[llvm-commits] [dragonegg] r164936 - in /dragonegg/trunk/src: Backend.cpp Convert.cpp

[Duncan Sands]

Author: baldrick
Date: Mon Oct  1 07:04:14 2012
New Revision: 164936

URL: http://llvm.org/viewvc/llvm-project?rev=164936&view=rev
Log:
Give variables the alignment that GCC says they should have rather than trying
to second guess GCC: remove some strange DECL_USER_ALIGN logic inherited from
llvm-gcc that I never understood the point of.

Modified:
    dragonegg/trunk/src/Backend.cpp
    dragonegg/trunk/src/Convert.cpp

Modified: dragonegg/trunk/src/Backend.cpp
URL: http://llvm.org/viewvc/llvm-project/dragonegg/trunk/src/Backend.cpp?rev=164936&r1=164935&r2=164936&view=diff
==============================================================================
--- dragonegg/trunk/src/Backend.cpp (original)
+++ dragonegg/trunk/src/Backend.cpp Mon Oct  1 07:04:14 2012
@@ -975,7 +975,6 @@
 /// emit_global - Emit the specified VAR_DECL or aggregate CONST_DECL to LLVM as
 /// a global variable.  This function implements the end of assemble_variable.
 static void emit_global(tree decl) {
-  // FIXME: Support alignment on globals: DECL_ALIGN.
   // FIXME: DECL_PRESERVE_P indicates the var is marked with attribute 'used'.
 
   // Global register variables don't turn into LLVM GlobalVariables.
@@ -1119,23 +1118,18 @@
 #endif
     }
 
-    // Set the alignment for the global if one of the following condition is met
-    // 1) DECL_ALIGN is better than the alignment as per ABI specification
-    // 2) DECL_ALIGN is set by user.
-    if (DECL_ALIGN(decl)) {
-      unsigned TargetAlign =
-        getTargetData().getABITypeAlignment(GV->getType()->getElementType());
-      if (DECL_USER_ALIGN(decl) ||
-          8 * TargetAlign < (unsigned)DECL_ALIGN(decl)) {
-        GV->setAlignment(DECL_ALIGN(decl) / 8);
-      }
+    GV->setAlignment(DECL_ALIGN(decl) / 8);
 #ifdef TARGET_ADJUST_CSTRING_ALIGN
-      else if (DECL_INITIAL(decl) != error_mark_node && // uninitialized?
-               DECL_INITIAL(decl) && isa<STRING_CST>(DECL_INITIAL(decl))) {
-        TARGET_ADJUST_CSTRING_ALIGN(GV);
-      }
+    if (DECL_INITIAL(decl) != error_mark_node && // uninitialized?
+        DECL_INITIAL(decl) && isa<STRING_CST>(DECL_INITIAL(decl)))
+      TARGET_ADJUST_CSTRING_ALIGN(GV);
 #endif
-    }
+
+    // If this is the alignment we would have given the variable anyway then don't
+    // use an explicit alignment, making the IR look more portable.
+    if (GV->getAlignment() ==
+        getTargetData().getABITypeAlignment(GV->getType()->getElementType()))
+      GV->setAlignment(0);
 
     // Handle used decls
     if (DECL_PRESERVE_P (decl)) {

Modified: dragonegg/trunk/src/Convert.cpp
URL: http://llvm.org/viewvc/llvm-project/dragonegg/trunk/src/Convert.cpp?rev=164936&r1=164935&r2=164936&view=diff
==============================================================================
--- dragonegg/trunk/src/Convert.cpp (original)
+++ dragonegg/trunk/src/Convert.cpp Mon Oct  1 07:04:14 2012
@@ -1015,8 +1015,8 @@
     register_ctor_dtor(Fn, DECL_FINI_PRIORITY(FnDecl), false);
 
   // Handle attribute "aligned".
-  if (DECL_ALIGN (FnDecl) != FUNCTION_BOUNDARY)
-    Fn->setAlignment(DECL_ALIGN (FnDecl) / 8);
+  if (DECL_ALIGN(FnDecl) != FUNCTION_BOUNDARY)
+    Fn->setAlignment(DECL_ALIGN(FnDecl) / 8);
 
   // Handle functions in specified sections.
   if (DECL_SECTION_NAME(FnDecl))
@@ -2364,16 +2364,12 @@
     Ty = Type::getInt8Ty(Context);
   }
 
-  unsigned Alignment = 0; // Alignment in bytes.
+  unsigned Alignment = DECL_ALIGN(decl) / 8; // Alignment in octets.
 
-  // Set the alignment for the local if one of the following condition is met
-  // 1) DECL_ALIGN is better than the alignment as per ABI specification
-  // 2) DECL_ALIGN is set by user.
-  if (DECL_ALIGN(decl)) {
-    unsigned TargetAlign = getTargetData().getABITypeAlignment(Ty);
-    if (DECL_USER_ALIGN(decl) || 8 * TargetAlign < (unsigned)DECL_ALIGN(decl))
-      Alignment = DECL_ALIGN(decl) / 8;
-  }
+  // If this is the alignment we would have given the variable anyway then don't
+  // use an explicit alignment, making the IR look more portable.
+  if (Alignment == getTargetData().getABITypeAlignment(Ty))
+    Alignment = 0;
 
   // Insert an alloca for this variable.
   AllocaInst *AI;
@@ -6208,12 +6204,9 @@
   // type void.
   if (Ty->isVoidTy()) Ty = StructType::get(Context);
   PointerType *PTy = Ty->getPointerTo();
-  // FIXME: If gcc wants less alignment, we should probably use that.
-  unsigned Alignment = Ty->isSized() ? TD.getABITypeAlignment(Ty) : 1;
-  if (DECL_ALIGN(exp)) {
-    if (DECL_USER_ALIGN(exp) || 8 * Alignment < (unsigned)DECL_ALIGN(exp))
-      Alignment = DECL_ALIGN(exp) / 8;
-  }
+  unsigned Alignment = DECL_ALIGN(exp) / 8;
+  if (!Alignment)
+    Alignment = 1;
 
   return LValue(Builder.CreateBitCast(Decl, PTy), Alignment);
 }