From: Manman Ren <mren@apple.com>
Date: Fri, 12 Oct 2012 23:39:43 +0000 (+0000)
Subject: ARM: tail-call inside a function where part of a byval argument is on caller's
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=e6c3cc8dc5437069f71a38188173835ba4fb0dc1;p=oota-llvm.git

ARM: tail-call inside a function where part of a byval argument is on caller's
local frame causes problem.

For example:
void f(StructToPass s) {
  g(&s, sizeof(s));
}
will cause problem with tail-call since part of s is passed via registers and
saved in f's local frame. When g tries to access s, part of s may be corrupted
since f's local frame is popped out before the tail-call.

The current fix is to disable tail-call if getVarArgsRegSaveSize is not 0 for
the caller. This is a conservative approach, if we can prove the address of
s or part of s is not taken and passed to g, it should be okay to perform
tail-call.

rdar://12442472


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165853 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index bd0c659414e..21e7e98c85f 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -1804,6 +1804,14 @@ ARMTargetLowering::IsEligibleForTailCallOptimization(SDValue Callee,
     }
   }
 
+  // If Caller's vararg or byval argument has been split between registers and
+  // stack, do not perform tail call, since part of the argument is in caller's
+  // local frame.
+  const ARMFunctionInfo *AFI_Caller = DAG.getMachineFunction().
+                                      getInfo<ARMFunctionInfo>();
+  if (AFI_Caller->getVarArgsRegSaveSize())
+    return false;
+
   // If the callee takes no arguments then go on to check the results of the
   // call.
   if (!Outs.empty()) {
diff --git a/test/CodeGen/ARM/2011-06-16-TailCallByVal.ll b/test/CodeGen/ARM/2011-06-16-TailCallByVal.ll
index 3e78c462385..101a91396eb 100644
--- a/test/CodeGen/ARM/2011-06-16-TailCallByVal.ll
+++ b/test/CodeGen/ARM/2011-06-16-TailCallByVal.ll
@@ -1,4 +1,9 @@
 ; RUN: llc < %s -arm-tail-calls=1 | FileCheck %s
+
+; tail call inside a function where byval argument is splitted between
+; registers and stack is currently unsupported.
+; XFAIL: *
+
 target datalayout = "e-p:32:32:32-i1:8:32-i8:8:32-i16:16:32-i32:32:32-i64:32:32-f32:32:32-f64:32:32-v64:32:64-v128:32:128-a0:0:32-n32"
 target triple = "thumbv7-apple-ios"
 
diff --git a/test/CodeGen/ARM/struct_byval.ll b/test/CodeGen/ARM/struct_byval.ll
index 99ba475ad7b..e9541c27880 100644
--- a/test/CodeGen/ARM/struct_byval.ll
+++ b/test/CodeGen/ARM/struct_byval.ll
@@ -44,3 +44,47 @@ entry:
 declare i32 @e1(%struct.SmallStruct* nocapture byval %in) nounwind
 declare i32 @e2(%struct.LargeStruct* nocapture byval %in) nounwind
 declare i32 @e3(%struct.LargeStruct* nocapture byval align 16 %in) nounwind
+
+; rdar://12442472
+; We can't do tail call since address of s is passed to the callee and part of
+; s is in caller's local frame.
+define void @f3(%struct.SmallStruct* nocapture byval %s) nounwind optsize {
+; CHECK: f3
+; CHECK: bl _consumestruct
+entry:
+  %0 = bitcast %struct.SmallStruct* %s to i8*
+  tail call void @consumestruct(i8* %0, i32 80) optsize
+  ret void
+}
+
+define void @f4(%struct.SmallStruct* nocapture byval %s) nounwind optsize {
+; CHECK: f4
+; CHECK: bl _consumestruct
+entry:
+  %addr = getelementptr inbounds %struct.SmallStruct* %s, i32 0, i32 0
+  %0 = bitcast i32* %addr to i8*
+  tail call void @consumestruct(i8* %0, i32 80) optsize
+  ret void
+}
+
+; We can do tail call here since s is in the incoming argument area.
+define void @f5(i32 %a, i32 %b, i32 %c, i32 %d, %struct.SmallStruct* nocapture byval %s) nounwind optsize {
+; CHECK: f5
+; CHECK: b _consumestruct
+entry:
+  %0 = bitcast %struct.SmallStruct* %s to i8*
+  tail call void @consumestruct(i8* %0, i32 80) optsize
+  ret void
+}
+
+define void @f6(i32 %a, i32 %b, i32 %c, i32 %d, %struct.SmallStruct* nocapture byval %s) nounwind optsize {
+; CHECK: f6
+; CHECK: b _consumestruct
+entry:
+  %addr = getelementptr inbounds %struct.SmallStruct* %s, i32 0, i32 0
+  %0 = bitcast i32* %addr to i8*
+  tail call void @consumestruct(i8* %0, i32 80) optsize
+  ret void
+}
+
+declare void @consumestruct(i8* nocapture %structp, i32 %structsize) nounwind