Add a comment noting that the fdiv -> fmul conversion won't generate
multiplication by a denormal, and some tests checking that.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@154431 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index b5b2028..ae7c941 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -5769,9 +5769,9 @@
APFloat N1APF = N1CFP->getValueAPF();
APFloat Recip(N1APF.getSemantics(), 1); // 1.0
APFloat::opStatus st = Recip.divide(N1APF, APFloat::rmNearestTiesToEven);
- // Only do the transform if the reciprocal is not too horrible (eg not NaN)
- // and the reciprocal is a legal fp imm.
- if ((st == APFloat::opOK || st == APFloat::opInexact) &&
+ // Only do the transform if the reciprocal is a legal fp immediate that
+ // isn't too nasty (eg NaN, denormal, ...).
+ if ((st == APFloat::opOK || st == APFloat::opInexact) && // Not too nasty
(!LegalOperations ||
// FIXME: custom lowering of ConstantFP might fail (see e.g. ARM
// backend)... we should handle this gracefully after Legalize.
diff --git a/test/CodeGen/X86/fdiv.ll b/test/CodeGen/X86/fdiv.ll
index 82b9190..0749682 100644
--- a/test/CodeGen/X86/fdiv.ll
+++ b/test/CodeGen/X86/fdiv.ll
@@ -23,3 +23,19 @@
%div = fdiv double %x, 0.0
ret double %div
}
+
+define double @denormal1(double %x) {
+; Don't generate multiplication by a denormal.
+; CHECK: @denormal1
+; CHECK: divsd
+ %div = fdiv double %x, 0x7FD0000000000001
+ ret double %div
+}
+
+define double @denormal2(double %x) {
+; Don't generate multiplication by a denormal.
+; CHECK: @denormal
+; CHECK: divsd
+ %div = fdiv double %x, 0x7FEFFFFFFFFFFFFF
+ ret double %div
+}