[Inliner] Don't treat inalloca allocas as static

They aren't static, and moving them to the entry block across something
else will only result in tears.

Root cause of http://crbug.com/636558.

llvm-svn: 278571

2 files changed, 73 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Utils/InlineFunction.cpp b/llvm/lib/Transforms/Utils/InlineFunction.cpp
index e101412bf79..6b2ff14f02d 100644
--- a/llvm/lib/Transforms/Utils/InlineFunction.cpp
+++ b/llvm/lib/Transforms/Utils/InlineFunction.cpp
@@ -1294,6 +1294,13 @@ updateInlinedAtInfo(const DebugLoc &DL, DILocation *InlinedAtNode,
   return DebugLoc::get(DL.getLine(), DL.getCol(), DL.getScope(), Last);
 }
 
+/// Return the result of AI->isStaticAlloca() if AI were moved to the entry
+/// block. Allocas used in inalloca calls and allocas of dynamic array size
+/// cannot be static.
+static bool allocaWouldBeStaticInEntry(const AllocaInst *AI ) {
+  return isa<Constant>(AI->getArraySize()) && !AI->isUsedWithInAlloca();
+}
+
 /// Update inlined instructions' line numbers to
 /// to encode location where these instructions are inlined.
 static void fixupLineNumbers(Function *Fn, Function::iterator FI,
@@ -1328,7 +1335,7 @@ static void fixupLineNumbers(Function *Fn, Function::iterator FI,
 
         // Don't update static allocas, as they may get moved later.
         if (auto *AI = dyn_cast<AllocaInst>(BI))
-          if (isa<Constant>(AI->getArraySize()))
+          if (allocaWouldBeStaticInEntry(AI))
             continue;
 
         BI->setDebugLoc(TheCallDL);
@@ -1626,7 +1633,7 @@ bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
         continue;
       }
 
-      if (!isa<Constant>(AI->getArraySize()))
+      if (!allocaWouldBeStaticInEntry(AI))
         continue;
       
       // Keep track of the static allocas that we inline into the caller.
@@ -1635,7 +1642,7 @@ bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
       // Scan for the block of allocas that we can move over, and move them
       // all at once.
       while (isa<AllocaInst>(I) &&
-             isa<Constant>(cast<AllocaInst>(I)->getArraySize())) {
+             allocaWouldBeStaticInEntry(cast<AllocaInst>(I))) {
         IFI.StaticAllocas.push_back(cast<AllocaInst>(I));
         ++I;
       }
diff --git a/llvm/test/Transforms/Inline/inalloca-not-static.ll b/llvm/test/Transforms/Inline/inalloca-not-static.ll
new file mode 100644
index 00000000000..e70e30d1a7e
--- /dev/null
+++ b/llvm/test/Transforms/Inline/inalloca-not-static.ll
@@ -0,0 +1,63 @@
+; RUN: opt -always-inline -S < %s | FileCheck %s
+
+; We used to misclassify inalloca as a static alloca in the inliner. This only
+; arose with for alwaysinline functions, because the normal inliner refuses to
+; inline such things.
+
+; Generated using this C++ source:
+; struct Foo {
+;   Foo();
+;   Foo(const Foo &o);
+;   ~Foo();
+;   int a;
+; };
+; __forceinline void h(Foo o) {}
+; __forceinline void g() { h(Foo()); }
+; void f() { g(); }
+
+; ModuleID = 't.cpp'
+source_filename = "t.cpp"
+target datalayout = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32"
+target triple = "i386-pc-windows-msvc19.0.24210"
+
+%struct.Foo = type { i32 }
+
+declare i8* @llvm.stacksave()
+declare void @llvm.stackrestore(i8*)
+
+declare x86_thiscallcc %struct.Foo* @"\01??0Foo@@QAE@XZ"(%struct.Foo* returned) unnamed_addr
+declare x86_thiscallcc void @"\01??1Foo@@QAE@XZ"(%struct.Foo*) unnamed_addr
+
+define void @f() {
+entry:
+  call void @g()
+  ret void
+}
+
+define internal void @g() alwaysinline {
+entry:
+  %inalloca.save = call i8* @llvm.stacksave()
+  %argmem = alloca inalloca <{ %struct.Foo }>, align 4
+  %0 = getelementptr inbounds <{ %struct.Foo }>, <{ %struct.Foo }>* %argmem, i32 0, i32 0
+  %call = call x86_thiscallcc %struct.Foo* @"\01??0Foo@@QAE@XZ"(%struct.Foo* %0)
+  call void @h(<{ %struct.Foo }>* inalloca %argmem)
+  call void @llvm.stackrestore(i8* %inalloca.save)
+  ret void
+}
+
+; Function Attrs: alwaysinline inlinehint nounwind
+define internal void @h(<{ %struct.Foo }>* inalloca) alwaysinline {
+entry:
+  %o = getelementptr inbounds <{ %struct.Foo }>, <{ %struct.Foo }>* %0, i32 0, i32 0
+  call x86_thiscallcc void @"\01??1Foo@@QAE@XZ"(%struct.Foo* %o)
+  ret void
+}
+
+; CHECK: define void @f()
+; CHECK:   %inalloca.save.i = call i8* @llvm.stacksave()
+; CHECK:   alloca inalloca <{ %struct.Foo }>, align 4
+; CHECK:   %call.i = call x86_thiscallcc %struct.Foo* @"\01??0Foo@@QAE@XZ"(%struct.Foo* %0)
+; CHECK:   %o.i.i = getelementptr inbounds <{ %struct.Foo }>, <{ %struct.Foo }>* %argmem.i, i32 0, i32 0
+; CHECK:   call x86_thiscallcc void @"\01??1Foo@@QAE@XZ"(%struct.Foo* %o.i.i)
+; CHECK:   call void @llvm.stackrestore(i8* %inalloca.save.i)
+; CHECK:   ret void