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

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-coroutines

Author: Weibo He (NewSigma)

<details>
<summary>Changes</summary>

Erase these allocas so that they do not take up extra stack space at -O0.

Close #<!-- -->57638

---
Full diff: https://github.com/llvm/llvm-project/pull/189295.diff


5 Files Affected:

- (modified) clang/test/CodeGenCoroutines/coro-suspend-cleanups.cpp (-2) 
- (modified) llvm/lib/Transforms/Coroutines/CoroFrame.cpp (+3) 
- (modified) llvm/test/Transforms/Coroutines/coro-await-suspend-lower-invoke.ll (-1) 
- (modified) llvm/test/Transforms/Coroutines/coro-await-suspend-lower.ll (-1) 
- (modified) llvm/test/Transforms/Coroutines/coro-split-sink-lifetime-01.ll (-1) 


``````````diff
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 83b40ee927b51..96dad79374160 100644
--- a/llvm/lib/Transforms/Coroutines/CoroFrame.cpp
+++ b/llvm/lib/Transforms/Coroutines/CoroFrame.cpp
@@ -1212,6 +1212,9 @@ 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]])

``````````

</details>


https://github.com/llvm/llvm-project/pull/189295