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differences between two blockaddress's don't cause a

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global variable initializer to require relocations.

llvm-svn: 92450
This commit is contained in:
Chris Lattner 2010-01-03 18:09:40 +00:00
parent eb68b810a8
commit 7246a69d2b
2 changed files with 39 additions and 0 deletions
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18
lib/VMCore/Constants.cpp
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@ -197,6 +197,24 @@ Constant::PossibleRelocationsTy Constant::getRelocationInfo() const {
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,

21
test/CodeGen/X86/addr-label-difference.ll Normal file
View File

@ -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.
@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
}