[SCEVExpand] do not hoist divisions by zero (PR30935)

SCEVExpand computes the insertion point for the components of a SCEV to be code
generated.  When it comes to generating code for a division, SCEVexpand would
not be able to check (at compilation time) all the conditions necessary to avoid
a division by zero.  The patch disables hoisting of expressions containing
divisions by anything other than non-zero constants in order to avoid hoisting
these expressions past conditions that should hold before doing the division.

The patch passes check-all on x86_64-linux.

Differential Revision: https://reviews.llvm.org/D27216

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@289412 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 94 insertions, 0 deletions

diff --git a/test/Transforms/LoopIdiom/pr30935.ll b/test/Transforms/LoopIdiom/pr30935.ll
new file mode 100644
index 00000000000..4daaf5ffcac
--- /dev/null
+++ b/test/Transforms/LoopIdiom/pr30935.ll
@@ -0,0 +1,94 @@
+; RUN: opt -loop-idiom -S < %s | FileCheck %s
+
+; CHECK-LABEL: define i32 @main(
+; CHECK: udiv
+; CHECK-NOT: udiv
+; CHECK: call void @llvm.memset.p0i8.i64
+
+@a = common local_unnamed_addr global [4 x i8] zeroinitializer, align 1
+@b = common local_unnamed_addr global i32 0, align 4
+@c = common local_unnamed_addr global i32 0, align 4
+@d = common local_unnamed_addr global i32 0, align 4
+@e = common local_unnamed_addr global i32 0, align 4
+@f = common local_unnamed_addr global i32 0, align 4
+@g = common local_unnamed_addr global i32 0, align 4
+@h = common local_unnamed_addr global i64 0, align 8
+
+
+define i32 @main() local_unnamed_addr #0 {
+entry:
+  %0 = load i32, i32* @e, align 4
+  %tobool19 = icmp eq i32 %0, 0
+  %1 = load i32, i32* @c, align 4
+  %cmp10 = icmp eq i32 %1, 0
+  %2 = load i32, i32* @g, align 4
+  %3 = load i32, i32* @b, align 4
+  %tobool = icmp eq i32 %0, 0
+  br label %for.cond
+
+for.cond.loopexit:                                ; preds = %for.inc14
+  br label %for.cond.backedge
+
+for.cond:                                         ; preds = %for.cond.backedge, %entry
+  %.pr = load i32, i32* @f, align 4
+  %cmp20 = icmp eq i32 %.pr, 0
+  br i1 %cmp20, label %for.cond2.preheader.preheader, label %for.cond.backedge
+
+for.cond.backedge:                                ; preds = %for.cond, %for.cond.loopexit
+  br label %for.cond
+
+for.cond2.preheader.preheader:                    ; preds = %for.cond
+  br label %for.cond2.preheader
+
+for.cond2.preheader:                              ; preds = %for.cond2.preheader.preheader, %for.inc14
+  br i1 %tobool19, label %for.cond9, label %for.body3.lr.ph
+
+for.body3.lr.ph:                                  ; preds = %for.cond2.preheader
+  %div = udiv i32 %2, %3
+  %conv = zext i32 %div to i64
+  br label %for.body3
+
+for.cond4.for.cond2.loopexit_crit_edge:           ; preds = %for.body6
+  store i32 0, i32* @d, align 4
+  br label %for.cond2.loopexit
+
+for.cond2.loopexit:                               ; preds = %for.cond4.for.cond2.loopexit_crit_edge, %for.body3
+  br i1 %tobool, label %for.cond2.for.cond9_crit_edge, label %for.body3
+
+for.body3:                                        ; preds = %for.body3.lr.ph, %for.cond2.loopexit
+  %.pr17 = load i32, i32* @d, align 4
+  %tobool518 = icmp eq i32 %.pr17, 0
+  br i1 %tobool518, label %for.cond2.loopexit, label %for.body6.preheader
+
+for.body6.preheader:                              ; preds = %for.body3
+  %4 = zext i32 %.pr17 to i64
+  br label %for.body6
+
+for.body6:                                        ; preds = %for.body6.preheader, %for.body6
+  %indvars.iv = phi i64 [ %4, %for.body6.preheader ], [ %indvars.iv.next, %for.body6 ]
+  %add = add nuw nsw i64 %conv, %indvars.iv
+  %arrayidx = getelementptr inbounds [4 x i8], [4 x i8]* @a, i64 0, i64 %add
+  store i8 1, i8* %arrayidx, align 1
+  %5 = trunc i64 %indvars.iv to i32
+  %inc = add i32 %5, 1
+  %tobool5 = icmp eq i32 %inc, 0
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  br i1 %tobool5, label %for.cond4.for.cond2.loopexit_crit_edge, label %for.body6
+
+for.cond2.for.cond9_crit_edge:                    ; preds = %for.cond2.loopexit
+  store i64 %conv, i64* @h, align 8
+  br label %for.cond9
+
+for.cond9:                                        ; preds = %for.cond2.for.cond9_crit_edge, %for.cond2.preheader
+  br i1 %cmp10, label %for.body12, label %for.inc14
+
+for.body12:                                       ; preds = %for.cond9
+  ret i32 0
+
+for.inc14:                                        ; preds = %for.cond9
+  %6 = load i32, i32* @f, align 4
+  %inc15 = add i32 %6, 1
+  store i32 %inc15, i32* @f, align 4
+  %cmp = icmp eq i32 %inc15, 0
+  br i1 %cmp, label %for.cond2.preheader, label %for.cond.loopexit
+}