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clang-p2996/llvm/test/Transforms/IndVarSimplify/pr39673.ll
Roman Lebedev 44edc6fd2c [SCEV] rewriteLoopExitValues(): even if have hard uses, still rewrite if cheap (PR44668) 
Summary:
Replacing uses of IV outside of the loop is likely generally useful,
but `rewriteLoopExitValues()` is cautious, and if it isn't told to always
perform the replacement, and there are hard uses of IV in loop,
it doesn't replace.

In [[ https://bugs.llvm.org/show_bug.cgi?id=44668 | PR44668 ]],
that prevents `-indvars` from replacing uses of induction variable
after the loop, which might be one of the optimization failures
preventing that code from being vectorized.

Instead, now that the cost model is fixed, i believe we should be
a little bit more optimistic, and also perform replacement
if we believe it is within our budget.

Fixes [[ https://bugs.llvm.org/show_bug.cgi?id=44668 | PR44668 ]].

Reviewers: reames, mkazantsev, asbirlea, fhahn, skatkov

Reviewed By: mkazantsev

Subscribers: nikic, hiraditya, zzheng, javed.absar, dmgreen, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D73501
2020-02-25 23:05:59 +03:00

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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -S -indvars -indvars-predicate-loops=0 < %s | FileCheck %s
define i16 @constant() {
; CHECK-LABEL: @constant(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP1:%.*]]
; CHECK: loop1:
; CHECK-NEXT: [[L1:%.*]] = phi i16 [ 0, [[ENTRY:%.*]] ], [ [[L1_ADD:%.*]], [[LOOP1]] ]
; CHECK-NEXT: [[L1_ADD]] = add nuw nsw i16 [[L1]], 1
; CHECK-NEXT: [[CMP1:%.*]] = icmp ult i16 [[L1_ADD]], 2
; CHECK-NEXT: br i1 [[CMP1]], label [[LOOP1]], label [[LOOP2_PREHEADER:%.*]]
; CHECK: loop2.preheader:
; CHECK-NEXT: br label [[LOOP2:%.*]]
; CHECK: loop2:
; CHECK-NEXT: [[K2:%.*]] = phi i16 [ [[K2_ADD:%.*]], [[LOOP2]] ], [ 182, [[LOOP2_PREHEADER]] ]
; CHECK-NEXT: [[L2:%.*]] = phi i16 [ [[L2_ADD:%.*]], [[LOOP2]] ], [ 0, [[LOOP2_PREHEADER]] ]
; CHECK-NEXT: [[L2_ADD]] = add nuw nsw i16 [[L2]], 1
; CHECK-NEXT: tail call void @foo(i16 [[K2]])
; CHECK-NEXT: [[K2_ADD]] = add nuw nsw i16 [[K2]], 1
; CHECK-NEXT: [[CMP2:%.*]] = icmp ult i16 [[L2_ADD]], 2
; CHECK-NEXT: br i1 [[CMP2]], label [[LOOP2]], label [[LOOP2_END:%.*]]
; CHECK: loop2.end:
; CHECK-NEXT: ret i16 184
;
entry:
br label %loop1
loop1: ; preds = %entry, %loop1
%k1 = phi i16 [ 180, %entry ], [ %k1.add, %loop1 ]
%l1 = phi i16 [ 0, %entry ], [ %l1.add, %loop1 ]
%k1.add = add nuw nsw i16 %k1, 1
%l1.add = add nuw nsw i16 %l1, 1
%cmp1 = icmp ult i16 %l1.add, 2
br i1 %cmp1, label %loop1, label %loop2.preheader
loop2.preheader: ; preds = %loop1
%k1.add.lcssa = phi i16 [ %k1.add, %loop1 ]
br label %loop2
loop2: ; preds = %loop2.preheader, %loop2
%k2 = phi i16 [ %k2.add, %loop2 ], [ %k1.add.lcssa, %loop2.preheader ]
%l2 = phi i16 [ %l2.add, %loop2 ], [ 0, %loop2.preheader ]
%l2.add = add nuw i16 %l2, 1
tail call void @foo(i16 %k2)
%k2.add = add nuw nsw i16 %k2, 1
%cmp2 = icmp ult i16 %l2.add, 2
br i1 %cmp2, label %loop2, label %loop2.end
loop2.end: ; preds = %loop2
%k2.add.lcssa = phi i16 [ %k2.add, %loop2 ]
ret i16 %k2.add.lcssa
}
define i16 @dom_argument(i16 %arg1, i16 %arg2) {
; CHECK-LABEL: @dom_argument(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP1:%.*]]
; CHECK: loop1:
; CHECK-NEXT: [[L1:%.*]] = phi i16 [ 0, [[ENTRY:%.*]] ], [ [[L1_ADD:%.*]], [[LOOP1]] ]
; CHECK-NEXT: [[L1_ADD]] = add nuw nsw i16 [[L1]], 1
; CHECK-NEXT: [[CMP1:%.*]] = icmp ult i16 [[L1_ADD]], 2
; CHECK-NEXT: br i1 [[CMP1]], label [[LOOP1]], label [[LOOP2_PREHEADER:%.*]]
; CHECK: loop2.preheader:
; CHECK-NEXT: br label [[LOOP2:%.*]]
; CHECK: loop2:
; CHECK-NEXT: [[K2:%.*]] = phi i16 [ [[K2_ADD:%.*]], [[LOOP2]] ], [ [[ARG2:%.*]], [[LOOP2_PREHEADER]] ]
; CHECK-NEXT: [[L2:%.*]] = phi i16 [ [[L2_ADD:%.*]], [[LOOP2]] ], [ 0, [[LOOP2_PREHEADER]] ]
; CHECK-NEXT: [[L2_ADD]] = add nuw nsw i16 [[L2]], 1
; CHECK-NEXT: tail call void @foo(i16 [[K2]])
; CHECK-NEXT: [[K2_ADD]] = add nuw nsw i16 [[K2]], 1
; CHECK-NEXT: [[CMP2:%.*]] = icmp ult i16 [[L2_ADD]], 2
; CHECK-NEXT: br i1 [[CMP2]], label [[LOOP2]], label [[LOOP2_END:%.*]]
; CHECK: loop2.end:
; CHECK-NEXT: [[TMP0:%.*]] = add i16 [[ARG2]], 2
; CHECK-NEXT: ret i16 [[TMP0]]
;
entry:
br label %loop1
loop1: ; preds = %entry, %loop1
%k1 = phi i16 [ 100, %entry ], [ %k1.add, %loop1 ]
%l1 = phi i16 [ 0, %entry ], [ %l1.add, %loop1 ]
%selector = phi i16 [ %arg1, %entry ], [ %arg2, %loop1 ]
%k1.add = add nuw nsw i16 %k1, 1
%l1.add = add nuw nsw i16 %l1, 1
%cmp1 = icmp ult i16 %l1.add, 2
br i1 %cmp1, label %loop1, label %loop2.preheader
loop2.preheader: ; preds = %loop1
%k1.add.lcssa = phi i16 [ %selector, %loop1 ]
br label %loop2
loop2: ; preds = %loop2.preheader, %loop2
%k2 = phi i16 [ %k2.add, %loop2 ], [ %k1.add.lcssa, %loop2.preheader ]
%l2 = phi i16 [ %l2.add, %loop2 ], [ 0, %loop2.preheader ]
%l2.add = add nuw i16 %l2, 1
tail call void @foo(i16 %k2)
%k2.add = add nuw nsw i16 %k2, 1
%cmp2 = icmp ult i16 %l2.add, 2
br i1 %cmp2, label %loop2, label %loop2.end
loop2.end: ; preds = %loop2
%k2.add.lcssa = phi i16 [ %k2.add, %loop2 ]
ret i16 %k2.add.lcssa
}
define i16 @dummy_phi_outside_loop(i16 %arg) {
; CHECK-LABEL: @dummy_phi_outside_loop(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP2_PREHEADER:%.*]]
; CHECK: loop2.preheader:
; CHECK-NEXT: [[DUMMY:%.*]] = phi i16 [ [[ARG:%.*]], [[ENTRY:%.*]] ]
; CHECK-NEXT: br label [[LOOP2:%.*]]
; CHECK: loop2:
; CHECK-NEXT: [[K2:%.*]] = phi i16 [ [[K2_ADD:%.*]], [[LOOP2]] ], [ [[DUMMY]], [[LOOP2_PREHEADER]] ]
; CHECK-NEXT: [[L2:%.*]] = phi i16 [ [[L2_ADD:%.*]], [[LOOP2]] ], [ 0, [[LOOP2_PREHEADER]] ]
; CHECK-NEXT: [[L2_ADD]] = add nuw nsw i16 [[L2]], 1
; CHECK-NEXT: tail call void @foo(i16 [[K2]])
; CHECK-NEXT: [[K2_ADD]] = add nuw nsw i16 [[K2]], 1
; CHECK-NEXT: [[CMP2:%.*]] = icmp ult i16 [[L2_ADD]], 2
; CHECK-NEXT: br i1 [[CMP2]], label [[LOOP2]], label [[LOOP2_END:%.*]]
; CHECK: loop2.end:
; CHECK-NEXT: [[TMP0:%.*]] = add i16 [[DUMMY]], 2
; CHECK-NEXT: ret i16 [[TMP0]]
;
entry:
br label %loop2.preheader
loop2.preheader: ; preds = %loop1
%dummy = phi i16 [ %arg, %entry ]
br label %loop2
loop2: ; preds = %loop2.preheader, %loop2
%k2 = phi i16 [ %k2.add, %loop2 ], [ %dummy, %loop2.preheader ]
%l2 = phi i16 [ %l2.add, %loop2 ], [ 0, %loop2.preheader ]
%l2.add = add nuw i16 %l2, 1
tail call void @foo(i16 %k2)
%k2.add = add nuw nsw i16 %k2, 1
%cmp2 = icmp ult i16 %l2.add, 2
br i1 %cmp2, label %loop2, label %loop2.end
loop2.end: ; preds = %loop2
%k2.add.lcssa = phi i16 [ %k2.add, %loop2 ]
ret i16 %k2.add.lcssa
}
define i16 @neg_loop_carried(i16 %arg) {
; CHECK-LABEL: @neg_loop_carried(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP1:%.*]]
; CHECK: loop1:
; CHECK-NEXT: [[L1:%.*]] = phi i16 [ 0, [[ENTRY:%.*]] ], [ [[L1_ADD:%.*]], [[LOOP1]] ]
; CHECK-NEXT: [[L1_ADD]] = add nuw nsw i16 [[L1]], 1
; CHECK-NEXT: [[CMP1:%.*]] = icmp ult i16 [[L1_ADD]], 2
; CHECK-NEXT: br i1 [[CMP1]], label [[LOOP1]], label [[LOOP2_PREHEADER:%.*]]
; CHECK: loop2.preheader:
; CHECK-NEXT: [[TMP0:%.*]] = add i16 [[ARG:%.*]], 2
; CHECK-NEXT: br label [[LOOP2:%.*]]
; CHECK: loop2:
; CHECK-NEXT: [[K2:%.*]] = phi i16 [ [[K2_ADD:%.*]], [[LOOP2]] ], [ [[TMP0]], [[LOOP2_PREHEADER]] ]
; CHECK-NEXT: [[L2:%.*]] = phi i16 [ [[L2_ADD:%.*]], [[LOOP2]] ], [ 0, [[LOOP2_PREHEADER]] ]
; CHECK-NEXT: [[L2_ADD]] = add nuw nsw i16 [[L2]], 1
; CHECK-NEXT: tail call void @foo(i16 [[K2]])
; CHECK-NEXT: [[K2_ADD]] = add nuw nsw i16 [[K2]], 1
; CHECK-NEXT: [[CMP2:%.*]] = icmp ult i16 [[L2_ADD]], 2
; CHECK-NEXT: br i1 [[CMP2]], label [[LOOP2]], label [[LOOP2_END:%.*]]
; CHECK: loop2.end:
; CHECK-NEXT: [[TMP1:%.*]] = add i16 [[TMP0]], 2
; CHECK-NEXT: ret i16 [[TMP1]]
;
entry:
br label %loop1
loop1: ; preds = %entry, %loop1
%k1 = phi i16 [ %arg, %entry ], [ %k1.add, %loop1 ]
%l1 = phi i16 [ 0, %entry ], [ %l1.add, %loop1 ]
%k1.add = add nuw nsw i16 %k1, 1
%l1.add = add nuw nsw i16 %l1, 1
%cmp1 = icmp ult i16 %l1.add, 2
br i1 %cmp1, label %loop1, label %loop2.preheader
loop2.preheader: ; preds = %loop1
%k1.add.lcssa = phi i16 [ %k1.add, %loop1 ]
br label %loop2
loop2: ; preds = %loop2.preheader, %loop2
%k2 = phi i16 [ %k2.add, %loop2 ], [ %k1.add.lcssa, %loop2.preheader ]
%l2 = phi i16 [ %l2.add, %loop2 ], [ 0, %loop2.preheader ]
%l2.add = add nuw i16 %l2, 1
tail call void @foo(i16 %k2)
%k2.add = add nuw nsw i16 %k2, 1
%cmp2 = icmp ult i16 %l2.add, 2
br i1 %cmp2, label %loop2, label %loop2.end
loop2.end: ; preds = %loop2
%k2.add.lcssa = phi i16 [ %k2.add, %loop2 ]
ret i16 %k2.add.lcssa
}
declare void @foo(i16)
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