[llvm-commits] [llvm] r92450 - in /llvm/trunk: lib/VMCore/Constants.cpp test/CodeGen/X86/addr-label-difference.ll

[Chris Lattner]

Author: lattner
Date: Sun Jan  3 12:09:40 2010
New Revision: 92450

URL: http://llvm.org/viewvc/llvm-project?rev=92450&view=rev
Log:
differences between two blockaddress's don't cause a 
global variable initializer to require relocations.

Added:
    llvm/trunk/test/CodeGen/X86/addr-label-difference.ll
Modified:
    llvm/trunk/lib/VMCore/Constants.cpp

Modified: llvm/trunk/lib/VMCore/Constants.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/VMCore/Constants.cpp?rev=92450&r1=92449&r2=92450&view=diff

==============================================================================
--- llvm/trunk/lib/VMCore/Constants.cpp (original)
+++ llvm/trunk/lib/VMCore/Constants.cpp Sun Jan  3 12:09:40 2010
@@ -197,6 +197,24 @@
   if (const BlockAddress *BA = dyn_cast<BlockAddress>(this))
     return BA->getFunction()->getRelocationInfo();
   
+  // While raw uses of blockaddress need to be relocated, differences between
+  // two of them don't when they are for labels in the same function.  This is a
+  // common idiom when creating a table for the indirect goto extension, so we
+  // handle it efficiently here.
+  if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(this))
+    if (CE->getOpcode() == Instruction::Sub) {
+      ConstantExpr *LHS = dyn_cast<ConstantExpr>(CE->getOperand(0));
+      ConstantExpr *RHS = dyn_cast<ConstantExpr>(CE->getOperand(1));
+      if (LHS && RHS &&
+          LHS->getOpcode() == Instruction::PtrToInt &&
+          RHS->getOpcode() == Instruction::PtrToInt &&
+          isa<BlockAddress>(LHS->getOperand(0)) &&
+          isa<BlockAddress>(RHS->getOperand(0)) &&
+          cast<BlockAddress>(LHS->getOperand(0))->getFunction() ==
+            cast<BlockAddress>(RHS->getOperand(0))->getFunction())
+        return NoRelocation;
+    }
+  
   PossibleRelocationsTy Result = NoRelocation;
   for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
     Result = std::max(Result,

Added: llvm/trunk/test/CodeGen/X86/addr-label-difference.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/addr-label-difference.ll?rev=92450&view=auto

==============================================================================
--- llvm/trunk/test/CodeGen/X86/addr-label-difference.ll (added)
+++ llvm/trunk/test/CodeGen/X86/addr-label-difference.ll Sun Jan  3 12:09:40 2010
@@ -0,0 +1,21 @@
+; RUN: llc %s -o - | grep {__TEXT,__const}
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128-n8:16:32"
+target triple = "i386-apple-darwin10.0"
+
+; This array should go into the __TEXT,__const section, not into the
+; __DATA,__const section, because the elements don't need relocations.
+ at test.array = internal constant [3 x i32] [i32 sub (i32 ptrtoint (i8* blockaddress(@test, %foo) to i32), i32 ptrtoint (i8* blockaddress(@test, %foo) to i32)), i32 sub (i32 ptrtoint (i8* blockaddress(@test, %bar) to i32), i32 ptrtoint (i8* blockaddress(@test, %foo) to i32)), i32 sub (i32 ptrtoint (i8* blockaddress(@test, %hack) to i32), i32 ptrtoint (i8* blockaddress(@test, %foo) to i32))] ; <[3 x i32]*> [#uses=1]
+
+define void @test(i32 %i) nounwind ssp {
+entry:
+  br label %foo
+
+foo:                                              ; preds = %indirectgoto, %indirectgoto, %indirectgoto, %indirectgoto, %indirectgoto
+  br label %bar
+
+bar:                                              ; preds = %foo, %indirectgoto
+  br label %hack
+
+hack:                                             ; preds = %bar, %indirectgoto
+  ret void
+}