[SCEV] Enhance SCEVFindUnsafe for division

This patch allows SCEVFindUnsafe algorithm to tread division by any non-positive
value as safe. Previously, it could only recognize non-zero constants.

Differential Revision: https://reviews.llvm.org/D39228

llvm-svn: 316568

1 files changed, 38 insertions, 2 deletions

diff --git a/llvm/test/Transforms/IndVarSimplify/udiv.ll b/llvm/test/Transforms/IndVarSimplify/udiv.ll
index b3f2c2a6a66..0f9a54e8c4f 100644
--- a/llvm/test/Transforms/IndVarSimplify/udiv.ll
+++ b/llvm/test/Transforms/IndVarSimplify/udiv.ll
@@ -130,11 +130,11 @@ declare i32 @printf(i8* nocapture, ...) nounwind
 ; IndVars doesn't emit a udiv in for.body.preheader since SCEVExpander::expand will
 ; find out there's already a udiv in the original code.
 
-; CHECK-LABEL: @foo(
+; CHECK-LABEL: @foo_01(
 ; CHECK: for.body.preheader:
 ; CHECK-NOT: udiv
 
-define void @foo(double* %p, i64 %n) nounwind {
+define void @foo_01(double* %p, i64 %n) nounwind {
 entry:
   %div0 = udiv i64 %n, 7                          ; <i64> [#uses=1]
   %div1 = add i64 %div0, 1
@@ -160,3 +160,39 @@ for.end.loopexit:                                 ; preds = %for.body
 for.end:                                          ; preds = %for.end.loopexit, %entry
   ret void
 }
+
+; Same as foo_01, but we divide by non-constant value.
+
+; CHECK-LABEL: @foo_02(
+; CHECK: for.body.preheader:
+; CHECK-NOT: udiv
+
+define void @foo_02(double* %p, i64 %n, i64* %lp) nounwind {
+entry:
+  %denom = load i64, i64* %lp, align 4, !range !0
+  %div0 = udiv i64 %n, %denom                          ; <i64> [#uses=1]
+  %div1 = add i64 %div0, 1
+  %cmp2 = icmp ult i64 0, %div1                   ; <i1> [#uses=1]
+  br i1 %cmp2, label %for.body.preheader, label %for.end
+
+for.body.preheader:                               ; preds = %entry
+  br label %for.body
+
+for.body:                                         ; preds = %for.body.preheader, %for.body
+  %i.03 = phi i64 [ %inc, %for.body ], [ 0, %for.body.preheader ] ; <i64> [#uses=2]
+  %arrayidx = getelementptr inbounds double, double* %p, i64 %i.03 ; <double*> [#uses=1]
+  store double 0.000000e+00, double* %arrayidx
+  %inc = add i64 %i.03, 1                         ; <i64> [#uses=2]
+  %divx = udiv i64 %n, %denom                           ; <i64> [#uses=1]
+  %div = add i64 %divx, 1
+  %cmp = icmp ult i64 %inc, %div                  ; <i1> [#uses=1]
+  br i1 %cmp, label %for.body, label %for.end.loopexit
+
+for.end.loopexit:                                 ; preds = %for.body
+  br label %for.end
+
+for.end:                                          ; preds = %for.end.loopexit, %entry
+  ret void
+}
+
+!0 = !{i64 1, i64 10}