Align ARM constant pool islands via their basic block.

Previously, all ARM::CONSTPOOL_ENTRY instructions had a hardwired
alignment of 4 bytes emitted by ARMAsmPrinter.  Now the same alignment
is set on the basic block.

This is in preparation of supporting ARM constant pool islands with
different alignments.

llvm-svn: 145890

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp b/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp
index fedbbad56fa..017e9082065 100644
--- a/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp
+++ b/llvm/lib/Target/ARM/ARMConstantIslandPass.cpp
@@ -398,6 +398,9 @@ void ARMConstantIslands::DoInitialPlacement(MachineFunction &MF,
   MachineBasicBlock *BB = MF.CreateMachineBasicBlock();
   MF.push_back(BB);
 
+  // Mark the basic block as 4-byte aligned as required by the const-pool.
+  BB->setAlignment(2);
+
   // Add all of the constants from the constant pool to the end block, use an
   // identity mapping of CPI's to CPE's.
   const std::vector<MachineConstantPoolEntry> &CPs =
@@ -1311,6 +1314,9 @@ bool ARMConstantIslands::HandleConstantPoolUser(MachineFunction &MF,
   CPEntries[CPI].push_back(CPEntry(U.CPEMI, ID, 1));
   ++NumCPEs;
 
+  // Mark the basic block as 4-byte aligned as required by the const-pool entry.
+  NewIsland->setAlignment(2);
+
   BBOffsets[NewIsland->getNumber()] = BBOffsets[NewMBB->getNumber()];
   // Compensate for .align 2 in thumb mode.
   if (isThumb && (BBOffsets[NewIsland->getNumber()]%4 != 0 || HasInlineAsm))