[llvm-dev] backend bind two machine instructions together

Boris Boesler via llvm-dev llvm-dev at lists.llvm.org
Wed Dec 2 07:55:08 PST 2015

> I lower "BR_CC" into two instructions: one is "CMP", the other is "Br". However, when I check the assembly (.s file), I find these two instructions are separated.  I mean, some other instructions such as "MOVE" instructions, are inserted between "CMP" and "Br". Is there a way that I can always make these "CMP" and "Br" instructions bind together? Thanks.

 Are your CMP and Br instructions connected with a GLUE edge? If they are connected with a GLUE edge then they will be placed in the same "scheduling unit" and no other instructions can be placed between them - AFAIK. A good starting point is ARMTargetLowering::LowerBR_CC() and the opcode descriptions for BRCOND and the ARM compare instructions in the ARM backend.


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