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

Seems that SCEV is not powerful enough to handle this.
This commit is contained in:
Max Kazantsev 2020-08-07 16:46:39 +07:00
parent be8b3f0c22
commit da9e7b1ab0
1 changed files with 73 additions and 0 deletions
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73
llvm/test/Analysis/ScalarEvolution/predicated_ranges.ll Normal file
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; 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}