Add support for using MI bundles as bundle-locked groups on x86

lib/Target/X86/X86NaClRewritePass.cpp

Index: lib/Target/X86/X86NaClRewritePass.cpp
diff --git a/lib/Target/X86/X86NaClRewritePass.cpp b/lib/Target/X86/X86NaClRewritePass.cpp
index 85004b734325e857f68388b6bb3d0a1404b4a3c8..a6cd65dcfb057c2f985b08dc3f6f311bd96e845d 100644
--- a/lib/Target/X86/X86NaClRewritePass.cpp
+++ b/lib/Target/X86/X86NaClRewritePass.cpp
@@ -260,11 +260,25 @@ bool X86NaClRewritePass::ApplyStackSFI(MachineBasicBlock &MBB,
     return true;
   }
 
-  //  Promote 32-bit lea to 64-bit lea (does this ever happen?)
   assert(Opc != X86::LEA32r && "Invalid opcode in 64-bit mode!");
-  if (Opc == X86::LEA64_32r) {
-    unsigned DestReg = MI.getOperand(0).getReg();
+  if (Opc == X86::LEA64_32r){
     unsigned BaseReg = MI.getOperand(1).getReg();
+    if (BaseReg != X86::EBP) {

[jvoung (off chromium), 2015/05/12 23:53:05]

Add a comment about why EBP is a special case?

Handled by NACL_SPADJ instead?

[Derek Schuff, 2015/05/13 00:44:50]

Done.

+      // Create a MachineInstr bundle (i.e. a bundle-locked group) and fix up
+      // the stack pointer by adding R15.  TODO(dschuff): generalize this for
+      // other uses if needed, and try to replace some pseudos if
+      // possible. Eventually replace with auto-sandboxing.
+      auto NextMBBI = MBBI;
+      ++NextMBBI;
+      BuildMI(MBB, NextMBBI, MBBI->getDebugLoc(),
+              TII->get(X86::ADD64rr), X86::RSP).addReg(X86::RSP).addReg(X86::R15);

[jvoung (off chromium), 2015/05/12 23:53:04]

80 col

[Derek Schuff, 2015/05/13 00:44:50]

Done.

+      MIBundleBuilder(MBB, MBBI, NextMBBI);
+      finalizeBundle(MBB, MBBI.getInstrIterator());
+      return true;
+    }
+
+    //  Promote 32-bit lea to 64-bit lea (does this ever happen?)
+    unsigned DestReg = MI.getOperand(0).getReg();
     unsigned Scale   = MI.getOperand(2).getImm();
     unsigned IndexReg = MI.getOperand(3).getReg();
     assert(DestReg == X86::ESP);