[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
llvm-svn: 361858
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index d46ddc4..6400637 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -3992,8 +3992,10 @@
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;
}
diff --git a/llvm/lib/IR/ConstantRange.cpp b/llvm/lib/IR/ConstantRange.cpp
index 0d44c38..30b6a27 100644
--- a/llvm/lib/IR/ConstantRange.cpp
+++ b/llvm/lib/IR/ConstantRange.cpp
@@ -1208,9 +1208,9 @@
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 @@
// 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 @@
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 @@
// 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 @@
(void) Min.umul_ov(OtherMin, Overflow);
if (Overflow)
- return OverflowResult::AlwaysOverflows;
+ return OverflowResult::AlwaysOverflowsHigh;
(void) Max.umul_ov(OtherMax, Overflow);
if (Overflow)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index e2813f9..a18043e 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -2064,7 +2064,7 @@
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 @@
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;
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index ab2da17..b3eb75e 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -3993,7 +3993,8 @@
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();