[LLVMdev] Question about anti-dependence breaker

Haishan
Wed, 09 Oct 2013 13:17:23 -0000

hi,
I have few question about breaking anti-dependence of postRAScheduler in LLVM.
when I use command line "clang -target arm -mcpu=cortex-a8 -O2
-integrated-as -c test.c -o test.o"
and get objdump file as follows:
ldrr1, [r0,#16]----(1
str r1, [r0,#32]----(2
ldr r1, [r0,#12]----(3
str r1, [r0,#36]----(4
ldr r1, [r0,#08]----(5
str r1, [r0,#40]----(6
However, I expect that instruction pairs (1,2), (3,4) and (5,6) use different
registers after postRAScheduler pass.
Then, I find that postRAScheduler only handle anti-dependence mode after debug
LLVM source code.
More while I use gcc to compile test.c and get expected result.
Is it this compiler's drawbacks? Is any developer doing this function?
it's my pleasure if any suggestion.
Thanks.
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