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llvm-mirror/test/Transforms/IndVarSimplify/eliminate-exit.ll
Philip Reames e57810463a [IndVars] Eliminate loop exits with equivalent exit counts 
We can end up with two loop exits whose exit counts are equivalent, but whose textual representation is different and non-obvious. For the sub-case where we have a series of exits which dominate one another (common), eliminate any exits which would iterate *after* a previous exit on the exiting iteration.

As noted in the TODO being removed, I'd always thought this was a good idea, but I've now seen this in a real workload as well.

Interestingly, in review, Nikita pointed out there's let another oppurtunity to leverage SCEV's reasoning.  If we kept track of the min of dominanting exits so far, we could discharge exits with EC >= MDE.  This is less powerful than the existing transform (since later exits aren't considered), but potentially more powerful for any case where SCEV can prove a >= b, but neither a == b or a > b.  I don't have an example to illustrate that oppurtunity, but won't be suprised if we find one and return to handle that case as well.  

Differential Revision: https://reviews.llvm.org/D69009

llvm-svn: 375379
2019-10-20 23:38:02 +00:00

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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -indvars -S < %s | FileCheck %s
define void @ult(i64 %n, i64 %m) {
; CHECK-LABEL: @ult(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[CMP0:%.*]] = icmp ult i64 [[N:%.*]], [[M:%.*]]
; CHECK-NEXT: br i1 [[CMP0]], label [[LOOP_PREHEADER:%.*]], label [[EXIT:%.*]]
; CHECK: loop.preheader:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i64 [ [[IV_NEXT:%.*]], [[LATCH:%.*]] ], [ 0, [[LOOP_PREHEADER]] ]
; CHECK-NEXT: [[IV_NEXT]] = add i64 [[IV]], 1
; CHECK-NEXT: [[CMP1:%.*]] = icmp ult i64 [[IV]], [[N]]
; CHECK-NEXT: br i1 [[CMP1]], label [[LATCH]], label [[EXIT_LOOPEXIT:%.*]]
; CHECK: latch:
; CHECK-NEXT: call void @side_effect()
; CHECK-NEXT: br i1 true, label [[LOOP]], label [[EXIT_LOOPEXIT]]
; CHECK: exit.loopexit:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
entry:
%cmp0 = icmp ult i64 %n, %m
br i1 %cmp0, label %loop, label %exit
loop:
%iv = phi i64 [ 0, %entry ], [ %iv.next, %latch ]
%iv.next = add i64 %iv, 1
%cmp1 = icmp ult i64 %iv, %n
br i1 %cmp1, label %latch, label %exit
latch:
call void @side_effect()
%cmp2 = icmp ult i64 %iv, %m
br i1 %cmp2, label %loop, label %exit
exit:
ret void
}
define void @ugt(i64 %n, i64 %m) {
; CHECK-LABEL: @ugt(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[CMP0:%.*]] = icmp ugt i64 [[N:%.*]], [[M:%.*]]
; CHECK-NEXT: br i1 [[CMP0]], label [[LOOP_PREHEADER:%.*]], label [[EXIT:%.*]]
; CHECK: loop.preheader:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i64 [ [[IV_NEXT:%.*]], [[LATCH:%.*]] ], [ 0, [[LOOP_PREHEADER]] ]
; CHECK-NEXT: [[IV_NEXT]] = add i64 [[IV]], 1
; CHECK-NEXT: br i1 true, label [[LATCH]], label [[EXIT_LOOPEXIT:%.*]]
; CHECK: latch:
; CHECK-NEXT: call void @side_effect()
; CHECK-NEXT: [[CMP2:%.*]] = icmp ult i64 [[IV]], [[M]]
; CHECK-NEXT: br i1 [[CMP2]], label [[LOOP]], label [[EXIT_LOOPEXIT]]
; CHECK: exit.loopexit:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
entry:
%cmp0 = icmp ugt i64 %n, %m
br i1 %cmp0, label %loop, label %exit
loop:
%iv = phi i64 [ 0, %entry ], [ %iv.next, %latch ]
%iv.next = add i64 %iv, 1
%cmp1 = icmp ult i64 %iv, %n
br i1 %cmp1, label %latch, label %exit
latch:
call void @side_effect()
%cmp2 = icmp ult i64 %iv, %m
br i1 %cmp2, label %loop, label %exit
exit:
ret void
}
define void @ule(i64 %n, i64 %m) {
; CHECK-LABEL: @ule(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[CMP0:%.*]] = icmp ule i64 [[N:%.*]], [[M:%.*]]
; CHECK-NEXT: br i1 [[CMP0]], label [[LOOP_PREHEADER:%.*]], label [[EXIT:%.*]]
; CHECK: loop.preheader:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i64 [ [[IV_NEXT:%.*]], [[LATCH:%.*]] ], [ 0, [[LOOP_PREHEADER]] ]
; CHECK-NEXT: [[IV_NEXT]] = add i64 [[IV]], 1
; CHECK-NEXT: [[CMP1:%.*]] = icmp ult i64 [[IV]], [[N]]
; CHECK-NEXT: br i1 [[CMP1]], label [[LATCH]], label [[EXIT_LOOPEXIT:%.*]]
; CHECK: latch:
; CHECK-NEXT: call void @side_effect()
; CHECK-NEXT: [[CMP2:%.*]] = icmp ult i64 [[IV]], [[M]]
; CHECK-NEXT: br i1 [[CMP2]], label [[LOOP]], label [[EXIT_LOOPEXIT]]
; CHECK: exit.loopexit:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
entry:
%cmp0 = icmp ule i64 %n, %m
br i1 %cmp0, label %loop, label %exit
loop:
%iv = phi i64 [ 0, %entry ], [ %iv.next, %latch ]
%iv.next = add i64 %iv, 1
%cmp1 = icmp ult i64 %iv, %n
br i1 %cmp1, label %latch, label %exit
latch:
call void @side_effect()
%cmp2 = icmp ult i64 %iv, %m
br i1 %cmp2, label %loop, label %exit
exit:
ret void
}
define void @uge(i64 %n, i64 %m) {
; CHECK-LABEL: @uge(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[CMP0:%.*]] = icmp uge i64 [[N:%.*]], [[M:%.*]]
; CHECK-NEXT: br i1 [[CMP0]], label [[LOOP_PREHEADER:%.*]], label [[EXIT:%.*]]
; CHECK: loop.preheader:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i64 [ [[IV_NEXT:%.*]], [[LATCH:%.*]] ], [ 0, [[LOOP_PREHEADER]] ]
; CHECK-NEXT: [[IV_NEXT]] = add i64 [[IV]], 1
; CHECK-NEXT: [[CMP1:%.*]] = icmp ult i64 [[IV]], [[N]]
; CHECK-NEXT: br i1 [[CMP1]], label [[LATCH]], label [[EXIT_LOOPEXIT:%.*]]
; CHECK: latch:
; CHECK-NEXT: call void @side_effect()
; CHECK-NEXT: [[CMP2:%.*]] = icmp ult i64 [[IV]], [[M]]
; CHECK-NEXT: br i1 [[CMP2]], label [[LOOP]], label [[EXIT_LOOPEXIT]]
; CHECK: exit.loopexit:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
entry:
%cmp0 = icmp uge i64 %n, %m
br i1 %cmp0, label %loop, label %exit
loop:
%iv = phi i64 [ 0, %entry ], [ %iv.next, %latch ]
%iv.next = add i64 %iv, 1
%cmp1 = icmp ult i64 %iv, %n
br i1 %cmp1, label %latch, label %exit
latch:
call void @side_effect()
%cmp2 = icmp ult i64 %iv, %m
br i1 %cmp2, label %loop, label %exit
exit:
ret void
}
define void @ult_const_max(i64 %n) {
; CHECK-LABEL: @ult_const_max(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[CMP0:%.*]] = icmp ult i64 [[N:%.*]], 20
; CHECK-NEXT: br i1 [[CMP0]], label [[LOOP_PREHEADER:%.*]], label [[EXIT:%.*]]
; CHECK: loop.preheader:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i64 [ [[IV_NEXT:%.*]], [[LATCH:%.*]] ], [ 0, [[LOOP_PREHEADER]] ]
; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
; CHECK-NEXT: br i1 true, label [[LATCH]], label [[EXIT_LOOPEXIT:%.*]]
; CHECK: latch:
; CHECK-NEXT: call void @side_effect()
; CHECK-NEXT: [[CMP2:%.*]] = icmp ult i64 [[IV]], [[N]]
; CHECK-NEXT: br i1 [[CMP2]], label [[LOOP]], label [[EXIT_LOOPEXIT]]
; CHECK: exit.loopexit:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
entry:
%cmp0 = icmp ult i64 %n, 20
br i1 %cmp0, label %loop, label %exit
loop:
%iv = phi i64 [ 0, %entry ], [ %iv.next, %latch ]
%iv.next = add i64 %iv, 1
%udiv = udiv i64 %iv, 10
%cmp1 = icmp ult i64 %udiv, 2
br i1 %cmp1, label %latch, label %exit
latch:
call void @side_effect()
%cmp2 = icmp ult i64 %iv, %n
br i1 %cmp2, label %loop, label %exit
exit:
ret void
}
define void @mixed_width(i32 %len) {
; CHECK-LABEL: @mixed_width(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[LEN_ZEXT:%.*]] = zext i32 [[LEN:%.*]] to i64
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ]
; CHECK-NEXT: [[IV_NEXT]] = add nuw nsw i64 [[IV]], 1
; CHECK-NEXT: [[CMP1:%.*]] = icmp ult i64 [[IV]], [[LEN_ZEXT]]
; CHECK-NEXT: br i1 [[CMP1]], label [[BACKEDGE]], label [[EXIT:%.*]]
; CHECK: backedge:
; CHECK-NEXT: call void @side_effect()
; CHECK-NEXT: br i1 true, label [[LOOP]], label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
entry:
%len.zext = zext i32 %len to i64
br label %loop
loop:
%iv = phi i64 [0, %entry], [%iv.next, %backedge]
%iv2 = phi i32 [0, %entry], [%iv2.next, %backedge]
%iv.next = add i64 %iv, 1
%iv2.next = add i32 %iv2, 1
%cmp1 = icmp ult i64 %iv, %len.zext
br i1 %cmp1, label %backedge, label %exit
backedge:
call void @side_effect()
%cmp2 = icmp ult i32 %iv2, %len
br i1 %cmp2, label %loop, label %exit
exit:
ret void
}
declare void @side_effect()
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