From: NAKAMURA Takumi <geek4civic@gmail.com>
Date: Fri, 15 May 2015 03:49:05 +0000 (+0000)
Subject: Revert r237385, "[CodeGen] Reuse stack space from unused function results"
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=c43f39339dafabbfc40eb7ed9ef26c493bb278d7;p=clang

Revert r237385, "[CodeGen] Reuse stack space from unused function results"

It broke clang stage2, at least tblgen.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@237418 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/CGCall.cpp b/lib/CodeGen/CGCall.cpp
index 26d9e1896d..2922a215ad 100644
--- a/lib/CodeGen/CGCall.cpp
+++ b/lib/CodeGen/CGCall.cpp
@@ -3077,18 +3077,10 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
   // If the call returns a temporary with struct return, create a temporary
   // alloca to hold the result, unless one is given to us.
   llvm::Value *SRetPtr = nullptr;
-  size_t UnusedReturnSize = 0;
   if (RetAI.isIndirect() || RetAI.isInAlloca()) {
     SRetPtr = ReturnValue.getValue();
-    if (!SRetPtr) {
+    if (!SRetPtr)
       SRetPtr = CreateMemTemp(RetTy);
-      if (HaveInsertPoint()) {
-        uint64_t size =
-            CGM.getDataLayout().getTypeAllocSize(ConvertTypeForMem(RetTy));
-        if (EmitLifetimeStart(size, SRetPtr))
-          UnusedReturnSize = size;
-      }
-    }
     if (IRFunctionArgs.hasSRetArg()) {
       IRCallArgs[IRFunctionArgs.getSRetArgNo()] = SRetPtr;
     } else {
@@ -3420,10 +3412,6 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
   // insertion point; this allows the rest of IRgen to discard
   // unreachable code.
   if (CS.doesNotReturn()) {
-    if (UnusedReturnSize)
-      EmitLifetimeEnd(llvm::ConstantInt::get(Int64Ty, UnusedReturnSize),
-                      SRetPtr);
-
     Builder.CreateUnreachable();
     Builder.ClearInsertionPoint();
 
@@ -3452,13 +3440,8 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
   RValue Ret = [&] {
     switch (RetAI.getKind()) {
     case ABIArgInfo::InAlloca:
-    case ABIArgInfo::Indirect: {
-      RValue ret = convertTempToRValue(SRetPtr, RetTy, SourceLocation());
-      if (UnusedReturnSize)
-        EmitLifetimeEnd(llvm::ConstantInt::get(Int64Ty, UnusedReturnSize),
-                        SRetPtr);
-      return ret;
-    }
+    case ABIArgInfo::Indirect:
+      return convertTempToRValue(SRetPtr, RetTy, SourceLocation());
 
     case ABIArgInfo::Ignore:
       // If we are ignoring an argument that had a result, make sure to
diff --git a/test/CodeGenCXX/stack-reuse.cpp b/test/CodeGenCXX/stack-reuse.cpp
deleted file mode 100644
index 67a0e4fe16..0000000000
--- a/test/CodeGenCXX/stack-reuse.cpp
+++ /dev/null
@@ -1,125 +0,0 @@
-// RUN: %clang -target armv7l-unknown-linux-gnueabihf -S %s -o - -emit-llvm -O1 -disable-llvm-optzns | FileCheck %s
-
-// Stack should be reused when possible, no need to allocate two separate slots
-// if they have disjoint lifetime.
-
-// Sizes of objects are related to previously existed threshold of 32.  In case
-// of S_large stack size is rounded to 40 bytes.
-
-// 32B
-struct S_small {
-  int a[8];
-};
-
-// 36B
-struct S_large {
-  int a[9];
-};
-
-extern S_small foo_small();
-extern S_large foo_large();
-extern void bar_small(S_small*);
-extern void bar_large(S_large*);
-
-// Prevent mangling of function names.
-extern "C" {
-
-void small_rvoed_unnamed_temporary_object() {
-// CHECK-LABEL: define void @small_rvoed_unnamed_temporary_object
-// CHECK: call void @llvm.lifetime.start
-// CHECK: call void @_Z9foo_smallv
-// CHECK: call void @llvm.lifetime.end
-// CHECK: call void @llvm.lifetime.start
-// CHECK: call void @_Z9foo_smallv
-// CHECK: call void @llvm.lifetime.end
-
-  foo_small();
-  foo_small();
-}
-
-void large_rvoed_unnamed_temporary_object() {
-// CHECK-LABEL: define void @large_rvoed_unnamed_temporary_object
-// CHECK: call void @llvm.lifetime.start
-// CHECK: call void @_Z9foo_largev
-// CHECK: call void @llvm.lifetime.end
-// CHECK: call void @llvm.lifetime.start
-// CHECK: call void @_Z9foo_largev
-// CHECK: call void @llvm.lifetime.end
-
-  foo_large();
-  foo_large();
-}
-
-void small_rvoed_named_temporary_object() {
-// CHECK-LABEL: define void @small_rvoed_named_temporary_object
-// CHECK: call void @llvm.lifetime.start
-// CHECK: call void @_Z9foo_smallv
-// CHECK: call void @llvm.lifetime.end
-// CHECK: call void @llvm.lifetime.start
-// CHECK: call void @_Z9foo_smallv
-// CHECK: call void @llvm.lifetime.end
-
-  {
-    S_small s = foo_small();
-  }
-  {
-    S_small s = foo_small();
-  }
-}
-
-void large_rvoed_named_temporary_object() {
-// CHECK-LABEL: define void @large_rvoed_named_temporary_object
-// CHECK: call void @llvm.lifetime.start
-// CHECK: call void @_Z9foo_largev
-// CHECK: call void @llvm.lifetime.end
-// CHECK: call void @llvm.lifetime.start
-// CHECK: call void @_Z9foo_largev
-// CHECK: call void @llvm.lifetime.end
-
-  {
-    S_large s = foo_large();
-  }
-  {
-    S_large s = foo_large();
-  }
-}
-
-void small_auto_object() {
-// CHECK-LABEL: define void @small_auto_object
-// CHECK: call void @llvm.lifetime.start
-// CHECK: call void @_Z9bar_smallP7S_small
-// CHECK: call void @llvm.lifetime.end
-// CHECK: call void @llvm.lifetime.start
-// CHECK: call void @_Z9bar_smallP7S_small
-// CHECK: call void @llvm.lifetime.end
-
-  {
-    S_small s;
-    bar_small(&s);
-  }
-  {
-    S_small s;
-    bar_small(&s);
-  }
-}
-
-void large_auto_object() {
-// CHECK-LABEL: define void @large_auto_object
-// CHECK: call void @llvm.lifetime.start
-// CHECK: call void @_Z9bar_largeP7S_large
-// CHECK: call void @llvm.lifetime.end
-// CHECK: call void @llvm.lifetime.start
-// CHECK: call void @_Z9bar_largeP7S_large
-// CHECK: call void @llvm.lifetime.end
-
-  {
-    S_large s;
-    bar_large(&s);
-  }
-  {
-    S_large s;
-    bar_large(&s);
-  }
-}
-
-}