[stackprotector] When finding the split point to splice off the end of a parentmbb...

Fix for PR16954.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188987 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 69391ca683a9ba08bd2d03973ab390625139157d..68367bbc67d4ccfa3664c98f6869497089c1b63d 100644 (file)
--- a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -1147,11 +1147,53 @@ void SelectionDAGISel::SelectAllBasicBlocks(const Function &Fn) {
   SDB->SPDescriptor.resetPerFunctionState();
 }
 
+/// Given that the input MI is before a partial terminator sequence TSeq, return
+/// true if M + TSeq also a partial terminator sequence.
+///
+/// A Terminator sequence is a sequence of MachineInstrs which at this point in
+/// lowering copy vregs into physical registers, which are then passed into
+/// terminator instructors so we can satisfy ABI constraints. A partial
+/// terminator sequence is an improper subset of a terminator sequence (i.e. it
+/// may be the whole terminator sequence).
+static bool MIIsInTerminatorSequence(const MachineInstr *MI) {
+  // If we do not have a copy or an implicit def, we return true if and only if
+  // MI is a debug value.
+  if (!MI->isCopy() && !MI->isImplicitDef())
+    // Sometimes DBG_VALUE MI sneak in between the copies from the vregs to the
+    // physical registers if there is debug info associated with the terminator
+    // of our mbb. We want to include said debug info in our terminator
+    // sequence, so we return true in that case.
+    return MI->isDebugValue();
+
+  // If we are not defining a register that is a physical register via a copy or
+  // are defining a register via an implicit def, we have left the terminator
+  // sequence.
+  MachineInstr::const_mop_iterator OPI = MI->operands_begin();  
+  if (!OPI->isReg() || !OPI->isDef() ||
+      (!TargetRegisterInfo::isPhysicalRegister(OPI->getReg()) &&
+       !MI->isImplicitDef()))
+    return false;
+
+  return true;
+}
+
 /// Find the split point at which to splice the end of BB into its success stack
 /// protector check machine basic block.
+///
+/// On many platforms, due to ABI constraints, terminators, even before register
+/// allocation, use physical registers. This creates an issue for us since
+/// physical registers at this point can not travel across basic
+/// blocks. Luckily, selectiondag always moves physical registers into vregs
+/// when they enter functions and moves them through a sequence of copies back
+/// into the physical registers right before the terminator creating a
+/// ``Terminator Sequence''. This function is searching for the beginning of the
+/// terminator sequence so that we can ensure that we splice off not just the
+/// terminator, but additionally the copies that move the vregs into the
+/// physical registers.
 static MachineBasicBlock::iterator
 FindSplitPointForStackProtector(MachineBasicBlock *BB, DebugLoc DL) {
-  MachineBasicBlock::iterator SplitPoint = BB->getFirstTerminator();
+  MachineBasicBlock::iterator SplitPoint = BB->getFirstTerminator();  
+  //
   if (SplitPoint == BB->begin())
     return SplitPoint;
 
@@ -1159,14 +1201,7 @@ FindSplitPointForStackProtector(MachineBasicBlock *BB, DebugLoc DL) {
   MachineBasicBlock::iterator Previous = SplitPoint;
   --Previous;
 
-  while (Previous->isCopy() || Previous->isImplicitDef()) {
-    MachineInstr::mop_iterator OPI = Previous->operands_begin();
-
-    if (!OPI->isReg() || !OPI->isDef() ||
-        (!TargetRegisterInfo::isPhysicalRegister(OPI->getReg()) &&
-         !Previous->isImplicitDef()))
-      break;
-
+  while (MIIsInTerminatorSequence(Previous)) {
     SplitPoint = Previous;
     if (Previous == Start)
       break;

diff --git a/test/CodeGen/X86/stack-protector-dbginfo.ll b/test/CodeGen/X86/stack-protector-dbginfo.ll
new file mode 100644 (file)
index 0000000..fa47e52
--- /dev/null
+++ b/test/CodeGen/X86/stack-protector-dbginfo.ll
@@ -0,0 +1,99 @@
+; RUN: llc -mtriple=x86_64-apple-darwin < %s -o -
+
+; PR16954
+;
+; Make sure that when we splice off the end of a machine basic block, we include
+; DBG_VALUE MI in the terminator sequence.
+
+@a = external global { i64, [56 x i8] }, align 32
+
+; Function Attrs: nounwind sspreq
+define i32 @_Z18read_response_sizev() #0 {
+entry:
+  tail call void @llvm.dbg.value(metadata !22, i64 0, metadata !23), !dbg !39
+  %0 = load i64* getelementptr inbounds ({ i64, [56 x i8] }* @a, i32 0, i32 0), align 8, !dbg !40, !tbaa !60
+  tail call void @llvm.dbg.value(metadata !63, i64 0, metadata !64), !dbg !71
+  %1 = trunc i64 %0 to i32
+  ret i32 %1
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.value(metadata, i64, metadata)
+
+attributes #0 = { sspreq }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!21}
+
+!0 = metadata !{i32 786449, metadata !1, i32 4, metadata !"clang version 3.4 ", i1 true, metadata !"", i32 0, metadata !2, metadata !5, metadata !8, metadata !20, metadata !5, metadata !""} ; [ DW_TAG_compile_unit ] [/Users/matt/ryan_bug/<unknown>] [DW_LANG_C_plus_plus]
+!1 = metadata !{metadata !"<unknown>", metadata !"/Users/matt/ryan_bug"}
+!2 = metadata !{metadata !3}
+!3 = metadata !{i32 786436, metadata !1, metadata !4, metadata !"", i32 20, i64 32, i64 32, i32 0, i32 0, null, metadata !6, i32 0, i32 0} ; [ DW_TAG_enumeration_type ] [line 20, size 32, align 32, offset 0] [def] [from ]
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