[SCEV] Add smin/umin support to getRangeRef

[reames]

Summary

We were failing to compute trip counts (both exact and maximum) for any loop which involved a comparison against either an umin or smin. It looks like this simply got missed when we added smin/umin to SCEV.

I'm more than a bit shocked that something this basis was missed for this long. Am I missing something?

[fhahn]

I've put up a patch for SCEVUmin D67177. I plan to land it tomorrow.

[reames]

Rebase over precommited tests.

[reames]

In D67514#1668282, @fhahn wrote:

I've put up a patch for SCEVUmin D67177. I plan to land it tomorrow.

Ok, could you review this one then? The umin portion looks identical, so assume I remove that after rebasing on your change.

[nikic]

LG. Note that umin/smin support is also missing from GetMinTrailingZerosImpl.

[nikic]

lib/Analysis/ScalarEvolution.cpp

5602 ↗

(On Diff #219971)

Just a side note: For operations that have an intrinsic sign preference, I think it would be better to pass on that specific signedness as the SignHint (here signed, below unsigned). Not sure if there's an assumption about a getRangeRef() chain always using the same signedness somewhere though.

[fhahn]

LGTM, thanks! I've just landed D67177, to avoid delays with this patch.

FYI my motivation for UMin support is improving SCEV results with information from loop guards: D67178.

llvm/trunk/lib/Analysis/ScalarEvolution.cpp

ScalarEvolution::getRangeRef(const SCEV *S,
   if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
     ConstantRange X = getRangeRef(UMax->getOperand(0), SignHint);
     for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
       X = X.umax(getRangeRef(UMax->getOperand(i), SignHint));
     return setRange(UMax, SignHint,
                     ConservativeResult.intersectWith(X, RangeType));
   }
 
+  if (const SCEVSMinExpr *SMin = dyn_cast<SCEVSMinExpr>(S)) {
+    ConstantRange X = getRangeRef(SMin->getOperand(0), SignHint);
+    for (unsigned i = 1, e = SMin->getNumOperands(); i != e; ++i)
+      X = X.smin(getRangeRef(SMin->getOperand(i), SignHint));
+    return setRange(SMin, SignHint,
+                    ConservativeResult.intersectWith(X, RangeType));
+  }
+
   if (const SCEVUMinExpr *UMin = dyn_cast<SCEVUMinExpr>(S)) {
     ConstantRange X = getRangeRef(UMin->getOperand(0), SignHint);
     for (unsigned i = 1, e = UMin->getNumOperands(); i != e; ++i)
       X = X.umin(getRangeRef(UMin->getOperand(i), SignHint));
     return setRange(UMin, SignHint,
                     ConservativeResult.intersectWith(X, RangeType));
   }
 

llvm/trunk/test/Analysis/ScalarEvolution/max-expr-cache.ll

bb4:
   %tmp40 = select i1 %tmp39, i32 %tmp38, i32 256
   %tmp41 = add nsw i32 %tmp40, 1
   %tmp42 = icmp sgt i32 %tmp8, %tmp41
   %tmp43 = select i1 %tmp42, i32 %tmp41, i32 %tmp8
   %tmp44 = add nsw i32 %tmp10, 7
   %tmp45 = icmp slt i32 %tmp43, 256
   %tmp46 = select i1 %tmp45, i32 %tmp43, i32 256
 ; CHECK:  %tmp46 = select i1 %tmp45, i32 %tmp43, i32 256
-; CHECK-NEXT:  -->  (256 smin (1 + (256 smin (1 + (256 smin (1 + (256 smin (1 + (256 smin (1 + (256 smin (1 + (256 smin (1 + (256 smin {%tmp3,+,-256}<%bb4>)) smin {%tmp3,+,-256}<%bb4>)) smin {%tmp3,+,-256}<%bb4>)) smin {%tmp3,+,-256}<%bb4>)) smin {%tmp3,+,-256}<%bb4>)) smin {%tmp3,+,-256}<%bb4>)) smin {%tmp3,+,-256}<%bb4>)) smin {%tmp3,+,-256}<%bb4>)
+; CHECK-NEXT:  -->  (256 smin (1 + (256 smin (1 + (256 smin (1 + (256 smin (1 + (256 smin (1 + (256 smin (1 + (256 smin (1 + (256 smin {%tmp3,+,-256}<%bb4>))<nsw> smin {%tmp3,+,-256}<%bb4>))<nsw> smin {%tmp3,+,-256}<%bb4>))<nsw> smin {%tmp3,+,-256}<%bb4>))<nsw> smin {%tmp3,+,-256}<%bb4>))<nsw> smin {%tmp3,+,-256}<%bb4>))<nsw> smin {%tmp3,+,-256}<%bb4>))<nsw> smin {%tmp3,+,-256}<%bb4>) U: [-2147483648,257) S: [-2147483648,257)
   %tmp47 = icmp sgt i32 %tmp44, %tmp46
   %tmp48 = select i1 %tmp47, i32 %tmp44, i32 %tmp46
   %tmp49 = ashr i32 %tmp48, 3
   %tmp50 = icmp sgt i32 %tmp49, 0
   %tmp51 = select i1 %tmp50, i32 %tmp49, i32 0
   %tmp52 = zext i32 %tmp51 to i64
   br label %bb53
 
bb4:
   %tmp40 = select i1 %tmp39, i32 %tmp38, i32 256
   %tmp41 = add nsw i32 %tmp40, 1
   %tmp42 = icmp ugt i32 %tmp8, %tmp41
   %tmp43 = select i1 %tmp42, i32 %tmp41, i32 %tmp8
   %tmp44 = add nsw i32 %tmp10, 7
   %tmp45 = icmp ult i32 %tmp43, 256
   %tmp46 = select i1 %tmp45, i32 %tmp43, i32 256
 ; CHECK:  %tmp46 = select i1 %tmp45, i32 %tmp43, i32 256
-; CHECK-NEXT:  -->  (256 umin (1 + (256 umin (1 + (256 umin (1 + (256 umin (1 + (256 umin (1 + (256 umin (1 + (256 umin (1 + (256 umin {%tmp3,+,-256}<%bb4>))<nuw><nsw> umin {%tmp3,+,-256}<%bb4>))<nuw><nsw> umin {%tmp3,+,-256}<%bb4>))<nuw><nsw> umin {%tmp3,+,-256}<%bb4>))<nuw><nsw> umin {%tmp3,+,-256}<%bb4>))<nuw><nsw> umin {%tmp3,+,-256}<%bb4>))<nuw><nsw> umin {%tmp3,+,-256}<%bb4>))<nuw><nsw> umin {%tmp3,+,-256}<%bb4>) U: [0,257) S: [0,257) Exits: <<Unknown>> LoopDispositions: { %bb4: Computable, %bb53: Invariant }
+; CHECK-NEXT:  --> (256 umin (1 + (256 umin (1 + (256 umin (1 + (256 umin (1 + (256 umin (1 + (256 umin (1 + (256 umin (1 + (256 umin {%tmp3,+,-256}<%bb4>))<nuw><nsw> umin {%tmp3,+,-256}<%bb4>))<nuw><nsw> umin {%tmp3,+,-256}<%bb4>))<nuw><nsw> umin {%tmp3,+,-256}<%bb4>))<nuw><nsw> umin {%tmp3,+,-256}<%bb4>))<nuw><nsw> umin {%tmp3,+,-256}<%bb4>))<nuw><nsw> umin {%tmp3,+,-256}<%bb4>))<nuw><nsw> umin {%tmp3,+,-256}<%bb4>) U: [0,257) S: [0,257)
   %tmp47 = icmp ugt i32 %tmp44, %tmp46
   %tmp48 = select i1 %tmp47, i32 %tmp44, i32 %tmp46
   %tmp49 = ashr i32 %tmp48, 3
   %tmp50 = icmp ugt i32 %tmp49, 0
   %tmp51 = select i1 %tmp50, i32 %tmp49, i32 0
   %tmp52 = zext i32 %tmp51 to i64
   br label %bb53
 

llvm/trunk/test/Analysis/ScalarEvolution/trip-count15.ll

 ; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py
 ; RUN: opt -S -analyze -scalar-evolution < %s | FileCheck %s
 
 define void @umin_unsigned_check(i64 %n) {
 ; CHECK-LABEL: 'umin_unsigned_check'
 ; CHECK-NEXT:  Classifying expressions for: @umin_unsigned_check
 ; CHECK-NEXT:    %min.n = select i1 %min.cmp, i64 4096, i64 %n
 ; CHECK-NEXT:    --> (4096 umin %n) U: [0,4097) S: [0,4097)
 ; CHECK-NEXT:    %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
 ; CHECK-NEXT:    --> {0,+,1}<%loop> U: [0,4098) S: [0,4098) Exits: (1 + (4096 umin %n))<nuw><nsw> LoopDispositions: { %loop: Computable }
 ; CHECK-NEXT:    %iv.next = add i64 %iv, 1
 ; CHECK-NEXT:    --> {1,+,1}<%loop> U: [1,4099) S: [1,4099) Exits: (2 + (4096 umin %n)) LoopDispositions: { %loop: Computable }
 ; CHECK-NEXT:  Determining loop execution counts for: @umin_unsigned_check
 ; CHECK-NEXT:  Loop %loop: backedge-taken count is (1 + (4096 umin %n))<nuw><nsw>
 ; CHECK-NEXT:  Loop %loop: max backedge-taken count is 4097
 ; CHECK-NEXT:  Loop %loop: Predicated backedge-taken count is (1 + (4096 umin %n))<nuw><nsw>
+; CHECK-NEXT:   Predicates:
+; CHECK:       Loop %loop: Trip multiple is 1
 ;
 entry:
   %min.cmp = icmp ult i64 4096, %n
   %min.n = select i1 %min.cmp, i64 4096, i64 %n
   br label %loop
 loop:
   %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
   %iv.next = add i64 %iv, 1

 ; CHECK-NEXT:    %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
 ; CHECK-NEXT:    --> {0,+,1}<%loop> U: [0,4098) S: [0,4098) Exits: (1 + (4096 umin %n))<nuw><nsw> LoopDispositions: { %loop: Computable }
 ; CHECK-NEXT:    %iv.next = add i64 %iv, 1
 ; CHECK-NEXT:    --> {1,+,1}<%loop> U: [1,4099) S: [1,4099) Exits: (2 + (4096 umin %n)) LoopDispositions: { %loop: Computable }
 ; CHECK-NEXT:  Determining loop execution counts for: @umin_signed_check
 ; CHECK-NEXT:  Loop %loop: backedge-taken count is (1 + (4096 umin %n))<nuw><nsw>
 ; CHECK-NEXT:  Loop %loop: max backedge-taken count is 4097
 ; CHECK-NEXT:  Loop %loop: Predicated backedge-taken count is (1 + (4096 umin %n))<nuw><nsw>
+; CHECK-NEXT:   Predicates:
+; CHECK:       Loop %loop: Trip multiple is 1
 ;
 entry:
   %min.cmp = icmp ult i64 4096, %n
   %min.n = select i1 %min.cmp, i64 4096, i64 %n
   br label %loop
 loop:
   %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
   %iv.next = add i64 %iv, 1
   %exit = icmp sgt i64 %iv, %min.n
   br i1 %exit, label %loop_exit, label %loop
 
 loop_exit:
   ret void
 }
 
 define void @smin_signed_check(i64 %n) {
 ; CHECK-LABEL: 'smin_signed_check'
 ; CHECK-NEXT:  Classifying expressions for: @smin_signed_check
 ; CHECK-NEXT:    %min.n = select i1 %min.cmp, i64 4096, i64 %n
-; CHECK-NEXT:    --> (4096 smin %n) U: full-set S: full-set
+; CHECK-NEXT:    --> (4096 smin %n) U: [-9223372036854775808,4097) S: [-9223372036854775808,4097)
 ; CHECK-NEXT:    %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
-; CHECK-NEXT:    --> {0,+,1}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
+; CHECK-NEXT:    --> {0,+,1}<%loop> U: [0,4098) S: [0,4098) Exits: (0 smax (1 + (4096 smin %n))<nsw>) LoopDispositions: { %loop: Computable }
 ; CHECK-NEXT:    %iv.next = add i64 %iv, 1
-; CHECK-NEXT:    --> {1,+,1}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
+; CHECK-NEXT:    --> {1,+,1}<%loop> U: [1,4099) S: [1,4099) Exits: (1 + (0 smax (1 + (4096 smin %n))<nsw>))<nuw><nsw> LoopDispositions: { %loop: Computable }
 ; CHECK-NEXT:  Determining loop execution counts for: @smin_signed_check
-; CHECK-NEXT:  Loop %loop: Unpredictable backedge-taken count.
-; CHECK-NEXT:  Loop %loop: Unpredictable max backedge-taken count.
-; CHECK-NEXT:  Loop %loop: Unpredictable predicated backedge-taken count.
+; CHECK-NEXT:  Loop %loop: backedge-taken count is (0 smax (1 + (4096 smin %n))<nsw>)
+; CHECK-NEXT:  Loop %loop: max backedge-taken count is 4097
+; CHECK-NEXT:  Loop %loop: Predicated backedge-taken count is (0 smax (1 + (4096 smin %n))<nsw>)
+; CHECK-NEXT:   Predicates:
+; CHECK:       Loop %loop: Trip multiple is 1
 ;
 entry:
   %min.cmp = icmp slt i64 4096, %n
   %min.n = select i1 %min.cmp, i64 4096, i64 %n
   br label %loop
 loop:
   %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
   %iv.next = add i64 %iv, 1
   %exit = icmp sgt i64 %iv, %min.n
   br i1 %exit, label %loop_exit, label %loop
 
 loop_exit:
   ret void
 }
 
 define void @smin_unsigned_check(i64 %n) {
 ; CHECK-LABEL: 'smin_unsigned_check'
 ; CHECK-NEXT:  Classifying expressions for: @smin_unsigned_check
 ; CHECK-NEXT:    %min.n = select i1 %min.cmp, i64 4096, i64 %n
-; CHECK-NEXT:    --> (4096 smin %n) U: full-set S: full-set
+; CHECK-NEXT:    --> (4096 smin %n) U: [-9223372036854775808,4097) S: [-9223372036854775808,4097)
 ; CHECK-NEXT:    %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
 ; CHECK-NEXT:    --> {0,+,1}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
 ; CHECK-NEXT:    %iv.next = add i64 %iv, 1
 ; CHECK-NEXT:    --> {1,+,1}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
 ; CHECK-NEXT:  Determining loop execution counts for: @smin_unsigned_check
 ; CHECK-NEXT:  Loop %loop: Unpredictable backedge-taken count.
 ; CHECK-NEXT:  Loop %loop: Unpredictable max backedge-taken count.
 ; CHECK-NEXT:  Loop %loop: Unpredictable predicated backedge-taken count.

llvm/trunk/test/Transforms/IRCE/rc-negative-bound.ll

 define void @test_03(i32 *%arr, i32 %n, i32 %bound) {
 ; CHECK-LABEL: @test_03(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[FIRST_ITR_CHECK:%.*]] = icmp sgt i32 [[N:%.*]], 0
 ; CHECK-NEXT:    br i1 [[FIRST_ITR_CHECK]], label [[LOOP_PREHEADER:%.*]], label [[EXIT:%.*]]
 ; CHECK:       loop.preheader:
 ; CHECK-NEXT:    [[TMP0:%.*]] = add i32 [[BOUND:%.*]], -2147483647
 ; CHECK-NEXT:    [[TMP1:%.*]] = icmp sgt i32 [[TMP0]], 0
-; CHECK-NEXT:    [[SMIN:%.*]] = select i1 [[TMP1]], i32 [[TMP0]], i32 0
-; CHECK-NEXT:    [[TMP2:%.*]] = sub i32 [[BOUND]], [[SMIN]]
+; CHECK-NEXT:    [[SMAX:%.*]] = select i1 [[TMP1]], i32 [[TMP0]], i32 0
+; CHECK-NEXT:    [[TMP2:%.*]] = sub i32 [[BOUND]], [[SMAX]]
 ; CHECK-NEXT:    [[TMP3:%.*]] = icmp slt i32 [[BOUND]], 0
-; CHECK-NEXT:    [[SMAX:%.*]] = select i1 [[TMP3]], i32 [[BOUND]], i32 0
-; CHECK-NEXT:    [[TMP4:%.*]] = icmp sgt i32 [[SMAX]], -1
-; CHECK-NEXT:    [[SMIN1:%.*]] = select i1 [[TMP4]], i32 [[SMAX]], i32 -1
-; CHECK-NEXT:    [[TMP5:%.*]] = add i32 [[SMIN1]], 1
+; CHECK-NEXT:    [[SMIN:%.*]] = select i1 [[TMP3]], i32 [[BOUND]], i32 0
+; CHECK-NEXT:    [[TMP4:%.*]] = icmp sgt i32 [[SMIN]], -1
+; CHECK-NEXT:    [[SMAX1:%.*]] = select i1 [[TMP4]], i32 [[SMIN]], i32 -1
+; CHECK-NEXT:    [[TMP5:%.*]] = add nsw i32 [[SMAX1]], 1
 ; CHECK-NEXT:    [[TMP6:%.*]] = mul i32 [[TMP2]], [[TMP5]]
 ; CHECK-NEXT:    [[TMP7:%.*]] = icmp slt i32 [[N]], [[TMP6]]
-; CHECK-NEXT:    [[SMAX2:%.*]] = select i1 [[TMP7]], i32 [[N]], i32 [[TMP6]]
-; CHECK-NEXT:    [[TMP8:%.*]] = icmp sgt i32 [[SMAX2]], 0
-; CHECK-NEXT:    [[EXIT_MAINLOOP_AT:%.*]] = select i1 [[TMP8]], i32 [[SMAX2]], i32 0
+; CHECK-NEXT:    [[SMIN2:%.*]] = select i1 [[TMP7]], i32 [[N]], i32 [[TMP6]]
+; CHECK-NEXT:    [[TMP8:%.*]] = icmp sgt i32 [[SMIN2]], 0
+; CHECK-NEXT:    [[EXIT_MAINLOOP_AT:%.*]] = select i1 [[TMP8]], i32 [[SMIN2]], i32 0
 ; CHECK-NEXT:    [[TMP9:%.*]] = icmp slt i32 0, [[EXIT_MAINLOOP_AT]]
 ; CHECK-NEXT:    br i1 [[TMP9]], label [[LOOP_PREHEADER4:%.*]], label [[MAIN_PSEUDO_EXIT:%.*]]
 ; CHECK:       loop.preheader4:
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
 ; CHECK-NEXT:    [[IDX:%.*]] = phi i32 [ [[IDX_NEXT:%.*]], [[IN_BOUNDS:%.*]] ], [ 0, [[LOOP_PREHEADER4]] ]
 ; CHECK-NEXT:    [[IDX_NEXT]] = add i32 [[IDX]], 1
 ; CHECK-NEXT:    [[ABC:%.*]] = icmp slt i32 [[IDX]], [[BOUND]]

 ; expand runtime checks against bound being positive or negative.
 define void @test_04(i32 *%arr, i32 %n, i32 %bound) {
 ; CHECK-LABEL: @test_04(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[FIRST_ITR_CHECK:%.*]] = icmp sgt i32 [[N:%.*]], 0
 ; CHECK-NEXT:    br i1 [[FIRST_ITR_CHECK]], label [[LOOP_PREHEADER:%.*]], label [[EXIT:%.*]]
 ; CHECK:       loop.preheader:
 ; CHECK-NEXT:    [[TMP0:%.*]] = icmp slt i32 [[BOUND:%.*]], 0
-; CHECK-NEXT:    [[SMAX:%.*]] = select i1 [[TMP0]], i32 [[BOUND]], i32 0
-; CHECK-NEXT:    [[TMP1:%.*]] = sub i32 [[BOUND]], [[SMAX]]
-; CHECK-NEXT:    [[TMP2:%.*]] = icmp sgt i32 [[SMAX]], -1
-; CHECK-NEXT:    [[SMIN:%.*]] = select i1 [[TMP2]], i32 [[SMAX]], i32 -1
-; CHECK-NEXT:    [[TMP3:%.*]] = add i32 [[SMIN]], 1
+; CHECK-NEXT:    [[SMIN:%.*]] = select i1 [[TMP0]], i32 [[BOUND]], i32 0
+; CHECK-NEXT:    [[TMP1:%.*]] = sub i32 [[BOUND]], [[SMIN]]
+; CHECK-NEXT:    [[TMP2:%.*]] = icmp sgt i32 [[SMIN]], -1
+; CHECK-NEXT:    [[SMAX:%.*]] = select i1 [[TMP2]], i32 [[SMIN]], i32 -1
+; CHECK-NEXT:    [[TMP3:%.*]] = add nsw i32 [[SMAX]], 1
 ; CHECK-NEXT:    [[TMP4:%.*]] = mul i32 [[TMP1]], [[TMP3]]
 ; CHECK-NEXT:    [[TMP5:%.*]] = icmp ult i32 [[N]], [[TMP4]]
 ; CHECK-NEXT:    [[EXIT_MAINLOOP_AT:%.*]] = select i1 [[TMP5]], i32 [[N]], i32 [[TMP4]]
 ; CHECK-NEXT:    [[TMP6:%.*]] = icmp ult i32 0, [[EXIT_MAINLOOP_AT]]
 ; CHECK-NEXT:    br i1 [[TMP6]], label [[LOOP_PREHEADER1:%.*]], label [[MAIN_PSEUDO_EXIT:%.*]]
 ; CHECK:       loop.preheader1:
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:

 define void @test_07(i32 *%arr, i32 %n, i32 %bound) {
 ; CHECK-LABEL: @test_07(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[FIRST_ITR_CHECK:%.*]] = icmp sgt i32 [[N:%.*]], 0
 ; CHECK-NEXT:    br i1 [[FIRST_ITR_CHECK]], label [[LOOP_PREHEADER:%.*]], label [[EXIT:%.*]]
 ; CHECK:       loop.preheader:
 ; CHECK-NEXT:    [[TMP0:%.*]] = add i32 [[BOUND:%.*]], -2147483647
 ; CHECK-NEXT:    [[TMP1:%.*]] = icmp sgt i32 [[TMP0]], 0
-; CHECK-NEXT:    [[SMIN:%.*]] = select i1 [[TMP1]], i32 [[TMP0]], i32 0
-; CHECK-NEXT:    [[TMP2:%.*]] = sub i32 [[BOUND]], [[SMIN]]
+; CHECK-NEXT:    [[SMAX:%.*]] = select i1 [[TMP1]], i32 [[TMP0]], i32 0
+; CHECK-NEXT:    [[TMP2:%.*]] = sub i32 [[BOUND]], [[SMAX]]
 ; CHECK-NEXT:    [[TMP3:%.*]] = icmp slt i32 [[BOUND]], 0
-; CHECK-NEXT:    [[SMAX:%.*]] = select i1 [[TMP3]], i32 [[BOUND]], i32 0
-; CHECK-NEXT:    [[TMP4:%.*]] = icmp sgt i32 [[SMAX]], -1
-; CHECK-NEXT:    [[SMIN1:%.*]] = select i1 [[TMP4]], i32 [[SMAX]], i32 -1
-; CHECK-NEXT:    [[TMP5:%.*]] = add i32 [[SMIN1]], 1
+; CHECK-NEXT:    [[SMIN:%.*]] = select i1 [[TMP3]], i32 [[BOUND]], i32 0
+; CHECK-NEXT:    [[TMP4:%.*]] = icmp sgt i32 [[SMIN]], -1
+; CHECK-NEXT:    [[SMAX1:%.*]] = select i1 [[TMP4]], i32 [[SMIN]], i32 -1
+; CHECK-NEXT:    [[TMP5:%.*]] = add nsw i32 [[SMAX1]], 1
 ; CHECK-NEXT:    [[TMP6:%.*]] = mul i32 [[TMP2]], [[TMP5]]
 ; CHECK-NEXT:    [[TMP7:%.*]] = icmp slt i32 [[N]], [[TMP6]]
-; CHECK-NEXT:    [[SMAX2:%.*]] = select i1 [[TMP7]], i32 [[N]], i32 [[TMP6]]
-; CHECK-NEXT:    [[TMP8:%.*]] = icmp sgt i32 [[SMAX2]], 0
-; CHECK-NEXT:    [[EXIT_MAINLOOP_AT:%.*]] = select i1 [[TMP8]], i32 [[SMAX2]], i32 0
+; CHECK-NEXT:    [[SMIN2:%.*]] = select i1 [[TMP7]], i32 [[N]], i32 [[TMP6]]
+; CHECK-NEXT:    [[TMP8:%.*]] = icmp sgt i32 [[SMIN2]], 0
+; CHECK-NEXT:    [[EXIT_MAINLOOP_AT:%.*]] = select i1 [[TMP8]], i32 [[SMIN2]], i32 0
 ; CHECK-NEXT:    [[TMP9:%.*]] = icmp slt i32 0, [[EXIT_MAINLOOP_AT]]
 ; CHECK-NEXT:    br i1 [[TMP9]], label [[LOOP_PREHEADER4:%.*]], label [[MAIN_PSEUDO_EXIT:%.*]]
 ; CHECK:       loop.preheader4:
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
 ; CHECK-NEXT:    [[IDX:%.*]] = phi i32 [ [[IDX_NEXT:%.*]], [[IN_BOUNDS:%.*]] ], [ 0, [[LOOP_PREHEADER4]] ]
 ; CHECK-NEXT:    [[IDX_NEXT]] = add i32 [[IDX]], 1
 ; CHECK-NEXT:    [[ABC:%.*]] = icmp ult i32 [[IDX]], [[BOUND]]

 ; computeSafeIterationSpace).
 define void @test_08(i32 *%arr, i32 %n, i32 %bound) {
 ; CHECK-LABEL: @test_08(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[FIRST_ITR_CHECK:%.*]] = icmp sgt i32 [[N:%.*]], 0
 ; CHECK-NEXT:    br i1 [[FIRST_ITR_CHECK]], label [[LOOP_PREHEADER:%.*]], label [[EXIT:%.*]]
 ; CHECK:       loop.preheader:
 ; CHECK-NEXT:    [[TMP0:%.*]] = icmp slt i32 [[BOUND:%.*]], 0
-; CHECK-NEXT:    [[SMAX:%.*]] = select i1 [[TMP0]], i32 [[BOUND]], i32 0
-; CHECK-NEXT:    [[TMP1:%.*]] = sub i32 [[BOUND]], [[SMAX]]
-; CHECK-NEXT:    [[TMP2:%.*]] = icmp sgt i32 [[SMAX]], -1
-; CHECK-NEXT:    [[SMIN:%.*]] = select i1 [[TMP2]], i32 [[SMAX]], i32 -1
-; CHECK-NEXT:    [[TMP3:%.*]] = add i32 [[SMIN]], 1
+; CHECK-NEXT:    [[SMIN:%.*]] = select i1 [[TMP0]], i32 [[BOUND]], i32 0
+; CHECK-NEXT:    [[TMP1:%.*]] = sub i32 [[BOUND]], [[SMIN]]
+; CHECK-NEXT:    [[TMP2:%.*]] = icmp sgt i32 [[SMIN]], -1
+; CHECK-NEXT:    [[SMAX:%.*]] = select i1 [[TMP2]], i32 [[SMIN]], i32 -1
+; CHECK-NEXT:    [[TMP3:%.*]] = add nsw i32 [[SMAX]], 1
 ; CHECK-NEXT:    [[TMP4:%.*]] = mul i32 [[TMP1]], [[TMP3]]
 ; CHECK-NEXT:    [[TMP5:%.*]] = icmp ult i32 [[N]], [[TMP4]]
 ; CHECK-NEXT:    [[EXIT_MAINLOOP_AT:%.*]] = select i1 [[TMP5]], i32 [[N]], i32 [[TMP4]]
 ; CHECK-NEXT:    [[TMP6:%.*]] = icmp ult i32 0, [[EXIT_MAINLOOP_AT]]
 ; CHECK-NEXT:    br i1 [[TMP6]], label [[LOOP_PREHEADER1:%.*]], label [[MAIN_PSEUDO_EXIT:%.*]]
 ; CHECK:       loop.preheader1:
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop: