Re-enable "[SCEV] Make isLoopEntryGuardedByCond a bit smarter"

The failures happened because of assert which was overconfident about
SCEV's proving capabilities and is generally not valid.

Differential Revision: https://reviews.llvm.org/D42835

llvm-svn: 324473

4 files changed, 116 insertions, 6 deletions

diff --git a/llvm/test/Transforms/IRCE/conjunctive-checks.ll b/llvm/test/Transforms/IRCE/conjunctive-checks.ll
index f6a909e432c..b1a7063523d 100644
--- a/llvm/test/Transforms/IRCE/conjunctive-checks.ll
+++ b/llvm/test/Transforms/IRCE/conjunctive-checks.ll
@@ -4,10 +4,10 @@ define void @f_0(i32 *%arr, i32 *%a_len_ptr, i32 %n, i1* %cond_buf) {
 ; CHECK-LABEL: @f_0(
 
 ; CHECK: loop.preheader:
-; CHECK: [[not_n:[^ ]+]] = sub i32 -1, %n
 ; CHECK: [[not_safe_range_end:[^ ]+]] = sub i32 3, %len
-; CHECK: [[not_exit_main_loop_at_hiclamp_cmp:[^ ]+]] = icmp sgt i32 [[not_n]], [[not_safe_range_end]]
-; CHECK: [[not_exit_main_loop_at_hiclamp:[^ ]+]] = select i1 [[not_exit_main_loop_at_hiclamp_cmp]], i32 [[not_n]], i32 [[not_safe_range_end]]
+; CHECK: [[not_n:[^ ]+]] = sub i32 -1, %n
+; CHECK: [[not_exit_main_loop_at_hiclamp_cmp:[^ ]+]] = icmp sgt i32 [[not_safe_range_end]], [[not_n]]
+; CHECK: [[not_exit_main_loop_at_hiclamp:[^ ]+]] = select i1 [[not_exit_main_loop_at_hiclamp_cmp]], i32 [[not_safe_range_end]], i32 [[not_n]]
 ; CHECK: [[exit_main_loop_at_hiclamp:[^ ]+]] = sub i32 -1, [[not_exit_main_loop_at_hiclamp]]
 ; CHECK: [[exit_main_loop_at_loclamp_cmp:[^ ]+]] = icmp sgt i32 [[exit_main_loop_at_hiclamp]], 0
 ; CHECK: [[exit_main_loop_at_loclamp:[^ ]+]] = select i1 [[exit_main_loop_at_loclamp_cmp]], i32 [[exit_main_loop_at_hiclamp]], i32 0
diff --git a/llvm/test/Transforms/IRCE/decrementing-loop.ll b/llvm/test/Transforms/IRCE/decrementing-loop.ll
index fac873b4a24..e50479afe52 100644
--- a/llvm/test/Transforms/IRCE/decrementing-loop.ll
+++ b/llvm/test/Transforms/IRCE/decrementing-loop.ll
@@ -38,5 +38,85 @@ define void @decrementing_loop(i32 *%arr, i32 *%a_len_ptr, i32 %n) {
 ; CHECK:   %exit.preloop.at = add i32 [[not_exit_preloop_at]], -1
 }
 
+; Make sure that we can eliminate the range check when the loop looks like:
+; for (i = len.a - 1; i >= 0; --i)
+;   b[i] = a[i];
+define void @test_01(i32* %a, i32* %b, i32* %a_len_ptr, i32* %b_len_ptr) {
+
+; CHECK-LABEL: test_01
+; CHECK:       mainloop:
+; CHECK-NEXT:    br label %loop
+; CHECK:       loop:
+; CHECK:         %rc = and i1 true, true
+; CHECK:       loop.preloop:
+
+ entry:
+  %len.a = load i32, i32* %a_len_ptr, !range !0
+  %len.b = load i32, i32* %b_len_ptr, !range !0
+  %first.itr.check = icmp ne i32 %len.a, 0
+  br i1 %first.itr.check, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ %len.a, %entry ] , [ %idx.next, %in.bounds ]
+  %idx.next = sub i32 %idx, 1
+  %rca = icmp ult i32 %idx.next, %len.a
+  %rcb = icmp ult i32 %idx.next, %len.b
+  %rc = and i1 %rca, %rcb
+  br i1 %rc, label %in.bounds, label %out.of.bounds, !prof !1
+
+ in.bounds:
+  %el.a = getelementptr i32, i32* %a, i32 %idx.next
+  %el.b = getelementptr i32, i32* %b, i32 %idx.next
+  %v = load i32, i32* %el.a
+  store i32 %v, i32* %el.b
+  %loop.cond = icmp slt i32 %idx, 2
+  br i1 %loop.cond, label %exit, label %loop
+
+ out.of.bounds:
+  ret void
+
+ exit:
+  ret void
+}
+
+; Same as test_01, but the latch condition is unsigned
+define void @test_02(i32* %a, i32* %b, i32* %a_len_ptr, i32* %b_len_ptr) {
+
+; CHECK-LABEL: test_02
+; CHECK:       mainloop:
+; CHECK-NEXT:    br label %loop
+; CHECK:       loop:
+; CHECK:         %rc = and i1 true, true
+; CHECK:       loop.preloop:
+
+ entry:
+  %len.a = load i32, i32* %a_len_ptr, !range !0
+  %len.b = load i32, i32* %b_len_ptr, !range !0
+  %first.itr.check = icmp ne i32 %len.a, 0
+  br i1 %first.itr.check, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ %len.a, %entry ] , [ %idx.next, %in.bounds ]
+  %idx.next = sub i32 %idx, 1
+  %rca = icmp ult i32 %idx.next, %len.a
+  %rcb = icmp ult i32 %idx.next, %len.b
+  %rc = and i1 %rca, %rcb
+  br i1 %rc, label %in.bounds, label %out.of.bounds, !prof !1
+
+ in.bounds:
+  %el.a = getelementptr i32, i32* %a, i32 %idx.next
+  %el.b = getelementptr i32, i32* %b, i32 %idx.next
+  %v = load i32, i32* %el.a
+  store i32 %v, i32* %el.b
+  %loop.cond = icmp ult i32 %idx, 2
+  br i1 %loop.cond, label %exit, label %loop
+
+ out.of.bounds:
+  ret void
+
+ exit:
+  ret void
+}
+
 !0 = !{i32 0, i32 2147483647}
 !1 = !{!"branch_weights", i32 64, i32 4}
diff --git a/llvm/test/Transforms/IRCE/single-access-no-preloop.ll b/llvm/test/Transforms/IRCE/single-access-no-preloop.ll
index 53f430d0ba3..c9da4e28950 100644
--- a/llvm/test/Transforms/IRCE/single-access-no-preloop.ll
+++ b/llvm/test/Transforms/IRCE/single-access-no-preloop.ll
@@ -85,10 +85,10 @@ define void @single_access_no_preloop_with_offset(i32 *%arr, i32 *%a_len_ptr, i3
 ; CHECK-LABEL: @single_access_no_preloop_with_offset(
 
 ; CHECK: loop.preheader:
-; CHECK: [[not_n:[^ ]+]] = sub i32 -1, %n
 ; CHECK: [[not_safe_range_end:[^ ]+]] = sub i32 3, %len
-; CHECK: [[not_exit_main_loop_at_hiclamp_cmp:[^ ]+]] = icmp sgt i32 [[not_n]], [[not_safe_range_end]]
-; CHECK: [[not_exit_main_loop_at_hiclamp:[^ ]+]] = select i1 [[not_exit_main_loop_at_hiclamp_cmp]], i32 [[not_n]], i32 [[not_safe_range_end]]
+; CHECK: [[not_n:[^ ]+]] = sub i32 -1, %n
+; CHECK: [[not_exit_main_loop_at_hiclamp_cmp:[^ ]+]] = icmp sgt i32 [[not_safe_range_end]], [[not_n]]
+; CHECK: [[not_exit_main_loop_at_hiclamp:[^ ]+]] = select i1 [[not_exit_main_loop_at_hiclamp_cmp]], i32 [[not_safe_range_end]], i32 [[not_n]]
 ; CHECK: [[exit_main_loop_at_hiclamp:[^ ]+]] = sub i32 -1, [[not_exit_main_loop_at_hiclamp]]
 ; CHECK: [[exit_main_loop_at_loclamp_cmp:[^ ]+]] = icmp sgt i32 [[exit_main_loop_at_hiclamp]], 0
 ; CHECK: [[exit_main_loop_at_loclamp:[^ ]+]] = select i1 [[exit_main_loop_at_loclamp_cmp]], i32 [[exit_main_loop_at_hiclamp]], i32 0
diff --git a/llvm/test/Transforms/IndVarSimplify/loop-invariant-conditions.ll b/llvm/test/Transforms/IndVarSimplify/loop-invariant-conditions.ll
index 70cf714ba9f..30249828107 100644
--- a/llvm/test/Transforms/IndVarSimplify/loop-invariant-conditions.ll
+++ b/llvm/test/Transforms/IndVarSimplify/loop-invariant-conditions.ll
@@ -325,6 +325,36 @@ exit:
   ret void
 }
 
+; check that we can figure out that iv.next > 1 from the facts that iv >= 0 and
+; iv.start != 0.
+define void @test11(i64* %inc_ptr) {
+; CHECK-LABEL: @test11
+entry:
+  %inc = load i64, i64* %inc_ptr, !range !0
+  %ne.cond = icmp ne i64 %inc, 0
+  br i1 %ne.cond, label %loop, label %exit
+
+loop:
+  %iv = phi i64 [ %inc, %entry ], [ %iv.next, %backedge ]
+  %iv.next = add i64 %iv, 1
+  %brcond = icmp sgt i64 %iv.next, 1
+  ; CHECK: br i1 true, label %if.true, label %if.false
+  br i1 %brcond, label %if.true, label %if.false
+
+if.true:
+  br label %backedge
+
+if.false:
+  br label %backedge
+
+backedge:
+  %loopcond = icmp slt i64 %iv, 200
+  br i1 %loopcond, label %loop, label %exit
+
+exit:
+  ret void
+}
+
 !1 = !{i64 -1, i64 100}