Some platforms may treat denormals as zero, on other platforms multiplication
with a subnormal is slower than dividing by a normal.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128555
91177308-0d34-0410-b5e6-
96231b3b80d8
if (reciprocal.divide(*this, rmNearestTiesToEven) != opOK)
return false;
+ // Avoid multiplication with a denormal, it is not safe on all platforms and
+ // may be slower than a normal division.
+ if (reciprocal.significandMSB() + 1 < reciprocal.semantics->precision)
+ return false;
+
+ assert(reciprocal.category == fcNormal &&
+ reciprocal.significandLSB() == reciprocal.semantics->precision - 1);
+
if (inv)
*inv = reciprocal;
ret float %div
; CHECK: @test2
-; CHECK-NEXT: fmul float %x, 0x3800000000000000
+; CHECK-NEXT: fdiv float %x, 0x47E0000000000000
}
define float @test3(float %x) nounwind readnone ssp {
EXPECT_TRUE(APFloat(1.17549435e-38f).getExactInverse(&inv));
EXPECT_TRUE(inv.bitwiseIsEqual(APFloat(8.5070592e+37f)));
- // Large float
- EXPECT_TRUE(APFloat(1.7014118e38f).getExactInverse(&inv));
- EXPECT_TRUE(inv.bitwiseIsEqual(APFloat(5.8774718e-39f)));
-
+ // Large float, inverse is a denormal.
+ EXPECT_FALSE(APFloat(1.7014118e38f).getExactInverse(0));
// Zero
EXPECT_FALSE(APFloat(0.0).getExactInverse(0));
// Denormalized float