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Use movw/movt instead of constant pool loads to lower byval parameter copies 

Summary:
The ARM backend can use a loop to implement copying byval parameters before
a call. In non-thumb2 mode it uses a constant pool load to materialize the
trip count. For targets that need movt instead (e.g. Native Client), use
the same code as in thumb2 mode to materialize the trip count.

Reviewers: jfb, t.p.northover

Differential Revision: http://reviews.llvm.org/D8442

llvm-svn: 233324
This commit is contained in:
Derek Schuff 2015-03-26 22:11:00 +00:00
parent 8f4d3ff146
commit b051389f04
2 changed files with 26 additions and 5 deletions
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14
llvm/lib/Target/ARM/ARMISelLowering.cpp
View File

@ -7105,16 +7105,20 @@ ARMTargetLowering::EmitStructByval(MachineInstr *MI,
// Load an immediate to varEnd.
unsigned varEnd = MRI.createVirtualRegister(TRC);
if (IsThumb2) {
if (Subtarget->useMovt(*MF)) {
unsigned Vtmp = varEnd;
if ((LoopSize & 0xFFFF0000) != 0)
Vtmp = MRI.createVirtualRegister(TRC);
AddDefaultPred(BuildMI(BB, dl, TII->get(ARM::t2MOVi16), Vtmp)
.addImm(LoopSize & 0xFFFF));
AddDefaultPred(BuildMI(BB, dl,
TII->get(IsThumb2 ? ARM::t2MOVi16 : ARM::MOVi16),
Vtmp).addImm(LoopSize & 0xFFFF));
if ((LoopSize & 0xFFFF0000) != 0)
AddDefaultPred(BuildMI(BB, dl, TII->get(ARM::t2MOVTi16), varEnd)
.addReg(Vtmp).addImm(LoopSize >> 16));
AddDefaultPred(BuildMI(BB, dl,
TII->get(IsThumb2 ? ARM::t2MOVTi16 : ARM::MOVTi16),
varEnd)
.addReg(Vtmp)
.addImm(LoopSize >> 16));
} else {
MachineConstantPool *ConstantPool = MF->getConstantPool();
Type *Int32Ty = Type::getInt32Ty(MF->getFunction()->getContext());

17
llvm/test/CodeGen/ARM/struct_byval.ll
View File

@ -1,5 +1,9 @@
; RUN: llc < %s -mtriple=armv7-apple-ios6.0 | FileCheck %s
; RUN: llc < %s -mtriple=thumbv7-apple-ios6.0 | FileCheck %s -check-prefix=THUMB
; RUN: llc < %s -mtriple=armv7-unknown-nacl-gnueabi | FileCheck %s -check-prefix=NACL
; RUN: llc < %s -mtriple=armv5-none-linux-gnueabi | FileCheck %s -check-prefix=NOMOVT
; NOMOVT-NOT: movt
; rdar://9877866
%struct.SmallStruct = type { i32, [8 x i32], [37 x i8] }
@ -33,6 +37,14 @@ entry:
; THUMB: sub
; THUMB: str
; THUMB: bne
; NACL-LABEL: g:
; Ensure that use movw instead of constpool for the loop trip count. But don't
; match the __stack_chk_guard movw
; NACL: movw r{{[1-9]}}, #
; NACL: ldr
; NACL: sub
; NACL: str
; NACL: bne
%st = alloca %struct.LargeStruct, align 4
%call = call i32 @e2(%struct.LargeStruct* byval %st)
ret i32 0
@ -51,6 +63,11 @@ entry:
; THUMB: sub
; THUMB: vst1
; THUMB: bne
; NACL: movw r{{[1-9]}}, #
; NACL: vld1
; NACL: sub
; NACL: vst1
; NACL: bne
%st = alloca %struct.LargeStruct, align 16
%call = call i32 @e3(%struct.LargeStruct* byval align 16 %st)
ret i32 0