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[ValueTracking] Let isGuaranteedNotToBeUndefOrPoison use canCreateUnd…
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…efOrPoison
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@nikic
nikic committed Jul 19, 2020
1 parent ef66e3d commit 081c255
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Showing 6 changed files with 49 additions and 61 deletions.
3 changes: 2 additions & 1 deletion llvm/include/llvm/Analysis/ValueTracking.h
View file
Expand Up @@ -607,7 +607,8 @@ class Value;
bool canCreatePoison(const Operator *Op);

/// Return true if this function can prove that V is never undef value
/// or poison value.
/// or poison value. If V is an aggregate value or vector, check whether all
/// elements (except padding) are not undef or poison.
/// Note that this is different from canCreateUndefOrPoison because the
/// function assumes Op's operands are not poison/undef.
///
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55 changes: 18 additions & 37 deletions llvm/lib/Analysis/ValueTracking.cpp
View file
Expand Up @@ -4779,23 +4779,13 @@ bool llvm::isGuaranteedNotToBeUndefOrPoison(const Value *V,
if (Depth >= MaxDepth)
return false;

// If the value is a freeze instruction, then it can never
// be undef or poison.
if (isa<FreezeInst>(V))
return true;
// TODO: Some instructions are guaranteed to return neither undef
// nor poison if their arguments are not poison/undef.

if (auto *A = dyn_cast<Argument>(V)) {
// NoUndef does not guarantee that paddings are not undef.
if (const auto *A = dyn_cast<Argument>(V)) {
if (A->hasAttribute(Attribute::NoUndef))
return true;
}

if (auto *C = dyn_cast<Constant>(V)) {
// TODO: We can analyze ConstExpr by opcode to determine if there is any
// possibility of poison.
if (isa<UndefValue>(C) || isa<ConstantExpr>(C))
if (isa<UndefValue>(C))
return false;

if (isa<ConstantInt>(C) || isa<GlobalVariable>(C) || isa<ConstantFP>(V) ||
Expand All @@ -4804,9 +4794,6 @@ bool llvm::isGuaranteedNotToBeUndefOrPoison(const Value *V,

if (C->getType()->isVectorTy())
return !C->containsUndefElement() && !C->containsConstantExpression();

// TODO: Recursively analyze aggregates or other constants.
return false;
}

// Strip cast operations from a pointer value.
Expand All @@ -4826,31 +4813,25 @@ bool llvm::isGuaranteedNotToBeUndefOrPoison(const Value *V,
return isGuaranteedNotToBeUndefOrPoison(V, CtxI, DT, Depth + 1);
};

if (auto *I = dyn_cast<Instruction>(V)) {
switch (I->getOpcode()) {
case Instruction::GetElementPtr: {
auto *GEPI = dyn_cast<GetElementPtrInst>(I);
if (!GEPI->isInBounds() && llvm::all_of(GEPI->operands(), OpCheck))
return true;
break;
}
case Instruction::FCmp: {
auto *FI = dyn_cast<FCmpInst>(I);
if (FI->getFastMathFlags().none() &&
llvm::all_of(FI->operands(), OpCheck))
return true;
break;
}
case Instruction::BitCast:
case Instruction::PHI:
case Instruction::ICmp:
if (llvm::all_of(I->operands(), OpCheck))
if (auto *Opr = dyn_cast<Operator>(V)) {
// If the value is a freeze instruction, then it can never
// be undef or poison.
if (isa<FreezeInst>(V))
return true;

if (const auto *CB = dyn_cast<CallBase>(V)) {
if (CB->hasRetAttr(Attribute::NoUndef))
return true;
break;
default:
break;
}

if (canCreateUndefOrPoison(Opr))
return false;

if (all_of(Opr->operands(), OpCheck))
return true;
}

if (auto *I = dyn_cast<Instruction>(V)) {
if (programUndefinedIfPoison(I) && I->getType()->isIntegerTy(1))
// Note: once we have an agreement that poison is a value-wise concept,
// we can remove the isIntegerTy(1) constraint.
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5 changes: 2 additions & 3 deletions llvm/test/Transforms/DivRemPairs/PowerPC/div-expanded-rem-pair.ll
View file
Expand Up @@ -106,12 +106,11 @@ define i32 @srem_of_srem_unexpanded(i32 %X, i32 %Y, i32 %Z) {
; CHECK-NEXT: [[T2:%.*]] = mul nsw i32 [[T0]], [[T1]]
; CHECK-NEXT: [[TMP1:%.*]] = mul i32 [[T1]], [[T0_FROZEN]]
; CHECK-NEXT: [[T3_DECOMPOSED:%.*]] = sub i32 [[X_FROZEN]], [[TMP1]]
; CHECK-NEXT: [[T3_DECOMPOSED_FROZEN:%.*]] = freeze i32 [[T3_DECOMPOSED]]
; CHECK-NEXT: [[Y_FROZEN:%.*]] = freeze i32 [[Y]]
; CHECK-NEXT: [[T4:%.*]] = sdiv i32 [[T3_DECOMPOSED_FROZEN]], [[Y_FROZEN]]
; CHECK-NEXT: [[T4:%.*]] = sdiv i32 [[T3_DECOMPOSED]], [[Y_FROZEN]]
; CHECK-NEXT: [[T5:%.*]] = mul nsw i32 [[T4]], [[Y]]
; CHECK-NEXT: [[TMP2:%.*]] = mul i32 [[T4]], [[Y_FROZEN]]
; CHECK-NEXT: [[T6_DECOMPOSED:%.*]] = sub i32 [[T3_DECOMPOSED_FROZEN]], [[TMP2]]
; CHECK-NEXT: [[T6_DECOMPOSED:%.*]] = sub i32 [[T3_DECOMPOSED]], [[TMP2]]
; CHECK-NEXT: ret i32 [[T6_DECOMPOSED]]
;
%t0 = mul nsw i32 %Z, %Y
Expand Down
5 changes: 2 additions & 3 deletions llvm/test/Transforms/DivRemPairs/PowerPC/div-rem-pairs.ll
View file
Expand Up @@ -175,12 +175,11 @@ define i32 @srem_of_srem_unexpanded(i32 %X, i32 %Y, i32 %Z) {
; CHECK-NEXT: [[T2:%.*]] = mul nsw i32 [[T0]], [[T1]]
; CHECK-NEXT: [[TMP1:%.*]] = mul i32 [[T1]], [[T0_FROZEN]]
; CHECK-NEXT: [[T3_DECOMPOSED:%.*]] = sub i32 [[X_FROZEN]], [[TMP1]]
; CHECK-NEXT: [[T3_DECOMPOSED_FROZEN:%.*]] = freeze i32 [[T3_DECOMPOSED]]
; CHECK-NEXT: [[Y_FROZEN:%.*]] = freeze i32 [[Y]]
; CHECK-NEXT: [[T4:%.*]] = sdiv i32 [[T3_DECOMPOSED_FROZEN]], [[Y_FROZEN]]
; CHECK-NEXT: [[T4:%.*]] = sdiv i32 [[T3_DECOMPOSED]], [[Y_FROZEN]]
; CHECK-NEXT: [[T5:%.*]] = mul nsw i32 [[T4]], [[Y]]
; CHECK-NEXT: [[TMP2:%.*]] = mul i32 [[T4]], [[Y_FROZEN]]
; CHECK-NEXT: [[T6_DECOMPOSED:%.*]] = sub i32 [[T3_DECOMPOSED_FROZEN]], [[TMP2]]
; CHECK-NEXT: [[T6_DECOMPOSED:%.*]] = sub i32 [[T3_DECOMPOSED]], [[TMP2]]
; CHECK-NEXT: ret i32 [[T6_DECOMPOSED]]
;
%t0 = mul nsw i32 %Z, %Y
Expand Down
15 changes: 4 additions & 11 deletions llvm/test/Transforms/InstSimplify/freeze-noundef.ll
View file
Expand Up @@ -19,12 +19,10 @@ define i1 @icmp(i8 noundef %x, i8 noundef %y) {
ret i1 %f
}

; TODO: should look into binary operations
define i1 @or(i1 noundef %x, i1 noundef %x2) {
; CHECK-LABEL: @or(
; CHECK-NEXT: [[Y:%.*]] = or i1 [[X:%.*]], [[X2:%.*]]
; CHECK-NEXT: [[Z:%.*]] = freeze i1 [[Y]]
; CHECK-NEXT: ret i1 [[Z]]
; CHECK-NEXT: ret i1 [[Y]]
;
%y = or i1 %x, %x2
%z = freeze i1 %y
Expand All @@ -42,12 +40,10 @@ define i1 @or2(i1 noundef %x, i1 %x2) {
ret i1 %z
}

; TODO: should look into binary operations
define i8 @add(i8 noundef %x) {
; CHECK-LABEL: @add(
; CHECK-NEXT: [[Y:%.*]] = add i8 [[X:%.*]], 1
; CHECK-NEXT: [[Z:%.*]] = freeze i8 [[Y]]
; CHECK-NEXT: ret i8 [[Z]]
; CHECK-NEXT: ret i8 [[Y]]
;
%y = add i8 %x, 1
%z = freeze i8 %y
Expand Down Expand Up @@ -77,21 +73,18 @@ define {i8, i32} @aggr({i8, i32} noundef %x) {
define i32 @extract({i8, i32} noundef %x) {
; CHECK-LABEL: @extract(
; CHECK-NEXT: [[Y:%.*]] = extractvalue { i8, i32 } [[X:%.*]], 1
; CHECK-NEXT: [[Z:%.*]] = freeze i32 [[Y]]
; CHECK-NEXT: ret i32 [[Z]]
; CHECK-NEXT: ret i32 [[Y]]
;
%y = extractvalue {i8, i32} %x, 1
%z = freeze i32 %y
ret i32 %z
}

; TODO: should look into extract operations
define i32 @extract2({i8, {i8, i32}} noundef %x) {
; CHECK-LABEL: @extract2(
; CHECK-NEXT: [[Y:%.*]] = extractvalue { i8, { i8, i32 } } [[X:%.*]], 1
; CHECK-NEXT: [[Z:%.*]] = extractvalue { i8, i32 } [[Y]], 1
; CHECK-NEXT: [[W:%.*]] = freeze i32 [[Z]]
; CHECK-NEXT: ret i32 [[W]]
; CHECK-NEXT: ret i32 [[Z]]
;
%y = extractvalue {i8, {i8, i32}} %x, 1
%z = extractvalue {i8, i32} %y, 1
Expand Down
27 changes: 21 additions & 6 deletions llvm/test/Transforms/InstSimplify/freeze.ll
View file
Expand Up @@ -116,13 +116,28 @@ define <2 x float> @constvector_FP_noopt() {

define float @constant_expr() {
; CHECK-LABEL: @constant_expr(
; CHECK-NEXT: [[R:%.*]] = freeze float bitcast (i32 ptrtoint (i16* @g to i32) to float)
; CHECK-NEXT: ret float [[R]]
; CHECK-NEXT: ret float bitcast (i32 ptrtoint (i16* @g to i32) to float)
;
%r = freeze float bitcast (i32 ptrtoint (i16* @g to i32) to float)
ret float %r
}

define i8* @constant_expr2() {
; CHECK-LABEL: @constant_expr2(
; CHECK-NEXT: ret i8* bitcast (i16* @g to i8*)
;
%r = freeze i8* bitcast (i16* @g to i8*)
ret i8* %r
}

define i32* @constant_expr3() {
; CHECK-LABEL: @constant_expr3(
; CHECK-NEXT: ret i32* getelementptr (i32, i32* @glb, i64 3)
;
%r = freeze i32* getelementptr (i32, i32* @glb, i64 3)
ret i32* %r
}

; Negative test

define <2 x i31> @vector_element_constant_expr() {
Expand All @@ -136,7 +151,7 @@ define <2 x i31> @vector_element_constant_expr() {

define void @alloca() {
; CHECK-LABEL: @alloca(
; CHECK-NEXT: [[P:%.*]] = alloca i8
; CHECK-NEXT: [[P:%.*]] = alloca i8, align 1
; CHECK-NEXT: call void @f3(i8* [[P]])
; CHECK-NEXT: ret void
;
Expand All @@ -148,7 +163,7 @@ define void @alloca() {

define i8* @gep() {
; CHECK-LABEL: @gep(
; CHECK-NEXT: [[P:%.*]] = alloca [4 x i8]
; CHECK-NEXT: [[P:%.*]] = alloca [4 x i8], align 1
; CHECK-NEXT: [[Q:%.*]] = getelementptr [4 x i8], [4 x i8]* [[P]], i32 0, i32 6
; CHECK-NEXT: ret i8* [[Q]]
;
Expand All @@ -171,7 +186,7 @@ define i8* @gep_noopt(i32 %arg) {

define i8* @gep_inbounds() {
; CHECK-LABEL: @gep_inbounds(
; CHECK-NEXT: [[P:%.*]] = alloca [4 x i8]
; CHECK-NEXT: [[P:%.*]] = alloca [4 x i8], align 1
; CHECK-NEXT: [[Q:%.*]] = getelementptr inbounds [4 x i8], [4 x i8]* [[P]], i32 0, i32 0
; CHECK-NEXT: ret i8* [[Q]]
;
Expand All @@ -183,7 +198,7 @@ define i8* @gep_inbounds() {

define i8* @gep_inbounds_noopt(i32 %arg) {
; CHECK-LABEL: @gep_inbounds_noopt(
; CHECK-NEXT: [[P:%.*]] = alloca [4 x i8]
; CHECK-NEXT: [[P:%.*]] = alloca [4 x i8], align 1
; CHECK-NEXT: [[Q:%.*]] = getelementptr inbounds [4 x i8], [4 x i8]* [[P]], i32 0, i32 [[ARG:%.*]]
; CHECK-NEXT: [[Q2:%.*]] = freeze i8* [[Q]]
; CHECK-NEXT: ret i8* [[Q2]]
Expand Down

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