1 files changed, 188 insertions, 0 deletions
diff --git a/llvm/test/Transforms/SimpleLoopUnswitch/update-scev.ll b/llvm/test/Transforms/SimpleLoopUnswitch/update-scev.ll
new file mode 100644
index 00000000000..3a2d7618817
--- /dev/null
+++ b/llvm/test/Transforms/SimpleLoopUnswitch/update-scev.ll
@@ -0,0 +1,188 @@
+; RUN: opt -passes='print<scalar-evolution>,loop(unswitch,loop-instsimplify),print<scalar-evolution>' -enable-nontrivial-unswitch -S < %s 2>%t.scev | FileCheck %s
+; RUN: FileCheck %s --check-prefix=SCEV < %t.scev
+
+target triple = "x86_64-unknown-linux-gnu"
+
+declare void @f()
+
+; Check that trivially unswitching an inner loop resets both the inner and outer
+; loop trip count.
+define void @test1(i32 %n, i32 %m, i1 %cond) {
+; Check that SCEV has no trip count before unswitching.
+; SCEV-LABEL: Determining loop execution counts for: @test1
+; SCEV: Loop %inner_loop_begin: <multiple exits> Unpredictable backedge-taken count.
+; SCEV: Loop %outer_loop_begin: Unpredictable backedge-taken count.
+;
+; Now check that after unswitching and simplifying instructions we get clean
+; backedge-taken counts.
+; SCEV-LABEL: Determining loop execution counts for: @test1
+; SCEV: Loop %inner_loop_begin: backedge-taken count is (-1 + (1 smax %m))<nsw>
+; SCEV: Loop %outer_loop_begin: backedge-taken count is (-1 + (1 smax %n))<nsw>
+;
+; And verify the code matches what we expect.
+; CHECK-LABEL: define void @test1(
+entry:
+  br label %outer_loop_begin
+; Ensure the outer loop didn't get unswitched.
+; CHECK:       entry:
+; CHECK-NEXT:    br label %outer_loop_begin
+
+outer_loop_begin:
+  %i = phi i32 [ %i.next, %outer_loop_latch ], [ 0, %entry ]
+  ; Block unswitching of the outer loop with a noduplicate call.
+  call void @f() noduplicate
+  br label %inner_loop_begin
+; Ensure the inner loop got unswitched into the outer loop.
+; CHECK:       outer_loop_begin:
+; CHECK-NEXT:    %{{.*}} = phi i32
+; CHECK-NEXT:    call void @f()
+; CHECK-NEXT:    br i1 %cond,
+
+inner_loop_begin:
+  %j = phi i32 [ %j.next, %inner_loop_latch ], [ 0, %outer_loop_begin ]
+  br i1 %cond, label %inner_loop_latch, label %inner_loop_early_exit
+
+inner_loop_latch:
+  %j.next = add nsw i32 %j, 1
+  %j.cmp = icmp slt i32 %j.next, %m
+  br i1 %j.cmp, label %inner_loop_begin, label %inner_loop_late_exit
+
+inner_loop_early_exit:
+  %j.lcssa = phi i32 [ %i, %inner_loop_begin ]
+  br label %outer_loop_latch
+
+inner_loop_late_exit:
+  br label %outer_loop_latch
+
+outer_loop_latch:
+  %i.phi = phi i32 [ %j.lcssa, %inner_loop_early_exit ], [ %i, %inner_loop_late_exit ]
+  %i.next = add nsw i32 %i.phi, 1
+  %i.cmp = icmp slt i32 %i.next, %n
+  br i1 %i.cmp, label %outer_loop_begin, label %exit
+
+exit:
+  ret void
+}
+
+; Check that trivially unswitching an inner loop resets both the inner and outer
+; loop trip count.
+define void @test2(i32 %n, i32 %m, i32 %cond) {
+; Check that SCEV has no trip count before unswitching.
+; SCEV-LABEL: Determining loop execution counts for: @test2
+; SCEV: Loop %inner_loop_begin: <multiple exits> Unpredictable backedge-taken count.
+; SCEV: Loop %outer_loop_begin: Unpredictable backedge-taken count.
+;
+; Now check that after unswitching and simplifying instructions we get clean
+; backedge-taken counts.
+; SCEV-LABEL: Determining loop execution counts for: @test2
+; SCEV: Loop %inner_loop_begin: backedge-taken count is (-1 + (1 smax %m))<nsw>
+; FIXME: The following backedge taken count should be known but isn't apparently
+; just because of a switch in the outer loop.
+; SCEV: Loop %outer_loop_begin: Unpredictable backedge-taken count.
+;
+; CHECK-LABEL: define void @test2(
+entry:
+  br label %outer_loop_begin
+; Ensure the outer loop didn't get unswitched.
+; CHECK:       entry:
+; CHECK-NEXT:    br label %outer_loop_begin
+
+outer_loop_begin:
+  %i = phi i32 [ %i.next, %outer_loop_latch ], [ 0, %entry ]
+  ; Block unswitching of the outer loop with a noduplicate call.
+  call void @f() noduplicate
+  br label %inner_loop_begin
+; Ensure the inner loop got unswitched into the outer loop.
+; CHECK:       outer_loop_begin:
+; CHECK-NEXT:    %{{.*}} = phi i32
+; CHECK-NEXT:    call void @f()
+; CHECK-NEXT:    switch i32 %cond,
+
+inner_loop_begin:
+  %j = phi i32 [ %j.next, %inner_loop_latch ], [ 0, %outer_loop_begin ]
+  switch i32 %cond, label %inner_loop_early_exit [
+    i32 1, label %inner_loop_latch
+    i32 2, label %inner_loop_latch
+  ]
+
+inner_loop_latch:
+  %j.next = add nsw i32 %j, 1
+  %j.cmp = icmp slt i32 %j.next, %m
+  br i1 %j.cmp, label %inner_loop_begin, label %inner_loop_late_exit
+
+inner_loop_early_exit:
+  %j.lcssa = phi i32 [ %i, %inner_loop_begin ]
+  br label %outer_loop_latch
+
+inner_loop_late_exit:
+  br label %outer_loop_latch
+
+outer_loop_latch:
+  %i.phi = phi i32 [ %j.lcssa, %inner_loop_early_exit ], [ %i, %inner_loop_late_exit ]
+  %i.next = add nsw i32 %i.phi, 1
+  %i.cmp = icmp slt i32 %i.next, %n
+  br i1 %i.cmp, label %outer_loop_begin, label %exit
+
+exit:
+  ret void
+}
+
+; Check that non-trivial unswitching of a branch in an inner loop into the outer
+; loop invalidates both inner and outer.
+define void @test3(i32 %n, i32 %m, i1 %cond) {
+; Check that SCEV has no trip count before unswitching.
+; SCEV-LABEL: Determining loop execution counts for: @test3
+; SCEV: Loop %inner_loop_begin: <multiple exits> Unpredictable backedge-taken count.
+; SCEV: Loop %outer_loop_begin: Unpredictable backedge-taken count.
+;
+; Now check that after unswitching and simplifying instructions we get clean
+; backedge-taken counts.
+; SCEV-LABEL: Determining loop execution counts for: @test3
+; SCEV: Loop %inner_loop_begin{{.*}}: backedge-taken count is (-1 + (1 smax %m))<nsw>
+; SCEV: Loop %outer_loop_begin: backedge-taken count is (-1 + (1 smax %n))<nsw>
+;
+; And verify the code matches what we expect.
+; CHECK-LABEL: define void @test3(
+entry:
+  br label %outer_loop_begin
+; Ensure the outer loop didn't get unswitched.
+; CHECK:       entry:
+; CHECK-NEXT:    br label %outer_loop_begin
+
+outer_loop_begin:
+  %i = phi i32 [ %i.next, %outer_loop_latch ], [ 0, %entry ]
+  ; Block unswitching of the outer loop with a noduplicate call.
+  call void @f() noduplicate
+  br label %inner_loop_begin
+; Ensure the inner loop got unswitched into the outer loop.
+; CHECK:       outer_loop_begin:
+; CHECK-NEXT:    %{{.*}} = phi i32
+; CHECK-NEXT:    call void @f()
+; CHECK-NEXT:    br i1 %cond,
+
+inner_loop_begin:
+  %j = phi i32 [ %j.next, %inner_loop_latch ], [ 0, %outer_loop_begin ]
+  %j.tmp = add nsw i32 %j, 1
+  br i1 %cond, label %inner_loop_latch, label %inner_loop_early_exit
+
+inner_loop_latch:
+  %j.next = add nsw i32 %j, 1
+  %j.cmp = icmp slt i32 %j.next, %m
+  br i1 %j.cmp, label %inner_loop_begin, label %inner_loop_late_exit
+
+inner_loop_early_exit:
+  %j.lcssa = phi i32 [ %j.tmp, %inner_loop_begin ]
+  br label %outer_loop_latch
+
+inner_loop_late_exit:
+  br label %outer_loop_latch
+
+outer_loop_latch:
+  %inc.phi = phi i32 [ %j.lcssa, %inner_loop_early_exit ], [ 1, %inner_loop_late_exit ]
+  %i.next = add nsw i32 %i, %inc.phi
+  %i.cmp = icmp slt i32 %i.next, %n
+  br i1 %i.cmp, label %outer_loop_begin, label %exit
+
+exit:
+  ret void
+}