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pr6652: Use LDM to restore PC to the return address on ARMv4.

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Patch by John Tytgat!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@99096 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bob Wilson 2010-03-20 22:20:40 +00:00
parent 226036ee73
commit c88d072293
2 changed files with 24 additions and 6 deletions
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17
lib/Target/ARM/ARMLoadStoreOptimizer.cpp
View File

@ -1155,19 +1155,24 @@ namespace {
};
}
/// MergeReturnIntoLDM - If this is a exit BB, try merging the return op
/// (bx lr) into the preceeding stack restore so it directly restore the value
/// of LR into pc.
/// ldmfd sp!, {r7, lr}
/// MergeReturnIntoLDM - If this is a exit BB, try merging the return ops
/// ("bx lr" and "mov pc, lr") into the preceeding stack restore so it
/// directly restore the value of LR into pc.
/// ldmfd sp!, {..., lr}
/// bx lr
/// or
/// ldmfd sp!, {..., lr}
/// mov pc, lr
/// =>
/// ldmfd sp!, {r7, pc}
/// ldmfd sp!, {..., pc}
bool ARMLoadStoreOpt::MergeReturnIntoLDM(MachineBasicBlock &MBB) {
if (MBB.empty()) return false;
MachineBasicBlock::iterator MBBI = prior(MBB.end());
if (MBBI != MBB.begin() &&
(MBBI->getOpcode() == ARM::BX_RET || MBBI->getOpcode() == ARM::tBX_RET)) {
(MBBI->getOpcode() == ARM::BX_RET ||
MBBI->getOpcode() == ARM::tBX_RET ||
MBBI->getOpcode() == ARM::MOVPCLR)) {
MachineInstr *PrevMI = prior(MBBI);
if (PrevMI->getOpcode() == ARM::LDM_UPD ||
PrevMI->getOpcode() == ARM::t2LDM_UPD) {

13
test/CodeGen/ARM/2010-03-18-ldm-rtrn.ll Normal file
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@ -0,0 +1,13 @@
; RUN: llc < %s -mtriple=armv4-unknown-eabi | FileCheck %s
; RUN: llc < %s -mtriple=armv5-unknown-eabi | FileCheck %s
; RUN: llc < %s -mtriple=armv6-unknown-eabi | FileCheck %s
define i32 @bar(i32 %a) nounwind {
entry:
%0 = tail call i32 @foo(i32 %a) nounwind ; <i32> [#uses=1]
%1 = add nsw i32 %0, 3 ; <i32> [#uses=1]
; CHECK: ldmia sp!, {r11, pc}
ret i32 %1
}
declare i32 @foo(i32)