History log of /llvm-project-15.0.7/llvm/lib/Target/PowerPC/PPCFrameLowering.h (Results 1 – 25 of 51)
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Revision tags: llvmorg-20.1.0, llvmorg-20.1.0-rc3, llvmorg-20.1.0-rc2, llvmorg-20.1.0-rc1, llvmorg-21-init, llvmorg-19.1.7, llvmorg-19.1.6, llvmorg-19.1.5, llvmorg-19.1.4, llvmorg-19.1.3, llvmorg-19.1.2, llvmorg-19.1.1, llvmorg-19.1.0, llvmorg-19.1.0-rc4, llvmorg-19.1.0-rc3, llvmorg-19.1.0-rc2, llvmorg-19.1.0-rc1, llvmorg-20-init, llvmorg-18.1.8, llvmorg-18.1.7, llvmorg-18.1.6, llvmorg-18.1.5, llvmorg-18.1.4, llvmorg-18.1.3, llvmorg-18.1.2, llvmorg-18.1.1, llvmorg-18.1.0, llvmorg-18.1.0-rc4, llvmorg-18.1.0-rc3, llvmorg-18.1.0-rc2, llvmorg-18.1.0-rc1, llvmorg-19-init, llvmorg-17.0.6, llvmorg-17.0.5, llvmorg-17.0.4, llvmorg-17.0.3, llvmorg-17.0.2, llvmorg-17.0.1, llvmorg-17.0.0, llvmorg-17.0.0-rc4, llvmorg-17.0.0-rc3, llvmorg-17.0.0-rc2, llvmorg-17.0.0-rc1, llvmorg-18-init, llvmorg-16.0.6, llvmorg-16.0.5, llvmorg-16.0.4, llvmorg-16.0.3, llvmorg-16.0.2, llvmorg-16.0.1, llvmorg-16.0.0, llvmorg-16.0.0-rc4, llvmorg-16.0.0-rc3, llvmorg-16.0.0-rc2, llvmorg-16.0.0-rc1, llvmorg-17-init, llvmorg-15.0.7, llvmorg-15.0.6, llvmorg-15.0.5, llvmorg-15.0.4, llvmorg-15.0.3, llvmorg-15.0.2, llvmorg-15.0.1, llvmorg-15.0.0, llvmorg-15.0.0-rc3, llvmorg-15.0.0-rc2, llvmorg-15.0.0-rc1, llvmorg-16-init, llvmorg-14.0.6, llvmorg-14.0.5, llvmorg-14.0.4, llvmorg-14.0.3, llvmorg-14.0.2, llvmorg-14.0.1, llvmorg-14.0.0, llvmorg-14.0.0-rc4, llvmorg-14.0.0-rc3, llvmorg-14.0.0-rc2, llvmorg-14.0.0-rc1, llvmorg-15-init, llvmorg-13.0.1, llvmorg-13.0.1-rc3, llvmorg-13.0.1-rc2, llvmorg-13.0.1-rc1, llvmorg-13.0.0, llvmorg-13.0.0-rc4, llvmorg-13.0.0-rc3, llvmorg-13.0.0-rc2
# 7165e671 23-Aug-2021 Kai Luo <[email protected]>

[PowerPC] Use int64_t to represent stack object offset and frame size

This is the first step to enable PPC64 support huge frame size(>2G). Also fix an assertion error for frame size, i.e.,`int x; !i

[PowerPC] Use int64_t to represent stack object offset and frame size

This is the first step to enable PPC64 support huge frame size(>2G). Also fix an assertion error for frame size, i.e.,`int x; !isInt<32>(x);` should be always evaluated false, so the guard code for frame size is impossible to hit.

Reviewed By: jsji

Differential Revision: https://reviews.llvm.org/D107435

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Revision tags: llvmorg-13.0.0-rc1, llvmorg-14-init, llvmorg-12.0.1, llvmorg-12.0.1-rc4, llvmorg-12.0.1-rc3, llvmorg-12.0.1-rc2, llvmorg-12.0.1-rc1
# 2432d80d 20-Apr-2021 Qiu Chaofan <[email protected]>

[PowerPC] Use mtvsrdd to put callee-saved GPR into VSR

This patch exploits mtvsrdd instruction (available in ISA3.0+) to save
two callee-saved GPR registers into a single VSR, making it more
efficie

[PowerPC] Use mtvsrdd to put callee-saved GPR into VSR

This patch exploits mtvsrdd instruction (available in ISA3.0+) to save
two callee-saved GPR registers into a single VSR, making it more
efficient.

Reviewed By: jsji, nemanjai

Differential Revision: https://reviews.llvm.org/D62565

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Revision tags: llvmorg-12.0.0, llvmorg-12.0.0-rc5, llvmorg-12.0.0-rc4, llvmorg-12.0.0-rc3, llvmorg-12.0.0-rc2, llvmorg-11.1.0, llvmorg-11.1.0-rc3, llvmorg-12.0.0-rc1, llvmorg-13-init, llvmorg-11.1.0-rc2, llvmorg-11.1.0-rc1, llvmorg-11.0.1, llvmorg-11.0.1-rc2, llvmorg-11.0.1-rc1, llvmorg-11.0.0, llvmorg-11.0.0-rc6, llvmorg-11.0.0-rc5, llvmorg-11.0.0-rc4, llvmorg-11.0.0-rc3, llvmorg-11.0.0-rc2, llvmorg-11.0.0-rc1, llvmorg-12-init, llvmorg-10.0.1, llvmorg-10.0.1-rc4, llvmorg-10.0.1-rc3
# c352e088 03-Jul-2020 Kai Luo <[email protected]>

[PowerPC] Implement probing for prologue

This patch is part of supporting `-fstack-clash-protection`. Implemented
probing when emitting prologue.

Differential Revision: https://reviews.llvm.org/D81

[PowerPC] Implement probing for prologue

This patch is part of supporting `-fstack-clash-protection`. Implemented
probing when emitting prologue.

Differential Revision: https://reviews.llvm.org/D81460

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Revision tags: llvmorg-10.0.1-rc2, llvmorg-10.0.1-rc1
# 4dad4914 19-May-2020 Matt Arsenault <[email protected]>

CodeGen: Use Register


Revision tags: llvmorg-10.0.0, llvmorg-10.0.0-rc6, llvmorg-10.0.0-rc5, llvmorg-10.0.0-rc4, llvmorg-10.0.0-rc3
# 186dd631 29-Feb-2020 Benjamin Kramer <[email protected]>

ArrayRef'ize restoreCalleeSavedRegisters. NFCI.

restoreCalleeSavedRegisters can mutate the contents of the
CalleeSavedInfos, so use a MutableArrayRef.


# 8efc2f57 24-Feb-2020 Sean Fertile <[email protected]>

[PowerPC][AIX] Spill/restore the callee-saved condition register bits.

Extends the existing support for spilling and restoring the condition
register to the linkage area for 32-bit targets, and enab

[PowerPC][AIX] Spill/restore the callee-saved condition register bits.

Extends the existing support for spilling and restoring the condition
register to the linkage area for 32-bit targets, and enables for AIX.

Differential Revision: https://reviews.llvm.org/D74349

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Revision tags: llvmorg-10.0.0-rc2
# e4230a9f 08-Feb-2020 Benjamin Kramer <[email protected]>

ArrayRef'ize spillCalleeSavedRegisters. NFCI.


Revision tags: llvmorg-10.0.0-rc1, llvmorg-11-init, llvmorg-9.0.1, llvmorg-9.0.1-rc3, llvmorg-9.0.1-rc2, llvmorg-9.0.1-rc1, llvmorg-9.0.0, llvmorg-9.0.0-rc6, llvmorg-9.0.0-rc5, llvmorg-9.0.0-rc4, llvmorg-9.0.0-rc3
# 09967050 13-Aug-2019 Hubert Tong <[email protected]>

Reland r368691: "[AIX] Implement LR prolog/epilog save/restore"

Trying again with the code changes (and not just the new test).

Summary:
This patch fixes the offsets of fields in the stack frame li

Reland r368691: "[AIX] Implement LR prolog/epilog save/restore"

Trying again with the code changes (and not just the new test).

Summary:
This patch fixes the offsets of fields in the stack frame linkage save
area for AIX.

Reviewers: sfertile, hubert.reinterpretcast, jasonliu, Xiangling_L, xingxue, ZarkoCA, daltenty

Reviewed By: hubert.reinterpretcast

Subscribers: wuzish, nemanjai, hiraditya, kbarton, MaskRay, jsji, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64424

Patch by Chris Bowler!

llvm-svn: 368721

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Revision tags: llvmorg-9.0.0-rc2, llvmorg-9.0.0-rc1
# 9bd22fec 26-Jul-2019 Sean Fertile <[email protected]>

[PowerPC] Add getCRSaveOffset to improve readability. [NFC]

In preperation for AIX support in FrameLowering: replace a number of literal
'8' that represent the stack offset of the condition register

[PowerPC] Add getCRSaveOffset to improve readability. [NFC]

In preperation for AIX support in FrameLowering: replace a number of literal
'8' that represent the stack offset of the condition register save area with
a member in PPCFrameLowering.

Patch by Chris Bowler.

llvm-svn: 367111

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Revision tags: llvmorg-10-init, llvmorg-8.0.1, llvmorg-8.0.1-rc4, llvmorg-8.0.1-rc3, llvmorg-8.0.1-rc2
# 6fc4c1cc 05-Jun-2019 Dmitri Gribenko <[email protected]>

Include what you use in PPCFrameLowering.h

llvm-svn: 362590


Revision tags: llvmorg-8.0.1-rc1, llvmorg-8.0.0, llvmorg-8.0.0-rc5, llvmorg-8.0.0-rc4
# bd5429ef 28-Feb-2019 Stefan Pintilie <[email protected]>

[PowerPC] Move the stack pointer update instruction later in the prologue and earlier in the epilogue.

Move the stdu instruction in the prologue and epilogue.
This should provide a small performance

[PowerPC] Move the stack pointer update instruction later in the prologue and earlier in the epilogue.

Move the stdu instruction in the prologue and epilogue.
This should provide a small performance boost in functions that are able to do
this. I've kept this change rather conservative at the moment and functions
with frame pointers or base pointers will not try to move the stack pointer
update.

Differential Revision: https://reviews.llvm.org/D42590

llvm-svn: 355085

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Revision tags: llvmorg-8.0.0-rc3, llvmorg-7.1.0, llvmorg-7.1.0-rc1, llvmorg-8.0.0-rc2, llvmorg-8.0.0-rc1
# 2946cd70 19-Jan-2019 Chandler Carruth <[email protected]>

Update the file headers across all of the LLVM projects in the monorepo
to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the ne

Update the file headers across all of the LLVM projects in the monorepo
to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351636

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Revision tags: llvmorg-7.0.1, llvmorg-7.0.1-rc3
# 5c179bf1 09-Nov-2018 Zaara Syeda <[email protected]>

[Power9] Allow gpr callee saved spills in prologue to vectors registers

Currently in llvm, CalleeSavedInfo can only assign a callee saved register to
stack frame index to be spilled in the prologue.

[Power9] Allow gpr callee saved spills in prologue to vectors registers

Currently in llvm, CalleeSavedInfo can only assign a callee saved register to
stack frame index to be spilled in the prologue. We would like to enable
spilling gprs to vector registers. This patch adds the capability to spill to
other registers aside from just the stack. It also adds the changes for power9
to spill gprs to volatile vector registers when they are available.
This happens only for leaf functions when using the option
-ppc-enable-pe-vector-spills.

Differential Revision: https://reviews.llvm.org/D39386

llvm-svn: 346512

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Revision tags: llvmorg-7.0.1-rc2, llvmorg-7.0.1-rc1, llvmorg-7.0.0, llvmorg-7.0.0-rc3, llvmorg-7.0.0-rc2, llvmorg-7.0.0-rc1, llvmorg-6.0.1, llvmorg-6.0.1-rc3, llvmorg-6.0.1-rc2
# 5f8f34e4 01-May-2018 Adrian Prantl <[email protected]>

Remove \brief commands from doxygen comments.

We've been running doxygen with the autobrief option for a couple of
years now. This makes the \brief markers into our comments
redundant. Since they ar

Remove \brief commands from doxygen comments.

We've been running doxygen with the autobrief option for a couple of
years now. This makes the \brief markers into our comments
redundant. Since they are a visual distraction and we don't want to
encourage more \brief markers in new code either, this patch removes
them all.

Patch produced by

for i in $(git grep -l '\\brief'); do perl -pi -e 's/\\brief //g' $i & done

Differential Revision: https://reviews.llvm.org/D46290

llvm-svn: 331272

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Revision tags: llvmorg-6.0.1-rc1, llvmorg-5.0.2, llvmorg-5.0.2-rc2, llvmorg-5.0.2-rc1, llvmorg-6.0.0, llvmorg-6.0.0-rc3, llvmorg-6.0.0-rc2, llvmorg-6.0.0-rc1, llvmorg-5.0.1, llvmorg-5.0.1-rc3, llvmorg-5.0.1-rc2
# 1be62f03 03-Nov-2017 David Blaikie <[email protected]>

Move TargetFrameLowering.h to CodeGen where it's implemented

This header already includes a CodeGen header and is implemented in
lib/CodeGen, so move the header there to match.

This fixes a link er

Move TargetFrameLowering.h to CodeGen where it's implemented

This header already includes a CodeGen header and is implemented in
lib/CodeGen, so move the header there to match.

This fixes a link error with modular codegeneration builds - where a
header and its implementation are circularly dependent and so need to be
in the same library, not split between two like this.

llvm-svn: 317379

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Revision tags: llvmorg-5.0.1-rc1, llvmorg-5.0.0, llvmorg-5.0.0-rc5, llvmorg-5.0.0-rc4, llvmorg-5.0.0-rc3, llvmorg-5.0.0-rc2
# bea30c62 10-Aug-2017 Krzysztof Parzyszek <[email protected]>

Add "Restored" flag to CalleeSavedInfo

The liveness-tracking code assumes that the registers that were saved
in the function's prolog are live outside of the function. Specifically,
that registers t

Add "Restored" flag to CalleeSavedInfo

The liveness-tracking code assumes that the registers that were saved
in the function's prolog are live outside of the function. Specifically,
that registers that were saved are also live-on-exit from the function.
This isn't always the case as illustrated by the LR register on ARM.

Differential Revision: https://reviews.llvm.org/D36160

llvm-svn: 310619

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Revision tags: llvmorg-5.0.0-rc1, llvmorg-4.0.1, llvmorg-4.0.1-rc3, llvmorg-4.0.1-rc2, llvmorg-4.0.1-rc1, llvmorg-4.0.0, llvmorg-4.0.0-rc4, llvmorg-4.0.0-rc3, llvmorg-4.0.0-rc2, llvmorg-4.0.0-rc1, llvmorg-3.9.1, llvmorg-3.9.1-rc3, llvmorg-3.9.1-rc2, llvmorg-3.9.1-rc1, llvmorg-3.9.0, llvmorg-3.9.0-rc3, llvmorg-3.9.0-rc2, llvmorg-3.9.0-rc1, llvmorg-3.8.1, llvmorg-3.8.1-rc1
# f8b592f2 01-Apr-2016 Chuang-Yu Cheng <[email protected]>

[PPC64] Bug fix: when enabling sibling-call-opt and shrink-wrapping, the tail call branch instruction might disappear

Bug Pattern:
# BB#0: # %entry
cmpldi 3

[PPC64] Bug fix: when enabling sibling-call-opt and shrink-wrapping, the tail call branch instruction might disappear

Bug Pattern:
# BB#0: # %entry
cmpldi 3, 0
beq- 0, .LBB0_2
# BB#1: # %exit
lwz 4, 0(3)
#TC_RETURNd8 LVComputationKind 0
.LBB0_2: # %cond.false
mflr 0
std 0, 16(1)
stdu 1, -96(1)
.Ltmp0:
.cfi_def_cfa_offset 96
.Ltmp1:
.cfi_offset lr, 16
bl __assert_fail
nop

The branch instruction for tail call return is not generated, because the
shrink-wrapping pass choosing a new Restore Point: %cond.false, so %exit
block is not sent to emitEpilogue, that's why the branch is not generated.

Thanks Kit's opinions!
Reviewers: nemanjai hfinkel tjablin kbarton

http://reviews.llvm.org/D17606

llvm-svn: 265112

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# e1a2e90f 31-Mar-2016 Hans Wennborg <[email protected]>

Change eliminateCallFramePseudoInstr() to return an iterator

This will become necessary in a subsequent change to make this method
merge adjacent stack adjustments, i.e. it might erase the previous

Change eliminateCallFramePseudoInstr() to return an iterator

This will become necessary in a subsequent change to make this method
merge adjacent stack adjustments, i.e. it might erase the previous
and/or next instruction.

It also greatly simplifies the calls to this function from Prolog-
EpilogInserter. Previously, that had a bunch of logic to resume iteration
after the call; now it just continues with the returned iterator.

Note that this changes the behaviour of PEI a little. Previously,
it attempted to re-visit the new instruction created by
eliminateCallFramePseudoInstr(). That code was added in r36625,
but I can't see any reason for it: the new instructions will obviously
not be pseudo instructions, they will not have FrameIndex operands,
and we have already accounted for the stack adjustment.

Differential Revision: http://reviews.llvm.org/D18627

llvm-svn: 265036

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Revision tags: llvmorg-3.8.0, llvmorg-3.8.0-rc3
# ae22101c 20-Feb-2016 Nemanja Ivanovic <[email protected]>

Fix for PR 26500

This patch corresponds to review:
http://reviews.llvm.org/D17294

It ensures that whatever block we are emitting the prologue/epilogue into, we
have the necessary scratch registers.

Fix for PR 26500

This patch corresponds to review:
http://reviews.llvm.org/D17294

It ensures that whatever block we are emitting the prologue/epilogue into, we
have the necessary scratch registers. It takes away the hard-coded register
numbers for use as scratch registers as registers that are guaranteed to be
available in the function prologue/epilogue are not guaranteed to be available
within the function body. Since we shrink-wrap, the prologue/epilogue may end
up in the function body.

llvm-svn: 261441

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Revision tags: llvmorg-3.8.0-rc2, llvmorg-3.8.0-rc1, llvmorg-3.7.1, llvmorg-3.7.1-rc2, llvmorg-3.7.1-rc1
# 9c432ae1 16-Nov-2015 Kit Barton <[email protected]>

Find available scratch register to use in function prologue and epilogue as part of shrink wrapping.

Phabricator: http://reviews.llvm.org/D13955
llvm-svn: 253247


# d3b904d4 10-Sep-2015 Kit Barton <[email protected]>

Enable the shrink wrapping optimization for PPC64.

The changes in this patch are as follows:
1. Modify the emitPrologue and emitEpilogue methods to work properly when the prologue and epilogue blo

Enable the shrink wrapping optimization for PPC64.

The changes in this patch are as follows:
1. Modify the emitPrologue and emitEpilogue methods to work properly when the prologue and epilogue blocks are not the first/last blocks in the function
2. Fix a bug in PPCEarlyReturn optimization caused by an empty entry block in the function
3. Override the runShrinkWrap PredicateFtor (defined in TargetMachine) to check whether shrink wrapping should run:
Shrink wrapping will run on PPC64 (Little Endian and Big Endian) unless -enable-shrink-wrap=false is specified on command line

A new test case, ppc-shrink-wrapping.ll was created based on the existing shrink wrapping tests for x86, arm, and arm64.

Phabricator review: http://reviews.llvm.org/D11817

llvm-svn: 247237

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Revision tags: llvmorg-3.7.0, llvmorg-3.7.0-rc4, llvmorg-3.7.0-rc3, llvmorg-3.7.0-rc2, llvmorg-3.7.0-rc1
# 02564865 14-Jul-2015 Matthias Braun <[email protected]>

PrologEpilogInserter: Rewrite API to determine callee save regsiters.

This changes TargetFrameLowering::processFunctionBeforeCalleeSavedScan():

- Rename the function to determineCalleeSaves()
- Pas

PrologEpilogInserter: Rewrite API to determine callee save regsiters.

This changes TargetFrameLowering::processFunctionBeforeCalleeSavedScan():

- Rename the function to determineCalleeSaves()
- Pass a bitset of callee saved registers by reference, thus avoiding
the function-global PhysRegUsed bitset in MachineRegisterInfo.
- Without PhysRegUsed the implementation is fine tuned to not save
physcial registers which are only read but never modified.

Related to rdar://21539507

Differential Revision: http://reviews.llvm.org/D10909

llvm-svn: 242165

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Revision tags: llvmorg-3.6.2, llvmorg-3.6.2-rc1
# f00654e3 23-Jun-2015 Alexander Kornienko <[email protected]>

Revert r240137 (Fixed/added namespace ending comments using clang-tidy. NFC)

Apparently, the style needs to be agreed upon first.

llvm-svn: 240390


# 70bc5f13 19-Jun-2015 Alexander Kornienko <[email protected]>

Fixed/added namespace ending comments using clang-tidy. NFC

The patch is generated using this command:

tools/clang/tools/extra/clang-tidy/tool/run-clang-tidy.py -fix \
-checks=-*,llvm-namespace-c

Fixed/added namespace ending comments using clang-tidy. NFC

The patch is generated using this command:

tools/clang/tools/extra/clang-tidy/tool/run-clang-tidy.py -fix \
-checks=-*,llvm-namespace-comment -header-filter='llvm/.*|clang/.*' \
llvm/lib/


Thanks to Eugene Kosov for the original patch!

llvm-svn: 240137

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Revision tags: llvmorg-3.6.1, llvmorg-3.6.1-rc1
# 61b305ed 05-May-2015 Quentin Colombet <[email protected]>

[ShrinkWrap] Add (a simplified version) of shrink-wrapping.

This patch introduces a new pass that computes the safe point to insert the
prologue and epilogue of the function.
The interest is to find

[ShrinkWrap] Add (a simplified version) of shrink-wrapping.

This patch introduces a new pass that computes the safe point to insert the
prologue and epilogue of the function.
The interest is to find safe points that are cheaper than the entry and exits
blocks.

As an example and to avoid regressions to be introduce, this patch also
implements the required bits to enable the shrink-wrapping pass for AArch64.


** Context **

Currently we insert the prologue and epilogue of the method/function in the
entry and exits blocks. Although this is correct, we can do a better job when
those are not immediately required and insert them at less frequently executed
places.
The job of the shrink-wrapping pass is to identify such places.


** Motivating example **

Let us consider the following function that perform a call only in one branch of
a if:
define i32 @f(i32 %a, i32 %b) {
%tmp = alloca i32, align 4
%tmp2 = icmp slt i32 %a, %b
br i1 %tmp2, label %true, label %false

true:
store i32 %a, i32* %tmp, align 4
%tmp4 = call i32 @doSomething(i32 0, i32* %tmp)
br label %false

false:
%tmp.0 = phi i32 [ %tmp4, %true ], [ %a, %0 ]
ret i32 %tmp.0
}

On AArch64 this code generates (removing the cfi directives to ease
readabilities):
_f: ; @f
; BB#0:
stp x29, x30, [sp, #-16]!
mov x29, sp
sub sp, sp, #16 ; =16
cmp w0, w1
b.ge LBB0_2
; BB#1: ; %true
stur w0, [x29, #-4]
sub x1, x29, #4 ; =4
mov w0, wzr
bl _doSomething
LBB0_2: ; %false
mov sp, x29
ldp x29, x30, [sp], #16
ret

With shrink-wrapping we could generate:
_f: ; @f
; BB#0:
cmp w0, w1
b.ge LBB0_2
; BB#1: ; %true
stp x29, x30, [sp, #-16]!
mov x29, sp
sub sp, sp, #16 ; =16
stur w0, [x29, #-4]
sub x1, x29, #4 ; =4
mov w0, wzr
bl _doSomething
add sp, x29, #16 ; =16
ldp x29, x30, [sp], #16
LBB0_2: ; %false
ret

Therefore, we would pay the overhead of setting up/destroying the frame only if
we actually do the call.


** Proposed Solution **

This patch introduces a new machine pass that perform the shrink-wrapping
analysis (See the comments at the beginning of ShrinkWrap.cpp for more details).
It then stores the safe save and restore point into the MachineFrameInfo
attached to the MachineFunction.
This information is then used by the PrologEpilogInserter (PEI) to place the
related code at the right place. This pass runs right before the PEI.

Unlike the original paper of Chow from PLDI’88, this implementation of
shrink-wrapping does not use expensive data-flow analysis and does not need hack
to properly avoid frequently executed point. Instead, it relies on dominance and
loop properties.

The pass is off by default and each target can opt-in by setting the
EnableShrinkWrap boolean to true in their derived class of TargetPassConfig.
This setting can also be overwritten on the command line by using
-enable-shrink-wrap.

Before you try out the pass for your target, make sure you properly fix your
emitProlog/emitEpilog/adjustForXXX method to cope with basic blocks that are not
necessarily the entry block.


** Design Decisions **

1. ShrinkWrap is its own pass right now. It could frankly be merged into PEI but
for debugging and clarity I thought it was best to have its own file.
2. Right now, we only support one save point and one restore point. At some
point we can expand this to several save point and restore point, the impacted
component would then be:
- The pass itself: New algorithm needed.
- MachineFrameInfo: Hold a list or set of Save/Restore point instead of one
pointer.
- PEI: Should loop over the save point and restore point.
Anyhow, at least for this first iteration, I do not believe this is interesting
to support the complex cases. We should revisit that when we motivating
examples.

Differential Revision: http://reviews.llvm.org/D9210

<rdar://problem/3201744>

llvm-svn: 236507

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