.i.i, label %.preheader.i.i ``` As `%78` is not equal to `%98` in BB `.preheader.preheader.i.i`, we can prove `%101` is non-zero. Then we can simplify the loop exit condition. Addresses regression introduced by #112742.
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‎llvm/lib/Analysis/LazyValueInfo.cpp

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@@ -1188,6 +1188,20 @@ std::optional<ValueLatticeElement> LazyValueInfoImpl::getValueFromICmpCondition(
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return ValueLatticeElement::getRange(*CR);
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}
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// a - b or ptrtoint(a) - ptrtoint(b) ==/!= 0 if a ==/!= b
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Value *X, *Y;
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if (ICI->isEquality() && match(Val, m_Sub(m_Value(X), m_Value(Y)))) {
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// Peek through ptrtoints
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match(X, m_PtrToIntSameSize(DL, m_Value(X)));
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match(Y, m_PtrToIntSameSize(DL, m_Value(Y)));
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if ((X == LHS && Y == RHS) || (X == RHS && Y == LHS)) {
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Constant *NullVal = Constant::getNullValue(Val->getType());
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if (EdgePred == ICmpInst::ICMP_EQ)
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return ValueLatticeElement::get(NullVal);
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return ValueLatticeElement::getNot(NullVal);
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}
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}
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return ValueLatticeElement::getOverdefined();
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}
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‎llvm/test/Transforms/CorrelatedValuePropagation/umax.ll

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@@ -0,0 +1,168 @@
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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
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; RUN: opt < %s -passes=correlated-propagation -S | FileCheck %s
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target datalayout = "p:32:32"
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define i32 @infer_range_from_dom_equality(i32 %x, i32 %y) {
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; CHECK-LABEL: define range(i32 1, 0) i32 @infer_range_from_dom_equality(
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; CHECK-SAME: i32 [[X:%.*]], i32 [[Y:%.*]]) {
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; CHECK-NEXT: [[ENTRY:.*:]]
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; CHECK-NEXT: [[COND:%.*]] = icmp eq i32 [[X]], [[Y]]
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; CHECK-NEXT: [[SUB:%.*]] = sub i32 [[X]], [[Y]]
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; CHECK-NEXT: br i1 [[COND]], label %[[IF_THEN:.*]], label %[[IF_ELSE:.*]]
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; CHECK: [[IF_THEN]]:
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; CHECK-NEXT: ret i32 1
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; CHECK: [[IF_ELSE]]:
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; CHECK-NEXT: ret i32 [[SUB]]
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;
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entry:
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%cond = icmp eq i32 %x, %y
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%sub = sub i32 %x, %y
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br i1 %cond, label %if.then, label %if.else
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if.then:
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%max1 = call i32 @llvm.umax.i32(i32 %sub, i32 1)
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ret i32 %max1
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if.else:
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%max2 = call i32 @llvm.umax.i32(i32 %sub, i32 1)
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ret i32 %max2
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}
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define i32 @infer_range_from_dom_equality_commuted1(i32 %x, i32 %y) {
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; CHECK-LABEL: define range(i32 1, 0) i32 @infer_range_from_dom_equality_commuted1(
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; CHECK-SAME: i32 [[X:%.*]], i32 [[Y:%.*]]) {
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; CHECK-NEXT: [[ENTRY:.*:]]
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; CHECK-NEXT: [[COND:%.*]] = icmp eq i32 [[X]], [[Y]]
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; CHECK-NEXT: [[SUB:%.*]] = sub i32 [[Y]], [[X]]
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; CHECK-NEXT: br i1 [[COND]], label %[[IF_THEN:.*]], label %[[IF_ELSE:.*]]
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; CHECK: [[IF_THEN]]:
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; CHECK-NEXT: ret i32 1
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; CHECK: [[IF_ELSE]]:
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; CHECK-NEXT: ret i32 [[SUB]]
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;
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entry:
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%cond = icmp eq i32 %x, %y
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%sub = sub i32 %y, %x
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br i1 %cond, label %if.then, label %if.else
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if.then:
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%max1 = call i32 @llvm.umax.i32(i32 %sub, i32 1)
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ret i32 %max1
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if.else:
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%max2 = call i32 @llvm.umax.i32(i32 %sub, i32 1)
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ret i32 %max2
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}
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define i32 @infer_range_from_dom_equality_commuted2(i32 %x, i32 %y) {
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; CHECK-LABEL: define range(i32 1, 0) i32 @infer_range_from_dom_equality_commuted2(
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; CHECK-SAME: i32 [[X:%.*]], i32 [[Y:%.*]]) {
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; CHECK-NEXT: [[ENTRY:.*:]]
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; CHECK-NEXT: [[COND:%.*]] = icmp eq i32 [[Y]], [[X]]
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; CHECK-NEXT: [[SUB:%.*]] = sub i32 [[X]], [[Y]]
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; CHECK-NEXT: br i1 [[COND]], label %[[IF_THEN:.*]], label %[[IF_ELSE:.*]]
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; CHECK: [[IF_THEN]]:
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; CHECK-NEXT: ret i32 1
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; CHECK: [[IF_ELSE]]:
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; CHECK-NEXT: ret i32 [[SUB]]
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;
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entry:
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%cond = icmp eq i32 %y, %x
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%sub = sub i32 %x, %y
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br i1 %cond, label %if.then, label %if.else
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if.then:
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%max1 = call i32 @llvm.umax.i32(i32 %sub, i32 1)
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ret i32 %max1
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if.else:
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%max2 = call i32 @llvm.umax.i32(i32 %sub, i32 1)
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ret i32 %max2
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}
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define i32 @infer_range_from_dom_equality_ptrdiff(ptr %x, ptr %y) {
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; CHECK-LABEL: define range(i32 1, 0) i32 @infer_range_from_dom_equality_ptrdiff(
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; CHECK-SAME: ptr [[X:%.*]], ptr [[Y:%.*]]) {
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; CHECK-NEXT: [[COND:%.*]] = icmp eq ptr [[X]], [[Y]]
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; CHECK-NEXT: [[XI:%.*]] = ptrtoint ptr [[X]] to i32
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; CHECK-NEXT: [[YI:%.*]] = ptrtoint ptr [[Y]] to i32
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; CHECK-NEXT: [[SUB:%.*]] = sub i32 [[XI]], [[YI]]
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; CHECK-NEXT: br i1 [[COND]], label %[[IF_THEN:.*]], label %[[IF_ELSE:.*]]
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; CHECK: [[IF_THEN]]:
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; CHECK-NEXT: ret i32 1
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; CHECK: [[IF_ELSE]]:
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; CHECK-NEXT: ret i32 [[SUB]]
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;
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%cond = icmp eq ptr %x, %y
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%xi = ptrtoint ptr %x to i32
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%yi = ptrtoint ptr %y to i32
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%sub = sub i32 %xi, %yi
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br i1 %cond, label %if.then, label %if.else
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if.then:
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%max1 = call i32 @llvm.umax.i32(i32 %sub, i32 1)
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ret i32 %max1
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if.else:
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%max2 = call i32 @llvm.umax.i32(i32 %sub, i32 1)
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ret i32 %max2
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}
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; Negative tests
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define i32 @infer_range_from_dom_slt(i32 %x, i32 %y) {
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; CHECK-LABEL: define range(i32 1, 0) i32 @infer_range_from_dom_slt(
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; CHECK-SAME: i32 [[X:%.*]], i32 [[Y:%.*]]) {
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; CHECK-NEXT: [[ENTRY:.*:]]
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; CHECK-NEXT: [[COND:%.*]] = icmp slt i32 [[X]], [[Y]]
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; CHECK-NEXT: [[SUB:%.*]] = sub i32 [[X]], [[Y]]
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; CHECK-NEXT: br i1 [[COND]], label %[[IF_THEN:.*]], label %[[IF_ELSE:.*]]
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; CHECK: [[IF_THEN]]:
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; CHECK-NEXT: [[MAX1:%.*]] = call i32 @llvm.umax.i32(i32 [[SUB]], i32 1)
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; CHECK-NEXT: ret i32 [[MAX1]]
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; CHECK: [[IF_ELSE]]:
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; CHECK-NEXT: [[MAX2:%.*]] = call i32 @llvm.umax.i32(i32 [[SUB]], i32 1)
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; CHECK-NEXT: ret i32 [[MAX2]]
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;
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entry:
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%cond = icmp slt i32 %x, %y
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%sub = sub i32 %x, %y
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br i1 %cond, label %if.then, label %if.else
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if.then:
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%max1 = call i32 @llvm.umax.i32(i32 %sub, i32 1)
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ret i32 %max1
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if.else:
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%max2 = call i32 @llvm.umax.i32(i32 %sub, i32 1)
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ret i32 %max2
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}
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define i32 @infer_range_from_dom_equality_not_match(i32 %x, i32 %y, i32 %z) {
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; CHECK-LABEL: define range(i32 1, 0) i32 @infer_range_from_dom_equality_not_match(
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; CHECK-SAME: i32 [[X:%.*]], i32 [[Y:%.*]], i32 [[Z:%.*]]) {
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; CHECK-NEXT: [[ENTRY:.*:]]
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; CHECK-NEXT: [[COND:%.*]] = icmp eq i32 [[X]], [[Z]]
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; CHECK-NEXT: [[SUB:%.*]] = sub i32 [[X]], [[Y]]
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; CHECK-NEXT: br i1 [[COND]], label %[[IF_THEN:.*]], label %[[IF_ELSE:.*]]
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; CHECK: [[IF_THEN]]:
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; CHECK-NEXT: [[MAX1:%.*]] = call i32 @llvm.umax.i32(i32 [[SUB]], i32 1)
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; CHECK-NEXT: ret i32 [[MAX1]]
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; CHECK: [[IF_ELSE]]:
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; CHECK-NEXT: [[MAX2:%.*]] = call i32 @llvm.umax.i32(i32 [[SUB]], i32 1)
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; CHECK-NEXT: ret i32 [[MAX2]]
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;
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entry:
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%cond = icmp eq i32 %x, %z
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%sub = sub i32 %x, %y
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br i1 %cond, label %if.then, label %if.else
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if.then:
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%max1 = call i32 @llvm.umax.i32(i32 %sub, i32 1)
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ret i32 %max1
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if.else:
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%max2 = call i32 @llvm.umax.i32(i32 %sub, i32 1)
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ret i32 %max2
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}

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