3c810b76b9
This adds initial support to LoopVectorizationLegality to analyze loops
with side effects (particularly stores to memory) and an uncountable
exit. This patch alone doesn't enable any new transformations, but
does give clearer reasons for rejecting vectorization for such a loop.
The intent is for a loop like the following to pass the specific checks,
and only be rejected at the end until the transformation code is
committed:
```
// Assume a is marked restrict
// Assume b is known to be large enough to access up to b[N-1]
for (int i = 0; i < N; ++) {
a[i]++;
if (b[i] > threshold)
break;
}
```
78 lines
3.2 KiB
LLVM
78 lines
3.2 KiB
LLVM
; RUN: opt < %s -passes=loop-vectorize -force-vector-width=4 -S -pass-remarks-missed='loop-vectorize' 2>&1 | FileCheck %s
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; C/C++ code for control flow test
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; int test(int *A, int Length) {
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; for (int i = 0; i < Length; i++) {
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; if (A[i] > 10.0) goto end;
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; A[i] = 0;
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; }
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; end:
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; return 0;
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; }
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; CHECK: remark: source.cpp:5:9: loop not vectorized: Cannot vectorize potentially faulting early exit loop
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; CHECK: remark: source.cpp:5:9: loop not vectorized
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; CHECK: _Z4testPii
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; CHECK-NOT: x i32>
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; CHECK: ret
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target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
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; Function Attrs: nounwind optsize ssp uwtable
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define i32 @_Z4testPii(ptr nocapture %A, i32 %Length) #0 !dbg !4 {
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entry:
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%cmp8 = icmp sgt i32 %Length, 0, !dbg !10
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br i1 %cmp8, label %for.body.preheader, label %end, !dbg !10
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for.body.preheader: ; preds = %entry
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br label %for.body, !dbg !12
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for.body: ; preds = %for.body.preheader, %if.else
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%indvars.iv = phi i64 [ %indvars.iv.next, %if.else ], [ 0, %for.body.preheader ]
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%arrayidx = getelementptr inbounds i32, ptr %A, i64 %indvars.iv, !dbg !12
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%0 = load i32, ptr %arrayidx, align 4, !dbg !12, !tbaa !15
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%cmp1 = icmp sgt i32 %0, 10, !dbg !12
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br i1 %cmp1, label %end.loopexit, label %if.else, !dbg !12
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if.else: ; preds = %for.body
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store i32 0, ptr %arrayidx, align 4, !dbg !19, !tbaa !15
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%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1, !dbg !10
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%1 = trunc i64 %indvars.iv.next to i32, !dbg !10
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%cmp = icmp slt i32 %1, %Length, !dbg !10
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br i1 %cmp, label %for.body, label %end.loopexit, !dbg !10
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end.loopexit: ; preds = %if.else, %for.body
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br label %end
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end: ; preds = %end.loopexit, %entry
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ret i32 0, !dbg !20
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}
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attributes #0 = { nounwind }
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!llvm.dbg.cu = !{!0}
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!llvm.module.flags = !{!7, !8}
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!llvm.ident = !{!9}
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!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang version 3.5.0", isOptimized: true, runtimeVersion: 6, emissionKind: LineTablesOnly, file: !1, enums: !2, retainedTypes: !2, globals: !2, imports: !2)
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!1 = !DIFile(filename: "source.cpp", directory: ".")
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!2 = !{}
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!4 = distinct !DISubprogram(name: "test", line: 1, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: true, unit: !0, scopeLine: 2, file: !1, scope: !5, type: !6, retainedNodes: !2)
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!5 = !DIFile(filename: "source.cpp", directory: ".")
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!6 = !DISubroutineType(types: !2)
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!7 = !{i32 2, !"Dwarf Version", i32 2}
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!8 = !{i32 2, !"Debug Info Version", i32 3}
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!9 = !{!"clang version 3.5.0"}
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!10 = !DILocation(line: 3, column: 8, scope: !11)
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!11 = distinct !DILexicalBlock(line: 3, column: 3, file: !1, scope: !4)
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!12 = !DILocation(line: 5, column: 9, scope: !13)
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!13 = distinct !DILexicalBlock(line: 5, column: 9, file: !1, scope: !14)
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!14 = distinct !DILexicalBlock(line: 4, column: 3, file: !1, scope: !11)
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!15 = !{!16, !16, i64 0}
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!16 = !{!"int", !17, i64 0}
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!17 = !{!"omnipotent char", !18, i64 0}
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!18 = !{!"Simple C/C++ TBAA"}
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!19 = !DILocation(line: 8, column: 7, scope: !13)
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!20 = !DILocation(line: 12, column: 3, scope: !4)
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