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Use .set expression for x86 pic jump table reference to reduce assembly relocation. rdar://7738756

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@101085 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2010-04-12 23:07:17 +00:00
parent 6ab10f69a9
commit 82865a10f8
2 changed files with 16 additions and 2 deletions
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9
lib/Target/X86/AsmPrinter/X86MCInstLower.cpp
View File

@ -169,6 +169,15 @@ MCOperand X86MCInstLower::LowerSymbolOperand(const MachineOperand &MO,
Expr = MCBinaryExpr::CreateSub(Expr,
MCSymbolRefExpr::Create(GetPICBaseSymbol(), Ctx),
Ctx);
if (MO.isJTI() && AsmPrinter.MAI->hasSetDirective()) {
// If .set directive is supported, use it to reduce the number of
// relocations the assembler will generate for differences between
// local labels. This is only safe when the symbols are in the same
// section so we are restricting it to jumptable references.
MCSymbol *Label = Ctx.CreateTempSymbol();
AsmPrinter.OutStreamer.EmitAssignment(Label, Expr);
Expr = MCSymbolRefExpr::Create(Label, Ctx);
}
break;
}

9
test/CodeGen/X86/pic_jumptable.ll
View File

@ -1,13 +1,18 @@
; RUN: llc < %s -relocation-model=pic -mtriple=i386-linux-gnu -asm-verbose=false | not grep -F .text
; RUN: llc < %s -relocation-model=pic -mtriple=i686-apple-darwin -asm-verbose=false | not grep lea
; RUN: llc < %s -relocation-model=pic -mtriple=i686-apple-darwin -asm-verbose=false | grep add | count 2
; RUN: llc < %s -relocation-model=pic -mtriple=i686-apple-darwin -asm-verbose=false | FileCheck %s
; RUN: llc < %s -mtriple=x86_64-apple-darwin | not grep 'lJTI'
; rdar://6971437
; rdar://7738756
declare void @_Z3bari(i32)
define linkonce void @_Z3fooILi1EEvi(i32 %Y) nounwind {
entry:
; CHECK: L1$pb
; CHECK-NOT: leal
; CHECK: Ltmp0 = LJTI1_0-L1$pb
; CHECK-NEXT: addl Ltmp0(%eax,%ecx,4)
; CHECK-NEXT: jmpl *%eax
%Y_addr = alloca i32 ; <i32*> [#uses=2]
%"alloca point" = bitcast i32 0 to i32 ; <i32> [#uses=0]
store i32 %Y, i32* %Y_addr