[llvm] da9e7b1 - [Test] Added test showing missing range check elimination opportunity in IndVars

[Max Kazantsev via llvm-commits]

Author: Max Kazantsev
Date: 2020-08-07T16:47:25+07:00
New Revision: da9e7b1ab03be92b0c3060cf149ab882d61e634f

URL: https://github.com/llvm/llvm-project/commit/da9e7b1ab03be92b0c3060cf149ab882d61e634f
DIFF: https://github.com/llvm/llvm-project/commit/da9e7b1ab03be92b0c3060cf149ab882d61e634f.diff

LOG: [Test] Added test showing missing range check elimination opportunity in IndVars

Seems that SCEV is not powerful enough to handle this.

Added: 
    llvm/test/Analysis/ScalarEvolution/predicated_ranges.ll

Modified: 
    

Removed: 
    


################################################################################
diff  --git a/llvm/test/Analysis/ScalarEvolution/predicated_ranges.ll b/llvm/test/Analysis/ScalarEvolution/predicated_ranges.ll
new file mode 100644
index 000000000000..4a4d70aa39fe
--- /dev/null
+++ b/llvm/test/Analysis/ScalarEvolution/predicated_ranges.ll
@@ -0,0 +1,73 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -indvars -S < %s | FileCheck %s
+; RUN: opt -passes=indvars -S < %s | FileCheck %s
+
+; TODO: should be able to remove the range check basing on the following facts:
+; 0 <= len <= MAX_INT, start ult len, therefore
+;   0 <= start < MAX_INT [1];
+; iv starts from len and goes down stopping at zero and [1], therefore
+;   0 <= iv <= len [2];
+; 3. In range_check_block, iv != 0 and [2], therefore
+;   1 <= iv <= len [3];
+; 4. iv.next = iv - 1 and [3], therefore
+;   0 <= iv.next < len.
+define void @test_predicated_simple(i32 %start, i32* %p, i32* %arr) {
+; CHECK-LABEL: @test_predicated_simple(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[LEN:%.*]] = load i32, i32* [[P:%.*]], align 4, !range !0
+; CHECK-NEXT:    [[GUARD_COND:%.*]] = icmp ult i32 [[START:%.*]], [[LEN]]
+; CHECK-NEXT:    br i1 [[GUARD_COND]], label [[PREHEADER:%.*]], label [[FAIL:%.*]]
+; CHECK:       preheader:
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[IV:%.*]] = phi i32 [ [[LEN]], [[PREHEADER]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ]
+; CHECK-NEXT:    [[ZERO_COND:%.*]] = icmp eq i32 [[IV]], 0
+; CHECK-NEXT:    br i1 [[ZERO_COND]], label [[EXIT:%.*]], label [[RANGE_CHECK_BLOCK:%.*]]
+; CHECK:       range_check_block:
+; CHECK-NEXT:    [[IV_NEXT]] = sub i32 [[IV]], 1
+; CHECK-NEXT:    [[RANGE_CHECK:%.*]] = icmp ult i32 [[IV_NEXT]], [[LEN]]
+; CHECK-NEXT:    br i1 [[RANGE_CHECK]], label [[BACKEDGE]], label [[FAIL_LOOPEXIT:%.*]]
+; CHECK:       backedge:
+; CHECK-NEXT:    [[EL_PTR:%.*]] = getelementptr i32, i32* [[P]], i32 [[IV]]
+; CHECK-NEXT:    [[EL:%.*]] = load i32, i32* [[EL_PTR]], align 4
+; CHECK-NEXT:    [[LOOP_COND:%.*]] = icmp eq i32 [[EL]], 0
+; CHECK-NEXT:    br i1 [[LOOP_COND]], label [[LOOP]], label [[EXIT]]
+; CHECK:       exit:
+; CHECK-NEXT:    ret void
+; CHECK:       fail.loopexit:
+; CHECK-NEXT:    br label [[FAIL]]
+; CHECK:       fail:
+; CHECK-NEXT:    unreachable
+;
+entry:
+  %len = load i32, i32* %p, !range !0
+  %guard_cond = icmp ult i32 %start, %len
+  br i1 %guard_cond, label %preheader, label %fail
+
+preheader:
+  br label %loop
+
+loop:
+  %iv = phi i32 [%len, %preheader], [%iv.next, %backedge]
+  %zero_cond = icmp eq i32 %iv, 0
+  br i1 %zero_cond, label %exit, label %range_check_block
+
+range_check_block:
+  %iv.next = sub i32 %iv, 1
+  %range_check = icmp ult i32 %iv.next, %len
+  br i1 %range_check, label %backedge, label %fail
+
+backedge:
+  %el.ptr = getelementptr i32, i32* %p, i32 %iv
+  %el = load i32, i32* %el.ptr
+  %loop.cond = icmp eq i32 %el, 0
+  br i1 %loop.cond, label %loop, label %exit
+
+exit:
+  ret void
+
+fail:
+  unreachable
+}
+
+!0 = !{i32 0, i32 2147483647}