[llvm-dev] Code selection problem in LLVM backend

[Liu winter via llvm-dev]

Hi,


I'm currently writing a backend for a specific platform. On the target platform, "add/sub" always write a flag result. I used SDNode pattern "add/sub" for these  two instructions, however this leading to a wrongly code as follows,

cmp

...

add ...

...

beq


"add" changes the flag. Desired code is:


add...

cmp

...         ;No add/sub

beq


Then I tried to use SDNode pattern "addc/subc" instead, but it doesn't matter and cause some other errors. What should I do to generate code that no "add/sub" between "cmp" and "branch"?
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