[LoopUnrollRuntime] Support multiple exit blocks unrolling when prolog remainder...

With the NFC refactoring in rL307417 (git SHA 987dd01), all the logic
is in place to support multiple exit/exiting blocks when prolog
remainder is generated.
This patch removed the assert that multiple exit blocks unrolling is only
supported when epilog remainder is generated.

Also, added test runs and checks with PROLOG prefix in
runtime-loop-multiple-exits.ll test cases.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@307435 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Utils/LoopUnrollRuntime.cpp b/lib/Transforms/Utils/LoopUnrollRuntime.cpp
index 5b3282c59402de040f11126bfac804d4b84fb060..8733a1388dfc4e488b048d69316145c5e31664aa 100644 (file)
--- a/lib/Transforms/Utils/LoopUnrollRuntime.cpp
+++ b/lib/Transforms/Utils/LoopUnrollRuntime.cpp
@@ -497,8 +497,6 @@ bool llvm::UnrollRuntimeLoopRemainder(Loop *L, unsigned Count,
   // Support runtime unrolling for multiple exit blocks and multiple exiting
   // blocks.
   if (!LatchExit) {
-    assert(UseEpilogRemainder && "Multi exit unrolling is currently supported "
-                                 "unrolling with epilog remainder only!");
     LatchExit = LatchBR->getSuccessor(ExitIndex);
     // We rely on LCSSA form being preserved when the exit blocks are
     // transformed.

diff --git a/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll b/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll
index 5cff94906d8ec939d8d336677fd82b32d2b1a8b4..eaff2d6a743a7d59b44ccd71cd20adc4266c67b9 100644 (file)
--- a/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll
+++ b/test/Transforms/LoopUnroll/runtime-loop-multiple-exits.ll
@@ -1,29 +1,51 @@
-; RUN: opt < %s -loop-unroll -unroll-runtime=true -unroll-runtime-epilog=true -unroll-runtime-multi-exit=true -verify-dom-info -verify-loop-info -instcombine -S| FileCheck %s
+; RUN: opt < %s -loop-unroll -unroll-runtime=true -unroll-runtime-epilog=true -unroll-runtime-multi-exit=true -verify-dom-info -verify-loop-info -instcombine -S | FileCheck %s -check-prefix=EPILOG
 ; RUN: opt < %s -loop-unroll -unroll-runtime -unroll-count=2 -unroll-runtime-epilog=true -unroll-runtime-multi-exit=true -verify-dom-info -verify-loop-info -instcombine
+; RUN: opt < %s -loop-unroll -unroll-runtime=true -unroll-runtime-epilog=false -unroll-runtime-multi-exit=true -verify-dom-info -verify-loop-info -instcombine -S | FileCheck %s -check-prefix=PROLOG
+; RUN: opt < %s -loop-unroll -unroll-runtime -unroll-runtime-epilog=false -unroll-count=2 -unroll-runtime-multi-exit=true -verify-dom-info -verify-loop-info -instcombine
 
-; the second RUN generates an epilog remainder block for all the test
+; the second and fourth RUNs generate an epilog/prolog remainder block for all the test
 ; cases below (it does not generate a loop).
 
 ; test with three exiting and three exit blocks.
 ; none of the exit blocks have successors
 define void @test1(i64 %trip, i1 %cond) {
-; CHECK-LABEL: test1
-; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[TMP0:%.*]] = add i64 [[TRIP:%.*]], -1
-; CHECK-NEXT:    [[XTRAITER:%.*]] = and i64 [[TRIP]], 7
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp ult i64 [[TMP0]], 7
-; CHECK-NEXT:    br i1 [[TMP1]], label %exit2.loopexit.unr-lcssa, label [[ENTRY_NEW:%.*]]
-; CHECK:       entry.new:
-; CHECK-NEXT:    [[UNROLL_ITER:%.*]] = sub i64 [[TRIP]], [[XTRAITER]]
-; CHECK-NEXT:    br label [[LOOP_HEADER:%.*]]
-; CHECK-LABEL:  loop_latch.epil:
-; CHECK-NEXT:     %epil.iter.sub = add i64 %epil.iter, -1
-; CHECK-NEXT:     %epil.iter.cmp = icmp eq i64 %epil.iter.sub, 0
-; CHECK-NEXT:     br i1 %epil.iter.cmp, label %exit2.loopexit.epilog-lcssa, label %loop_header.epil
-; CHECK-LABEL:  loop_latch.7:
-; CHECK-NEXT:     %niter.nsub.7 = add i64 %niter, -8
-; CHECK-NEXT:     %niter.ncmp.7 = icmp eq i64 %niter.nsub.7, 0
-; CHECK-NEXT:     br i1 %niter.ncmp.7, label %exit2.loopexit.unr-lcssa.loopexit, label %loop_header
+; EPILOG: test1(
+; EPILOG-NEXT:  entry:
+; EPILOG-NEXT:    [[TMP0:%.*]] = add i64 [[TRIP:%.*]], -1
+; EPILOG-NEXT:    [[XTRAITER:%.*]] = and i64 [[TRIP]], 7
+; EPILOG-NEXT:    [[TMP1:%.*]] = icmp ult i64 [[TMP0]], 7
+; EPILOG-NEXT:    br i1 [[TMP1]], label %exit2.loopexit.unr-lcssa, label [[ENTRY_NEW:%.*]]
+; EPILOG:       entry.new:
+; EPILOG-NEXT:    [[UNROLL_ITER:%.*]] = sub i64 [[TRIP]], [[XTRAITER]]
+; EPILOG-NEXT:    br label [[LOOP_HEADER:%.*]]
+; EPILOG:  loop_latch.epil:
+; EPILOG-NEXT:     %epil.iter.sub = add i64 %epil.iter, -1
+; EPILOG-NEXT:     %epil.iter.cmp = icmp eq i64 %epil.iter.sub, 0
+; EPILOG-NEXT:     br i1 %epil.iter.cmp, label %exit2.loopexit.epilog-lcssa, label %loop_header.epil
+; EPILOG:  loop_latch.7:
+; EPILOG-NEXT:     %niter.nsub.7 = add i64 %niter, -8
+; EPILOG-NEXT:     %niter.ncmp.7 = icmp eq i64 %niter.nsub.7, 0
+; EPILOG-NEXT:     br i1 %niter.ncmp.7, label %exit2.loopexit.unr-lcssa.loopexit, label %loop_header
+
+; PROLOG: test1(
+; PROLOG-NEXT:  entry:
+; PROLOG-NEXT:    [[TMP0:%.*]] = add i64 [[TRIP:%.*]], -1
+; PROLOG-NEXT:    [[XTRAITER:%.*]] = and i64 [[TRIP]], 7
+; PROLOG-NEXT:    [[TMP1:%.*]] = icmp eq i64 [[XTRAITER]], 0
+; PROLOG-NEXT:    br i1 [[TMP1]], label %loop_header.prol.loopexit, label %loop_header.prol.preheader
+; PROLOG:       loop_header.prol:
+; PROLOG-NEXT:    %iv.prol = phi i64 [ 0, %loop_header.prol.preheader ], [ %iv_next.prol, %loop_latch.prol ]
+; PROLOG-NEXT:    %prol.iter = phi i64 [ [[XTRAITER]], %loop_header.prol.preheader ], [ %prol.iter.sub, %loop_latch.prol ]
+; PROLOG-NEXT:    br i1 %cond, label %loop_latch.prol, label %loop_exiting_bb1.prol
+; PROLOG:       loop_latch.prol:
+; PROLOG-NEXT:    %iv_next.prol = add i64 %iv.prol, 1
+; PROLOG-NEXT:    %prol.iter.sub = add i64 %prol.iter, -1
+; PROLOG-NEXT:    %prol.iter.cmp = icmp eq i64 %prol.iter.sub, 0
+; PROLOG-NEXT:    br i1 %prol.iter.cmp, label %loop_header.prol.loopexit.unr-lcssa, label %loop_header.prol
+; PROLOG:  loop_latch.7:
+; PROLOG-NEXT:     %iv_next.7 = add i64 %iv, 8
+; PROLOG-NEXT:     %cmp.7 = icmp eq i64 %iv_next.7, %trip
+; PROLOG-NEXT:     br i1 %cmp.7, label %exit2.loopexit.unr-lcssa, label %loop_header
 entry:
   br label %loop_header
 
@@ -59,17 +81,30 @@ exit2.loopexit:
 ; %sum.02 and %add. Both of these are incoming values for phi from every exiting
 ; unrolled block.
 define i32 @test2(i32* nocapture %a, i64 %n) {
-; CHECK-LABEL: test2
-; CHECK-LABEL: for.exit2.loopexit:
-; CHECK-NEXT:    %retval.ph = phi i32 [ 42, %for.exiting_block ], [ %sum.02, %header ], [ %add, %for.body ], [ 42, %for.exiting_block.1 ], [ %add.1, %for.body.1 ], [ 42, %for.exiting_block.2 ], [ %add.2, %for.body.2 ], [ 42, %for.exiting_block.3 ],
-; CHECK-NEXT:    br label %for.exit2
-; CHECK-LABEL: for.exit2.loopexit2:
-; CHECK-NEXT:    %retval.ph3 = phi i32 [ 42, %for.exiting_block.epil ], [ %sum.02.epil, %header.epil ]
-; CHECK-NEXT:    br label %for.exit2
-; CHECK-LABEL: for.exit2:
-; CHECK-NEXT:    %retval = phi i32 [ %retval.ph, %for.exit2.loopexit ], [ %retval.ph3, %for.exit2.loopexit2 ]
-; CHECK-NEXT:    ret i32 %retval
-; CHECK: %niter.nsub.7 = add i64 %niter, -8
+; EPILOG: test2(
+; EPILOG: for.exit2.loopexit:
+; EPILOG-NEXT:    %retval.ph = phi i32 [ 42, %for.exiting_block ], [ %sum.02, %header ], [ %add, %for.body ], [ 42, %for.exiting_block.1 ], [ %add.1, %for.body.1 ], [ 42, %for.exiting_block.2 ], [ %add.2, %for.body.2 ], [ 42, %for.exiting_block.3 ],
+; EPILOG-NEXT:    br label %for.exit2
+; EPILOG: for.exit2.loopexit2:
+; EPILOG-NEXT:    %retval.ph3 = phi i32 [ 42, %for.exiting_block.epil ], [ %sum.02.epil, %header.epil ]
+; EPILOG-NEXT:    br label %for.exit2
+; EPILOG: for.exit2:
+; EPILOG-NEXT:    %retval = phi i32 [ %retval.ph, %for.exit2.loopexit ], [ %retval.ph3, %for.exit2.loopexit2 ]
+; EPILOG-NEXT:    ret i32 %retval
+; EPILOG: %niter.nsub.7 = add i64 %niter, -8
+
+; PROLOG: test2(
+; PROLOG: for.exit2.loopexit:
+; PROLOG-NEXT:    %retval.ph = phi i32 [ 42, %for.exiting_block ], [ %sum.02, %header ], [ %add, %for.body ], [ 42, %for.exiting_block.1 ], [ %add.1, %for.body.1 ], [ 42, %for.exiting_block.2 ], [ %add.2, %for.body.2 ], [ 42, %for.exiting_block.3 ],
+; PROLOG-NEXT:    br label %for.exit2
+; PROLOG: for.exit2.loopexit1:
+; PROLOG-NEXT:    %retval.ph2 = phi i32 [ 42, %for.exiting_block.prol ], [ %sum.02.prol, %header.prol ]
+; PROLOG-NEXT:    br label %for.exit2
+; PROLOG: for.exit2:
+; PROLOG-NEXT:    %retval = phi i32 [ %retval.ph, %for.exit2.loopexit ], [ %retval.ph2, %for.exit2.loopexit1 ]
+; PROLOG-NEXT:    ret i32 %retval
+; PROLOG: %indvars.iv.next.7 = add i64 %indvars.iv, 8
+
 entry:
   br label %header
 
@@ -102,25 +137,42 @@ for.exit2:
 ; test with two exiting and three exit blocks.
 ; the non-latch exiting block has a switch.
 define void @test3(i64 %trip, i64 %add) {
-; CHECK-LABEL: test3
-; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[TMP0:%.*]] = add i64 [[TRIP:%.*]], -1
-; CHECK-NEXT:    [[XTRAITER:%.*]] = and i64 [[TRIP]], 7
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp ult i64 [[TMP0]], 7
-; CHECK-NEXT:    br i1 [[TMP1]], label %exit2.loopexit.unr-lcssa, label [[ENTRY_NEW:%.*]]
-; CHECK:       entry.new:
-; CHECK-NEXT:    %unroll_iter = sub i64 [[TRIP]], [[XTRAITER]]
-; CHECK-NEXT:    br label [[LOOP_HEADER:%.*]]
-; CHECK-LABEL:  loop_header:
-; CHECK-NEXT:     %sum = phi i64 [ 0, %entry.new ], [ %sum.next.7, %loop_latch.7 ]
-; CHECK-NEXT:     %niter = phi i64 [ %unroll_iter, %entry.new ], [ %niter.nsub.7, %loop_latch.7 ]
-; CHECK-LABEL:  loop_exiting_bb1.7:
-; CHECK-NEXT:     switch i64 %sum.next.6, label %loop_latch.7
-; CHECK-LABEL:  loop_latch.7:
-; CHECK-NEXT:     %sum.next.7 = add i64 %sum.next.6, %add
-; CHECK-NEXT:     %niter.nsub.7 = add i64 %niter, -8
-; CHECK-NEXT:     %niter.ncmp.7 = icmp eq i64 %niter.nsub.7, 0
-; CHECK-NEXT:     br i1 %niter.ncmp.7, label %exit2.loopexit.unr-lcssa.loopexit, label %loop_header
+; EPILOG: test3(
+; EPILOG-NEXT:  entry:
+; EPILOG-NEXT:    [[TMP0:%.*]] = add i64 [[TRIP:%.*]], -1
+; EPILOG-NEXT:    [[XTRAITER:%.*]] = and i64 [[TRIP]], 7
+; EPILOG-NEXT:    [[TMP1:%.*]] = icmp ult i64 [[TMP0]], 7
+; EPILOG-NEXT:    br i1 [[TMP1]], label %exit2.loopexit.unr-lcssa, label [[ENTRY_NEW:%.*]]
+; EPILOG:       entry.new:
+; EPILOG-NEXT:    %unroll_iter = sub i64 [[TRIP]], [[XTRAITER]]
+; EPILOG-NEXT:    br label [[LOOP_HEADER:%.*]]
+; EPILOG:  loop_header:
+; EPILOG-NEXT:     %sum = phi i64 [ 0, %entry.new ], [ %sum.next.7, %loop_latch.7 ]
+; EPILOG-NEXT:     %niter = phi i64 [ %unroll_iter, %entry.new ], [ %niter.nsub.7, %loop_latch.7 ]
+; EPILOG:  loop_exiting_bb1.7:
+; EPILOG-NEXT:     switch i64 %sum.next.6, label %loop_latch.7
+; EPILOG:  loop_latch.7:
+; EPILOG-NEXT:     %sum.next.7 = add i64 %sum.next.6, %add
+; EPILOG-NEXT:     %niter.nsub.7 = add i64 %niter, -8
+; EPILOG-NEXT:     %niter.ncmp.7 = icmp eq i64 %niter.nsub.7, 0
+; EPILOG-NEXT:     br i1 %niter.ncmp.7, label %exit2.loopexit.unr-lcssa.loopexit, label %loop_header
+
+; PROLOG:  test3(
+; PROLOG-NEXT:  entry:
+; PROLOG-NEXT:    [[TMP0:%.*]] = add i64 [[TRIP:%.*]], -1
+; PROLOG-NEXT:    [[XTRAITER:%.*]] = and i64 [[TRIP]], 7
+; PROLOG-NEXT:    [[TMP1:%.*]] = icmp eq i64 [[XTRAITER]], 0
+; PROLOG-NEXT:    br i1 [[TMP1]], label %loop_header.prol.loopexit, label %loop_header.prol.preheader
+; PROLOG:  loop_header:
+; PROLOG-NEXT:     %iv = phi i64 [ %iv.unr, %entry.new ], [ %iv_next.7, %loop_latch.7 ]
+; PROLOG-NEXT:     %sum = phi i64 [ %sum.unr, %entry.new ], [ %sum.next.7, %loop_latch.7 ]
+; PROLOG:  loop_exiting_bb1.7:
+; PROLOG-NEXT:     switch i64 %sum.next.6, label %loop_latch.7
+; PROLOG:  loop_latch.7:
+; PROLOG-NEXT:     %iv_next.7 = add nsw i64 %iv, 8
+; PROLOG-NEXT:     %sum.next.7 = add i64 %sum.next.6, %add
+; PROLOG-NEXT:     %cmp.7 = icmp eq i64 %iv_next.7, %trip
+; PROLOG-NEXT:     br i1 %cmp.7, label %exit2.loopexit.unr-lcssa, label %loop_header
 entry:
   br label %loop_header
 
@@ -153,9 +205,13 @@ exit2.loopexit:
 
 ; FIXME: Support multiple exiting blocks to the same latch exit block.
 define i32 @test4(i32* nocapture %a, i64 %n, i1 %cond) {
-; CHECK-LABEL: test4
-; CHECK-NOT: .unr
-; CHECK-NOT: .epil
+; EPILOG: test4(
+; EPILOG-NOT: .unr
+; EPILOG-NOT: .epil
+
+; PROLOG: test4(
+; PROLOG-NOT: .unr
+; PROLOG-NOT: .prol
 entry:
   br label %header
 
@@ -186,9 +242,13 @@ for.exit2:
 
 ; FIXME: Support multiple exiting blocks to the unique exit block.
 define void @unique_exit(i32 %arg) {
-; CHECK-LABEL: unique_exit
-; CHECK-NOT: .unr
-; CHECK-NOT: .epil
+; EPILOG: unique_exit(
+; EPILOG-NOT: .unr
+; EPILOG-NOT: .epil
+
+; PROLOG: unique_exit(
+; PROLOG-NOT: .unr
+; PROLOG-NOT: .prol
 entry:
   %tmp = icmp sgt i32 undef, %arg
   br i1 %tmp, label %preheader, label %returnblock
@@ -217,18 +277,31 @@ latch:                                            ; preds = %header
 ; two exiting and two exit blocks.
 ; the non-latch exiting block has duplicate edges to the non-latch exit block.
 define i64 @test5(i64 %trip, i64 %add, i1 %cond) {
-; CHECK-LABEL: test5
-; CHECK-LABEL:   exit1.loopexit:
-; CHECK-NEXT:      %result.ph = phi i64 [ %ivy, %loop_exiting ], [ %ivy, %loop_exiting ], [ %ivy.1, %loop_exiting.1 ], [ %ivy.1, %loop_exiting.1 ], [ %ivy.2, %loop_exiting.2 ],
-; CHECK-NEXT:      br label %exit1
-; CHECK-LABEL:   exit1.loopexit2:
-; CHECK-NEXT:      %ivy.epil = add i64 %iv.epil, %add
-; CHECK-NEXT:      br label %exit1
-; CHECK-LABEL:   exit1:
-; CHECK-NEXT:      %result = phi i64 [ %result.ph, %exit1.loopexit ], [ %ivy.epil, %exit1.loopexit2 ]
-; CHECK-NEXT:      ret i64 %result
-; CHECK-LABEL:   loop_latch.7:
-; CHECK: %niter.nsub.7 = add i64 %niter, -8
+; EPILOG: test5(
+; EPILOG:   exit1.loopexit:
+; EPILOG-NEXT:      %result.ph = phi i64 [ %ivy, %loop_exiting ], [ %ivy, %loop_exiting ], [ %ivy.1, %loop_exiting.1 ], [ %ivy.1, %loop_exiting.1 ], [ %ivy.2, %loop_exiting.2 ],
+; EPILOG-NEXT:      br label %exit1
+; EPILOG:   exit1.loopexit2:
+; EPILOG-NEXT:      %ivy.epil = add i64 %iv.epil, %add
+; EPILOG-NEXT:      br label %exit1
+; EPILOG:   exit1:
+; EPILOG-NEXT:      %result = phi i64 [ %result.ph, %exit1.loopexit ], [ %ivy.epil, %exit1.loopexit2 ]
+; EPILOG-NEXT:      ret i64 %result
+; EPILOG:   loop_latch.7:
+; EPILOG:      %niter.nsub.7 = add i64 %niter, -8
+
+; PROLOG: test5(
+; PROLOG:   exit1.loopexit:
+; PROLOG-NEXT:      %result.ph = phi i64 [ %ivy, %loop_exiting ], [ %ivy, %loop_exiting ], [ %ivy.1, %loop_exiting.1 ], [ %ivy.1, %loop_exiting.1 ], [ %ivy.2, %loop_exiting.2 ],
+; PROLOG-NEXT:      br label %exit1
+; PROLOG:   exit1.loopexit1:
+; PROLOG-NEXT:      %ivy.prol = add i64 %iv.prol, %add
+; PROLOG-NEXT:      br label %exit1
+; PROLOG:   exit1:
+; PROLOG-NEXT:      %result = phi i64 [ %result.ph, %exit1.loopexit ], [ %ivy.prol, %exit1.loopexit1 ]
+; PROLOG-NEXT:      ret i64 %result
+; PROLOG:   loop_latch.7:
+; PROLOG:      %iv_next.7 = add nsw i64 %iv, 8
 entry:
   br label %loop_header
 
@@ -260,18 +333,31 @@ latchexit:
 
 ; test when exit blocks have successors.
 define i32 @test6(i32* nocapture %a, i64 %n, i1 %cond, i32 %x) {
-; CHECK-LABEL: test6
-; CHECK-LABEL:   for.exit2.loopexit:
-; CHECK-NEXT:      %retval.ph = phi i32 [ 42, %for.exiting_block ], [ %sum.02, %header ], [ %add, %latch ], [ 42, %for.exiting_block.1 ], [ %add.1, %latch.1 ], [ 42, %for.exiting_block.2 ], [ %add.2, %latch.2 ],
-; CHECK-NEXT:      br label %for.exit2
-; CHECK-LABEL:   for.exit2.loopexit2:
-; CHECK-NEXT:      %retval.ph3 = phi i32 [ 42, %for.exiting_block.epil ], [ %sum.02.epil, %header.epil ]
-; CHECK-NEXT:      br label %for.exit2
-; CHECK-LABEL:   for.exit2:
-; CHECK-NEXT:      %retval = phi i32 [ %retval.ph, %for.exit2.loopexit ], [ %retval.ph3, %for.exit2.loopexit2 ]
-; CHECK-NEXT:      br i1 %cond, label %exit_true, label %exit_false
-; CHECK-LABEL:   latch.7:
-; CHECK:           %niter.nsub.7 = add i64 %niter, -8
+; EPILOG: test6(
+; EPILOG:   for.exit2.loopexit:
+; EPILOG-NEXT:      %retval.ph = phi i32 [ 42, %for.exiting_block ], [ %sum.02, %header ], [ %add, %latch ], [ 42, %for.exiting_block.1 ], [ %add.1, %latch.1 ], [ 42, %for.exiting_block.2 ], [ %add.2, %latch.2 ],
+; EPILOG-NEXT:      br label %for.exit2
+; EPILOG:   for.exit2.loopexit2:
+; EPILOG-NEXT:      %retval.ph3 = phi i32 [ 42, %for.exiting_block.epil ], [ %sum.02.epil, %header.epil ]
+; EPILOG-NEXT:      br label %for.exit2
+; EPILOG:   for.exit2:
+; EPILOG-NEXT:      %retval = phi i32 [ %retval.ph, %for.exit2.loopexit ], [ %retval.ph3, %for.exit2.loopexit2 ]
+; EPILOG-NEXT:      br i1 %cond, label %exit_true, label %exit_false
+; EPILOG:   latch.7:
+; EPILOG:           %niter.nsub.7 = add i64 %niter, -8
+
+; PROLOG: test6(
+; PROLOG:   for.exit2.loopexit:
+; PROLOG-NEXT:      %retval.ph = phi i32 [ 42, %for.exiting_block ], [ %sum.02, %header ], [ %add, %latch ], [ 42, %for.exiting_block.1 ], [ %add.1, %latch.1 ], [ 42, %for.exiting_block.2 ], [ %add.2, %latch.2 ],
+; PROLOG-NEXT:      br label %for.exit2
+; PROLOG:   for.exit2.loopexit1:
+; PROLOG-NEXT:      %retval.ph2 = phi i32 [ 42, %for.exiting_block.prol ], [ %sum.02.prol, %header.prol ]
+; PROLOG-NEXT:      br label %for.exit2
+; PROLOG:   for.exit2:
+; PROLOG-NEXT:      %retval = phi i32 [ %retval.ph, %for.exit2.loopexit ], [ %retval.ph2, %for.exit2.loopexit1 ]
+; PROLOG-NEXT:      br i1 %cond, label %exit_true, label %exit_false
+; PROLOG: latch.7:
+; PROLOG:   %indvars.iv.next.7 = add i64 %indvars.iv, 8
 entry:
   br label %header