Check for dynamic allocas and inline asm that clobbers sp before building

selection dag (PR19012)

In X86SelectionDagInfo::EmitTargetCodeForMemcpy we check with MachineFrameInfo
to make sure that ESI isn't used as a base pointer register before we choose to
emit rep movs (which clobbers esi).

The problem is that MachineFrameInfo wouldn't know about dynamic allocas or
inline asm that clobbers the stack pointer until SelectionDAGBuilder has
encountered them.

This patch fixes the problem by checking for such things when building the
FunctionLoweringInfo.

Differential Revision: http://llvm-reviews.chandlerc.com/D2954

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202930 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 45 insertions, 9 deletions

diff --git a/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp b/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
index d842fabae2..3c24f95039 100644
--- a/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
+++ b/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
@@ -33,6 +33,7 @@
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/Target/TargetFrameLowering.h"
 #include "llvm/Target/TargetLowering.h"
 #include "llvm/Target/TargetOptions.h"
 #include "llvm/Target/TargetRegisterInfo.h"
@@ -55,7 +56,8 @@ static bool isUsedOutsideOfDefiningBlock(const Instruction *I) {
   return false;
 }
 
-void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf) {
+void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf,
+                               SelectionDAG *DAG) {
   const TargetLowering *TLI = TM.getTargetLowering();
 
   Fn = &fn;
@@ -98,6 +100,43 @@ void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf) {
   for (; BB != EB; ++BB)
     for (BasicBlock::const_iterator I = BB->begin(), E = BB->end();
          I != E; ++I) {
+      // Look for dynamic allocas.
+      if (const AllocaInst *AI = dyn_cast<AllocaInst>(I)) {
+        if (!AI->isStaticAlloca()) {
+          unsigned Align = std::max(
+              (unsigned)TLI->getDataLayout()->getPrefTypeAlignment(
+                AI->getAllocatedType()),
+              AI->getAlignment());
+          unsigned StackAlign = TM.getFrameLowering()->getStackAlignment();
+          if (Align <= StackAlign)
+            Align = 0;
+          // Inform the Frame Information that we have variable-sized objects.
+          MF->getFrameInfo()->CreateVariableSizedObject(Align ? Align : 1, AI);
+        }
+      }
+
+      // Look for inline asm that clobbers the SP register.
+      if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
+        ImmutableCallSite CS(I);
+        if (const InlineAsm *IA = dyn_cast<InlineAsm>(CS.getCalledValue())) {
+          unsigned SP = TLI->getStackPointerRegisterToSaveRestore();
+          std::vector<TargetLowering::AsmOperandInfo> Ops =
+            TLI->ParseConstraints(CS);
+          for (size_t I = 0, E = Ops.size(); I != E; ++I) {
+            TargetLowering::AsmOperandInfo &Op = Ops[I];
+            if (Op.Type == InlineAsm::isClobber) {
+              // Clobbers don't have SDValue operands, hence SDValue().
+              TLI->ComputeConstraintToUse(Op, SDValue(), DAG);
+              std::pair<unsigned, const TargetRegisterClass*> PhysReg =
+                TLI->getRegForInlineAsmConstraint(Op.ConstraintCode,
+                                                  Op.ConstraintVT);
+              if (PhysReg.first == SP)
+                MF->getFrameInfo()->setHasInlineAsmWithSPAdjust(true);
+            }
+          }
+        }
+      }
+
       // Mark values used outside their block as exported, by allocating
       // a virtual register for them.
       if (isUsedOutsideOfDefiningBlock(I))
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index ed66b8205f..406adbd6e0 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -860,10 +860,10 @@ void RegsForValue::AddInlineAsmOperands(unsigned Code, bool HasMatching,
       unsigned TheReg = Regs[Reg++];
       Ops.push_back(DAG.getRegister(TheReg, RegisterVT));
 
-      // Notice if we clobbered the stack pointer.  Yes, inline asm can do this.
       if (TheReg == SP && Code == InlineAsm::Kind_Clobber) {
-        MachineFrameInfo *MFI = DAG.getMachineFunction().getFrameInfo();
-        MFI->setHasInlineAsmWithSPAdjust(true);
+        // If we clobbered the stack pointer, MFI should know about it.
+        assert(DAG.getMachineFunction().getFrameInfo()->
+            hasInlineAsmWithSPAdjust());
       }
     }
   }
@@ -3437,9 +3437,7 @@ void SelectionDAGBuilder::visitAlloca(const AllocaInst &I) {
   setValue(&I, DSA);
   DAG.setRoot(DSA.getValue(1));
 
-  // Inform the Frame Information that we have just allocated a variable-sized
-  // object.
-  FuncInfo.MF->getFrameInfo()->CreateVariableSizedObject(Align ? Align : 1, &I);
+  assert(FuncInfo.MF->getFrameInfo()->hasVarSizedObjects());
 }
 
 void SelectionDAGBuilder::visitLoad(const LoadInst &I) {
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 01c343818b..787810f8db 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -417,7 +417,7 @@ bool SelectionDAGISel::runOnMachineFunction(MachineFunction &mf) {
   SplitCriticalSideEffectEdges(const_cast<Function&>(Fn), this);
 
   CurDAG->init(*MF, TLI);
-  FuncInfo->set(Fn, *MF);
+  FuncInfo->set(Fn, *MF, CurDAG);
 
   if (UseMBPI && OptLevel != CodeGenOpt::None)
     FuncInfo->BPI = &getAnalysis<BranchProbabilityInfo>();
@@ -427,7 +427,6 @@ bool SelectionDAGISel::runOnMachineFunction(MachineFunction &mf) {
   SDB->init(GFI, *AA, LibInfo);
 
   MF->setHasInlineAsm(false);
-  MF->getFrameInfo()->setHasInlineAsmWithSPAdjust(false);
 
   SelectAllBasicBlocks(Fn);