When placing constant islands and adjusting for alignment padding, inline

assembly can confuse things utterly, as it's assumed that instructions in
inline assembly are 4 bytes wide. For Thumb mode, that's often not true,
so the calculations for when alignment padding will be present get thrown off,
ultimately leading to out of range constant pool entry references. Making
more conservative assumptions that padding may be necessary when inline asm
is present avoids this situation.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89403 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/ARM/ARMConstantIslandPass.cpp b/lib/Target/ARM/ARMConstantIslandPass.cpp
index 9742d2d7911d69e5d83e83ba75226db8ae59eb1e..d11fafd4cb39fcc7f5f525d370c1d6af4790701c 100644 (file)
--- a/lib/Target/ARM/ARMConstantIslandPass.cpp
+++ b/lib/Target/ARM/ARMConstantIslandPass.cpp
@@ -162,6 +162,9 @@ namespace {
     /// the branch fix up pass.
     bool HasFarJump;
 
+    /// HasInlineAsm - True if the function contains inline assembly.
+    bool HasInlineAsm;
+
     const TargetInstrInfo *TII;
     const ARMSubtarget *STI;
     ARMFunctionInfo *AFI;
@@ -218,10 +221,45 @@ namespace {
     unsigned GetOffsetOf(MachineInstr *MI) const;
     void dumpBBs();
     void verify(MachineFunction &MF);
+    void verifySizes(MachineFunction &MF);
   };
   char ARMConstantIslands::ID = 0;
 }
 
+// verifySizes - Recalculate BB sizes from scratch and validate that the result
+// matches the values we've been using.
+void ARMConstantIslands::verifySizes(MachineFunction &MF) {
+  unsigned Offset = 0;
+  for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end();
+       MBBI != E; ++MBBI) {
+    MachineBasicBlock &MBB = *MBBI;
+    unsigned MBBSize = 0;
+    for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
+         I != E; ++I) {
+      // Add instruction size to MBBSize.
+      MBBSize += TII->GetInstSizeInBytes(I);
+    }
+    // In thumb mode, if this block is a constpool island, we may need padding
+    // so it's aligned on 4 byte boundary.
+    if (isThumb &&
+        !MBB.empty() &&
+        MBB.begin()->getOpcode() == ARM::CONSTPOOL_ENTRY &&
+        ((Offset%4) != 0 || HasInlineAsm))
+      MBBSize += 2;
+    Offset += MBBSize;
+
+    DEBUG(errs() << "block #" << MBB.getNumber() << ": "
+          << MBBSize << " bytes (expecting " << BBSizes[MBB.getNumber()]
+          << (MBB.begin()->getOpcode() == ARM::CONSTPOOL_ENTRY ?
+              " CONSTANTPOOL" : "") <<  ")\n");
+#ifndef NDEBUG
+    if (MBBSize != BBSizes[MBB.getNumber()])
+      MBB.dump();
+#endif
+    assert (MBBSize == BBSizes[MBB.getNumber()] && "block size mismatch!");
+  }
+}
+
 /// verify - check BBOffsets, BBSizes, alignment of islands
 void ARMConstantIslands::verify(MachineFunction &MF) {
   assert(BBOffsets.size() == BBSizes.size());
@@ -236,11 +274,17 @@ void ARMConstantIslands::verify(MachineFunction &MF) {
     if (!MBB->empty() &&
         MBB->begin()->getOpcode() == ARM::CONSTPOOL_ENTRY) {
       unsigned MBBId = MBB->getNumber();
-      assert((BBOffsets[MBBId]%4 == 0 && BBSizes[MBBId]%4 == 0) ||
+      assert(HasInlineAsm ||
+             (BBOffsets[MBBId]%4 == 0 && BBSizes[MBBId]%4 == 0) ||
              (BBOffsets[MBBId]%4 != 0 && BBSizes[MBBId]%4 != 0));
     }
   }
 #endif
+  for (unsigned i = 0, e = CPUsers.size(); i != e; ++i) {
+    CPUser &U = CPUsers[i];
+    unsigned UserOffset = GetOffsetOf(U.MI) + (isThumb ? 4 : 8);
+    assert (CPEIsInRange(U.MI, UserOffset, U.CPEMI, U.MaxDisp, U.NegOk, true));
+  }
 }
 
 /// print block size and offset information - debugging
@@ -269,6 +313,7 @@ bool ARMConstantIslands::runOnMachineFunction(MachineFunction &MF) {
   isThumb2 = AFI->isThumb2Function();
 
   HasFarJump = false;
+  HasInlineAsm = false;
 
   // Renumber all of the machine basic blocks in the function, guaranteeing that
   // the numbers agree with the position of the block in the function.
@@ -347,6 +392,7 @@ bool ARMConstantIslands::runOnMachineFunction(MachineFunction &MF) {
 
   // After a while, this might be made debug-only, but it is not expensive.
   verify(MF);
+  verifySizes(MF);
 
   // If LR has been forced spilled and no far jumps (i.e. BL) has been issued.
   // Undo the spill / restore of LR if possible.
@@ -452,6 +498,19 @@ void ARMConstantIslands::JumpTableFunctionScan(MachineFunction &MF) {
 /// and finding all of the constant pool users.
 void ARMConstantIslands::InitialFunctionScan(MachineFunction &MF,
                                  const std::vector<MachineInstr*> &CPEMIs) {
+  // First thing, see if the function has any inline assembly in it. If so,
+  // we have to be conservative about alignment assumptions, as we don't
+  // know for sure the size of any instructions in the inline assembly.
+  for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end();
+       MBBI != E; ++MBBI) {
+    MachineBasicBlock &MBB = *MBBI;
+    for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
+         I != E; ++I)
+      if (I->getOpcode() == ARM::INLINEASM)
+        HasInlineAsm = true;
+  }
+
+  // Now go back through the instructions and build up our data structures
   unsigned Offset = 0;
   for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end();
        MBBI != E; ++MBBI) {
@@ -481,7 +540,7 @@ void ARMConstantIslands::InitialFunctionScan(MachineFunction &MF,
           // A Thumb1 table jump may involve padding; for the offsets to
           // be right, functions containing these must be 4-byte aligned.
           AFI->setAlign(2U);
-          if ((Offset+MBBSize)%4 != 0)
+          if ((Offset+MBBSize)%4 != 0 || HasInlineAsm)
             // FIXME: Add a pseudo ALIGN instruction instead.
             MBBSize += 2;           // padding
           continue;   // Does not get an entry in ImmBranches
@@ -609,7 +668,7 @@ void ARMConstantIslands::InitialFunctionScan(MachineFunction &MF,
     if (isThumb &&
         !MBB.empty() &&
         MBB.begin()->getOpcode() == ARM::CONSTPOOL_ENTRY &&
-        (Offset%4) != 0)
+        ((Offset%4) != 0 || HasInlineAsm))
       MBBSize += 2;
 
     BBSizes.push_back(MBBSize);
@@ -633,7 +692,7 @@ unsigned ARMConstantIslands::GetOffsetOf(MachineInstr *MI) const {
   // alignment padding, and compensate if so.
   if (isThumb &&
       MI->getOpcode() == ARM::CONSTPOOL_ENTRY &&
-      Offset%4 != 0)
+      (Offset%4 != 0 || HasInlineAsm))
     Offset += 2;
 
   // Sum instructions before MI in MBB.
@@ -829,7 +888,7 @@ bool ARMConstantIslands::CPEIsInRange(MachineInstr *MI, unsigned UserOffset,
                                       MachineInstr *CPEMI, unsigned MaxDisp,
                                       bool NegOk, bool DoDump) {
   unsigned CPEOffset  = GetOffsetOf(CPEMI);
-  assert(CPEOffset%4 == 0 && "Misaligned CPE");
+  assert((CPEOffset%4 == 0 || HasInlineAsm) && "Misaligned CPE");
 
   if (DoDump) {
     DEBUG(errs() << "User of CPE#" << CPEMI->getOperand(0).getImm()
@@ -870,7 +929,7 @@ void ARMConstantIslands::AdjustBBOffsetsAfter(MachineBasicBlock *BB,
     if (!isThumb)
       continue;
     MachineBasicBlock *MBB = MBBI;
-    if (!MBB->empty()) {
+    if (!MBB->empty() && !HasInlineAsm) {
       // Constant pool entries require padding.
       if (MBB->begin()->getOpcode() == ARM::CONSTPOOL_ENTRY) {
         unsigned OldOffset = BBOffsets[i] - delta;
@@ -1226,7 +1285,7 @@ bool ARMConstantIslands::HandleConstantPoolUser(MachineFunction &MF,
 
   BBOffsets[NewIsland->getNumber()] = BBOffsets[NewMBB->getNumber()];
   // Compensate for .align 2 in thumb mode.
-  if (isThumb && BBOffsets[NewIsland->getNumber()]%4 != 0)
+  if (isThumb && (BBOffsets[NewIsland->getNumber()]%4 != 0 || HasInlineAsm))
     Size += 2;
   // Increase the size of the island block to account for the new entry.
   BBSizes[NewIsland->getNumber()] += Size;