Re: [TCWG CI] 401.bzip2 grew in size by 11% after llvm: [MachineSink] Disable if there are any irreducible cycles - linaro-toolchain

29 Mar 2022

Hi Nikita,
Your patch seems to increase code-size of 401.bzip2 by 11% at -Oz.  This is due to BZ2_decompress() function growing by 56%.
Would you please investigate and see if this regression can be avoided?
Please let us know if you need help reproducing or analyzing the problem.
Regards,
--
Maxim Kuvyrkov
https://www.linaro.org
...
On Mar 27, 2022, at 11:26 AM, ci_notify@linaro.org wrote:
After llvm commit 6fde0439512580df793f3f48f95757b47de40d2b
Author: Nikita Popov npopov@redhat.com
[MachineSink] Disable if there are any irreducible cycles
the following benchmarks grew in size by more than 1%:

401.bzip2 grew in size by 11% from 36213 to 40325 bytes
401.bzip2:[.] BZ2_decompress grew in size by 56% from 7400 to 11560 bytes

Below reproducer instructions can be used to re-build both "first_bad" and "last_good" cross-toolchains used in this bisection.  Naturally, the scripts will fail when triggerring benchmarking jobs if you don't have access to Linaro TCWG CI.
For your convenience, we have uploaded tarballs with pre-processed source and assembly files at:

First_bad save-temps: https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_apm-llvm-master-a...
Last_good save-temps: https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_apm-llvm-master-a...
Baseline save-temps: https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_apm-llvm-master-a...

Configuration:

Benchmark: SPEC CPU2006
Toolchain: Clang + Glibc + LLVM Linker
Version: all components were built from their tip of trunk
Target: arm-linux-gnueabihf
Compiler flags: -Oz -mthumb
Hardware: APM Mustang 8x X-Gene1

This benchmarking CI is work-in-progress, and we welcome feedback and suggestions at linaro-toolchain@lists.linaro.org .  In our improvement plans is to add support for SPEC CPU2017 benchmarks and provide "perf report/annotate" data behind these reports.
THIS IS THE END OF INTERESTING STUFF.  BELOW ARE LINKS TO BUILDS, REPRODUCTION INSTRUCTIONS, AND THE RAW COMMIT.
This commit has regressed these CI configurations:

tcwg_bmk_llvm_apm/llvm-master-arm-spec2k6-Oz
tcwg_bmk_llvm_apm/llvm-master-arm-spec2k6-Oz_LTO

First_bad build: https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_apm-llvm-master-a...
Last_good build: https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_apm-llvm-master-a...
Baseline build: https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_apm-llvm-master-a...
Even more details: https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_apm-llvm-master-a...
Reproduce builds:
<cut>
mkdir investigate-llvm-6fde0439512580df793f3f48f95757b47de40d2b
cd investigate-llvm-6fde0439512580df793f3f48f95757b47de40d2b
# Fetch scripts
git clone https://git.linaro.org/toolchain/jenkins-scripts
# Fetch manifests and test.sh script
mkdir -p artifacts/manifests
curl -o artifacts/manifests/build-baseline.sh https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_apm-llvm-master-a... --fail
curl -o artifacts/manifests/build-parameters.sh https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_apm-llvm-master-a... --fail
curl -o artifacts/test.sh https://ci.linaro.org/job/tcwg_bmk_ci_llvm-bisect-tcwg_bmk_apm-llvm-master-a... --fail
chmod +x artifacts/test.sh
# Reproduce the baseline build (build all pre-requisites)
./jenkins-scripts/tcwg_bmk-build.sh @@ artifacts/manifests/build-baseline.sh
# Save baseline build state (which is then restored in artifacts/test.sh)
mkdir -p ./bisect
rsync -a --del --delete-excluded --exclude /bisect/ --exclude /artifacts/ --exclude /llvm/ ./ ./bisect/baseline/
cd llvm
# Reproduce first_bad build
git checkout --detach 6fde0439512580df793f3f48f95757b47de40d2b
../artifacts/test.sh
# Reproduce last_good build
git checkout --detach eb27da7dec67f1a36505b589b786ba1a499c274a
../artifacts/test.sh
cd ..
</cut>
Full commit (up to 1000 lines):
<cut>
commit 6fde0439512580df793f3f48f95757b47de40d2b
Author: Nikita Popov <npopov@redhat.com>
Date:   Thu Feb 24 10:09:49 2022 +0100
[MachineSink] Disable if there are any irreducible cycles
This is an alternative to D120330, which disables MachineSink for
   functions with irreducible cycles entirely. This avoids both the
   correctness problem, and ensures we don't perform non-profitable
   sinks into cycles. At the same time, it may also disable
   profitable sinks in the same function. This can be made more
   precise by using MachineCycleInfo in the future.
Fixes https://github.com/llvm/llvm-project/issues/53990.
Differential Revision: https://reviews.llvm.org/D120800
llvm/lib/CodeGen/MachineSink.cpp                   | 12 +++
llvm/test/CodeGen/X86/callbr-asm-branch-folding.ll | 22 +++--
llvm/test/CodeGen/X86/pr38795.ll                   | 93 +++++++++++-----------
.../CodeGen/X86/pr53990-incorrect-machine-sink.ll  |  9 +--
llvm/test/CodeGen/X86/x86-shrink-wrapping.ll       | 36 ++++-----
5 files changed, 87 insertions(+), 85 deletions(-)

diff --git a/llvm/lib/CodeGen/MachineSink.cpp b/llvm/lib/CodeGen/MachineSink.cpp
index 7ed33f9fdeac..301cc73a0530 100644
--- a/llvm/lib/CodeGen/MachineSink.cpp
+++ b/llvm/lib/CodeGen/MachineSink.cpp
@@ -18,12 +18,14 @@
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/PointerIntPair.h"
+#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/SparseBitVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/CFG.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
@@ -429,6 +431,16 @@ bool MachineSinking::runOnMachineFunction(MachineFunction &MF) {
  AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
  RegClassInfo.runOnMachineFunction(MF);

// MachineSink currently uses MachineLoopInfo, which only recognizes natural

// loops. As such, we could sink instructions into irreducible cycles, which

// would be non-profitable.

// WARNING: The current implementation of hasStoreBetween() is incorrect for

// sinking into irreducible cycles (PR53990), this bailout is currently

// necessary for correctness, not just profitability.

ReversePostOrderTraversal<MachineBasicBlock *> RPOT(&*MF.begin());

if (containsIrreducibleCFG<MachineBasicBlock *>(RPOT, *LI))

return false;

bool EverMadeChange = false;
while (true) {


diff --git a/llvm/test/CodeGen/X86/callbr-asm-branch-folding.ll b/llvm/test/CodeGen/X86/callbr-asm-branch-folding.ll
index 024b6c608aba..f93e181d157c 100644
--- a/llvm/test/CodeGen/X86/callbr-asm-branch-folding.ll
+++ b/llvm/test/CodeGen/X86/callbr-asm-branch-folding.ll
@@ -24,7 +24,7 @@ define dso_local void @n(i32* %o, i32 %p, i32 %u) nounwind {
; CHECK-NEXT:    movq %r15, %rdi
; CHECK-NEXT:    callq l
; CHECK-NEXT:    testl %eax, %eax
-; CHECK-NEXT:    jne .LBB0_10
+; CHECK-NEXT:    jne .LBB0_9
; CHECK-NEXT:  # %bb.1: # %if.end
; CHECK-NEXT:    movl %ebx, {{[-0-9]+}}(%r{{[sb]}}p) # 4-byte Spill
; CHECK-NEXT:    cmpl $0, e(%rip)
@@ -44,21 +44,19 @@ define dso_local void @n(i32* %o, i32 %p, i32 %u) nounwind {
; CHECK-NEXT:    callq i
; CHECK-NEXT:    movl %eax, %ebp
; CHECK-NEXT:    orl %r14d, %ebp
-; CHECK-NEXT:    testl %r13d, %r13d
-; CHECK-NEXT:    je .LBB0_6
-; CHECK-NEXT:  # %bb.5:
; CHECK-NEXT:    andl $4, %ebx
-; CHECK-NEXT:    jmp .LBB0_3
-; CHECK-NEXT:  .LBB0_6: # %if.end12
+; CHECK-NEXT:    testl %r13d, %r13d
+; CHECK-NEXT:    jne .LBB0_3
+; CHECK-NEXT:  # %bb.5: # %if.end12
; CHECK-NEXT:    testl %ebp, %ebp
-; CHECK-NEXT:    je .LBB0_9
-; CHECK-NEXT:  # %bb.7: # %if.then14
+; CHECK-NEXT:    je .LBB0_8
+; CHECK-NEXT:  # %bb.6: # %if.then14
; CHECK-NEXT:    movl {{[-0-9]+}}(%r{{[sb]}}p), %eax # 4-byte Reload
; CHECK-NEXT:    #APP
; CHECK-NEXT:    #NO_APP
-; CHECK-NEXT:    jmp .LBB0_10
+; CHECK-NEXT:    jmp .LBB0_9
; CHECK-NEXT:  .Ltmp0: # Block address taken
-; CHECK-NEXT:  # %bb.8: # %if.then20.critedge
+; CHECK-NEXT:  # %bb.7: # %if.then20.critedge
; CHECK-NEXT:    movl j(%rip), %edi
; CHECK-NEXT:    movslq %eax, %rcx
; CHECK-NEXT:    movl $1, %esi
@@ -71,9 +69,9 @@ define dso_local void @n(i32* %o, i32 %p, i32 %u) nounwind {
; CHECK-NEXT:    popq %r15
; CHECK-NEXT:    popq %rbp
; CHECK-NEXT:    jmp k # TAILCALL
-; CHECK-NEXT:  .LBB0_9: # %if.else
+; CHECK-NEXT:  .LBB0_8: # %if.else
; CHECK-NEXT:    incq 0
-; CHECK-NEXT:  .LBB0_10: # %cleanup
+; CHECK-NEXT:  .LBB0_9: # %cleanup
; CHECK-NEXT:    addq $8, %rsp
; CHECK-NEXT:    popq %rbx
; CHECK-NEXT:    popq %r12
diff --git a/llvm/test/CodeGen/X86/pr38795.ll b/llvm/test/CodeGen/X86/pr38795.ll
index d805dcad8b6e..b526e4f471b1 100644
--- a/llvm/test/CodeGen/X86/pr38795.ll
+++ b/llvm/test/CodeGen/X86/pr38795.ll
@@ -32,13 +32,14 @@ define dso_local void @fn() {
; CHECK-NEXT:    # implicit-def: $ebp
; CHECK-NEXT:    jmp .LBB0_1
; CHECK-NEXT:    .p2align 4, 0x90
-; CHECK-NEXT:  .LBB0_16: # %for.inc
+; CHECK-NEXT:  .LBB0_15: # %for.inc
; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    movl %esi, %ecx
; CHECK-NEXT:    movb %dl, {{[-0-9]+}}(%e{{[sb]}}p) # 1-byte Spill
; CHECK-NEXT:    movb %dh, %dl
; CHECK-NEXT:  .LBB0_1: # %for.cond
; CHECK-NEXT:    # =>This Loop Header: Depth=1
-; CHECK-NEXT:    # Child Loop BB0_20 Depth 2
+; CHECK-NEXT:    # Child Loop BB0_19 Depth 2
; CHECK-NEXT:    cmpb $8, %dl
; CHECK-NEXT:    movb %dl, {{[-0-9]+}}(%e{{[sb]}}p) # 1-byte Spill
; CHECK-NEXT:    ja .LBB0_3
@@ -55,7 +56,7 @@ define dso_local void @fn() {
; CHECK-NEXT:    movb %cl, %dh
; CHECK-NEXT:    movl $0, h
; CHECK-NEXT:    cmpb $8, %dl
-; CHECK-NEXT:    jg .LBB0_8
+; CHECK-NEXT:    jg .LBB0_9
; CHECK-NEXT:  # %bb.5: # %if.then13
; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
; CHECK-NEXT:    movl %eax, %esi
@@ -64,12 +65,10 @@ define dso_local void @fn() {
; CHECK-NEXT:    calll printf
; CHECK-NEXT:    movb {{[-0-9]+}}(%e{{[sb]}}p), %dh # 1-byte Reload
; CHECK-NEXT:    testb %bl, %bl
-; CHECK-NEXT:    movl %esi, %ecx
; CHECK-NEXT:    # implicit-def: $eax
-; CHECK-NEXT:    movb {{[-0-9]+}}(%e{{[sb]}}p), %dl # 1-byte Reload
-; CHECK-NEXT:    movb %dl, {{[-0-9]+}}(%e{{[sb]}}p) # 1-byte Spill
+; CHECK-NEXT:    movb {{[-0-9]+}}(%e{{[sb]}}p), %cl # 1-byte Reload
; CHECK-NEXT:    movb %dh, %dl
-; CHECK-NEXT:    jne .LBB0_16
+; CHECK-NEXT:    jne .LBB0_15
; CHECK-NEXT:    jmp .LBB0_6
; CHECK-NEXT:    .p2align 4, 0x90
; CHECK-NEXT:  .LBB0_3: # %if.then
@@ -78,82 +77,82 @@ define dso_local void @fn() {
; CHECK-NEXT:    calll printf
; CHECK-NEXT:    movb {{[-0-9]+}}(%e{{[sb]}}p), %dl # 1-byte Reload
; CHECK-NEXT:    # implicit-def: $eax
+; CHECK-NEXT:    movb {{[-0-9]+}}(%e{{[sb]}}p), %cl # 1-byte Reload
+; CHECK-NEXT:    jmp .LBB0_6
+; CHECK-NEXT:    .p2align 4, 0x90
+; CHECK-NEXT:  .LBB0_9: # %if.end21
+; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    # implicit-def: $ebp
+; CHECK-NEXT:    jmp .LBB0_10
+; CHECK-NEXT:    .p2align 4, 0x90
; CHECK-NEXT:  .LBB0_6: # %for.cond35
; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    movb %dl, %dh
; CHECK-NEXT:    testl %edi, %edi
-; CHECK-NEXT:    je .LBB0_7
-; CHECK-NEXT:  .LBB0_11: # %af
+; CHECK-NEXT:    movl %edi, %esi
+; CHECK-NEXT:    movl $0, %edi
+; CHECK-NEXT:    movb %cl, %dl
+; CHECK-NEXT:    je .LBB0_19
+; CHECK-NEXT:  # %bb.7: # %af
; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
; CHECK-NEXT:    testb %bl, %bl
-; CHECK-NEXT:    jne .LBB0_12
-; CHECK-NEXT:  .LBB0_17: # %if.end39
+; CHECK-NEXT:    jne .LBB0_8
+; CHECK-NEXT:  .LBB0_16: # %if.end39
; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
; CHECK-NEXT:    testl %eax, %eax
-; CHECK-NEXT:    je .LBB0_19
-; CHECK-NEXT:  # %bb.18: # %if.then41
+; CHECK-NEXT:    je .LBB0_18
+; CHECK-NEXT:  # %bb.17: # %if.then41
; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
; CHECK-NEXT:    movl $0, {{[0-9]+}}(%esp)
; CHECK-NEXT:    movl $fn, {{[0-9]+}}(%esp)
; CHECK-NEXT:    movl $.str, (%esp)
; CHECK-NEXT:    calll printf
-; CHECK-NEXT:  .LBB0_19: # %for.end46
+; CHECK-NEXT:  .LBB0_18: # %for.end46
; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    movl %esi, %edi
; CHECK-NEXT:    # implicit-def: $dl
; CHECK-NEXT:    # implicit-def: $dh
; CHECK-NEXT:    # implicit-def: $ebp
-; CHECK-NEXT:    jmp .LBB0_20
-; CHECK-NEXT:    .p2align 4, 0x90
-; CHECK-NEXT:  .LBB0_8: # %if.end21
-; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
-; CHECK-NEXT:    # implicit-def: $ebp
-; CHECK-NEXT:    jmp .LBB0_9
; CHECK-NEXT:    .p2align 4, 0x90
-; CHECK-NEXT:  .LBB0_7: # in Loop: Header=BB0_1 Depth=1
-; CHECK-NEXT:    xorl %edi, %edi
-; CHECK-NEXT:    movb %dl, %dh
-; CHECK-NEXT:    movb {{[-0-9]+}}(%e{{[sb]}}p), %dl # 1-byte Reload
-; CHECK-NEXT:    .p2align 4, 0x90
-; CHECK-NEXT:  .LBB0_20: # %for.cond47
+; CHECK-NEXT:  .LBB0_19: # %for.cond47
; CHECK-NEXT:    # Parent Loop BB0_1 Depth=1
; CHECK-NEXT:    # => This Inner Loop Header: Depth=2
; CHECK-NEXT:    testb %bl, %bl
-; CHECK-NEXT:    jne .LBB0_20
-; CHECK-NEXT:  # %bb.21: # %for.cond47
-; CHECK-NEXT:    # in Loop: Header=BB0_20 Depth=2
+; CHECK-NEXT:    jne .LBB0_19
+; CHECK-NEXT:  # %bb.20: # %for.cond47
+; CHECK-NEXT:    # in Loop: Header=BB0_19 Depth=2
; CHECK-NEXT:    testb %bl, %bl
-; CHECK-NEXT:    jne .LBB0_20
-; CHECK-NEXT:  .LBB0_9: # %ae
+; CHECK-NEXT:    jne .LBB0_19
+; CHECK-NEXT:  .LBB0_10: # %ae
; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
; CHECK-NEXT:    testb %bl, %bl
-; CHECK-NEXT:    jne .LBB0_10
-; CHECK-NEXT:  # %bb.13: # %if.end26
+; CHECK-NEXT:    jne .LBB0_11
+; CHECK-NEXT:  # %bb.12: # %if.end26
; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
-; CHECK-NEXT:    xorl %ecx, %ecx
+; CHECK-NEXT:    xorl %esi, %esi
; CHECK-NEXT:    testb %dl, %dl
-; CHECK-NEXT:    je .LBB0_16
-; CHECK-NEXT:  # %bb.14: # %if.end26
+; CHECK-NEXT:    je .LBB0_15
+; CHECK-NEXT:  # %bb.13: # %if.end26
; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
; CHECK-NEXT:    testl %ebp, %ebp
-; CHECK-NEXT:    jne .LBB0_16
-; CHECK-NEXT:  # %bb.15: # %if.then31
+; CHECK-NEXT:    jne .LBB0_15
+; CHECK-NEXT:  # %bb.14: # %if.then31
; CHECK-NEXT:    # in Loop: Header=BB0_1 Depth=1
-; CHECK-NEXT:    xorl %ecx, %ecx
+; CHECK-NEXT:    xorl %esi, %esi
; CHECK-NEXT:    xorl %ebp, %ebp
-; CHECK-NEXT:    jmp .LBB0_16
+; CHECK-NEXT:    jmp .LBB0_15
; CHECK-NEXT:    .p2align 4, 0x90
-; CHECK-NEXT:  .LBB0_10: # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:  .LBB0_11: # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    movl %edi, %esi
; CHECK-NEXT:    # implicit-def: $eax
; CHECK-NEXT:    testb %bl, %bl
-; CHECK-NEXT:    je .LBB0_17
-; CHECK-NEXT:  .LBB0_12: # in Loop: Header=BB0_1 Depth=1
+; CHECK-NEXT:    je .LBB0_16
+; CHECK-NEXT:  .LBB0_8: # in Loop: Header=BB0_1 Depth=1
; CHECK-NEXT:    # implicit-def: $edi
; CHECK-NEXT:    # implicit-def: $cl
-; CHECK-NEXT:    # kill: killed $cl
; CHECK-NEXT:    # implicit-def: $dl
; CHECK-NEXT:    # implicit-def: $ebp
-; CHECK-NEXT:    testl %edi, %edi
-; CHECK-NEXT:    jne .LBB0_11
-; CHECK-NEXT:    jmp .LBB0_7
+; CHECK-NEXT:    jmp .LBB0_6
entry:
  br label %for.cond
diff --git a/llvm/test/CodeGen/X86/pr53990-incorrect-machine-sink.ll b/llvm/test/CodeGen/X86/pr53990-incorrect-machine-sink.ll
index 3d7ff6cbe676..4f56d7b16a87 100644
--- a/llvm/test/CodeGen/X86/pr53990-incorrect-machine-sink.ll
+++ b/llvm/test/CodeGen/X86/pr53990-incorrect-machine-sink.ll
@@ -7,18 +7,15 @@ define void @test(i1 %c, i64* %p, i64* noalias %p2) nounwind {
; CHECK-LABEL: test:
; CHECK:       # %bb.0: # %entry
; CHECK-NEXT:    pushq %rbp
-; CHECK-NEXT:    pushq %r15
; CHECK-NEXT:    pushq %r14
; CHECK-NEXT:    pushq %rbx
-; CHECK-NEXT:    pushq %rax
; CHECK-NEXT:    movq %rdx, %rbx
-; CHECK-NEXT:    movq %rsi, %r14
-; CHECK-NEXT:    movl %edi, %r15d
+; CHECK-NEXT:    movl %edi, %r14d
+; CHECK-NEXT:    movq (%rsi), %rbp
; CHECK-NEXT:    xorl %eax, %eax
; CHECK-NEXT:    jmpq *.LJTI0_0(,%rax,8)
; CHECK-NEXT:  .LBB0_1: # %split.3
-; CHECK-NEXT:    movq (%r14), %rbp
-; CHECK-NEXT:    testb $1, %r15b
+; CHECK-NEXT:    testb $1, %r14b
; CHECK-NEXT:    je .LBB0_3
; CHECK-NEXT:  # %bb.2: # %clobber
; CHECK-NEXT:    callq clobber@PLT
diff --git a/llvm/test/CodeGen/X86/x86-shrink-wrapping.ll b/llvm/test/CodeGen/X86/x86-shrink-wrapping.ll
index 0f8bb837f82a..b44895293b41 100644
--- a/llvm/test/CodeGen/X86/x86-shrink-wrapping.ll
+++ b/llvm/test/CodeGen/X86/x86-shrink-wrapping.ll
@@ -1377,6 +1377,8 @@ define i32 @irreducibleCFG() #4 {
; ENABLE-NEXT:    pushq %rbx
; ENABLE-NEXT:    pushq %rax
; ENABLE-NEXT:    .cfi_offset %rbx, -24
+; ENABLE-NEXT:    movq _irreducibleCFGa@GOTPCREL(%rip), %rax
+; ENABLE-NEXT:    movl (%rax), %edi
; ENABLE-NEXT:    movq _irreducibleCFGf@GOTPCREL(%rip), %rax
; ENABLE-NEXT:    cmpb $0, (%rax)
; ENABLE-NEXT:    je LBB16_2
@@ -1386,24 +1388,20 @@ define i32 @irreducibleCFG() #4 {
; ENABLE-NEXT:    jmp LBB16_1
; ENABLE-NEXT:  LBB16_2: ## %split
; ENABLE-NEXT:    movq _irreducibleCFGb@GOTPCREL(%rip), %rax
+; ENABLE-NEXT:    xorl %ebx, %ebx
; ENABLE-NEXT:    cmpl $0, (%rax)
-; ENABLE-NEXT:    je LBB16_3
-; ENABLE-NEXT:  ## %bb.4: ## %for.body4.i
-; ENABLE-NEXT:    movq _irreducibleCFGa@GOTPCREL(%rip), %rax
-; ENABLE-NEXT:    movl (%rax), %edi
+; ENABLE-NEXT:    je LBB16_4
+; ENABLE-NEXT:  ## %bb.3: ## %for.body4.i
; ENABLE-NEXT:    xorl %ebx, %ebx
; ENABLE-NEXT:    xorl %eax, %eax
; ENABLE-NEXT:    callq _something
-; ENABLE-NEXT:    jmp LBB16_5
-; ENABLE-NEXT:  LBB16_3:
-; ENABLE-NEXT:    xorl %ebx, %ebx
; ENABLE-NEXT:    .p2align 4, 0x90
-; ENABLE-NEXT:  LBB16_5: ## %for.inc
+; ENABLE-NEXT:  LBB16_4: ## %for.inc
; ENABLE-NEXT:    ## =>This Inner Loop Header: Depth=1
; ENABLE-NEXT:    incl %ebx
; ENABLE-NEXT:    cmpl $7, %ebx
-; ENABLE-NEXT:    jl LBB16_5
-; ENABLE-NEXT:  ## %bb.6: ## %fn1.exit
+; ENABLE-NEXT:    jl LBB16_4
+; ENABLE-NEXT:  ## %bb.5: ## %fn1.exit
; ENABLE-NEXT:    xorl %eax, %eax
; ENABLE-NEXT:    addq $8, %rsp
; ENABLE-NEXT:    popq %rbx
@@ -1420,6 +1418,8 @@ define i32 @irreducibleCFG() #4 {
; DISABLE-NEXT:    pushq %rbx
; DISABLE-NEXT:    pushq %rax
; DISABLE-NEXT:    .cfi_offset %rbx, -24
+; DISABLE-NEXT:    movq _irreducibleCFGa@GOTPCREL(%rip), %rax
+; DISABLE-NEXT:    movl (%rax), %edi
; DISABLE-NEXT:    movq _irreducibleCFGf@GOTPCREL(%rip), %rax
; DISABLE-NEXT:    cmpb $0, (%rax)
; DISABLE-NEXT:    je LBB16_2
@@ -1429,24 +1429,20 @@ define i32 @irreducibleCFG() #4 {
; DISABLE-NEXT:    jmp LBB16_1
; DISABLE-NEXT:  LBB16_2: ## %split
; DISABLE-NEXT:    movq _irreducibleCFGb@GOTPCREL(%rip), %rax
+; DISABLE-NEXT:    xorl %ebx, %ebx
; DISABLE-NEXT:    cmpl $0, (%rax)
-; DISABLE-NEXT:    je LBB16_3
-; DISABLE-NEXT:  ## %bb.4: ## %for.body4.i
-; DISABLE-NEXT:    movq _irreducibleCFGa@GOTPCREL(%rip), %rax
-; DISABLE-NEXT:    movl (%rax), %edi
+; DISABLE-NEXT:    je LBB16_4
+; DISABLE-NEXT:  ## %bb.3: ## %for.body4.i
; DISABLE-NEXT:    xorl %ebx, %ebx
; DISABLE-NEXT:    xorl %eax, %eax
; DISABLE-NEXT:    callq _something
-; DISABLE-NEXT:    jmp LBB16_5
-; DISABLE-NEXT:  LBB16_3:
-; DISABLE-NEXT:    xorl %ebx, %ebx
; DISABLE-NEXT:    .p2align 4, 0x90
-; DISABLE-NEXT:  LBB16_5: ## %for.inc
+; DISABLE-NEXT:  LBB16_4: ## %for.inc
; DISABLE-NEXT:    ## =>This Inner Loop Header: Depth=1
; DISABLE-NEXT:    incl %ebx
; DISABLE-NEXT:    cmpl $7, %ebx
-; DISABLE-NEXT:    jl LBB16_5
-; DISABLE-NEXT:  ## %bb.6: ## %fn1.exit
+; DISABLE-NEXT:    jl LBB16_4
+; DISABLE-NEXT:  ## %bb.5: ## %fn1.exit
; DISABLE-NEXT:    xorl %eax, %eax
; DISABLE-NEXT:    addq $8, %rsp
; DISABLE-NEXT:    popq %rbx
</cut>

    