Add a utility function that detects whether a loop is guaranteed to be finite.

Use it to safely handle less-than-or-equals-to exit conditions in loops. These
also occur when the loop exit branch is exit on true because SCEV inverses the
icmp predicate.

Use it again to handle non-zero strides, but only with an unsigned comparison
in the exit condition.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@59528 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 91 insertions, 0 deletions

diff --git a/test/Analysis/ScalarEvolution/2008-11-18-LessThanOrEqual.ll b/test/Analysis/ScalarEvolution/2008-11-18-LessThanOrEqual.ll
new file mode 100644
index 0000000000..6bacfabd4d
--- /dev/null
+++ b/test/Analysis/ScalarEvolution/2008-11-18-LessThanOrEqual.ll
@@ -0,0 +1,31 @@
+; RUN: llvm-as < %s | opt -analyze -scalar-evolution |& \
+; RUN: grep {Loop bb: (7 + (-1 \\* %argc)) iterations!}
+
+define i32 @main(i32 %argc, i8** %argv) nounwind {
+entry:
+	%0 = icmp ugt i32 %argc, 7		; <i1> [#uses=1]
+	br i1 %0, label %bb2, label %bb.nph
+
+bb.nph:		; preds = %entry
+	br label %bb
+
+bb:		; preds = %bb.nph, %bb1
+	%indvar = phi i32 [ 0, %bb.nph ], [ %indvar.next, %bb1 ]		; <i32> [#uses=2]
+	%argc_addr.04 = add i32 %indvar, %argc		; <i32> [#uses=1]
+	tail call void (...)* @Test() nounwind
+	%1 = add i32 %argc_addr.04, 1		; <i32> [#uses=1]
+	br label %bb1
+
+bb1:		; preds = %bb
+	%phitmp = icmp ugt i32 %1, 7		; <i1> [#uses=1]
+	%indvar.next = add i32 %indvar, 1		; <i32> [#uses=1]
+	br i1 %phitmp, label %bb1.bb2_crit_edge, label %bb
+
+bb1.bb2_crit_edge:		; preds = %bb1
+	br label %bb2
+
+bb2:		; preds = %bb1.bb2_crit_edge, %entry
+	ret i32 0
+}
+
+declare void @Test(...)
diff --git a/test/Analysis/ScalarEvolution/2008-11-18-Stride1.ll b/test/Analysis/ScalarEvolution/2008-11-18-Stride1.ll
new file mode 100644
index 0000000000..78cda0e175
--- /dev/null
+++ b/test/Analysis/ScalarEvolution/2008-11-18-Stride1.ll
@@ -0,0 +1,30 @@
+; RUN: llvm-as < %s | opt -analyze -scalar-evolution |& grep {/u 3}
+
+define i32 @f(i32 %x) nounwind readnone {
+entry:
+	%0 = icmp ugt i32 %x, 4		; <i1> [#uses=1]
+	br i1 %0, label %bb.nph, label %bb2
+
+bb.nph:		; preds = %entry
+	br label %bb
+
+bb:		; preds = %bb.nph, %bb1
+	%indvar = phi i32 [ 0, %bb.nph ], [ %indvar.next, %bb1 ]		; <i32> [#uses=2]
+	%tmp = mul i32 %indvar, -3		; <i32> [#uses=1]
+	%x_addr.04 = add i32 %tmp, %x		; <i32> [#uses=1]
+	%1 = add i32 %x_addr.04, -3		; <i32> [#uses=2]
+	br label %bb1
+
+bb1:		; preds = %bb
+	%2 = icmp ugt i32 %1, 4		; <i1> [#uses=1]
+	%indvar.next = add i32 %indvar, 1		; <i32> [#uses=1]
+	br i1 %2, label %bb, label %bb1.bb2_crit_edge
+
+bb1.bb2_crit_edge:		; preds = %bb1
+	%.lcssa = phi i32 [ %1, %bb1 ]		; <i32> [#uses=1]
+	br label %bb2
+
+bb2:		; preds = %bb1.bb2_crit_edge, %entry
+	%x_addr.0.lcssa = phi i32 [ %.lcssa, %bb1.bb2_crit_edge ], [ %x, %entry ]		; <i32> [#uses=1]
+	ret i32 %x_addr.0.lcssa
+}
diff --git a/test/Analysis/ScalarEvolution/2008-11-18-Stride2.ll b/test/Analysis/ScalarEvolution/2008-11-18-Stride2.ll
new file mode 100644
index 0000000000..a8db01e29b
--- /dev/null
+++ b/test/Analysis/ScalarEvolution/2008-11-18-Stride2.ll
@@ -0,0 +1,30 @@
+; RUN: llvm-as < %s | opt -analyze -scalar-evolution |& grep {/u 3}
+
+define i32 @f(i32 %x) nounwind readnone {
+entry:
+	%0 = icmp ugt i32 %x, 999		; <i1> [#uses=1]
+	br i1 %0, label %bb2, label %bb.nph
+
+bb.nph:		; preds = %entry
+	br label %bb
+
+bb:		; preds = %bb.nph, %bb1
+	%indvar = phi i32 [ 0, %bb.nph ], [ %indvar.next, %bb1 ]		; <i32> [#uses=2]
+	%tmp = mul i32 %indvar, 3		; <i32> [#uses=1]
+	%x_addr.04 = add i32 %tmp, %x		; <i32> [#uses=1]
+	%1 = add i32 %x_addr.04, 3		; <i32> [#uses=2]
+	br label %bb1
+
+bb1:		; preds = %bb
+	%2 = icmp ugt i32 %1, 999		; <i1> [#uses=1]
+	%indvar.next = add i32 %indvar, 1		; <i32> [#uses=1]
+	br i1 %2, label %bb1.bb2_crit_edge, label %bb
+
+bb1.bb2_crit_edge:		; preds = %bb1
+	%.lcssa = phi i32 [ %1, %bb1 ]		; <i32> [#uses=1]
+	br label %bb2
+
+bb2:		; preds = %bb1.bb2_crit_edge, %entry
+	%x_addr.0.lcssa = phi i32 [ %.lcssa, %bb1.bb2_crit_edge ], [ %x, %entry ]		; <i32> [#uses=1]
+	ret i32 %x_addr.0.lcssa
+}