[LoopDataPrefetch] Fix crash when TTI doesn't set CacheLineSize

[Allen]

Summary

Fix https://github.com/llvm/llvm-project/issues/56681

[RKSimon]

please can you add the test case ?

[Allen]

Add test case

[Allen]

In D130418#3673814, @RKSimon wrote:

please can you add the test case ?

Done, thanks @RKSimon

[RKSimon]

llvm/test/Transforms/LoopDataPrefetch/AArch64/pr56681.ll

6

If you're going to check a debug message, I think you need "; REQUIRES: asserts" ?

[tschuett]

Do you force all targets to provide PrefetchDistance and PrefetchDistance or could it be an llvm::optional ?

[Allen]

In D130418#3675649, @tschuett wrote:

Do you force all targets to provide PrefetchDistance and PrefetchDistance or could it be an llvm::optional ?

Thanks, I think it is unfriendly to crash at the moment. Use a default value when they are not specified can be independent next step, if you feel the need.

[RKSimon]

llvm/test/Transforms/LoopDataPrefetch/AArch64/pr56681.ll

2

Is the update script necessary? Did it manage to generate up the CHECK ?

[RKSimon]

LGTM - ideally we'd still check some IR (even if its just a ret void)

[Allen]

delete option -disable-output

llvm/lib/Transforms/Scalar/LoopDataPrefetch.cpp

bool LoopDataPrefetchLegacyPass::runOnFunction(Function &F) {
 
   LoopDataPrefetch LDP(AC, DT, LI, SE, TTI, ORE);
   return LDP.run();
 }
 
 bool LoopDataPrefetch::run() {
   // If PrefetchDistance is not set, don't run the pass.  This gives an
   // opportunity for targets to run this pass for selected subtargets only
-  // (whose TTI sets PrefetchDistance).
-  if (getPrefetchDistance() == 0)
+  // (whose TTI sets PrefetchDistance and CacheLineSize).
+  if (getPrefetchDistance() == 0 || TTI->getCacheLineSize() == 0) {
+    LLVM_DEBUG(dbgs() << "Please set both PrefetchDistance and CacheLineSize "
+                         "for loop data prefetch.\n");
     return false;
-  assert(TTI->getCacheLineSize() && "Cache line size is not set for target");
+  }
 
   bool MadeChange = false;
 
   for (Loop *I : *LI)
     for (Loop *L : depth_first(I))
       MadeChange |= runOnLoop(L);
 
   return MadeChange;

llvm/test/Transforms/LoopDataPrefetch/AArch64/pr56681.ll

+; RUN: opt --loop-data-prefetch --prefetch-distance=3000 -debug-only=loop-data-prefetch -S -disable-output < %s 2>&1 | FileCheck %s
+
+; REQUIRES: asserts
+
+; CHECK:  Please set both PrefetchDistance and CacheLineSize for loop data prefetch
+
+define void @calc() {
+entry:
+  ret void
+}