DCE math library calls with a constant operand.
On platforms which use -fmath-errno, math libcalls without any uses
require some extra checks to figure out if they are actually dead.
Fixes https://llvm.org/bugs/show_bug.cgi?id=30464 .
Differential Revision: https://reviews.llvm.org/D25970
llvm-svn: 285857
diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 1df724a..ec442ce 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -1967,3 +1967,152 @@
return ConstantFoldScalarCall(Name, F->getIntrinsicID(), Ty, Operands, TLI);
}
+
+bool llvm::isMathLibCallNoop(CallSite CS, const TargetLibraryInfo *TLI) {
+ // FIXME: Refactor this code; this duplicates logic in LibCallsShrinkWrap
+ // (and to some extent ConstantFoldScalarCall).
+ Function *F = CS.getCalledFunction();
+ if (!F)
+ return false;
+
+ LibFunc::Func Func;
+ if (!TLI || !TLI->getLibFunc(*F, Func))
+ return false;
+
+ if (CS.getNumArgOperands() == 1) {
+ if (ConstantFP *OpC = dyn_cast<ConstantFP>(CS.getArgOperand(0))) {
+ const APFloat &Op = OpC->getValueAPF();
+ switch (Func) {
+ case LibFunc::logl:
+ case LibFunc::log:
+ case LibFunc::logf:
+ case LibFunc::log2l:
+ case LibFunc::log2:
+ case LibFunc::log2f:
+ case LibFunc::log10l:
+ case LibFunc::log10:
+ case LibFunc::log10f:
+ return Op.isNaN() || (!Op.isZero() && !Op.isNegative());
+
+ case LibFunc::expl:
+ case LibFunc::exp:
+ case LibFunc::expf:
+ // FIXME: These boundaries are slightly conservative.
+ if (OpC->getType()->isDoubleTy())
+ return Op.compare(APFloat(-745.0)) != APFloat::cmpLessThan &&
+ Op.compare(APFloat(709.0)) != APFloat::cmpGreaterThan;
+ if (OpC->getType()->isFloatTy())
+ return Op.compare(APFloat(-103.0f)) != APFloat::cmpLessThan &&
+ Op.compare(APFloat(88.0f)) != APFloat::cmpGreaterThan;
+ break;
+
+ case LibFunc::exp2l:
+ case LibFunc::exp2:
+ case LibFunc::exp2f:
+ // FIXME: These boundaries are slightly conservative.
+ if (OpC->getType()->isDoubleTy())
+ return Op.compare(APFloat(-1074.0)) != APFloat::cmpLessThan &&
+ Op.compare(APFloat(1023.0)) != APFloat::cmpGreaterThan;
+ if (OpC->getType()->isFloatTy())
+ return Op.compare(APFloat(-149.0f)) != APFloat::cmpLessThan &&
+ Op.compare(APFloat(127.0f)) != APFloat::cmpGreaterThan;
+ break;
+
+ case LibFunc::sinl:
+ case LibFunc::sin:
+ case LibFunc::sinf:
+ case LibFunc::cosl:
+ case LibFunc::cos:
+ case LibFunc::cosf:
+ return !Op.isInfinity();
+
+ case LibFunc::tanl:
+ case LibFunc::tan:
+ case LibFunc::tanf: {
+ // FIXME: Stop using the host math library.
+ // FIXME: The computation isn't done in the right precision.
+ Type *Ty = OpC->getType();
+ if (Ty->isDoubleTy() || Ty->isFloatTy() || Ty->isHalfTy()) {
+ double OpV = getValueAsDouble(OpC);
+ return ConstantFoldFP(tan, OpV, Ty) != nullptr;
+ }
+ break;
+ }
+
+ case LibFunc::asinl:
+ case LibFunc::asin:
+ case LibFunc::asinf:
+ case LibFunc::acosl:
+ case LibFunc::acos:
+ case LibFunc::acosf:
+ return Op.compare(APFloat(Op.getSemantics(), "-1")) !=
+ APFloat::cmpLessThan &&
+ Op.compare(APFloat(Op.getSemantics(), "1")) !=
+ APFloat::cmpGreaterThan;
+
+ case LibFunc::sinh:
+ case LibFunc::cosh:
+ case LibFunc::sinhf:
+ case LibFunc::coshf:
+ case LibFunc::sinhl:
+ case LibFunc::coshl:
+ // FIXME: These boundaries are slightly conservative.
+ if (OpC->getType()->isDoubleTy())
+ return Op.compare(APFloat(-710.0)) != APFloat::cmpLessThan &&
+ Op.compare(APFloat(710.0)) != APFloat::cmpGreaterThan;
+ if (OpC->getType()->isFloatTy())
+ return Op.compare(APFloat(-89.0f)) != APFloat::cmpLessThan &&
+ Op.compare(APFloat(89.0f)) != APFloat::cmpGreaterThan;
+ break;
+
+ case LibFunc::sqrtl:
+ case LibFunc::sqrt:
+ case LibFunc::sqrtf:
+ return Op.isNaN() || Op.isZero() || !Op.isNegative();
+
+ // FIXME: Add more functions: sqrt_finite, atanh, expm1, log1p,
+ // maybe others?
+ default:
+ break;
+ }
+ }
+ }
+
+ if (CS.getNumArgOperands() == 2) {
+ ConstantFP *Op0C = dyn_cast<ConstantFP>(CS.getArgOperand(0));
+ ConstantFP *Op1C = dyn_cast<ConstantFP>(CS.getArgOperand(1));
+ if (Op0C && Op1C) {
+ const APFloat &Op0 = Op0C->getValueAPF();
+ const APFloat &Op1 = Op1C->getValueAPF();
+
+ switch (Func) {
+ case LibFunc::powl:
+ case LibFunc::pow:
+ case LibFunc::powf: {
+ // FIXME: Stop using the host math library.
+ // FIXME: The computation isn't done in the right precision.
+ Type *Ty = Op0C->getType();
+ if (Ty->isDoubleTy() || Ty->isFloatTy() || Ty->isHalfTy()) {
+ if (Ty == Op1C->getType()) {
+ double Op0V = getValueAsDouble(Op0C);
+ double Op1V = getValueAsDouble(Op1C);
+ return ConstantFoldBinaryFP(pow, Op0V, Op1V, Ty) != nullptr;
+ }
+ }
+ break;
+ }
+
+ case LibFunc::fmodl:
+ case LibFunc::fmod:
+ case LibFunc::fmodf:
+ return Op0.isNaN() || Op1.isNaN() ||
+ (!Op0.isInfinity() && !Op1.isZero());
+
+ default:
+ break;
+ }
+ }
+ }
+
+ return false;
+}