Add diagnostics to the vectorizer cost model.

When the cost model determines vectorization is not possible/profitable these remarks print an analysis of that decision.

Note that in selectVectorizationFactor() we can assume that OptForSize and ForceVectorization are mutually exclusive.

Reviewed by Arnold Schwaighofer

llvm-svn: 214599

1 files changed, 58 insertions, 0 deletions

diff --git a/llvm/test/Transforms/LoopVectorize/conditional-assignment.ll b/llvm/test/Transforms/LoopVectorize/conditional-assignment.ll
new file mode 100644
index 00000000000..f1c76bd2315
--- /dev/null
+++ b/llvm/test/Transforms/LoopVectorize/conditional-assignment.ll
@@ -0,0 +1,58 @@
+; RUN: opt < %s -loop-vectorize -S -pass-remarks-missed='loop-vectorize' -pass-remarks-analysis='loop-vectorize' 2>&1 | FileCheck %s
+
+; CHECK: remark: source.c:2:8: loop not vectorized: store that is conditionally executed prevents vectorization
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.9.0"
+
+; Function Attrs: nounwind ssp uwtable
+define void @conditional_store(i32* noalias nocapture %indices) #0 {
+entry:
+  br label %for.body, !dbg !10
+
+for.body:                                         ; preds = %for.inc, %entry
+  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.inc ]
+  %arrayidx = getelementptr inbounds i32* %indices, i64 %indvars.iv, !dbg !12
+  %0 = load i32* %arrayidx, align 4, !dbg !12, !tbaa !14
+  %cmp1 = icmp eq i32 %0, 1024, !dbg !12
+  br i1 %cmp1, label %if.then, label %for.inc, !dbg !12
+
+if.then:                                          ; preds = %for.body
+  store i32 0, i32* %arrayidx, align 4, !dbg !18, !tbaa !14
+  br label %for.inc, !dbg !18
+
+for.inc:                                          ; preds = %for.body, %if.then
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1, !dbg !10
+  %exitcond = icmp eq i64 %indvars.iv.next, 4096, !dbg !10
+  br i1 %exitcond, label %for.end, label %for.body, !dbg !10
+
+for.end:                                          ; preds = %for.inc
+  ret void, !dbg !19
+}
+
+attributes #0 = { nounwind }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!7, !8}
+!llvm.ident = !{!9}
+
+!0 = metadata !{i32 786449, metadata !1, i32 12, metadata !"clang version 3.6.0", i1 true, metadata !"", i32 0, metadata !2, metadata !2, metadata !3, metadata !2, metadata !2, metadata !"", i32 2}
+!1 = metadata !{metadata !"source.c", metadata !"."}
+!2 = metadata !{}
+!3 = metadata !{metadata !4}
+!4 = metadata !{i32 786478, metadata !1, metadata !5, metadata !"conditional_store", metadata !"conditional_store", metadata !"", i32 1, metadata !6, i1 false, i1 true, i32 0, i32 0, null, i32 256, i1 true, void (i32*)* @conditional_store, null, null, metadata !2, i32 1}
+!5 = metadata !{i32 786473, metadata !1}
+!6 = metadata !{i32 786453, i32 0, null, metadata !"", i32 0, i64 0, i64 0, i64 0, i32 0, null, metadata !2, i32 0, null, null, null}
+!7 = metadata !{i32 2, metadata !"Dwarf Version", i32 2}
+!8 = metadata !{i32 2, metadata !"Debug Info Version", i32 1}
+!9 = metadata !{metadata !"clang version 3.6.0"}
+!10 = metadata !{i32 2, i32 8, metadata !11, null}
+!11 = metadata !{i32 786443, metadata !1, metadata !4, i32 2, i32 3, i32 0, i32 0}
+!12 = metadata !{i32 3, i32 9, metadata !13, null}
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+!14 = metadata !{metadata !15, metadata !15, i64 0}
+!15 = metadata !{metadata !"int", metadata !16, i64 0}
+!16 = metadata !{metadata !"omnipotent char", metadata !17, i64 0}
+!17 = metadata !{metadata !"Simple C/C++ TBAA"}
+!18 = metadata !{i32 3, i32 29, metadata !13, null}
+!19 = metadata !{i32 4, i32 1, metadata !4, null}