similar to: Function LICM for readonly, nocapture functions

Hi Nadav, On 08/09/12 22:51, Nadav Rotem wrote: > > On Aug 19, 2012, at 2:55 PM, "Kuperstein, Michael M" > <michael.m.kuperstein at intel.com <mailto:michael.m.kuperstein at intel.com>> wrote: > >> Hello, >> Currently, llvm::isSafeToSpeculativelyExecute() always returns false for Call >> instructions. >> This has actual performance

Hi, I recently looked into the LICM(Loop Invariant Code Motion) pass of LLVM and got a question about hoist load instruction to loop preheader. I would like to show two examples: Example 1: int func(int n, int *fp) { int i; int a[1000]; for (i = 0; i < n; ++i) { a[i] += *fp; // load from *fp pointer, no hoist } } Here, load *fp CAN NOT be hoisted to loop preheader. If replace *fp

On Aug 19, 2012, at 2:55 PM, "Kuperstein, Michael M" <michael.m.kuperstein at intel.com> wrote: > Hello, > > Currently, llvm::isSafeToSpeculativelyExecute() always returns false for Call instructions. > This has actual performance implications, because loop-invariant code motion makes this check, and will never hoist instructions that are not safe to speculatively

Hello, Currently, llvm::isSafeToSpeculativelyExecute() always returns false for Call instructions. This has actual performance implications, because loop-invariant code motion makes this check, and will never hoist instructions that are not safe to speculatively execute. Unfortunately, there is currently no way to signal to LICM that a function is safe to speculatively execute. The

I am using LLVM 2.6 and I have a question on the use of the BasicBlock::iterator to hoist loop invariant instructions to the loop preheader. When I process the instructions backward as shown in the following code, I got the following error right after the "hoist(I)" is done. Can anyone advise whether I am misusing BasicBlock::iterator? /opt/llvms/src/llvm_26/

Hi Gang-Ryung! Your reverse iteration of instructions in the BB > * for (BasicBlock::iterator II = BB->end(); II != BB->begin(); ) *{ > > Instruction &I = *--II; > > if (isLoopInvariantInst(I) && canSinkOrHoistInst(I) && > isSafeToExecuteUnconditionally(I)) > * hoist(I);* >

Hi, I'm writing a new loop pass, and has a need to call LICM(Loop Invariant Code Motion) 'PromoteAliasSet' on modified loop. For now I didn't found any why to call 'PromoteAliasSet' from my pass explicitly. The only way is to schedule LICM pass after my pass. For some reason my pass need more control and preferring to call LICM 'PromoteAliasSet' instead running

hi, I applied licm with basicaa on the following codes: int j = atoi(argc[1]); int lower[] = {10, 9, 8, 7, 6, 5, 4, 3, 2, 1}; int upper[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; for(i = lower[j]; a[i] < 100 && i < upper[j]; i ++); I notice that upper[j] is not hoisted out from the loop. Is this because j could be larger than 10? Thanks a lot! Best,

Sent from my iPhone > On Nov 2, 2013, at 1:52 AM, Andrew Trick <atrick at apple.com> wrote: > > >> On Oct 31, 2013, at 6:06 AM, Hal Finkel <hfinkel at anl.gov> wrote: >> >> Hello, >> >> We currently generate suboptimal code for this loop: >> >> for (int i = 1; i < LEN; i++) { >> a[i] = a[0] + b[i]; >> } >>

Hi all, I just noticed that LICM does not hoist/sink the following store out of the loop: int array[20]; int i; for (i = 0; i<100; i++) { array [0] = 0; } The getElementPtr instruction is hoisted out of the loop; the store is not. Did I miss something obvious? Bitcode file attached. Generated using LLVM 2.5 and llvm-gcc -c -emit-llvm

Hi All, I'm looking into converting LICM to use MemorySSA instead of AliasSets to determine when it is safe to hoist/sink/promote loads and stores to get around the issue of alias set collapse (see discussion [1]). I have a prototype implementation, but have run into two issues that I could use input from the designers of MemorySSA to resolve: 1) Is MemorySSA intended to be

On Oct 31, 2013, at 6:06 AM, Hal Finkel <hfinkel at anl.gov> wrote: > Hello, > > We currently generate suboptimal code for this loop: > > for (int i = 1; i < LEN; i++) { > a[i] = a[0] + b[i]; > } > > The largest problem is that we won't vectorize the loop because the loop vectorizer does not grok the independence of a[i] and a[0] (note that i starts at

One way you could go is to expose the interface in include/llvm/Transforms/Utils/LoopUtils.h. There's a similar approach in the LCSSA and LoopSimplify passes, both define functions used by other passes (e.g LoopUnroll and LICM). On Fri, Dec 19, 2014 at 10:58 PM, Philip Reames <listmail at philipreames.com> wrote: > I've come across similar use cases recently. In particular,

Hi, All, Suppose I define one memory read only intrinsic function "foo" in Intrinsics.td like this def int_foo : Intrinsic<[llvm_i32_ty], [llvm_i32_ty, llvm_i32_ty], [IntrReadMem]>; Suppose I have the following IR, which means the intrinsic function "foo" is called 10 times in a loop. Since the parameters of function "foo" are invariant and the function

Hello, We currently generate suboptimal code for this loop: for (int i = 1; i < LEN; i++) { a[i] = a[0] + b[i]; } The largest problem is that we won't vectorize the loop because the loop vectorizer does not grok the independence of a[i] and a[0] (note that i starts at 1 in this loop). While we can probably fix the vectorizer to handle this, I don't think that is the right place for

Hello! I'm compiling code which uses pointers as iterators. For some reason--probably a silly misunderstanding of the docs--I can't eliminate duplicate pointer loads. I'll probably figure this out eventually, but if somebody else sees the answer instantly, I certainly won't complain. :-) Here are the optimizers I'm running: opt -f -simplifycfg -dce -instcombine

I am studying the Transform/Scalar/LICM.cpp pass, and wrote a simple test program to validate. void testLICM(void){ int i,N=100; int data; for(i=0;i<N;i++){ data = 1; printf("i: %d\n",i); } printf("data: %d\n", data); } I expect the "data=1" will be moved out of loop (either hoist or sink). However, to my surprise, that statement

On Oct 27, 2009, at 9:26 AM, Nick Lewycky wrote: > 2009/10/27 Marc Brünink <marc at bruenink.de> > Hi all, > > I just noticed that LICM does not hoist/sink the following store out > of the loop: > > int array[20]; > int i; > for (i = 0; i<100; i++) { > array [0] = 0; > } > > The getElementPtr instruction

I don't think licm looks at loads/stores to allocas -- these are usually handled by mem2reg which happens much earlier (if you run your example with -mem2reg you'll see it already deleted the store). In fact, licm sinks the stores by converting them to stores to allocas first and running mem2reg on that. If you change your example to void testLICM(int* restrict p) { int i,N=100;

I'm attempting to add some support for hoisting/sinking of memory-using intrinsics in loops, and so I want to use MemoryDependenceAnalysis in LICM, but when I modify getAnalysisUsge to include this : virtual void getAnalysisUsage(AnalysisUsage &AU) const { AU.setPreservesCFG(); AU.addRequired<DominatorTree>(); AU.addRequired<LoopInfo>();