[llvm] [X86, SimplifyCFG] Support hoisting load/store with conditional faulting (Part II) (PR #108812)

[Phoebe Wang via llvm-commits]

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@@ -7854,6 +7877,35 @@ bool SimplifyCFGOpt::simplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) {
       if (HoistCommon &&
           hoistCommonCodeFromSuccessors(BI, !Options.HoistCommonInsts))
         return requestResimplify();
+
+      if (BI && HoistLoadsStoresWithCondFaulting &&
+          Options.HoistLoadsStoresWithCondFaulting &&
+          isProfitableToSpeculate(BI, std::nullopt, TTI)) {
+        SmallVector<Instruction *, 2> SpeculatedConditionalLoadsStores;
+        auto CanSpeculateConditionalLoadsStores = [&]() {
+          for (auto *Succ : successors(BB)) {
+            for (Instruction &I : *Succ) {
+              if (I.isTerminator()) {
+                if (I.getNumSuccessors() > 1)
+                  return false;
+                continue;
+              } else if (!isSafeCheapLoadStore(&I, TTI) ||
+                         SpeculatedConditionalLoadsStores.size() ==
+                             HoistLoadsStoresWithCondFaultingThreshold) {
+                return false;
+              }
+              SpeculatedConditionalLoadsStores.push_back(&I);
+            }
+          }
+          return !SpeculatedConditionalLoadsStores.empty();
+        };
+
+        if (CanSpeculateConditionalLoadsStores()) {
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phoebewang wrote:

The advantage to use lambda is we can direct break inner loop by return. We have to use goto or more flags if change to non lambda code.

https://github.com/llvm/llvm-project/pull/108812