[llvm] [SDAG] Read-only intrinsics must have WillReturn attribute to be treated as loads (PR #99999)

[Kevin McAfee via llvm-commits]

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@@ -5225,7 +5225,10 @@ void SelectionDAGBuilder::visitTargetIntrinsic(const CallInst &I,
   // definition.
   const Function *F = I.getCalledFunction();
   bool HasChain = !F->doesNotAccessMemory();
-  bool OnlyLoad = HasChain && F->onlyReadsMemory();
+  bool OnlyLoad = HasChain && F->onlyReadsMemory() && F->willReturn();
+
+  bool PrevOnlyLoad = HasChain && F->onlyReadsMemory();
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kalxr wrote:

`PrevOnlyLoad` and the assert are temporary, I wanted to use the test infrastructure to find cases where `OnlyLoad` would have been `true` and will now be `false` after the addition of the willReturn check.

https://github.com/llvm/llvm-project/pull/99999