Hello,
I am trying to use Dependence analysis to figure out some information form
my benchmarks. However, I got different results by using LLVM analysis and
my own pass. For example I have this case:
*int test(int a, int* out, int N)*
*{*
* int sum = 0;*
* for(i = 2; i < N; ++i) {*
* out[i] = a + i;*
* sum += out[i - 2]; }*
* return sum;*
*}*
I compiled this C code by using the following command:
*clang -fno-unroll-loops -emit-llvm -O2 -c -o test.bc test.c*
Then I run DependenceAnalysis pass:
*opt -basicaa -mem2reg -indvars -instcombine -instnamer -loop-simplify
-mergereturn -da -analyze test.bc > /dev/null*
and got this result:
*Printing analysis 'Dependence Analysis' for function 'test':*
*da analyze - none!*
*da analyze - consistent flow [2]!*
*da analyze - none!*
Actually this what I expect to got. However if I write a pass like this:
*TestPass.h*
* virtual void getAnalysisUsage(AnalysisUsage &AU) const*
* {*
* AU.setPreservesAll();*
* AU.addRequired<DependenceAnalysis>();*
* }*
*TestPass.cpp*
*bool TestPass::runOnFunction(Function& F)*
*{*
* llvmDependenceAnalysis = &(getAnalysis<DependenceAnalysis>(F));*
* // The following code is copied from
DependenceAnalysis.cpp:dumpExampleDependence (157 - 182)*
* for (inst_iterator SrcI = inst_begin(F), SrcE = inst_end(F); SrcI !SrcE;
++SrcI) { ... SKIP... }*
* return true; *
*}*
And I executed this pass by using the following command:
*opt -basicaa **-mem2reg -indvars -instcombine -instnamer -loop-simplify
-mergereturn** -load ./TestPass.so -test-pass test.bc > /dev/null*
at this time I got:
*da analyze - confused!*
*da analyze - confused!*
*da analyze - confused!*
Am I doing a wrong usage about this analysis?
Hao
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