  Understanding the physics of star formation is one of the key problems facing
modern astrophysics. The Cosmic Infrared Background (CIB), sourced by the
emission from all dusty star-forming galaxies since the epoch of reionisation,
is a complementary probe to study the star formation history, as well as an
important extragalactic foreground for studies of the Cosmic Microwave
Background (CMB). Understanding the physics of the CIB is therefore of high
importance for both cosmology and galaxy formation studies. In this paper, we
make high signal-to-noise measurements of the cross-correlation between maps of
the CIB from the Planck experiment, and cosmic shear measurements from the Dark
Energy Survey and Kilo-Degree Survey. Cosmic shear, sourced mainly by the weak
gravitational lensing of photons emitted by background galaxies, is a direct
tracer of the matter distribution, and thus we can use its cross-correlation
with the CIB to directly test our understanding of the link between the star
formation rate (SFR) density and the matter density. We use our measurements to
place constraints on a halo-based model of the SFR that parametrises the
efficiency with which gas is transformed into stars as a function of halo mass
and redshift. These constraints are enhanced by combining our data with
model-independent measurements of the bias-weighted SFR density extracted from
the tomographic cross-correlation of galaxies and the CIB. We are able to place
constraints on the peak efficiency at low redshifts,
$\eta=0.445^{+0.055}_{-0.11}$, and on the halo mass at which this peak
efficiency is achieved today $\log_{10}(M_1/M_\odot) = 12.17\pm0.25$. Our
constraints are in excellent agreement with direct measurements of the SFR
density, as well as other CIB-based studies.
