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In Thumb2 mode, lower frame indix references to:

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add <rd>, sp, #<imm8>
ldr <rd>, [sp, #<imm8>]
When the offset from sp is multiple of 4 and in range of 0-1020.
This saves code size by utilizing 16-bit instructions.

rdar://9321541


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129971 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng
2011-04-22 01:42:52 +00:00
parent d8a1624122
commit db6cbe1ff1
3 changed files with 36 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files

19
lib/Target/ARM/ARMFrameLowering.cpp
View File

@ -445,8 +445,7 @@ ARMFrameLowering::getFrameIndexReference(const MachineFunction &MF, int FI,
int int
ARMFrameLowering::ResolveFrameIndexReference(const MachineFunction &MF, ARMFrameLowering::ResolveFrameIndexReference(const MachineFunction &MF,
int FI, int FI, unsigned &FrameReg,
unsigned &FrameReg,
int SPAdj) const { int SPAdj) const {
const MachineFrameInfo *MFI = MF.getFrameInfo(); const MachineFrameInfo *MFI = MF.getFrameInfo();
const ARMBaseRegisterInfo *RegInfo = const ARMBaseRegisterInfo *RegInfo =
@ -490,19 +489,23 @@ ARMFrameLowering::ResolveFrameIndexReference(const MachineFunction &MF,
return FPOffset; return FPOffset;
} else if (MFI->hasVarSizedObjects()) { } else if (MFI->hasVarSizedObjects()) {
assert(RegInfo->hasBasePointer(MF) && "missing base pointer!"); assert(RegInfo->hasBasePointer(MF) && "missing base pointer!");
// Try to use the frame pointer if we can, else use the base pointer
// since it's available. This is handy for the emergency spill slot, in
// particular.
if (AFI->isThumb2Function()) { if (AFI->isThumb2Function()) {
// Try to use the frame pointer if we can, else use the base pointer
// since it's available. This is handy for the emergency spill slot, in
// particular.
if (FPOffset >= -255 && FPOffset < 0) { if (FPOffset >= -255 && FPOffset < 0) {
FrameReg = RegInfo->getFrameRegister(MF); FrameReg = RegInfo->getFrameRegister(MF);
return FPOffset; return FPOffset;
} }
} else }
FrameReg = RegInfo->getBaseRegister();
} else if (AFI->isThumb2Function()) { } else if (AFI->isThumb2Function()) {
// Use add <rd>, sp, #<imm8>
// ldr <rd>, [sp, #<imm8>]
// if at all possible to save space.
if (Offset >= 0 && (Offset & 3) == 0 && Offset <= 1020)
return Offset;
// In Thumb2 mode, the negative offset is very limited. Try to avoid // In Thumb2 mode, the negative offset is very limited. Try to avoid
// out of range references. // out of range references. ldr <rt>,[<rn>, #-<imm8>]
if (FPOffset >= -255 && FPOffset < 0) { if (FPOffset >= -255 && FPOffset < 0) {
FrameReg = RegInfo->getFrameRegister(MF); FrameReg = RegInfo->getFrameRegister(MF);
return FPOffset; return FPOffset;

3
lib/Target/ARM/ARMFrameLowering.h
View File

@ -51,7 +51,8 @@ public:
bool canSimplifyCallFramePseudos(const MachineFunction &MF) const; bool canSimplifyCallFramePseudos(const MachineFunction &MF) const;
int getFrameIndexReference(const MachineFunction &MF, int FI, int getFrameIndexReference(const MachineFunction &MF, int FI,
unsigned &FrameReg) const; unsigned &FrameReg) const;
int ResolveFrameIndexReference(const MachineFunction &MF, int FI, int ResolveFrameIndexReference(const MachineFunction &MF,
int FI,
unsigned &FrameReg, int SPAdj) const; unsigned &FrameReg, int SPAdj) const;
int getFrameIndexOffset(const MachineFunction &MF, int FI) const; int getFrameIndexOffset(const MachineFunction &MF, int FI) const;

23
test/CodeGen/Thumb2/2011-04-21-FILoweringBug.ll Normal file
View File

@ -0,0 +1,23 @@
; RUN: llc < %s -mtriple=thumbv7-apple-darwin | FileCheck %s
; Use sp, #imm to lower frame indices when the offset is multiple of 4
; and in the range of 0-1020. This saves code size by utilizing
; 16-bit instructions.
; rdar://9321541
define i32 @t() nounwind {
entry:
; CHECK: t:
; CHECK: sub sp, #12
; CHECK-NOT: sub
; CHECK: add r0, sp, #4
; CHECK: add r1, sp, #8
; CHECK: mov r2, sp
%size = alloca i32, align 4
%count = alloca i32, align 4
%index = alloca i32, align 4
%0 = call i32 @foo(i32* %count, i32* %size, i32* %index) nounwind
ret i32 %0
}
declare i32 @foo(i32*, i32*, i32*)