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clang-p2996/llvm/test/Transforms/LoopDeletion/mustprogress.ll
Atmn Patel f88a797521 [LoopDeletion] Allows deletion of possibly infinite side-effect free loops 
From C11 and C++11 onwards, a forward-progress requirement has been
introduced for both languages. In the case of C, loops with non-constant
conditionals that do not have any observable side-effects (as defined by
6.8.5p6) can be assumed by the implementation to terminate, and in the
case of C++, this assumption extends to all functions. The clang
frontend will emit the `mustprogress` function attribute for C++
functions (D86233, D85393, D86841) and emit the loop metadata
`llvm.loop.mustprogress` for every loop in C11 or later that has a
non-constant conditional.

This patch modifies LoopDeletion so that only loops with
the `llvm.loop.mustprogress` metadata or loops contained in functions
that are required to make progress (`mustprogress` or `willreturn`) are
checked for observable side-effects. If these loops do not have an
observable side-effect, then we delete them.

Loops without observable side-effects that do not satisfy the above
conditions will not be deleted.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D86844
2021-01-05 09:56:16 -05:00

238 lines
6.5 KiB
LLVM
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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --check-attributes
; RUN: opt < %s -loop-deletion -verify-dom-info -S | FileCheck %s
;; Original C Code:
;; void unknown_tripcount_mustprogress_attr_mustprogress_loopmd(int a, int b) {
;; for (; a < b;) ;
;; for (;;) ;
;; }
define void @unknown_tripcount_mustprogress_attr_mustprogress_loopmd(i32 %a, i32 %b) #0 {
; CHECK: Function Attrs: mustprogress
; CHECK-LABEL: define {{[^@]+}}@unknown_tripcount_mustprogress_attr_mustprogress_loopmd
; CHECK-SAME: (i32 [[A:%.*]], i32 [[B:%.*]]) [[ATTR0:#.*]] {
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[FOR_END:%.*]]
; CHECK: for.end:
; CHECK-NEXT: unreachable
;
entry:
br label %for.cond
for.cond:
%cmp = icmp slt i32 %a, %b
br i1 %cmp, label %for.body, label %for.end
for.body:
br label %for.cond, !llvm.loop !2
for.end:
br label %for.cond1
for.cond1:
br label %for.cond1
}
;; Original C Code:
;; void unknown_tripcount_mustprogress_attr_no_mustprogress_loopmd(int a, int b) {
;; for (; a < b;) ;
;; for (;;) ;
;; }
;; => Removed mustprogress loop attribute
define void @unknown_tripcount_mustprogress_attr_no_mustprogess_loopmd(i32 %a, i32 %b) #0 {
; CHECK: Function Attrs: mustprogress
; CHECK-LABEL: define {{[^@]+}}@unknown_tripcount_mustprogress_attr_no_mustprogess_loopmd
; CHECK-SAME: (i32 [[A:%.*]], i32 [[B:%.*]]) [[ATTR0]] {
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[FOR_END:%.*]]
; CHECK: for.end:
; CHECK-NEXT: unreachable
;
entry:
br label %for.cond
for.cond:
%cmp = icmp slt i32 %a, %b
br i1 %cmp, label %for.body, label %for.end
for.body:
br label %for.cond
for.end:
br label %for.cond1
for.cond1:
br label %for.cond1
}
;; Original C Code:
;; void known_tripcount_no_mustprogress_attr_no_mustprogress_loopmd() {
;; for (int i = 0; i < 5; i++) ;
;; }
define void @known_tripcount_no_mustprogress_attr_no_mustprogress_loopmd() {
; CHECK-LABEL: define {{[^@]+}}@known_tripcount_no_mustprogress_attr_no_mustprogress_loopmd() {
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[FOR_END:%.*]]
; CHECK: for.end:
; CHECK-NEXT: ret void
;
entry:
br label %for.cond
for.cond:
%i.0 = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
%cmp = icmp slt i32 %i.0, 5
br i1 %cmp, label %for.body, label %for.end
for.body:
br label %for.inc
for.inc:
%inc = add nsw i32 %i.0, 1
br label %for.cond
for.end:
ret void
}
;; Original C Code:
;; void known_tripcount_no_mustprogress_attr_mustprogress_loopmd() {
;; for (int i = 0; i < 5; i++) ;
;; }
;; => Added mustprogress loop attribute
define void @known_tripcount_no_mustprogress_attr_mustprogress_loopmd() {
; CHECK-LABEL: define {{[^@]+}}@known_tripcount_no_mustprogress_attr_mustprogress_loopmd() {
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[FOR_END:%.*]]
; CHECK: for.end:
; CHECK-NEXT: ret void
;
entry:
br label %for.cond
for.cond:
%i.0 = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
%cmp = icmp slt i32 %i.0, 5
br i1 %cmp, label %for.body, label %for.end
for.body:
br label %for.inc
for.inc:
%inc = add nsw i32 %i.0, 1
br label %for.cond, !llvm.loop !4
for.end:
ret void
}
;; Original C Code:
;; void known_tripcount_mustprogress_attr_no_mustprogress_loopmd() {
;; for (int i = 0; i < 5; i++) ;
;; }
;; => Added mustprogress function attribute
define void @known_tripcount_mustprogress_attr_no_mustprogress_loopmd() #0 {
; CHECK: Function Attrs: mustprogress
; CHECK-LABEL: define {{[^@]+}}@known_tripcount_mustprogress_attr_no_mustprogress_loopmd
; CHECK-SAME: () [[ATTR0]] {
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[FOR_END:%.*]]
; CHECK: for.end:
; CHECK-NEXT: ret void
;
entry:
br label %for.cond
for.cond:
%i.0 = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
%cmp = icmp slt i32 %i.0, 5
br i1 %cmp, label %for.body, label %for.end
for.body:
br label %for.inc
for.inc:
%inc = add nsw i32 %i.0, 1
br label %for.cond
for.end:
ret void
}
;; Original C Code:
;; void known_tripcount_mustprogress_attr_mustprogress_loopmd() {
;; for (int i = 0; i < 5; i++) ;
;; }
;; => Added mustprogress function and mustprogress loop attribute
define void @known_tripcount_mustprogress_attr_mustprogress_loopmd() #0 {
; CHECK: Function Attrs: mustprogress
; CHECK-LABEL: define {{[^@]+}}@known_tripcount_mustprogress_attr_mustprogress_loopmd
; CHECK-SAME: () [[ATTR0]] {
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[FOR_END:%.*]]
; CHECK: for.end:
; CHECK-NEXT: ret void
;
entry:
br label %for.cond
for.cond:
%i.0 = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
%cmp = icmp slt i32 %i.0, 5
br i1 %cmp, label %for.body, label %for.end
for.body:
br label %for.inc
for.inc:
%inc = add nsw i32 %i.0, 1
br label %for.cond, !llvm.loop !5
for.end:
ret void
}
;; Original C Code:
;; void unknown_tripcount_no_mustprogress_attr_mustprogress_loopmd(int a, int b) {
;; for (; a < b;) ;
;; }
;; => Added mustprogress loop attribute
define void @unknown_tripcount_no_mustprogress_attr_mustprogress_loopmd(i32 %a, i32 %b) {
; CHECK-LABEL: define {{[^@]+}}@unknown_tripcount_no_mustprogress_attr_mustprogress_loopmd
; CHECK-SAME: (i32 [[A:%.*]], i32 [[B:%.*]]) {
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[FOR_END:%.*]]
; CHECK: for.end:
; CHECK-NEXT: ret void
;
entry:
br label %for.cond
for.cond:
%cmp = icmp slt i32 %a, %b
br i1 %cmp, label %for.body, label %for.end
for.body:
br label %for.cond, !llvm.loop !6
for.end:
ret void
}
;; Original C Code:
;; void unknown_tripcount_no_mustprogress_attr_no_mustprogress_loopmd(int a, int b) {
;; for (; a < b;) ;
;; }
define void @unknown_tripcount_no_mustprogress_attr_no_mustprogress_loopmd(i32 %a, i32 %b) {
; CHECK-LABEL: define {{[^@]+}}@unknown_tripcount_no_mustprogress_attr_no_mustprogress_loopmd
; CHECK-SAME: (i32 [[A:%.*]], i32 [[B:%.*]]) {
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[FOR_COND:%.*]]
; CHECK: for.cond:
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[A]], [[B]]
; CHECK-NEXT: br i1 [[CMP]], label [[FOR_BODY:%.*]], label [[FOR_END:%.*]]
; CHECK: for.body:
; CHECK-NEXT: br label [[FOR_COND]]
; CHECK: for.end:
; CHECK-NEXT: ret void
;
entry:
br label %for.cond
for.cond:
%cmp = icmp slt i32 %a, %b
br i1 %cmp, label %for.body, label %for.end
for.body:
br label %for.cond
for.end:
ret void
}
; CHECK: attributes [[ATTR0]] = { mustprogress }
attributes #0 = { mustprogress }
!2 = distinct !{!2, !3}
!3 = !{!"llvm.loop.mustprogress"}
!4 = distinct !{!4, !3}
!5 = distinct !{!5, !3}
!6 = distinct !{!6, !3}
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