ScalarEvolution: HowFarToZero was wrongly using signed division
HowFarToZero was supposed to use unsigned division in order to calculate
the backedge taken count. However, SCEVDivision::divide performs signed
division. Unless I am mistaken, no users of SCEVDivision actually want
signed arithmetic: switch to udiv and urem.
This fixes PR21578.
llvm-svn: 222093
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 55472ec..2026f8a 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -675,32 +675,32 @@
}
}
-static const APInt srem(const SCEVConstant *C1, const SCEVConstant *C2) {
+static const APInt urem(const SCEVConstant *C1, const SCEVConstant *C2) {
APInt A = C1->getValue()->getValue();
APInt B = C2->getValue()->getValue();
uint32_t ABW = A.getBitWidth();
uint32_t BBW = B.getBitWidth();
if (ABW > BBW)
- B = B.sext(ABW);
+ B = B.zext(ABW);
else if (ABW < BBW)
- A = A.sext(BBW);
+ A = A.zext(BBW);
- return APIntOps::srem(A, B);
+ return APIntOps::urem(A, B);
}
-static const APInt sdiv(const SCEVConstant *C1, const SCEVConstant *C2) {
+static const APInt udiv(const SCEVConstant *C1, const SCEVConstant *C2) {
APInt A = C1->getValue()->getValue();
APInt B = C2->getValue()->getValue();
uint32_t ABW = A.getBitWidth();
uint32_t BBW = B.getBitWidth();
if (ABW > BBW)
- B = B.sext(ABW);
+ B = B.zext(ABW);
else if (ABW < BBW)
- A = A.sext(BBW);
+ A = A.zext(BBW);
- return APIntOps::sdiv(A, B);
+ return APIntOps::udiv(A, B);
}
namespace {
@@ -803,8 +803,8 @@
void visitConstant(const SCEVConstant *Numerator) {
if (const SCEVConstant *D = dyn_cast<SCEVConstant>(Denominator)) {
- Quotient = SE.getConstant(sdiv(Numerator, D));
- Remainder = SE.getConstant(srem(Numerator, D));
+ Quotient = SE.getConstant(udiv(Numerator, D));
+ Remainder = SE.getConstant(urem(Numerator, D));
return;
}
}