Stackplot fails for small numbers

[svaberg]

Bug report

Bug summary

It appears that stackplot fails for small numbers in version 3.2.1, or at least something goes wrong in my clean installation, see figures below.

Code for reproduction

import numpy as np
import matplotlib.pyplot as plt

x =  [0, 1]
y1 = 1e-8*np.ones_like(x)
y2 = 1e-9*np.ones_like(x)

fig, axs = plt.subplots(2, 1)
axs[0].stackplot(x, y1, y2)  # This plot is fine
axs[1].stackplot(x, y1/10, y2/10)  # This plot is wrong
plt.show()

Actual outcome

Something went wrong in the second subplot.

Expected outcome
Expected this, as generated with matplotlib version 3.1.2

Matplotlib version

• Operating system: macOS 10.12.6 (Sierra)
• Matplotlib version: 3.2.1
• Matplotlib backend (print(matplotlib.get_backend())): MacOSX
• Python version: 3.8.3

Created a conda environment with only thenumpy package, then installed matplotlib with pip.

[jklymak]

Bisects to 0911f8a, #13980 ping @anntzer