[llvm] r361858 - [ValueTracking][ConstantRange] Distinguish low/high always overflow
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Tue May 28 11:08:31 PDT 2019
Author: nikic
Date: Tue May 28 11:08:31 2019
New Revision: 361858
URL: http://llvm.org/viewvc/llvm-project?rev=361858&view=rev
Log:
[ValueTracking][ConstantRange] Distinguish low/high always overflow
In order to fold an always overflowing signed saturating add/sub,
we need to know in which direction the always overflow occurs.
This patch splits up AlwaysOverflows into AlwaysOverflowsLow and
AlwaysOverflowsHigh to pass through this information (but it is
not used yet).
Differential Revision: https://reviews.llvm.org/D62463
Modified:
llvm/trunk/include/llvm/Analysis/ValueTracking.h
llvm/trunk/include/llvm/IR/ConstantRange.h
llvm/trunk/lib/Analysis/ValueTracking.cpp
llvm/trunk/lib/IR/ConstantRange.cpp
llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
llvm/trunk/unittests/IR/ConstantRangeTest.cpp
Modified: llvm/trunk/include/llvm/Analysis/ValueTracking.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/ValueTracking.h?rev=361858&r1=361857&r2=361858&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Analysis/ValueTracking.h (original)
+++ llvm/trunk/include/llvm/Analysis/ValueTracking.h Tue May 28 11:08:31 2019
@@ -412,7 +412,16 @@ class Value;
bool isValidAssumeForContext(const Instruction *I, const Instruction *CxtI,
const DominatorTree *DT = nullptr);
- enum class OverflowResult { AlwaysOverflows, MayOverflow, NeverOverflows };
+ enum class OverflowResult {
+ /// Always overflows in the direction of signed/unsigned min value.
+ AlwaysOverflowsLow,
+ /// Always overflows in the direction of signed/unsigned max value.
+ AlwaysOverflowsHigh,
+ /// May or may not overflow.
+ MayOverflow,
+ /// Never overflows.
+ NeverOverflows,
+ };
OverflowResult computeOverflowForUnsignedMul(const Value *LHS,
const Value *RHS,
Modified: llvm/trunk/include/llvm/IR/ConstantRange.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/ConstantRange.h?rev=361858&r1=361857&r2=361858&view=diff
==============================================================================
--- llvm/trunk/include/llvm/IR/ConstantRange.h (original)
+++ llvm/trunk/include/llvm/IR/ConstantRange.h Tue May 28 11:08:31 2019
@@ -416,7 +416,16 @@ public:
/// Represents whether an operation on the given constant range is known to
/// always or never overflow.
- enum class OverflowResult { AlwaysOverflows, MayOverflow, NeverOverflows };
+ enum class OverflowResult {
+ /// Always overflows in the direction of signed/unsigned min value.
+ AlwaysOverflowsLow,
+ /// Always overflows in the direction of signed/unsigned max value.
+ AlwaysOverflowsHigh,
+ /// May or may not overflow.
+ MayOverflow,
+ /// Never overflows.
+ NeverOverflows,
+ };
/// Return whether unsigned add of the two ranges always/never overflows.
OverflowResult unsignedAddMayOverflow(const ConstantRange &Other) const;
Modified: llvm/trunk/lib/Analysis/ValueTracking.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ValueTracking.cpp?rev=361858&r1=361857&r2=361858&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ValueTracking.cpp (original)
+++ llvm/trunk/lib/Analysis/ValueTracking.cpp Tue May 28 11:08:31 2019
@@ -3992,8 +3992,10 @@ static OverflowResult mapOverflowResult(
switch (OR) {
case ConstantRange::OverflowResult::MayOverflow:
return OverflowResult::MayOverflow;
- case ConstantRange::OverflowResult::AlwaysOverflows:
- return OverflowResult::AlwaysOverflows;
+ case ConstantRange::OverflowResult::AlwaysOverflowsLow:
+ return OverflowResult::AlwaysOverflowsLow;
+ case ConstantRange::OverflowResult::AlwaysOverflowsHigh:
+ return OverflowResult::AlwaysOverflowsHigh;
case ConstantRange::OverflowResult::NeverOverflows:
return OverflowResult::NeverOverflows;
}
Modified: llvm/trunk/lib/IR/ConstantRange.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/ConstantRange.cpp?rev=361858&r1=361857&r2=361858&view=diff
==============================================================================
--- llvm/trunk/lib/IR/ConstantRange.cpp (original)
+++ llvm/trunk/lib/IR/ConstantRange.cpp Tue May 28 11:08:31 2019
@@ -1208,9 +1208,9 @@ ConstantRange::OverflowResult ConstantRa
APInt Min = getUnsignedMin(), Max = getUnsignedMax();
APInt OtherMin = Other.getUnsignedMin(), OtherMax = Other.getUnsignedMax();
- // a u+ b overflows iff a u> ~b.
+ // a u+ b overflows high iff a u> ~b.
if (Min.ugt(~OtherMin))
- return OverflowResult::AlwaysOverflows;
+ return OverflowResult::AlwaysOverflowsHigh;
if (Max.ugt(~OtherMax))
return OverflowResult::MayOverflow;
return OverflowResult::NeverOverflows;
@@ -1231,10 +1231,10 @@ ConstantRange::OverflowResult ConstantRa
// a s+ b overflows low iff a s< 0 && b s< 0 && a s< smin - b.
if (Min.isNonNegative() && OtherMin.isNonNegative() &&
Min.sgt(SignedMax - OtherMin))
- return OverflowResult::AlwaysOverflows;
+ return OverflowResult::AlwaysOverflowsHigh;
if (Max.isNegative() && OtherMax.isNegative() &&
Max.slt(SignedMin - OtherMax))
- return OverflowResult::AlwaysOverflows;
+ return OverflowResult::AlwaysOverflowsLow;
if (Max.isNonNegative() && OtherMax.isNonNegative() &&
Max.sgt(SignedMax - OtherMax))
@@ -1254,9 +1254,9 @@ ConstantRange::OverflowResult ConstantRa
APInt Min = getUnsignedMin(), Max = getUnsignedMax();
APInt OtherMin = Other.getUnsignedMin(), OtherMax = Other.getUnsignedMax();
- // a u- b overflows iff a u< b.
+ // a u- b overflows low iff a u< b.
if (Max.ult(OtherMin))
- return OverflowResult::AlwaysOverflows;
+ return OverflowResult::AlwaysOverflowsLow;
if (Min.ult(OtherMax))
return OverflowResult::MayOverflow;
return OverflowResult::NeverOverflows;
@@ -1277,10 +1277,10 @@ ConstantRange::OverflowResult ConstantRa
// a s- b overflows low iff a s< 0 && b s>= 0 && a s< smin + b.
if (Min.isNonNegative() && OtherMax.isNegative() &&
Min.sgt(SignedMax + OtherMax))
- return OverflowResult::AlwaysOverflows;
+ return OverflowResult::AlwaysOverflowsHigh;
if (Max.isNegative() && OtherMin.isNonNegative() &&
Max.slt(SignedMin + OtherMin))
- return OverflowResult::AlwaysOverflows;
+ return OverflowResult::AlwaysOverflowsLow;
if (Max.isNonNegative() && OtherMin.isNegative() &&
Max.sgt(SignedMax + OtherMin))
@@ -1303,7 +1303,7 @@ ConstantRange::OverflowResult ConstantRa
(void) Min.umul_ov(OtherMin, Overflow);
if (Overflow)
- return OverflowResult::AlwaysOverflows;
+ return OverflowResult::AlwaysOverflowsHigh;
(void) Max.umul_ov(OtherMax, Overflow);
if (Overflow)
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp?rev=361858&r1=361857&r2=361858&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp Tue May 28 11:08:31 2019
@@ -2064,7 +2064,7 @@ Instruction *InstCombiner::visitCallInst
OR = computeOverflowForUnsignedAdd(Arg0, Arg1, II);
if (OR == OverflowResult::NeverOverflows)
return BinaryOperator::CreateNUWAdd(Arg0, Arg1);
- if (OR == OverflowResult::AlwaysOverflows)
+ if (OR == OverflowResult::AlwaysOverflowsHigh)
return replaceInstUsesWith(*II,
ConstantInt::getAllOnesValue(II->getType()));
break;
@@ -2072,7 +2072,7 @@ Instruction *InstCombiner::visitCallInst
OR = computeOverflowForUnsignedSub(Arg0, Arg1, II);
if (OR == OverflowResult::NeverOverflows)
return BinaryOperator::CreateNUWSub(Arg0, Arg1);
- if (OR == OverflowResult::AlwaysOverflows)
+ if (OR == OverflowResult::AlwaysOverflowsLow)
return replaceInstUsesWith(*II,
ConstantInt::getNullValue(II->getType()));
break;
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp?rev=361858&r1=361857&r2=361858&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp Tue May 28 11:08:31 2019
@@ -3993,7 +3993,8 @@ bool InstCombiner::OptimizeOverflowCheck
switch (computeOverflow(BinaryOp, IsSigned, LHS, RHS, &OrigI)) {
case OverflowResult::MayOverflow:
return false;
- case OverflowResult::AlwaysOverflows:
+ case OverflowResult::AlwaysOverflowsLow:
+ case OverflowResult::AlwaysOverflowsHigh:
Result = Builder.CreateBinOp(BinaryOp, LHS, RHS);
Result->takeName(&OrigI);
Overflow = Builder.getTrue();
Modified: llvm/trunk/unittests/IR/ConstantRangeTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/IR/ConstantRangeTest.cpp?rev=361858&r1=361857&r2=361858&view=diff
==============================================================================
--- llvm/trunk/unittests/IR/ConstantRangeTest.cpp (original)
+++ llvm/trunk/unittests/IR/ConstantRangeTest.cpp Tue May 28 11:08:31 2019
@@ -1487,8 +1487,10 @@ TEST(ConstantRange, MakeGuaranteedNoWrap
#define EXPECT_MAY_OVERFLOW(op) \
EXPECT_EQ(ConstantRange::OverflowResult::MayOverflow, (op))
-#define EXPECT_ALWAYS_OVERFLOWS(op) \
- EXPECT_EQ(ConstantRange::OverflowResult::AlwaysOverflows, (op))
+#define EXPECT_ALWAYS_OVERFLOWS_LOW(op) \
+ EXPECT_EQ(ConstantRange::OverflowResult::AlwaysOverflowsLow, (op))
+#define EXPECT_ALWAYS_OVERFLOWS_HIGH(op) \
+ EXPECT_EQ(ConstantRange::OverflowResult::AlwaysOverflowsHigh, (op))
#define EXPECT_NEVER_OVERFLOWS(op) \
EXPECT_EQ(ConstantRange::OverflowResult::NeverOverflows, (op))
@@ -1521,9 +1523,9 @@ TEST_F(ConstantRangeTest, UnsignedAddOve
ConstantRange C1(APInt(16, 0x0299), APInt(16, 0x0400));
ConstantRange C2(APInt(16, 0x0300), APInt(16, 0x0400));
EXPECT_MAY_OVERFLOW(A.unsignedAddMayOverflow(C1));
- EXPECT_ALWAYS_OVERFLOWS(A.unsignedAddMayOverflow(C2));
+ EXPECT_ALWAYS_OVERFLOWS_HIGH(A.unsignedAddMayOverflow(C2));
EXPECT_MAY_OVERFLOW(C1.unsignedAddMayOverflow(A));
- EXPECT_ALWAYS_OVERFLOWS(C2.unsignedAddMayOverflow(A));
+ EXPECT_ALWAYS_OVERFLOWS_HIGH(C2.unsignedAddMayOverflow(A));
}
TEST_F(ConstantRangeTest, UnsignedSubOverflow) {
@@ -1548,7 +1550,7 @@ TEST_F(ConstantRangeTest, UnsignedSubOve
ConstantRange A(APInt(16, 0x0000), APInt(16, 0x0100));
ConstantRange B(APInt(16, 0x0100), APInt(16, 0x0200));
EXPECT_NEVER_OVERFLOWS(B.unsignedSubMayOverflow(A));
- EXPECT_ALWAYS_OVERFLOWS(A.unsignedSubMayOverflow(B));
+ EXPECT_ALWAYS_OVERFLOWS_LOW(A.unsignedSubMayOverflow(B));
ConstantRange A1(APInt(16, 0x0000), APInt(16, 0x0101));
ConstantRange B1(APInt(16, 0x0100), APInt(16, 0x0201));
@@ -1591,7 +1593,7 @@ TEST_F(ConstantRangeTest, SignedAddOverf
ConstantRange B5(APInt(16, 0x0299), APInt(16, 0x0400));
ConstantRange B6(APInt(16, 0x0300), APInt(16, 0x0400));
EXPECT_MAY_OVERFLOW(A.signedAddMayOverflow(B5));
- EXPECT_ALWAYS_OVERFLOWS(A.signedAddMayOverflow(B6));
+ EXPECT_ALWAYS_OVERFLOWS_HIGH(A.signedAddMayOverflow(B6));
ConstantRange C(APInt(16, 0x8200), APInt(16, 0x8300));
ConstantRange D1(APInt(16, 0xfe00), APInt(16, 0xff00));
@@ -1605,7 +1607,7 @@ TEST_F(ConstantRangeTest, SignedAddOverf
ConstantRange D5(APInt(16, 0xfc00), APInt(16, 0xfd02));
ConstantRange D6(APInt(16, 0xfc00), APInt(16, 0xfd01));
EXPECT_MAY_OVERFLOW(C.signedAddMayOverflow(D5));
- EXPECT_ALWAYS_OVERFLOWS(C.signedAddMayOverflow(D6));
+ EXPECT_ALWAYS_OVERFLOWS_LOW(C.signedAddMayOverflow(D6));
ConstantRange E(APInt(16, 0xff00), APInt(16, 0x0100));
EXPECT_NEVER_OVERFLOWS(E.signedAddMayOverflow(E));
@@ -1637,7 +1639,7 @@ TEST_F(ConstantRangeTest, SignedSubOverf
ConstantRange B3(APInt(16, 0xfc00), APInt(16, 0xfd02));
ConstantRange B4(APInt(16, 0xfc00), APInt(16, 0xfd01));
EXPECT_MAY_OVERFLOW(A.signedSubMayOverflow(B3));
- EXPECT_ALWAYS_OVERFLOWS(A.signedSubMayOverflow(B4));
+ EXPECT_ALWAYS_OVERFLOWS_HIGH(A.signedSubMayOverflow(B4));
ConstantRange C(APInt(16, 0x8200), APInt(16, 0x8300));
ConstantRange D1(APInt(16, 0x0100), APInt(16, 0x0201));
@@ -1647,7 +1649,7 @@ TEST_F(ConstantRangeTest, SignedSubOverf
ConstantRange D3(APInt(16, 0x0299), APInt(16, 0x0400));
ConstantRange D4(APInt(16, 0x0300), APInt(16, 0x0400));
EXPECT_MAY_OVERFLOW(C.signedSubMayOverflow(D3));
- EXPECT_ALWAYS_OVERFLOWS(C.signedSubMayOverflow(D4));
+ EXPECT_ALWAYS_OVERFLOWS_LOW(C.signedSubMayOverflow(D4));
ConstantRange E(APInt(16, 0xff00), APInt(16, 0x0100));
EXPECT_NEVER_OVERFLOWS(E.signedSubMayOverflow(E));
@@ -1663,25 +1665,39 @@ static void TestOverflowExhaustive(Fn1 O
const ConstantRange &CR2) {
// Loop over all N1 in CR1 and N2 in CR2 and check whether any of the
// operations have overflow / have no overflow.
- bool RangeHasOverflow = false;
+ bool RangeHasOverflowLow = false;
+ bool RangeHasOverflowHigh = false;
bool RangeHasNoOverflow = false;
ForeachNumInConstantRange(CR1, [&](const APInt &N1) {
ForeachNumInConstantRange(CR2, [&](const APInt &N2) {
- if (OverflowFn(N1, N2))
- RangeHasOverflow = true;
- else
+ bool IsOverflowHigh;
+ if (!OverflowFn(IsOverflowHigh, N1, N2)) {
RangeHasNoOverflow = true;
+ return;
+ }
+
+ if (IsOverflowHigh)
+ RangeHasOverflowHigh = true;
+ else
+ RangeHasOverflowLow = true;
});
});
ConstantRange::OverflowResult OR = MayOverflowFn(CR1, CR2);
switch (OR) {
- case ConstantRange::OverflowResult::AlwaysOverflows:
- EXPECT_TRUE(RangeHasOverflow);
+ case ConstantRange::OverflowResult::AlwaysOverflowsLow:
+ EXPECT_TRUE(RangeHasOverflowLow);
+ EXPECT_FALSE(RangeHasOverflowHigh);
+ EXPECT_FALSE(RangeHasNoOverflow);
+ break;
+ case ConstantRange::OverflowResult::AlwaysOverflowsHigh:
+ EXPECT_TRUE(RangeHasOverflowHigh);
+ EXPECT_FALSE(RangeHasOverflowLow);
EXPECT_FALSE(RangeHasNoOverflow);
break;
case ConstantRange::OverflowResult::NeverOverflows:
- EXPECT_FALSE(RangeHasOverflow);
+ EXPECT_FALSE(RangeHasOverflowLow);
+ EXPECT_FALSE(RangeHasOverflowHigh);
EXPECT_TRUE(RangeHasNoOverflow);
break;
case ConstantRange::OverflowResult::MayOverflow:
@@ -1691,7 +1707,7 @@ static void TestOverflowExhaustive(Fn1 O
if (CR1.isEmptySet() || CR2.isEmptySet())
break;
- EXPECT_TRUE(RangeHasOverflow);
+ EXPECT_TRUE(RangeHasOverflowLow || RangeHasOverflowHigh);
EXPECT_TRUE(RangeHasNoOverflow);
break;
}
@@ -1700,9 +1716,10 @@ static void TestOverflowExhaustive(Fn1 O
TEST_F(ConstantRangeTest, UnsignedAddOverflowExhaustive) {
TestOverflowExhaustive(
- [](const APInt &N1, const APInt &N2) {
+ [](bool &IsOverflowHigh, const APInt &N1, const APInt &N2) {
bool Overflow;
(void) N1.uadd_ov(N2, Overflow);
+ IsOverflowHigh = true;
return Overflow;
},
[](const ConstantRange &CR1, const ConstantRange &CR2) {
@@ -1712,9 +1729,10 @@ TEST_F(ConstantRangeTest, UnsignedAddOve
TEST_F(ConstantRangeTest, UnsignedSubOverflowExhaustive) {
TestOverflowExhaustive(
- [](const APInt &N1, const APInt &N2) {
+ [](bool &IsOverflowHigh, const APInt &N1, const APInt &N2) {
bool Overflow;
(void) N1.usub_ov(N2, Overflow);
+ IsOverflowHigh = false;
return Overflow;
},
[](const ConstantRange &CR1, const ConstantRange &CR2) {
@@ -1724,9 +1742,10 @@ TEST_F(ConstantRangeTest, UnsignedSubOve
TEST_F(ConstantRangeTest, UnsignedMulOverflowExhaustive) {
TestOverflowExhaustive(
- [](const APInt &N1, const APInt &N2) {
+ [](bool &IsOverflowHigh, const APInt &N1, const APInt &N2) {
bool Overflow;
(void) N1.umul_ov(N2, Overflow);
+ IsOverflowHigh = true;
return Overflow;
},
[](const ConstantRange &CR1, const ConstantRange &CR2) {
@@ -1736,9 +1755,10 @@ TEST_F(ConstantRangeTest, UnsignedMulOve
TEST_F(ConstantRangeTest, SignedAddOverflowExhaustive) {
TestOverflowExhaustive(
- [](const APInt &N1, const APInt &N2) {
+ [](bool &IsOverflowHigh, const APInt &N1, const APInt &N2) {
bool Overflow;
(void) N1.sadd_ov(N2, Overflow);
+ IsOverflowHigh = N1.isNonNegative();
return Overflow;
},
[](const ConstantRange &CR1, const ConstantRange &CR2) {
@@ -1748,9 +1768,10 @@ TEST_F(ConstantRangeTest, SignedAddOverf
TEST_F(ConstantRangeTest, SignedSubOverflowExhaustive) {
TestOverflowExhaustive(
- [](const APInt &N1, const APInt &N2) {
+ [](bool &IsOverflowHigh, const APInt &N1, const APInt &N2) {
bool Overflow;
(void) N1.ssub_ov(N2, Overflow);
+ IsOverflowHigh = N1.isNonNegative();
return Overflow;
},
[](const ConstantRange &CR1, const ConstantRange &CR2) {
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