[clang] [llvm] Reland "[CoroSplit] Erase trivially dead allocas after spilling (#189295)" (PR #190124)

[Weibo He via llvm-commits]

https://github.com/NewSigma created https://github.com/llvm/llvm-project/pull/190124

The original PR contained a use-after-delete issue, which has been resolved in #189521. Since the PR has approval and no changes have been made since then, I will land it directly.

Reland #189295, which is reverted in #189311

>From fceda4df7eecf0e7d3eaec23d784c0c2489de1ed Mon Sep 17 00:00:00 2001
From: NewSigma <NewSigma at 163.com>
Date: Thu, 5 Mar 2026 11:18:42 +0800
Subject: [PATCH] [CoroSplit] Erase trivially dead allocas after spilling

---
 clang/test/CodeGenCoroutines/coro-suspend-cleanups.cpp         | 2 --
 llvm/lib/Transforms/Coroutines/CoroFrame.cpp                   | 3 +++
 .../Transforms/Coroutines/coro-await-suspend-lower-invoke.ll   | 1 -
 llvm/test/Transforms/Coroutines/coro-await-suspend-lower.ll    | 1 -
 llvm/test/Transforms/Coroutines/coro-split-sink-lifetime-01.ll | 1 -
 5 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/clang/test/CodeGenCoroutines/coro-suspend-cleanups.cpp b/clang/test/CodeGenCoroutines/coro-suspend-cleanups.cpp
index 77abc53ce2e71..5872a75b26de5 100644
--- a/clang/test/CodeGenCoroutines/coro-suspend-cleanups.cpp
+++ b/clang/test/CodeGenCoroutines/coro-suspend-cleanups.cpp
@@ -39,8 +39,6 @@ coroutine ArrayInitCoro() {
   //  - We activate the cleanup after the first element and deactivate it in await.ready (see cleanup.isactive).
 
   // CHECK-LABEL: define dso_local void @_Z13ArrayInitCorov
-  // CHECK: %arrayinit.endOfInit = alloca ptr, align 8
-  // CHECK: %cleanup.isactive = alloca i1, align 1
   Printy arr[2] = {
     Printy("a"),
     // CHECK:       store i1 true, ptr %cleanup.isactive.reload.addr, align 1
diff --git a/llvm/lib/Transforms/Coroutines/CoroFrame.cpp b/llvm/lib/Transforms/Coroutines/CoroFrame.cpp
index 446870d603061..36904c2119a25 100644
--- a/llvm/lib/Transforms/Coroutines/CoroFrame.cpp
+++ b/llvm/lib/Transforms/Coroutines/CoroFrame.cpp
@@ -1244,6 +1244,9 @@ static void insertSpills(const FrameDataInfo &FrameData, coro::Shape &Shape) {
 
     for (Instruction *I : UsersToUpdate)
       I->replaceUsesOfWith(Alloca, G);
+
+    if (Alloca->user_empty())
+      Alloca->eraseFromParent();
   }
   Builder.SetInsertPoint(&*Shape.getInsertPtAfterFramePtr());
   for (const auto &A : FrameData.Allocas) {
diff --git a/llvm/test/Transforms/Coroutines/coro-await-suspend-lower-invoke.ll b/llvm/test/Transforms/Coroutines/coro-await-suspend-lower-invoke.ll
index 78540d9363cc6..87309042f18bf 100644
--- a/llvm/test/Transforms/Coroutines/coro-await-suspend-lower-invoke.ll
+++ b/llvm/test/Transforms/Coroutines/coro-await-suspend-lower-invoke.ll
@@ -105,7 +105,6 @@ declare noalias ptr @malloc(i32)
 declare void @free(ptr)
 ; CHECK-LABEL: define void @f() personality i32 0 {
 ; CHECK-NEXT:  [[ENTRY:.*:]]
-; CHECK-NEXT:    [[AWAITER:%.*]] = alloca [[AWAITER:%.*]], align 8
 ; CHECK-NEXT:    [[ID:%.*]] = call token @llvm.coro.id(i32 0, ptr null, ptr @f, ptr @f.resumers)
 ; CHECK-NEXT:    [[ALLOC:%.*]] = call ptr @malloc(i32 24)
 ; CHECK-NEXT:    [[HDL:%.*]] = call noalias nonnull ptr @llvm.coro.begin(token [[ID]], ptr [[ALLOC]])
diff --git a/llvm/test/Transforms/Coroutines/coro-await-suspend-lower.ll b/llvm/test/Transforms/Coroutines/coro-await-suspend-lower.ll
index d6c93cad08a90..bb3fa099de763 100644
--- a/llvm/test/Transforms/Coroutines/coro-await-suspend-lower.ll
+++ b/llvm/test/Transforms/Coroutines/coro-await-suspend-lower.ll
@@ -82,7 +82,6 @@ declare noalias ptr @malloc(i32)
 declare void @free(ptr)
 ; CHECK-LABEL: define void @f() {
 ; CHECK-NEXT:  [[ENTRY:.*:]]
-; CHECK-NEXT:    [[AWAITER:%.*]] = alloca [[AWAITER:%.*]], align 8
 ; CHECK-NEXT:    [[ID:%.*]] = call token @llvm.coro.id(i32 0, ptr null, ptr @f, ptr @f.resumers)
 ; CHECK-NEXT:    [[ALLOC:%.*]] = call ptr @malloc(i32 24)
 ; CHECK-NEXT:    [[HDL:%.*]] = call noalias nonnull ptr @llvm.coro.begin(token [[ID]], ptr [[ALLOC]])
diff --git a/llvm/test/Transforms/Coroutines/coro-split-sink-lifetime-01.ll b/llvm/test/Transforms/Coroutines/coro-split-sink-lifetime-01.ll
index 2ebd52328de52..4cacbcf402adf 100644
--- a/llvm/test/Transforms/Coroutines/coro-split-sink-lifetime-01.ll
+++ b/llvm/test/Transforms/Coroutines/coro-split-sink-lifetime-01.ll
@@ -105,7 +105,6 @@ declare void @llvm.lifetime.end.p0(ptr nocapture) #4
 ; CHECK-SAME: ) #[[ATTR0:[0-9]+]] {
 ; CHECK-NEXT:  [[ENTRY:.*:]]
 ; CHECK-NEXT:    [[REF_TMP7:%.*]] = alloca %"struct.lean_future<int>::Awaiter", align 8
-; CHECK-NEXT:    [[TESTVAL:%.*]] = alloca i32, align 4
 ; CHECK-NEXT:    [[ID:%.*]] = call token @llvm.coro.id(i32 0, ptr null, ptr null, ptr @a_optnone.resumers)
 ; CHECK-NEXT:    [[ALLOC:%.*]] = call ptr @malloc(i64 16)
 ; CHECK-NEXT:    [[VFRAME:%.*]] = call noalias nonnull ptr @llvm.coro.begin(token [[ID]], ptr [[ALLOC]])