[llvm] [LICM] Simplify isLoadInvariantInLoop given opaque pointers (PR #65597)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms
            
<details>
<summary>Changes</summary>
Since we no longer support typed pointers in LLVM IR, the PtrASXTy
in isLoadInvariantInLoop was set to be equal to Addr->getType() (an
opaque ptr in the same address space). That made the loop looking
through bitcasts redundant.

--
Full diff: https://github.com/llvm/llvm-project/pull/65597.diff

1 Files Affected:

- (modified) llvm/lib/Transforms/Scalar/LICM.cpp (+1-16) 


<pre>
diff --git a/llvm/lib/Transforms/Scalar/LICM.cpp b/llvm/lib/Transforms/Scalar/LICM.cpp
index d6e77c904f3aa2c..4cb70cbdf093b36 100644
--- a/llvm/lib/Transforms/Scalar/LICM.cpp
+++ b/llvm/lib/Transforms/Scalar/LICM.cpp
@@ -1039,7 +1039,7 @@ bool llvm::hoistRegion(DomTreeNode *N, AAResults *AA, LoopInfo *LI,
 // invariant.start has no uses.
 static bool isLoadInvariantInLoop(LoadInst *LI, DominatorTree *DT,
                                   Loop *CurLoop) {
-  Value *Addr = LI-&gt;getOperand(0);
+  Value *Addr = LI-&gt;getPointerOperand();
   const DataLayout &amp;DL = LI-&gt;getModule()-&gt;getDataLayout();
   const TypeSize LocSizeInBits = DL.getTypeSizeInBits(LI-&gt;getType());
 
@@ -1055,21 +1055,6 @@ static bool isLoadInvariantInLoop(LoadInst *LI, DominatorTree *DT,
   if (LocSizeInBits.isScalable())
     return false;
 
-  // if the type is ptr addrspace(x), we know this is the type of
-  // llvm.invariant.start operand
-  auto *PtrASXTy = PointerType::get(LI-&gt;getContext(),
-                                    LI-&gt;getPointerAddressSpace());
-  unsigned BitcastsVisited = 0;
-  // Look through bitcasts until we reach the PtrASXTy type (this is
-  // invariant.start operand type).
-  // FIXME: We shouldn&#x27;t really find such bitcasts with opaque pointers.
-  while (Addr-&gt;getType() != PtrASXTy) {
-    auto *BC = dyn_cast&lt;BitCastInst&gt;(Addr);
-    // Avoid traversing high number of bitcast uses.
-    if (++BitcastsVisited &gt; MaxNumUsesTraversed || !BC)
-      return false;
-    Addr = BC-&gt;getOperand(0);
-  }
   // If we&#x27;ve ended up at a global/constant, bail. We shouldn&#x27;t be looking at
   // uselists for non-local Values in a loop pass.
   if (isa&lt;Constant&gt;(Addr))
</pre>
</details>


https://github.com/llvm/llvm-project/pull/65597