[LV] Teach vectorizer about variant value store into uniform address

Summary:
Teach vectorizer about vectorizing variant value stores to uniform
address. Similar to rL343028, we do not allow vectorization if we have
multiple stores to the same uniform address.

Cost model already has the change for considering the extract
instruction cost for a variant value store. See added test cases for how
vectorization is done.
The patch also contains changes to the ORE messages.

Reviewers: Ayal, mkuper, anemet, hsaito

Subscribers: rkruppe, llvm-commits

Differential Revision: https://reviews.llvm.org/D52656

llvm-svn: 344613

1 files changed, 64 insertions, 3 deletions

diff --git a/llvm/test/Transforms/LoopVectorize/X86/illegal-parallel-loop-uniform-write.ll b/llvm/test/Transforms/LoopVectorize/X86/illegal-parallel-loop-uniform-write.ll
index cbba5300b9c..c78bcdd1721 100644
--- a/llvm/test/Transforms/LoopVectorize/X86/illegal-parallel-loop-uniform-write.ll
+++ b/llvm/test/Transforms/LoopVectorize/X86/illegal-parallel-loop-uniform-write.ll
@@ -3,9 +3,23 @@
 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"
 target triple = "x86_64-unknown-linux-gnu"
 
-;CHECK-LABEL: @foo(
-;CHECK-NOT: <4 x i32>
-;CHECK: ret void
+; CHECK-LABEL: @foo(
+; CHECK: <4 x i32>
+; CHECK: ret void
+
+; PR15794
+; incorrect addition of llvm.mem.parallel_loop_access metadata is undefined
+; behaviour. Vectorizer ignores the memory dependency checks and goes ahead and
+; vectorizes this loop with uniform stores which has an output dependency.
+
+; void foo(int *a, int *b, int k, int m) {
+;   for (int i = 0; i < m; i++) {
+;     for (int j = 0; j < m; j++) {
+;       a[i] = a[i + j + k] + 1; <<<
+;     }
+;     b[i] = b[i] + 3;
+;   }
+; }
 
 ; Function Attrs: nounwind uwtable 
 define void @foo(i32* nocapture %a, i32* nocapture %b, i32 %k, i32 %m) #0 {
@@ -48,6 +62,53 @@ for.end15:                                        ; preds = %for.end.us, %entry
   ret void
 }
 
+; Same test as above, but without the invalid parallel_loop_access metadata.
+
+; Here we can see the vectorizer does the mem dep checks and decides it is
+; unsafe to vectorize.
+; CHECK-LABEL: no-par-mem-metadata(
+; CHECK-NOT: <4 x i32>
+; CHECK:     ret void
+define void @no-par-mem-metadata(i32* nocapture %a, i32* nocapture %b, i32 %k, i32 %m) #0 {
+entry:
+  %cmp27 = icmp sgt i32 %m, 0
+  br i1 %cmp27, label %for.body3.lr.ph.us, label %for.end15
+
+for.end.us:                                       ; preds = %for.body3.us
+  %arrayidx9.us = getelementptr inbounds i32, i32* %b, i64 %indvars.iv33
+  %0 = load i32, i32* %arrayidx9.us, align 4
+  %add10.us = add nsw i32 %0, 3
+  store i32 %add10.us, i32* %arrayidx9.us, align 4
+  %indvars.iv.next34 = add i64 %indvars.iv33, 1
+  %lftr.wideiv35 = trunc i64 %indvars.iv.next34 to i32
+  %exitcond36 = icmp eq i32 %lftr.wideiv35, %m
+  br i1 %exitcond36, label %for.end15, label %for.body3.lr.ph.us, !llvm.loop !5
+
+for.body3.us:                                     ; preds = %for.body3.us, %for.body3.lr.ph.us
+  %indvars.iv29 = phi i64 [ 0, %for.body3.lr.ph.us ], [ %indvars.iv.next30, %for.body3.us ]
+  %1 = trunc i64 %indvars.iv29 to i32
+  %add4.us = add i32 %add.us, %1
+  %idxprom.us = sext i32 %add4.us to i64
+  %arrayidx.us = getelementptr inbounds i32, i32* %a, i64 %idxprom.us
+  %2 = load i32, i32* %arrayidx.us, align 4
+  %add5.us = add nsw i32 %2, 1
+  store i32 %add5.us, i32* %arrayidx7.us, align 4
+  %indvars.iv.next30 = add i64 %indvars.iv29, 1
+  %lftr.wideiv31 = trunc i64 %indvars.iv.next30 to i32
+  %exitcond32 = icmp eq i32 %lftr.wideiv31, %m
+  br i1 %exitcond32, label %for.end.us, label %for.body3.us, !llvm.loop !4
+
+for.body3.lr.ph.us:                               ; preds = %for.end.us, %entry
+  %indvars.iv33 = phi i64 [ %indvars.iv.next34, %for.end.us ], [ 0, %entry ]
+  %3 = trunc i64 %indvars.iv33 to i32
+  %add.us = add i32 %3, %k
+  %arrayidx7.us = getelementptr inbounds i32, i32* %a, i64 %indvars.iv33
+  br label %for.body3.us
+
+for.end15:                                        ; preds = %for.end.us, %entry
+  ret void
+}
+
 attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-frame-pointer-elim-non-leaf"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "unsafe-fp-math"="false" "use-soft-float"="false" }
 
 !3 = !{!4, !5}