[llvm] [Coroutines] Remove one construction of DominatorTree (PR #93507)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Ruiling, Song (ruiling)

<details>
<summary>Changes</summary>

The DominatorTree can be reused if no CFG changes.

---
Full diff: https://github.com/llvm/llvm-project/pull/93507.diff


1 Files Affected:

- (modified) llvm/lib/Transforms/Coroutines/CoroFrame.cpp (+4-5) 


``````````diff
diff --git a/llvm/lib/Transforms/Coroutines/CoroFrame.cpp b/llvm/lib/Transforms/Coroutines/CoroFrame.cpp
index 38b8dab984db3..8e829a53aeca2 100644
--- a/llvm/lib/Transforms/Coroutines/CoroFrame.cpp
+++ b/llvm/lib/Transforms/Coroutines/CoroFrame.cpp
@@ -2756,12 +2756,11 @@ static void sinkSpillUsesAfterCoroBegin(Function &F,
 /// after the suspend block. Doing so minimizes the lifetime of each variable,
 /// hence minimizing the amount of data we end up putting on the frame.
 static void sinkLifetimeStartMarkers(Function &F, coro::Shape &Shape,
-                                     SuspendCrossingInfo &Checker) {
+                                     SuspendCrossingInfo &Checker,
+                                     const DominatorTree &DT) {
   if (F.hasOptNone())
     return;
 
-  DominatorTree DT(F);
-
   // Collect all possible basic blocks which may dominate all uses of allocas.
   SmallPtrSet<BasicBlock *, 4> DomSet;
   DomSet.insert(&F.getEntryBlock());
@@ -3149,12 +3148,13 @@ void coro::buildCoroutineFrame(
 
   doRematerializations(F, Checker, MaterializableCallback);
 
+  const DominatorTree DT(F);
   FrameDataInfo FrameData;
   SmallVector<CoroAllocaAllocInst*, 4> LocalAllocas;
   SmallVector<Instruction*, 4> DeadInstructions;
   if (Shape.ABI != coro::ABI::Async && Shape.ABI != coro::ABI::Retcon &&
       Shape.ABI != coro::ABI::RetconOnce)
-    sinkLifetimeStartMarkers(F, Shape, Checker);
+    sinkLifetimeStartMarkers(F, Shape, Checker, DT);
 
   // Collect the spills for arguments and other not-materializable values.
   for (Argument &A : F.args())
@@ -3162,7 +3162,6 @@ void coro::buildCoroutineFrame(
       if (Checker.isDefinitionAcrossSuspend(A, U))
         FrameData.Spills[&A].push_back(cast<Instruction>(U));
 
-  const DominatorTree DT(F);
   for (Instruction &I : instructions(F)) {
     // Values returned from coroutine structure intrinsics should not be part
     // of the Coroutine Frame.

``````````

</details>


https://github.com/llvm/llvm-project/pull/93507