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llvm-mirror/test/Transforms/InstCombine/result-of-add-of-negative-or-zero-is-non-zero-and-no-underflow.ll
Roman Lebedev 0d5754f5a2 [InstCombine] (a+b) <= a && (a+b) != 0 -> (0-b) < a (PR43259) 
Summary:
This is again motivated by D67122 sanitizer check enhancement.
That patch seemingly worsens `-fsanitize=pointer-overflow`
overhead from 25% to 50%, which strongly implies missing folds.

This pattern isn't exactly what we get there
(strict vs. non-strict predicate), but this pattern does not
require known-bits analysis, so it is best to handle it first.

```
Name: 0
  %adjusted = add i8 %base, %offset
  %not_null = icmp ne i8 %adjusted, 0
  %no_underflow = icmp ule i8 %adjusted, %base
  %r = and i1 %not_null, %no_underflow
=>
  %neg_offset = sub i8 0, %offset
  %r = icmp ugt i8 %base, %neg_offset
```
https://rise4fun.com/Alive/knp

There are 3 other variants of this pattern,
they all will go into InstSimplify:
https://rise4fun.com/Alive/bIDZ

https://bugs.llvm.org/show_bug.cgi?id=43259

Reviewers: spatel, xbolva00, nikic

Reviewed By: spatel

Subscribers: hiraditya, majnemer, vsk, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67846

llvm-svn: 372767
2019-09-24 16:10:38 +00:00

162 lines
5.9 KiB
LLVM
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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt %s -instcombine -S | FileCheck %s
declare void @use8(i8)
declare void @use1(i1)
declare void @llvm.assume(i1)
define i1 @t0(i8 %base, i8 %offset) {
; CHECK-LABEL: @t0(
; CHECK-NEXT: [[ADJUSTED:%.*]] = add i8 [[BASE:%.*]], [[OFFSET:%.*]]
; CHECK-NEXT: call void @use8(i8 [[ADJUSTED]])
; CHECK-NEXT: [[TMP1:%.*]] = sub i8 0, [[OFFSET]]
; CHECK-NEXT: [[TMP2:%.*]] = icmp ult i8 [[TMP1]], [[BASE]]
; CHECK-NEXT: ret i1 [[TMP2]]
;
%adjusted = add i8 %base, %offset
call void @use8(i8 %adjusted)
%not_null = icmp ne i8 %adjusted, 0
%no_underflow = icmp ule i8 %adjusted, %base
%r = and i1 %not_null, %no_underflow
ret i1 %r
}
; We need to produce extra instruction, so one of icmp's must go away.
define i1 @t1_oneuse0(i8 %base, i8 %offset) {
; CHECK-LABEL: @t1_oneuse0(
; CHECK-NEXT: [[ADJUSTED:%.*]] = add i8 [[BASE:%.*]], [[OFFSET:%.*]]
; CHECK-NEXT: call void @use8(i8 [[ADJUSTED]])
; CHECK-NEXT: [[NOT_NULL:%.*]] = icmp ne i8 [[ADJUSTED]], 0
; CHECK-NEXT: call void @use1(i1 [[NOT_NULL]])
; CHECK-NEXT: [[TMP1:%.*]] = sub i8 0, [[OFFSET]]
; CHECK-NEXT: [[TMP2:%.*]] = icmp ult i8 [[TMP1]], [[BASE]]
; CHECK-NEXT: ret i1 [[TMP2]]
;
%adjusted = add i8 %base, %offset
call void @use8(i8 %adjusted)
%not_null = icmp ne i8 %adjusted, 0
call void @use1(i1 %not_null)
%no_underflow = icmp ule i8 %adjusted, %base
%r = and i1 %not_null, %no_underflow
ret i1 %r
}
define i1 @t2_oneuse1(i8 %base, i8 %offset) {
; CHECK-LABEL: @t2_oneuse1(
; CHECK-NEXT: [[ADJUSTED:%.*]] = add i8 [[BASE:%.*]], [[OFFSET:%.*]]
; CHECK-NEXT: call void @use8(i8 [[ADJUSTED]])
; CHECK-NEXT: [[NO_UNDERFLOW:%.*]] = icmp ule i8 [[ADJUSTED]], [[BASE]]
; CHECK-NEXT: call void @use1(i1 [[NO_UNDERFLOW]])
; CHECK-NEXT: [[TMP1:%.*]] = sub i8 0, [[OFFSET]]
; CHECK-NEXT: [[TMP2:%.*]] = icmp ult i8 [[TMP1]], [[BASE]]
; CHECK-NEXT: ret i1 [[TMP2]]
;
%adjusted = add i8 %base, %offset
call void @use8(i8 %adjusted)
%not_null = icmp ne i8 %adjusted, 0
%no_underflow = icmp ule i8 %adjusted, %base
call void @use1(i1 %no_underflow)
%r = and i1 %not_null, %no_underflow
ret i1 %r
}
define i1 @n3_oneuse2_bad(i8 %base, i8 %offset) {
; CHECK-LABEL: @n3_oneuse2_bad(
; CHECK-NEXT: [[ADJUSTED:%.*]] = add i8 [[BASE:%.*]], [[OFFSET:%.*]]
; CHECK-NEXT: call void @use8(i8 [[ADJUSTED]])
; CHECK-NEXT: [[NOT_NULL:%.*]] = icmp ne i8 [[ADJUSTED]], 0
; CHECK-NEXT: call void @use1(i1 [[NOT_NULL]])
; CHECK-NEXT: [[NO_UNDERFLOW:%.*]] = icmp ule i8 [[ADJUSTED]], [[BASE]]
; CHECK-NEXT: call void @use1(i1 [[NO_UNDERFLOW]])
; CHECK-NEXT: [[R:%.*]] = and i1 [[NOT_NULL]], [[NO_UNDERFLOW]]
; CHECK-NEXT: ret i1 [[R]]
;
%adjusted = add i8 %base, %offset
call void @use8(i8 %adjusted)
%not_null = icmp ne i8 %adjusted, 0
call void @use1(i1 %not_null)
%no_underflow = icmp ule i8 %adjusted, %base
call void @use1(i1 %no_underflow)
%r = and i1 %not_null, %no_underflow
ret i1 %r
}
define i1 @t4_commutativity0(i8 %base, i8 %offset) {
; CHECK-LABEL: @t4_commutativity0(
; CHECK-NEXT: [[ADJUSTED:%.*]] = add i8 [[BASE:%.*]], [[OFFSET:%.*]]
; CHECK-NEXT: call void @use8(i8 [[ADJUSTED]])
; CHECK-NEXT: [[TMP1:%.*]] = sub i8 0, [[OFFSET]]
; CHECK-NEXT: [[TMP2:%.*]] = icmp ult i8 [[TMP1]], [[BASE]]
; CHECK-NEXT: ret i1 [[TMP2]]
;
%adjusted = add i8 %base, %offset
call void @use8(i8 %adjusted)
%not_null = icmp ne i8 %adjusted, 0
%no_underflow = icmp ule i8 %adjusted, %base
%r = and i1 %no_underflow, %not_null ; swapped
ret i1 %r
}
define i1 @t5_commutativity1(i8 %base, i8 %offset) {
; CHECK-LABEL: @t5_commutativity1(
; CHECK-NEXT: [[ADJUSTED:%.*]] = add i8 [[BASE:%.*]], [[OFFSET:%.*]]
; CHECK-NEXT: call void @use8(i8 [[ADJUSTED]])
; CHECK-NEXT: [[TMP1:%.*]] = sub i8 0, [[OFFSET]]
; CHECK-NEXT: [[TMP2:%.*]] = icmp ult i8 [[TMP1]], [[BASE]]
; CHECK-NEXT: ret i1 [[TMP2]]
;
%adjusted = add i8 %base, %offset
call void @use8(i8 %adjusted)
%not_null = icmp ne i8 %adjusted, 0
%no_underflow = icmp uge i8 %base, %adjusted ; swapped
%r = and i1 %not_null, %no_underflow
ret i1 %r
}
define i1 @t6_commutativity3(i8 %base, i8 %offset) {
; CHECK-LABEL: @t6_commutativity3(
; CHECK-NEXT: [[ADJUSTED:%.*]] = add i8 [[BASE:%.*]], [[OFFSET:%.*]]
; CHECK-NEXT: call void @use8(i8 [[ADJUSTED]])
; CHECK-NEXT: [[TMP1:%.*]] = sub i8 0, [[OFFSET]]
; CHECK-NEXT: [[TMP2:%.*]] = icmp ult i8 [[TMP1]], [[BASE]]
; CHECK-NEXT: ret i1 [[TMP2]]
;
%adjusted = add i8 %base, %offset
call void @use8(i8 %adjusted)
%not_null = icmp ne i8 %adjusted, 0
%no_underflow = icmp uge i8 %base, %adjusted ; swapped
%r = and i1 %no_underflow, %not_null ; swapped
ret i1 %r
}
; We could have the opposite question, did we get null or overflow happened?
define i1 @t7(i8 %base, i8 %offset) {
; CHECK-LABEL: @t7(
; CHECK-NEXT: [[ADJUSTED:%.*]] = add i8 [[BASE:%.*]], [[OFFSET:%.*]]
; CHECK-NEXT: call void @use8(i8 [[ADJUSTED]])
; CHECK-NEXT: [[TMP1:%.*]] = add i8 [[ADJUSTED]], -1
; CHECK-NEXT: [[TMP2:%.*]] = icmp uge i8 [[TMP1]], [[BASE]]
; CHECK-NEXT: ret i1 [[TMP2]]
;
%adjusted = add i8 %base, %offset
call void @use8(i8 %adjusted)
%not_null = icmp eq i8 %adjusted, 0
%no_underflow = icmp ugt i8 %adjusted, %base
%r = or i1 %not_null, %no_underflow
ret i1 %r
}
; The comparison can be with any of the values being added.
define i1 @t8(i8 %base, i8 %offset) {
; CHECK-LABEL: @t8(
; CHECK-NEXT: [[ADJUSTED:%.*]] = add i8 [[BASE:%.*]], [[OFFSET:%.*]]
; CHECK-NEXT: call void @use8(i8 [[ADJUSTED]])
; CHECK-NEXT: [[TMP1:%.*]] = sub i8 0, [[BASE]]
; CHECK-NEXT: [[TMP2:%.*]] = icmp ult i8 [[TMP1]], [[OFFSET]]
; CHECK-NEXT: ret i1 [[TMP2]]
;
%adjusted = add i8 %base, %offset
call void @use8(i8 %adjusted)
%not_null = icmp ne i8 %adjusted, 0
%no_underflow = icmp ule i8 %adjusted, %offset
%r = and i1 %not_null, %no_underflow
ret i1 %r
}
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