[llvm-commits] [llvm] r99529 - in /llvm/trunk: include/llvm/MC/MCAssembler.h lib/MC/MCAssembler.cpp

[Daniel Dunbar]

Author: ddunbar
Date: Thu Mar 25 13:16:42 2010
New Revision: 99529

URL: http://llvm.org/viewvc/llvm-project?rev=99529&view=rev
Log:
MC: Simplify main section layout process by moving alignment into LayoutSection.

Modified:
    llvm/trunk/include/llvm/MC/MCAssembler.h
    llvm/trunk/lib/MC/MCAssembler.cpp

Modified: llvm/trunk/include/llvm/MC/MCAssembler.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/MC/MCAssembler.h?rev=99529&r1=99528&r2=99529&view=diff
==============================================================================
--- llvm/trunk/include/llvm/MC/MCAssembler.h (original)
+++ llvm/trunk/include/llvm/MC/MCAssembler.h Thu Mar 25 13:16:42 2010
@@ -654,8 +654,11 @@
   /// LayoutSection - Assign the section the given \arg StartAddress, and then
   /// assign offsets and sizes to the fragments in the section \arg SD, and
   /// update the section size.
-  void LayoutSection(MCSectionData &SD, MCAsmLayout &Layout,
-                     uint64_t StartAddress);
+  ///
+  /// \return The address at the end of the section, for use in laying out the
+  /// succeeding section.
+  uint64_t LayoutSection(MCSectionData &SD, MCAsmLayout &Layout,
+                         uint64_t StartAddress);
 
   /// LayoutOnce - Perform one layout iteration and return true if any offsets
   /// were adjusted.

Modified: llvm/trunk/lib/MC/MCAssembler.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCAssembler.cpp?rev=99529&r1=99528&r2=99529&view=diff
==============================================================================
--- llvm/trunk/lib/MC/MCAssembler.cpp (original)
+++ llvm/trunk/lib/MC/MCAssembler.cpp Thu Mar 25 13:16:42 2010
@@ -364,9 +364,29 @@
   return IsResolved;
 }
 
-void MCAssembler::LayoutSection(MCSectionData &SD,
-                                MCAsmLayout &Layout,
-                                uint64_t StartAddress) {
+uint64_t MCAssembler::LayoutSection(MCSectionData &SD,
+                                    MCAsmLayout &Layout,
+                                    uint64_t StartAddress) {
+  bool IsVirtual = getBackend().isVirtualSection(SD.getSection());
+
+  // Align this section if necessary by adding padding bytes to the previous
+  // section. It is safe to adjust this out-of-band, because no symbol or
+  // fragment is allowed to point past the end of the section at any time.
+  if (uint64_t Pad = OffsetToAlignment(StartAddress, SD.getAlignment())) {
+    // Unless this section is virtual (where we are allowed to adjust the offset
+    // freely), the padding goes in the previous section.
+    if (!IsVirtual) {
+      // Find the previous non-virtual section.
+      iterator it = &SD;
+      assert(it != begin() && "Invalid initial section address!");
+      for (--it; getBackend().isVirtualSection(it->getSection()); --it) ;
+      Layout.setSectionFileSize(&*it, Layout.getSectionFileSize(&*it) + Pad);
+    }
+
+    StartAddress += Pad;
+  }
+
+  // Set the aligned section address.
   Layout.setSectionAddress(&SD, StartAddress);
 
   uint64_t Address = StartAddress;
@@ -440,10 +460,12 @@
 
   // Set the section sizes.
   Layout.setSectionSize(&SD, Address - StartAddress);
-  if (getBackend().isVirtualSection(SD.getSection()))
+  if (IsVirtual)
     Layout.setSectionFileSize(&SD, 0);
   else
     Layout.setSectionFileSize(&SD, Address - StartAddress);
+
+  return Address;
 }
 
 /// WriteFragmentData - Write the \arg F data to the output file.
@@ -675,43 +697,22 @@
 
   // Layout the concrete sections and fragments.
   uint64_t Address = 0;
-  MCSectionData *Prev = 0;
   for (iterator it = begin(), ie = end(); it != ie; ++it) {
-    MCSectionData &SD = *it;
-
     // Skip virtual sections.
-    if (getBackend().isVirtualSection(SD.getSection()))
+    if (getBackend().isVirtualSection(it->getSection()))
       continue;
 
-    // Align this section if necessary by adding padding bytes to the previous
-    // section.
-    if (uint64_t Pad = OffsetToAlignment(Address, it->getAlignment())) {
-      assert(Prev && "Missing prev section!");
-      Layout.setSectionFileSize(Prev, Layout.getSectionFileSize(Prev) + Pad);
-      Address += Pad;
-    }
-
     // Layout the section fragments and its size.
-    LayoutSection(SD, Layout, Address);
-    Address += Layout.getSectionFileSize(&SD);
-
-    Prev = &SD;
+    Address = LayoutSection(*it, Layout, Address);
   }
 
   // Layout the virtual sections.
   for (iterator it = begin(), ie = end(); it != ie; ++it) {
-    MCSectionData &SD = *it;
-
-    if (!getBackend().isVirtualSection(SD.getSection()))
+    if (!getBackend().isVirtualSection(it->getSection()))
       continue;
 
-    // Align this section if necessary by adding padding bytes to the previous
-    // section.
-    if (uint64_t Pad = OffsetToAlignment(Address, it->getAlignment()))
-      Address += Pad;
-
-    LayoutSection(SD, Layout, Address);
-    Address += Layout.getSectionSize(&SD);
+    // Layout the section fragments and its size.
+    Address = LayoutSection(*it, Layout, Address);
   }
 
   // Scan for fragments that need relaxation.