Use of the "h" register slices (bits 8..15) by compilers is thankfully pretty rare -- otherwise this would have been noticed much sooner!
Agner Fog's optimization guide says "Any use of the high 8-bit registers AH, BH, CH, DH should be avoided because it can cause false dependences and less efficient code."
Use of the "h" register slices (bits 8..15) by compilers is thankfully pretty rare -- otherwise this would have been noticed much sooner!
Agner Fog's optimization guide says "Any use of the high 8-bit registers AH, BH, CH, DH should be avoided because it can cause false dependences and less efficient code."