We study the core mass function ( CMF ) within 32 dense clumps in seven infrared dark clouds ( IRDCs ) with the Atacama Large Millimeter/submillimeter Array ( ALMA ) via 1.3 mm continuum emission at a resolution of \sim 1 \arcsec . We have identified 107 cores with the dendrogram algorithm , with a median radius of about 0.02 pc . Their masses range from 0.261 to 178 M _ { \odot } . After applying completeness corrections , we fit the combined IRDC CMF with a power law of the form dN / d\ > { log } M \propto M ^ { - \alpha } and derive an index of \alpha \simeq 0.86 \pm 0.11 for M \geq 0.79 \ > M _ { \odot } and \alpha \simeq 0.70 \pm 0.13 for M \geq 1.26 \ > M _ { \odot } , which is a significantly more top-heavy distribution than the Salpeter stellar initial mass function ( IMF ) index of 1.35 . We also make a direct comparison of these IRDC clump CMF results to those measured in the more evolved protocluster G286 derived with similar methods , which have \alpha \simeq 1.29 \pm 0.19 and 1.08 \pm 0.27 in these mass ranges , respectively . These results provide a hint that , especially for the M \geq 1.26 \ > M _ { \odot } range where completeness corrections are modest , the CMF in high pressure , early-stage environments of IRDC clumps may be top-heavy compared to that in the more evolved , global environment of the G286 protoclusters . However , larger samples of cores probing these different environments are needed to better establish the robustness of this potential CMF variation .