[LV] Hint at the new loop distribution pragma in optimization remark

When we encounter unsafe memory dependencies, loop distribution could
help.

Even though, the diagnostics is in LAA, it's only currently emitted in
the vectorizer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@268987 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Analysis/LoopAccessAnalysis.cpp b/lib/Analysis/LoopAccessAnalysis.cpp
index 6b1c5f22aa39ef52de33b362193c9505c37b3be2..cb7ee1cb246c6fee07d2c53ae0eca466a2d490d4 100644 (file)
--- a/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/lib/Analysis/LoopAccessAnalysis.cpp
@@ -1694,8 +1694,12 @@ void LoopAccessInfo::analyzeLoop(const ValueToValueMap &Strides) {
                  << (PtrRtChecking.Need ? "" : " don't")
                  << " need runtime memory checks.\n");
   else {
-    emitAnalysis(LoopAccessReport() <<
-                 "unsafe dependent memory operations in loop");
+    emitAnalysis(
+        LoopAccessReport()
+        << "unsafe dependent memory operations in loop. Use "
+           "#pragma loop distribute(enable) to allow loop distribution "
+           "to attempt to isolate the offending operations into a separate "
+           "loop");
     DEBUG(dbgs() << "LAA: unsafe dependent memory operations in loop\n");
   }
 }

diff --git a/test/Transforms/LoopVectorize/unsafe-dep-remark.ll b/test/Transforms/LoopVectorize/unsafe-dep-remark.ll
new file mode 100644 (file)
index 0000000..5fff825
--- /dev/null
+++ b/test/Transforms/LoopVectorize/unsafe-dep-remark.ll
@@ -0,0 +1,74 @@
+; RUN: opt -loop-vectorize -force-vector-width=2 -pass-remarks-analysis=loop-vectorize < %s 2>&1 | FileCheck %s
+
+; ModuleID = '/tmp/kk.c'
+source_filename = "/tmp/kk.c"
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.11.0"
+
+;     1        void success (char *A, char *B, char *C, char *D, char *E, int N) {
+;     2          for(int i = 0; i < N; i++) {
+;     3            A[i + 1] = A[i] + B[i];
+;     4            C[i] = D[i] * E[i];
+;     5          }
+;     6        }
+
+; CHECK: remark: /tmp/kk.c:3:16: loop not vectorized: unsafe dependent memory operations in loop. Use #pragma loop distribute(enable) to allow loop distribution to attempt to isolate the offending operations into a separate loop
+
+define void @success(i8* nocapture %A, i8* nocapture readonly %B, i8* nocapture %C, i8* nocapture readonly %D, i8* nocapture readonly %E, i32 %N) !dbg !6 {
+entry:
+  %cmp28 = icmp sgt i32 %N, 0, !dbg !8
+  br i1 %cmp28, label %for.body, label %for.cond.cleanup, !dbg !9
+
+for.body:                                         ; preds = %entry, %for.body
+  %indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
+  %arrayidx = getelementptr inbounds i8, i8* %A, i64 %indvars.iv, !dbg !11
+  %0 = load i8, i8* %arrayidx, align 1, !dbg !11, !tbaa !12
+  %arrayidx2 = getelementptr inbounds i8, i8* %B, i64 %indvars.iv, !dbg !15
+  %1 = load i8, i8* %arrayidx2, align 1, !dbg !15, !tbaa !12
+  %add = add i8 %1, %0, !dbg !16
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1, !dbg !9
+  %arrayidx7 = getelementptr inbounds i8, i8* %A, i64 %indvars.iv.next, !dbg !17
+  store i8 %add, i8* %arrayidx7, align 1, !dbg !18, !tbaa !12
+  %arrayidx9 = getelementptr inbounds i8, i8* %D, i64 %indvars.iv, !dbg !19
+  %2 = load i8, i8* %arrayidx9, align 1, !dbg !19, !tbaa !12
+  %arrayidx12 = getelementptr inbounds i8, i8* %E, i64 %indvars.iv, !dbg !20
+  %3 = load i8, i8* %arrayidx12, align 1, !dbg !20, !tbaa !12
+  %mul = mul i8 %3, %2, !dbg !21
+  %arrayidx16 = getelementptr inbounds i8, i8* %C, i64 %indvars.iv, !dbg !22
+  store i8 %mul, i8* %arrayidx16, align 1, !dbg !23, !tbaa !12
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32, !dbg !9
+  %exitcond = icmp eq i32 %lftr.wideiv, %N, !dbg !9
+  br i1 %exitcond, label %for.cond.cleanup, label %for.body, !dbg !9
+
+for.cond.cleanup:                                 ; preds = %for.body, %entry
+  ret void, !dbg !10
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4}
+!llvm.ident = !{!5}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 3.9.0 ", isOptimized: true, runtimeVersion: 0, emissionKind: NoDebug, enums: !2)
+!1 = !DIFile(filename: "/tmp/kk.c", directory: "/tmp")
+!2 = !{}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = !{i32 1, !"PIC Level", i32 2}
+!5 = !{!"clang version 3.9.0 "}
+!6 = distinct !DISubprogram(name: "success", scope: !1, file: !1, line: 1, type: !7, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !2)
+!7 = !DISubroutineType(types: !2)
+!8 = !DILocation(line: 2, column: 20, scope: !6)
+!9 = !DILocation(line: 2, column: 3, scope: !6)
+!10 = !DILocation(line: 6, column: 1, scope: !6)
+!11 = !DILocation(line: 3, column: 16, scope: !6)
+!12 = !{!13, !13, i64 0}
+!13 = !{!"omnipotent char", !14, i64 0}
+!14 = !{!"Simple C/C++ TBAA"}
+!15 = !DILocation(line: 3, column: 23, scope: !6)
+!16 = !DILocation(line: 3, column: 21, scope: !6)
+!17 = !DILocation(line: 3, column: 5, scope: !6)
+!18 = !DILocation(line: 3, column: 14, scope: !6)
+!19 = !DILocation(line: 4, column: 12, scope: !6)
+!20 = !DILocation(line: 4, column: 19, scope: !6)
+!21 = !DILocation(line: 4, column: 17, scope: !6)
+!22 = !DILocation(line: 4, column: 5, scope: !6)
+!23 = !DILocation(line: 4, column: 10, scope: !6)