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llvm-mirror/test/Transforms/LoopVectorize/runtime-check.ll
Ayal Zaks fd3659df66 [LV] Test once if vector trip count is zero, instead of twice
Generate a single test to decide if there are enough iterations to jump to the
vectorized loop, or else go to the scalar remainder loop. This test compares the
Scalar Trip Count: if STC < VF * UF go to the scalar loop. If
requiresScalarEpilogue() holds, at-least one iteration must remain scalar; the
rest can be used to form vector iterations. So in this case the test checks
instead if (STC - 1) < VF * UF by comparing STC <= VF * UF, and going to the
scalar loop if so. Otherwise the vector loop is entered for at-least one vector
iteration.

This test covers the case where incrementing the backedge-taken count will
overflow leading to an incorrect trip count of zero. In this (rare) case we will
also avoid the vector loop and jump to the scalar loop.

This patch simplifies the existing tests and effectively removes the basic-block
originally named "min.iters.checked", leaving the single test in block
"vector.ph".

Original observation and initial patch by Evgeny Stupachenko.

Differential Revision: https://reviews.llvm.org/D34150

llvm-svn: 308421
2017-07-19 05:16:39 +00:00

86 lines
3.6 KiB
LLVM

; RUN: opt < %s -loop-vectorize -force-vector-interleave=1 -force-vector-width=4 -dce -instcombine -S | FileCheck %s
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
; Make sure we vectorize this loop:
; int foo(float *a, float *b, int n) {
; for (int i=0; i<n; ++i)
; a[i] = b[i] * 3;
; }
;CHECK-LABEL: define i32 @foo
;CHECK: for.body.preheader:
;CHECK: br i1 %min.iters.check, label %scalar.ph, label %vector.memcheck, !dbg [[BODY_LOC:![0-9]+]]
;CHECK: vector.memcheck:
;CHECK: br i1 %memcheck.conflict, label %scalar.ph, label %vector.ph, !dbg [[BODY_LOC]]
;CHECK: load <4 x float>
define i32 @foo(float* nocapture %a, float* nocapture %b, i32 %n) nounwind uwtable ssp {
entry:
%cmp6 = icmp sgt i32 %n, 0, !dbg !6
br i1 %cmp6, label %for.body, label %for.end, !dbg !6
for.body: ; preds = %entry, %for.body
%indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ], !dbg !7
%arrayidx = getelementptr inbounds float, float* %b, i64 %indvars.iv, !dbg !7
%0 = load float, float* %arrayidx, align 4, !dbg !7
%mul = fmul float %0, 3.000000e+00, !dbg !7
%arrayidx2 = getelementptr inbounds float, float* %a, i64 %indvars.iv, !dbg !7
store float %mul, float* %arrayidx2, align 4, !dbg !7
%indvars.iv.next = add i64 %indvars.iv, 1, !dbg !7
%lftr.wideiv = trunc i64 %indvars.iv.next to i32, !dbg !7
%exitcond = icmp eq i32 %lftr.wideiv, %n, !dbg !7
br i1 %exitcond, label %for.end, label %for.body, !dbg !7
for.end: ; preds = %for.body, %entry
ret i32 undef, !dbg !8
}
; Make sure that we try to vectorize loops with a runtime check if the
; dependency check fails.
; CHECK-LABEL: test_runtime_check
; CHECK: <4 x float>
define void @test_runtime_check(float* %a, float %b, i64 %offset, i64 %offset2, i64 %n) {
entry:
br label %for.body
for.body:
%iv = phi i64 [ 0, %entry ], [ %iv.next, %for.body ]
%ind.sum = add i64 %iv, %offset
%arr.idx = getelementptr inbounds float, float* %a, i64 %ind.sum
%l1 = load float, float* %arr.idx, align 4
%ind.sum2 = add i64 %iv, %offset2
%arr.idx2 = getelementptr inbounds float, float* %a, i64 %ind.sum2
%l2 = load float, float* %arr.idx2, align 4
%m = fmul fast float %b, %l2
%ad = fadd fast float %l1, %m
store float %ad, float* %arr.idx, align 4
%iv.next = add nuw nsw i64 %iv, 1
%exitcond = icmp eq i64 %iv.next, %n
br i1 %exitcond, label %loopexit, label %for.body
loopexit:
ret void
}
; CHECK: [[BODY_LOC]] = !DILocation(line: 101, column: 1, scope: !{{.*}})
!llvm.module.flags = !{!0, !1}
!llvm.dbg.cu = !{!9}
!0 = !{i32 2, !"Dwarf Version", i32 4}
!1 = !{i32 2, !"Debug Info Version", i32 3}
!2 = !{}
!3 = !DISubroutineType(types: !2)
!4 = !DIFile(filename: "test.cpp", directory: "/tmp")
!5 = distinct !DISubprogram(name: "foo", scope: !4, file: !4, line: 99, type: !3, isLocal: false, isDefinition: true, scopeLine: 100, flags: DIFlagPrototyped, isOptimized: false, unit: !9, variables: !2)
!6 = !DILocation(line: 100, column: 1, scope: !5)
!7 = !DILocation(line: 101, column: 1, scope: !5)
!8 = !DILocation(line: 102, column: 1, scope: !5)
!9 = distinct !DICompileUnit(language: DW_LANG_C99, producer: "clang",
file: !10,
isOptimized: true, flags: "-O2",
splitDebugFilename: "abc.debug", emissionKind: 2)
!10 = !DIFile(filename: "path/to/file", directory: "/path/to/dir")
!11 = !{i32 2, !"Debug Info Version", i32 3}