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

llvm-svn: 202930

llvm/include/llvm/CodeGen/FunctionLoweringInfo.h

@@ -41,6 +41,7 @@ class MachineBasicBlock;
 class MachineFunction;
 class MachineModuleInfo;
 class MachineRegisterInfo;
+class SelectionDAG;
 class TargetLowering;
 class Value;
 
@@ -125,7 +126,7 @@ public:
   /// set - Initialize this FunctionLoweringInfo with the given Function
   /// and its associated MachineFunction.
   ///
-  void set(const Function &Fn, MachineFunction &MF);
+  void set(const Function &Fn, MachineFunction &MF, SelectionDAG *DAG);
 
   /// clear - Clear out all the function-specific state. This returns this
   /// FunctionLoweringInfo to an empty state, ready to be used for a

llvm/include/llvm/CodeGen/MachineFrameInfo.h

@@ -249,6 +249,7 @@ public:
     LocalFrameSize = 0;
     LocalFrameMaxAlign = 0;
     UseLocalStackAllocationBlock = false;
+    HasInlineAsmWithSPAdjust = false;
   }
 
   /// hasStackObjects - Return true if there are any stack objects in this

llvm/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))

llvm/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) {

llvm/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);
 

llvm/test/CodeGen/X86/inline-asm-sp-clobber-memcpy.ll

@@ -0,0 +1,17 @@
+; RUN: llc < %s -force-align-stack -mtriple i386-apple-darwin -mcpu=i486 | FileCheck %s
+
+%struct.foo = type { [88 x i8] }
+
+declare void @bar(i8* nocapture, %struct.foo* align 4 byval) nounwind
+
+; PR19012
+; Don't clobber %esi if we have inline asm that clobbers %esp.
+define void @test1(%struct.foo* nocapture %x, i32 %y, i8* %z) nounwind {
+  call void @bar(i8* %z, %struct.foo* align 4 byval %x)
+  call void asm sideeffect inteldialect "xor esp, esp", "=*m,~{flags},~{esp},~{esp},~{dirflag},~{fpsr},~{flags}"(i8* %z)
+  ret void
+
+; CHECK-LABEL: test1:
+; CHECK: movl %esp, %esi
+; CHECK-NOT: rep;movsl
+}

llvm/test/CodeGen/X86/stack-align-memcpy.ll

@@ -2,6 +2,9 @@
 
 %struct.foo = type { [88 x i8] }
 
+declare void @bar(i8* nocapture, %struct.foo* align 4 byval) nounwind
+declare void @baz(i8*) nounwind
+
 ; PR15249
 ; We can't use rep;movsl here because it clobbers the base pointer in %esi.
 define void @test1(%struct.foo* nocapture %x, i32 %y) nounwind {
@@ -15,4 +18,26 @@ define void @test1(%struct.foo* nocapture %x, i32 %y) nounwind {
 ; CHECK-NOT: rep;movsl
 }
 
-declare void @bar(i8* nocapture, %struct.foo* align 4 byval) nounwind
+; PR19012
+; Also don't clobber %esi if the dynamic alloca comes after the memcpy.
+define void @test2(%struct.foo* nocapture %x, i32 %y, i8* %z) nounwind {
+  call void @bar(i8* %z, %struct.foo* align 4 byval %x)
+  %dynalloc = alloca i8, i32 %y, align 1
+  call void @baz(i8* %dynalloc)
+  ret void
+
+; CHECK-LABEL: test2:
+; CHECK: movl %esp, %esi
+; CHECK-NOT: rep;movsl
+}
+
+; Check that we do use rep movs if we make the alloca static.
+define void @test3(%struct.foo* nocapture %x, i32 %y, i8* %z) nounwind {
+  call void @bar(i8* %z, %struct.foo* align 4 byval %x)
+  %statalloc = alloca i8, i32 8, align 1
+  call void @baz(i8* %statalloc)
+  ret void
+
+; CHECK-LABEL: test3:
+; CHECK: rep;movsl
+}