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Avoid emitting a PIC base register if no PIC addresses are needed.

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This fixes rdar://8396318.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@114201 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-09-17 20:24:24 +00:00
parent d4ef24344a
commit d8c0a51362
2 changed files with 31 additions and 2 deletions
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10
lib/Target/X86/X86InstrInfo.cpp
View File

@ -3108,6 +3108,13 @@ namespace {
if (TM->getRelocationModel() != Reloc::PIC_)
return false;
X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
unsigned GlobalBaseReg = X86FI->getGlobalBaseReg();
// If we didn't need a GlobalBaseReg, don't insert code.
if (GlobalBaseReg == 0)
return false;
// Insert the set of GlobalBaseReg into the first MBB of the function
MachineBasicBlock &FirstMBB = MF.front();
MachineBasicBlock::iterator MBBI = FirstMBB.begin();
@ -3119,7 +3126,7 @@ namespace {
if (TM->getSubtarget<X86Subtarget>().isPICStyleGOT())
PC = RegInfo.createVirtualRegister(X86::GR32RegisterClass);
else
PC = TII->getGlobalBaseReg(&MF);
PC = GlobalBaseReg;
// Operand of MovePCtoStack is completely ignored by asm printer. It's
// only used in JIT code emission as displacement to pc.
@ -3128,7 +3135,6 @@ namespace {
// If we're using vanilla 'GOT' PIC style, we should use relative addressing
// not to pc, but to _GLOBAL_OFFSET_TABLE_ external.
if (TM->getSubtarget<X86Subtarget>().isPICStyleGOT()) {
unsigned GlobalBaseReg = TII->getGlobalBaseReg(&MF);
// Generate addl $__GLOBAL_OFFSET_TABLE_ + [.-piclabel], %some_register
BuildMI(FirstMBB, MBBI, DL, TII->get(X86::ADD32ri), GlobalBaseReg)
.addReg(PC).addExternalSymbol("_GLOBAL_OFFSET_TABLE_",

23
test/CodeGen/X86/fast-isel-avoid-unnecessary-pic-base.ll Normal file
View File

@ -0,0 +1,23 @@
; RUN: llc -O0 -relocation-model=pic < %s | not grep call
; rdar://8396318
; Don't emit a PIC base register if no addresses are needed.
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-darwin11.0.0"
define i32 @foo(i32 %x, i32 %y, i32 %z) nounwind ssp {
entry:
%x.addr = alloca i32, align 4
%y.addr = alloca i32, align 4
%z.addr = alloca i32, align 4
store i32 %x, i32* %x.addr, align 4
store i32 %y, i32* %y.addr, align 4
store i32 %z, i32* %z.addr, align 4
%tmp = load i32* %x.addr, align 4
%tmp1 = load i32* %y.addr, align 4
%add = add nsw i32 %tmp, %tmp1
%tmp2 = load i32* %z.addr, align 4
%add3 = add nsw i32 %add, %tmp2
ret i32 %add3
}