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llvm-mirror/test/Transforms/LoopVectorize/tail-folding-counting-down.ll
Sjoerd Meijer 20938e0e91 [LV] Fallback strategies if tail-folding fails
This implements 2 different vectorisation fallback strategies if tail-folding
fails: 1) don't vectorise at all, or 2) vectorise using a scalar epilogue. This
can be controlled with option -prefer-predicate-over-epilogue, that has been
changed to take a numeric value corresponding to the tail-folding preference
and preferred fallback.

Patch by: Pierre van Houtryve, Sjoerd Meijer.

Differential Revision: https://reviews.llvm.org/D79783
2020-08-26 16:55:25 +01:00

75 lines
2.5 KiB
LLVM

; RUN: opt < %s -loop-vectorize -prefer-predicate-over-epilogue=predicate-dont-vectorize -force-vector-width=4 -S | FileCheck %s
; Check that a counting-down loop which has no primary induction variable
; is vectorized with preferred predication.
; CHECK-LABEL: vector.body:
; CHECK-LABEL: middle.block:
; CHECK-NEXT: br i1 true,
target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"
define dso_local void @foo(i8* noalias nocapture readonly %A, i8* noalias nocapture readonly %B, i8* noalias nocapture %C, i32 %N) {
entry:
%cmp6 = icmp eq i32 %N, 0
br i1 %cmp6, label %while.end, label %while.body.preheader
while.body.preheader:
br label %while.body
while.body:
%N.addr.010 = phi i32 [ %dec, %while.body ], [ %N, %while.body.preheader ]
%C.addr.09 = phi i8* [ %incdec.ptr4, %while.body ], [ %C, %while.body.preheader ]
%B.addr.08 = phi i8* [ %incdec.ptr1, %while.body ], [ %B, %while.body.preheader ]
%A.addr.07 = phi i8* [ %incdec.ptr, %while.body ], [ %A, %while.body.preheader ]
%incdec.ptr = getelementptr inbounds i8, i8* %A.addr.07, i32 1
%0 = load i8, i8* %A.addr.07, align 1
%incdec.ptr1 = getelementptr inbounds i8, i8* %B.addr.08, i32 1
%1 = load i8, i8* %B.addr.08, align 1
%add = add i8 %1, %0
%incdec.ptr4 = getelementptr inbounds i8, i8* %C.addr.09, i32 1
store i8 %add, i8* %C.addr.09, align 1
%dec = add i32 %N.addr.010, -1
%cmp = icmp eq i32 %dec, 0
br i1 %cmp, label %while.end.loopexit, label %while.body
while.end.loopexit:
br label %while.end
while.end:
ret void
}
; Make sure a loop is successfully vectorized with fold-tail when the backedge
; taken count is constant and used inside the loop. Issue revealed by D76992.
;
define void @reuse_const_btc(i8* %A) optsize {
; CHECK-LABEL: @reuse_const_btc
; CHECK: {{%.*}} = icmp ule <4 x i32> {{%.*}}, <i32 13, i32 13, i32 13, i32 13>
; CHECK: {{%.*}} = select <4 x i1> {{%.*}}, <4 x i32> <i32 12, i32 12, i32 12, i32 12>, <4 x i32> <i32 13, i32 13, i32 13, i32 13>
;
entry:
br label %loop
loop:
%riv = phi i32 [ 13, %entry ], [ %rivMinus1, %merge ]
%sub = sub nuw nsw i32 20, %riv
%arrayidx = getelementptr inbounds i8, i8* %A, i32 %sub
%cond0 = icmp eq i32 %riv, 7
br i1 %cond0, label %then, label %else
then:
br label %merge
else:
br label %merge
merge:
%blend = phi i32 [ 13, %then ], [ 12, %else ]
%trunc = trunc i32 %blend to i8
store i8 %trunc, i8* %arrayidx, align 1
%rivMinus1 = add nuw nsw i32 %riv, -1
%cond = icmp eq i32 %riv, 0
br i1 %cond, label %exit, label %loop
exit:
ret void
}