[GuardWidening] Choose right point for generating wide condition for …

…branches. PR60234

When guards are represented as widenable branches, there is a tricky
situation when the branch stays in loop but widenable condition doesn't.
It means that the widenable condition is loop-invariant, and some other
optimizations could have done changes using this fact.

If widening is allowed to create widened condition inside this loop,
and join the loop-invariant wc with some non-invariant facts, it can
cause miscompile. See example of this at #60234.

The solution is to adjust the point of generationg the wide condition,
and therefore of hoisting all related parts there. It should not be before
the branch, but before the widenable_condition call. The fact that `wc()`
and the wide condition are in the same block guarantees that they will
not violate the invariance property for any loop.

Differential Revision: https://reviews.llvm.org/D142693
Reviewed By: apilipenko

llvm/lib/Transforms/Scalar/GuardWidening.cpp

@@ -113,6 +113,23 @@ static void eliminateGuard(Instruction *GuardInst, MemorySSAUpdater *MSSAU) {
   ++GuardsEliminated;
 }
 
+/// Find a point at which the widened condition of \p Guard should be inserted.
+/// When it is represented as intrinsic call, we can do it right before the call
+/// instruction. However, when we are dealing with widenable branch, we must
+/// account for the following situation: widening should not turn a
+/// loop-invariant condition into a loop-variant. It means that if
+/// widenable.condition() call is invariant (w.r.t. any loop), the new wide
+/// condition should stay invariant. Otherwise there can be a miscompile, like
+/// the one described at https://github.com/llvm/llvm-project/issues/60234. The
+/// safest way to do it is to expand the new condition at WC's block.
+static Instruction *findInsertionPointForWideCondition(Instruction *Guard) {
+  Value *Condition, *WC;
+  BasicBlock *IfTrue, *IfFalse;
+  if (parseWidenableBranch(Guard, Condition, WC, IfTrue, IfFalse))
+    return cast<Instruction>(WC);
+  return Guard;
+}
+
 class GuardWideningImpl {
   DominatorTree &DT;
   PostDominatorTree *PDT;
@@ -263,8 +280,8 @@ class GuardWideningImpl {
   void widenGuard(Instruction *ToWiden, Value *NewCondition,
                   bool InvertCondition) {
     Value *Result;
-
-    widenCondCommon(getCondition(ToWiden), NewCondition, ToWiden, Result,
+    Instruction *InsertPt = findInsertionPointForWideCondition(ToWiden);
+    widenCondCommon(getCondition(ToWiden), NewCondition, InsertPt, Result,
                     InvertCondition);
     if (isGuardAsWidenableBranch(ToWiden)) {
       setWidenableBranchCond(cast<BranchInst>(ToWiden), Result);
@@ -422,7 +439,8 @@ GuardWideningImpl::computeWideningScore(Instruction *DominatedInstr,
     HoistingOutOfLoop = true;
   }
 
-  if (!isAvailableAt(getCondition(DominatedInstr), DominatingGuard))
+  auto *WideningPoint = findInsertionPointForWideCondition(DominatingGuard);
+  if (!isAvailableAt(getCondition(DominatedInstr), WideningPoint))
     return WS_IllegalOrNegative;
 
   // If the guard was conditional executed, it may never be reached

llvm/test/Transforms/GuardWidening/basic_widenable_condition_guards.ll

@@ -7,8 +7,8 @@
 define void @f_0(i1 %cond_0, i1 %cond_1) {
 ; CHECK-LABEL: @f_0(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[WIDE_CHK:%.*]] = and i1 [[COND_0:%.*]], [[COND_1:%.*]]
+; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[EXIPLICIT_GUARD_COND:%.*]] = and i1 [[WIDE_CHK]], [[WIDENABLE_COND]]
 ; CHECK-NEXT:    br i1 [[EXIPLICIT_GUARD_COND]], label [[GUARDED:%.*]], label [[DEOPT:%.*]], !prof [[PROF0:![0-9]+]]
 ; CHECK:       deopt:
@@ -50,8 +50,8 @@ guarded1:                                         ; preds = %guarded
 define void @f_1(i1 %cond_0, i1 %cond_1) {
 ; CHECK-LABEL: @f_1(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[WIDE_CHK:%.*]] = and i1 [[COND_0:%.*]], [[COND_1:%.*]]
+; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[EXIPLICIT_GUARD_COND:%.*]] = and i1 [[WIDE_CHK]], [[WIDENABLE_COND]]
 ; CHECK-NEXT:    br i1 [[EXIPLICIT_GUARD_COND]], label [[GUARDED:%.*]], label [[DEOPT:%.*]], !prof [[PROF0]]
 ; CHECK:       deopt:
@@ -110,9 +110,9 @@ define void @f_2(i32 %a, i32 %b) {
 ; CHECK-LABEL: @f_2(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[COND_0:%.*]] = icmp ult i32 [[A:%.*]], 10
-; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[COND_1:%.*]] = icmp ult i32 [[B:%.*]], 10
 ; CHECK-NEXT:    [[WIDE_CHK:%.*]] = and i1 [[COND_0]], [[COND_1]]
+; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[EXIPLICIT_GUARD_COND:%.*]] = and i1 [[WIDE_CHK]], [[WIDENABLE_COND]]
 ; CHECK-NEXT:    br i1 [[EXIPLICIT_GUARD_COND]], label [[GUARDED:%.*]], label [[DEOPT:%.*]], !prof [[PROF0]]
 ; CHECK:       deopt:
@@ -231,9 +231,9 @@ define void @f_4(i32 %a, i32 %b) {
 ; CHECK-LABEL: @f_4(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[COND_0:%.*]] = icmp ult i32 [[A:%.*]], 10
-; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[COND_1:%.*]] = icmp ult i32 [[B:%.*]], 10
 ; CHECK-NEXT:    [[WIDE_CHK:%.*]] = and i1 [[COND_0]], [[COND_1]]
+; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[EXIPLICIT_GUARD_COND:%.*]] = and i1 [[WIDE_CHK]], [[WIDENABLE_COND]]
 ; CHECK-NEXT:    br i1 [[EXIPLICIT_GUARD_COND]], label [[GUARDED:%.*]], label [[DEOPT:%.*]], !prof [[PROF0]]
 ; CHECK:       deopt:
@@ -289,8 +289,8 @@ define void @f_5(i32 %a) {
 ; CHECK-LABEL: @f_5(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[COND_0:%.*]] = icmp ugt i32 [[A:%.*]], 7
-; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[WIDE_CHK:%.*]] = icmp uge i32 [[A]], 11
+; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[EXIPLICIT_GUARD_COND:%.*]] = and i1 [[WIDE_CHK]], [[WIDENABLE_COND]]
 ; CHECK-NEXT:    br i1 [[EXIPLICIT_GUARD_COND]], label [[GUARDED:%.*]], label [[DEOPT:%.*]], !prof [[PROF0]]
 ; CHECK:       deopt:
@@ -397,9 +397,9 @@ define void @f_7(i32 %a, ptr %cond_buf) {
 ; CHECK-LABEL: @f_7(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[COND_1:%.*]] = load volatile i1, ptr [[COND_BUF:%.*]], align 1
-; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[COND_3:%.*]] = icmp ult i32 [[A:%.*]], 7
 ; CHECK-NEXT:    [[WIDE_CHK:%.*]] = and i1 [[COND_1]], [[COND_3]]
+; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[EXIPLICIT_GUARD_COND:%.*]] = and i1 [[WIDE_CHK]], [[WIDENABLE_COND]]
 ; CHECK-NEXT:    br i1 [[EXIPLICIT_GUARD_COND]], label [[GUARDED:%.*]], label [[DEOPT:%.*]], !prof [[PROF0]]
 ; CHECK:       deopt:
@@ -484,9 +484,9 @@ define void @f_8(i32 %a, i1 %cond_1, i1 %cond_2) {
 ; CHECK:       guarded:
 ; CHECK-NEXT:    br i1 undef, label [[LOOP]], label [[LEAVE:%.*]]
 ; CHECK:       leave:
-; CHECK-NEXT:    [[WIDENABLE_COND3:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[COND_3:%.*]] = icmp ult i32 [[A:%.*]], 7
 ; CHECK-NEXT:    [[WIDE_CHK:%.*]] = and i1 [[COND_2:%.*]], [[COND_3]]
+; CHECK-NEXT:    [[WIDENABLE_COND3:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[EXIPLICIT_GUARD_COND4:%.*]] = and i1 [[WIDE_CHK]], [[WIDENABLE_COND3]]
 ; CHECK-NEXT:    br i1 [[EXIPLICIT_GUARD_COND4]], label [[GUARDED1:%.*]], label [[DEOPT2:%.*]], !prof [[PROF0]]
 ; CHECK:       deopt2:
@@ -663,8 +663,8 @@ define void @f_11(i32 %a, i1 %cond_0, i1 %cond_1) {
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    br label [[OUTER_HEADER:%.*]]
 ; CHECK:       outer_header:
-; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[WIDE_CHK:%.*]] = and i1 [[COND_0:%.*]], [[COND_1:%.*]]
+; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[EXIPLICIT_GUARD_COND:%.*]] = and i1 [[WIDE_CHK]], [[WIDENABLE_COND]]
 ; CHECK-NEXT:    br i1 [[EXIPLICIT_GUARD_COND]], label [[GUARDED:%.*]], label [[DEOPT:%.*]], !prof [[PROF0]]
 ; CHECK:       deopt:
@@ -725,7 +725,6 @@ exit:                                             ; preds = %outer_latch
 define void @f_12(i32 %a0) {
 ; CHECK-LABEL: @f_12(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[A1:%.*]] = mul i32 [[A0:%.*]], [[A0]]
 ; CHECK-NEXT:    [[A2:%.*]] = mul i32 [[A1]], [[A1]]
 ; CHECK-NEXT:    [[A3:%.*]] = mul i32 [[A2]], [[A2]]
@@ -758,6 +757,7 @@ define void @f_12(i32 %a0) {
 ; CHECK-NEXT:    [[A30:%.*]] = mul i32 [[A29]], [[A29]]
 ; CHECK-NEXT:    [[COND:%.*]] = trunc i32 [[A30]] to i1
 ; CHECK-NEXT:    [[WIDE_CHK:%.*]] = and i1 true, [[COND]]
+; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[EXIPLICIT_GUARD_COND:%.*]] = and i1 [[WIDE_CHK]], [[WIDENABLE_COND]]
 ; CHECK-NEXT:    br i1 [[EXIPLICIT_GUARD_COND]], label [[GUARDED:%.*]], label [[DEOPT:%.*]], !prof [[PROF0]]
 ; CHECK:       deopt:
@@ -830,8 +830,8 @@ define void @f_13(i32 %a) {
 ; CHECK-LABEL: @f_13(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[COND_0:%.*]] = icmp ult i32 [[A:%.*]], 14
-; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[WIDE_CHK:%.*]] = icmp ult i32 [[A]], 10
+; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[EXIPLICIT_GUARD_COND:%.*]] = and i1 [[WIDE_CHK]], [[WIDENABLE_COND]]
 ; CHECK-NEXT:    br i1 [[EXIPLICIT_GUARD_COND]], label [[GUARDED:%.*]], label [[DEOPT:%.*]], !prof [[PROF0]]
 ; CHECK:       deopt:
@@ -1025,8 +1025,8 @@ guarded1:                                         ; preds = %guarded
 define void @swapped_wb(i1 %cond_0, i1 %cond_1) {
 ; CHECK-LABEL: @swapped_wb(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[WIDE_CHK:%.*]] = and i1 [[COND_0:%.*]], [[COND_1:%.*]]
+; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[EXIPLICIT_GUARD_COND:%.*]] = and i1 [[WIDENABLE_COND]], [[WIDE_CHK]]
 ; CHECK-NEXT:    br i1 [[EXIPLICIT_GUARD_COND]], label [[GUARDED:%.*]], label [[DEOPT:%.*]], !prof [[PROF0]]
 ; CHECK:       deopt:
@@ -1067,8 +1067,8 @@ guarded1:                                         ; preds = %guarded
 define void @trivial_wb(i1 %cond_0) {
 ; CHECK-LABEL: @trivial_wb(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[WIDE_CHK:%.*]] = and i1 true, [[COND_0:%.*]]
+; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[TMP0:%.*]] = and i1 [[WIDE_CHK]], [[WIDENABLE_COND]]
 ; CHECK-NEXT:    br i1 [[TMP0]], label [[GUARDED:%.*]], label [[DEOPT:%.*]], !prof [[PROF0]]
 ; CHECK:       deopt:

llvm/test/Transforms/GuardWidening/loop_invariant_widenable_condition.ll

@@ -3,17 +3,17 @@
 
 declare i32 @llvm.experimental.deoptimize.i32(...)
 
-; FIXME: Make sure the two loop-invariant conditions can be widened together,
-;        and the widening point is outside the loop.
+; Make sure the two loop-invariant conditions can be widened together,
+; and the widening point is outside the loop.
 define i32 @test_01(i32 %start, i32 %x) {
 ; CHECK-LABEL: @test_01(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[COND:%.*]] = icmp eq i32 [[START:%.*]], [[X:%.*]]
+; CHECK-NEXT:    [[WIDE_CHK:%.*]] = and i1 true, [[COND]]
 ; CHECK-NEXT:    [[WC1:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
 ; CHECK-NEXT:    [[IV:%.*]] = phi i32 [ [[START]], [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ]
-; CHECK-NEXT:    [[WIDE_CHK:%.*]] = and i1 true, [[COND]]
 ; CHECK-NEXT:    [[TMP0:%.*]] = and i1 [[WIDE_CHK]], [[WC1]]
 ; CHECK-NEXT:    br i1 [[TMP0]], label [[GUARD_BLOCK:%.*]], label [[EXIT_BY_WC:%.*]]
 ; CHECK:       exit_by_wc:
@@ -65,25 +65,23 @@ failure:
 }
 
 
-; FIXME: Make sure the loop-variant condition is not widened into loop-invariant.
+; Make sure the loop-variant condition is not widened into loop-invariant.
 define i32 @test_02(i32 %start, i32 %x) {
 ; CHECK-LABEL: @test_02(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[WC1:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
 ; CHECK-NEXT:    [[IV:%.*]] = phi i32 [ [[START:%.*]], [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ]
-; CHECK-NEXT:    [[COND:%.*]] = icmp eq i32 [[IV]], [[X:%.*]]
-; CHECK-NEXT:    [[WIDE_CHK:%.*]] = and i1 true, [[COND]]
-; CHECK-NEXT:    [[TMP0:%.*]] = and i1 [[WIDE_CHK]], [[WC1]]
-; CHECK-NEXT:    br i1 [[TMP0]], label [[GUARD_BLOCK:%.*]], label [[EXIT_BY_WC:%.*]]
+; CHECK-NEXT:    br i1 [[WC1]], label [[GUARD_BLOCK:%.*]], label [[EXIT_BY_WC:%.*]]
 ; CHECK:       exit_by_wc:
 ; CHECK-NEXT:    [[RVAL1:%.*]] = call i32 (...) @llvm.experimental.deoptimize.i32() [ "deopt"(i32 [[IV]]) ]
 ; CHECK-NEXT:    ret i32 [[RVAL1]]
 ; CHECK:       guard_block:
+; CHECK-NEXT:    [[COND:%.*]] = icmp eq i32 [[IV]], [[X:%.*]]
 ; CHECK-NEXT:    [[WC2:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[GUARD:%.*]] = and i1 [[COND]], [[WC2]]
-; CHECK-NEXT:    br i1 true, label [[BACKEDGE]], label [[FAILURE:%.*]]
+; CHECK-NEXT:    br i1 [[GUARD]], label [[BACKEDGE]], label [[FAILURE:%.*]]
 ; CHECK:       backedge:
 ; CHECK-NEXT:    call void @side_effect()
 ; CHECK-NEXT:    [[IV_NEXT]] = add i32 [[IV]], 1
@@ -125,16 +123,16 @@ failure:
   ret i32 %rval2
 }
 
-; FIXME: Same as test_01, but the initial condition is not immediately WC.
+; Same as test_01, but the initial condition is not immediately WC.
 define i32 @test_03(i32 %start, i32 %x, i1 %c) {
 ; CHECK-LABEL: @test_03(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[COND:%.*]] = icmp eq i32 [[START:%.*]], [[X:%.*]]
+; CHECK-NEXT:    [[WIDE_CHK:%.*]] = and i1 [[C:%.*]], [[COND]]
 ; CHECK-NEXT:    [[WC1:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
 ; CHECK-NEXT:    [[IV:%.*]] = phi i32 [ [[START]], [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ]
-; CHECK-NEXT:    [[WIDE_CHK:%.*]] = and i1 [[C:%.*]], [[COND]]
 ; CHECK-NEXT:    [[INVARIANT:%.*]] = and i1 [[WIDE_CHK]], [[WC1]]
 ; CHECK-NEXT:    br i1 [[INVARIANT]], label [[GUARD_BLOCK:%.*]], label [[EXIT_BY_WC:%.*]]
 ; CHECK:       exit_by_wc:

llvm/test/Transforms/GuardWidening/mixed_guards.ll

@@ -44,8 +44,8 @@ guarded1:                                         ; preds = %guarded
 define void @test_02(i1 %cond_0, i1 %cond_1) {
 ; CHECK-LABEL: @test_02(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[WIDE_CHK:%.*]] = and i1 [[COND_0:%.*]], [[COND_1:%.*]]
+; CHECK-NEXT:    [[WIDENABLE_COND:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[EXIPLICIT_GUARD_COND:%.*]] = and i1 [[WIDE_CHK]], [[WIDENABLE_COND]]
 ; CHECK-NEXT:    br i1 [[EXIPLICIT_GUARD_COND]], label [[GUARDED:%.*]], label [[DEOPT:%.*]], !prof [[PROF0]]
 ; CHECK:       deopt:

llvm/test/Transforms/GuardWidening/pr60234.ll

@@ -3,30 +3,28 @@
 
 declare i32 @llvm.experimental.deoptimize.i32(...)
 
-; FIXME: Make sure that guard widening does not turn loop-invariant condition
-;        (that then gets optimized basing on this fact) into non-invariant.
-;        https://github.com/llvm/llvm-project/issues/60234 explains how it causes
-;        a miscompile.
+; Make sure that guard widening does not turn loop-invariant condition
+; (that then gets optimized basing on this fact) into non-invariant.
+; https://github.com/llvm/llvm-project/issues/60234 explains how it causes
+; a miscompile.
 define i32 @test(i32 %start) {
 ; CHECK-LABEL: @test(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[WC1:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
 ; CHECK-NEXT:    [[IV:%.*]] = phi i32 [ [[START:%.*]], [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ]
-; CHECK-NEXT:    [[START_PLUS_1:%.*]] = add i32 [[START]], 1
-; CHECK-NEXT:    [[COND:%.*]] = icmp ne i32 [[START_PLUS_1]], [[IV]]
-; CHECK-NEXT:    [[WIDE_CHK:%.*]] = and i1 true, [[COND]]
-; CHECK-NEXT:    [[TMP0:%.*]] = and i1 [[WIDE_CHK]], [[WC1]]
-; CHECK-NEXT:    br i1 [[TMP0]], label [[GUARD_BLOCK:%.*]], label [[EXIT_BY_WC:%.*]]
+; CHECK-NEXT:    br i1 [[WC1]], label [[GUARD_BLOCK:%.*]], label [[EXIT_BY_WC:%.*]]
 ; CHECK:       exit_by_wc:
 ; CHECK-NEXT:    [[IV_LCSSA:%.*]] = phi i32 [ [[START]], [[LOOP]] ]
 ; CHECK-NEXT:    [[RVAL1:%.*]] = call i32 (...) @llvm.experimental.deoptimize.i32() [ "deopt"(i32 [[IV_LCSSA]]) ]
 ; CHECK-NEXT:    ret i32 [[RVAL1]]
 ; CHECK:       guard_block:
+; CHECK-NEXT:    [[START_PLUS_1:%.*]] = add i32 [[START]], 1
+; CHECK-NEXT:    [[COND:%.*]] = icmp ne i32 [[START_PLUS_1]], [[IV]]
 ; CHECK-NEXT:    [[WC2:%.*]] = call i1 @llvm.experimental.widenable.condition()
 ; CHECK-NEXT:    [[GUARD:%.*]] = and i1 [[COND]], [[WC2]]
-; CHECK-NEXT:    br i1 true, label [[BACKEDGE]], label [[FAILURE:%.*]]
+; CHECK-NEXT:    br i1 [[GUARD]], label [[BACKEDGE]], label [[FAILURE:%.*]]
 ; CHECK:       backedge:
 ; CHECK-NEXT:    call void @side_effect()
 ; CHECK-NEXT:    [[IV_NEXT]] = add i32 [[IV]], 1