Latest commit ad9bf96
Sep 6, 2013
On 64-bit Mac OS, gcc 4.2 (which comes with Xcode 4.6) generates code that assumes that an argument that is smaller than the register it is passed in has been sign- or zero-extended. But ghc thinks the types of the PopCnt*Op primops are Word# -> Word#, so it passes the entire argument word to the hs_popcnt* function as though it was declared to have an argument of type StgWord. Segfaults ensue. The easiest fix is to sidestep all this zero-extension business by declaring the hs_popcnt* functions to take a whole StgWord (when their argument would fit in a register), thereby matching the list of primops. Fixes #7684.