llvm Costmodel Analysis Pass is showing different result via opt compared to my own project
I have a llvm IR file that includes instructions like fadd and fmul. These instructions when calculating the cost with the cost-model pass
opt -analyze -targetlibinfo -cost-model myIRFile.ll
I have also created my own pass and run this pass in my code. But when I do this I am getting different results despite it runs on the same system. Mostly just 1's and 0's but never a 2 like when I run it with opts. See also attached screenshot, the top is the opt version and the bottom one my own pass.
Basically I reproduced the pass like described at the bottom of CostModel.cpp and this works perfectly except that the results are different. There are no errors whatsover but as you can see in the image the fadd and fmul instructions are rightfully so having a cost of 2. Sadly, in my own project it just turns out to be 1.
I have also tried to implement the entire cost analysis by calling all the instructions as described in TargetTransformInfoWrapperPass. This compiles also perfectly but it gives me the same results.
Another option I tried was posted here on stackoverflow:
Get cpu cycles of LLVM IR using CostModel. I had to make minor adjustments but the results are the same just 1 for both fmul and fadd on the same instruction.
Appearently, the cost-model pass via opt is doing something else that I am not aware of but I cannot find anything about this.
When you have read this entire post and are familiar with LLVM and have any clue what the cause might be or can point me in another direction I would be very grateful because this problem has been driving me nuts now for weeks.
optimization llvm llvm-clang llvm-ir instructions
asked Nov 27 '18 at 10:09
MarkMark
236
add a comment |
I have a llvm IR file that includes instructions like fadd and fmul. These instructions when calculating the cost with the cost-model pass
opt -analyze -targetlibinfo -cost-model myIRFile.ll
I have also created my own pass and run this pass in my code. But when I do this I am getting different results despite it runs on the same system. Mostly just 1's and 0's but never a 2 like when I run it with opts. See also attached screenshot, the top is the opt version and the bottom one my own pass.
Basically I reproduced the pass like described at the bottom of CostModel.cpp and this works perfectly except that the results are different. There are no errors whatsover but as you can see in the image the fadd and fmul instructions are rightfully so having a cost of 2. Sadly, in my own project it just turns out to be 1.
I have also tried to implement the entire cost analysis by calling all the instructions as described in TargetTransformInfoWrapperPass. This compiles also perfectly but it gives me the same results.
Another option I tried was posted here on stackoverflow:
Get cpu cycles of LLVM IR using CostModel. I had to make minor adjustments but the results are the same just 1 for both fmul and fadd on the same instruction.
Appearently, the cost-model pass via opt is doing something else that I am not aware of but I cannot find anything about this.
When you have read this entire post and are familiar with LLVM and have any clue what the cause might be or can point me in another direction I would be very grateful because this problem has been driving me nuts now for weeks.
optimization llvm llvm-clang llvm-ir instructions
asked Nov 27 '18 at 10:09
MarkMark
236
add a comment |
I have a llvm IR file that includes instructions like fadd and fmul. These instructions when calculating the cost with the cost-model pass
opt -analyze -targetlibinfo -cost-model myIRFile.ll
I have also created my own pass and run this pass in my code. But when I do this I am getting different results despite it runs on the same system. Mostly just 1's and 0's but never a 2 like when I run it with opts. See also attached screenshot, the top is the opt version and the bottom one my own pass.
Basically I reproduced the pass like described at the bottom of CostModel.cpp and this works perfectly except that the results are different. There are no errors whatsover but as you can see in the image the fadd and fmul instructions are rightfully so having a cost of 2. Sadly, in my own project it just turns out to be 1.
I have also tried to implement the entire cost analysis by calling all the instructions as described in TargetTransformInfoWrapperPass. This compiles also perfectly but it gives me the same results.
Another option I tried was posted here on stackoverflow:
Get cpu cycles of LLVM IR using CostModel. I had to make minor adjustments but the results are the same just 1 for both fmul and fadd on the same instruction.
Appearently, the cost-model pass via opt is doing something else that I am not aware of but I cannot find anything about this.
When you have read this entire post and are familiar with LLVM and have any clue what the cause might be or can point me in another direction I would be very grateful because this problem has been driving me nuts now for weeks.
optimization llvm llvm-clang llvm-ir instructions
asked Nov 27 '18 at 10:09
MarkMark
236
I have a llvm IR file that includes instructions like fadd and fmul. These instructions when calculating the cost with the cost-model pass
opt -analyze -targetlibinfo -cost-model myIRFile.ll
I have also created my own pass and run this pass in my code. But when I do this I am getting different results despite it runs on the same system. Mostly just 1's and 0's but never a 2 like when I run it with opts. See also attached screenshot, the top is the opt version and the bottom one my own pass.
Basically I reproduced the pass like described at the bottom of CostModel.cpp and this works perfectly except that the results are different. There are no errors whatsover but as you can see in the image the fadd and fmul instructions are rightfully so having a cost of 2. Sadly, in my own project it just turns out to be 1.
I have also tried to implement the entire cost analysis by calling all the instructions as described in TargetTransformInfoWrapperPass. This compiles also perfectly but it gives me the same results.
Another option I tried was posted here on stackoverflow:
Get cpu cycles of LLVM IR using CostModel. I had to make minor adjustments but the results are the same just 1 for both fmul and fadd on the same instruction.
Appearently, the cost-model pass via opt is doing something else that I am not aware of but I cannot find anything about this.
When you have read this entire post and are familiar with LLVM and have any clue what the cause might be or can point me in another direction I would be very grateful because this problem has been driving me nuts now for weeks.
optimization llvm llvm-clang llvm-ir instructions
optimization llvm llvm-clang llvm-ir instructions
asked Nov 27 '18 at 10:09
MarkMark
236
asked Nov 27 '18 at 10:09
MarkMark
236
edited Nov 27 '18 at 10:16
Mark
asked Nov 27 '18 at 10:09
MarkMark
236
asked Nov 27 '18 at 10:09
MarkMark
236
asked Nov 27 '18 at 10:09
MarkMark
236
236
add a comment |
add a comment |
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