[PATCH] Mark all loops as vectorized

[Arnold Schwaighofer]

LGTM,

One small concern (assert mode) see below.


thanks for fixing this Renato!


On Oct 24, 2013, at 6:05 AM, Renato Golin <renato.golin at linaro.org> wrote:

> Hi nadav,
> 
> Make sure we mark all loops (scalar and vector) when vectorizing, so that we don't try to vectorize them anymore. Also, set unroll to 1, since this is what we check for on early exit.
> 
> 
> http://llvm-reviews.chandlerc.com/D2011
> 
> Files:
>  lib/Transforms/Vectorize/LoopVectorize.cpp
>  test/Transforms/LoopVectorize/already-vectorized.ll
>  test/Transforms/LoopVectorize/vectorize-once.ll
> 
> Index: lib/Transforms/Vectorize/LoopVectorize.cpp
> ===================================================================
> --- lib/Transforms/Vectorize/LoopVectorize.cpp
> +++ lib/Transforms/Vectorize/LoopVectorize.cpp
> @@ -801,6 +801,7 @@
>         Vals.push_back(LoopID->getOperand(i));
> 
>     Vals.push_back(createHint(Context, Twine(Prefix(), "width").str(), Width));
> +    Vals.push_back(createHint(Context, Twine(Prefix(), "unroll").str(), 1));
> 
>     MDNode *NewLoopID = MDNode::get(Context, Vals);
>     // Set operand 0 to refer to the loop id itself.
> @@ -1785,6 +1786,9 @@
>   LoopExitBlock = ExitBlock;
>   LoopVectorBody = VecBody;
>   LoopScalarBody = OldBasicBlock;
> +
> +  LoopVectorizeHints Hints(Lp, true);
> +  Hints.setAlreadyVectorized(Lp);
> }
> 
> /// This function returns the identity element (or neutral element) for
> Index: test/Transforms/LoopVectorize/already-vectorized.ll
> ===================================================================
> --- /dev/null
> +++ test/Transforms/LoopVectorize/already-vectorized.ll
> @@ -0,0 +1,45 @@
> +; RUN: opt < %s -debug-only=loop-vectorize -O3 -S 2>&1 | FileCheck %s

This will only work in “…+Asserts” mode. I think you want to add:

; REQUIRES: asserts

> +; We want to make sure that we don't even try to vectorize loops again
> +; The vectorizer used to mark the un-vectorized loop only as already vectorized
> +; thus, trying to vectorize the vectorized loop again
> +
> +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"
> +
> + at a = external global [255 x i32]
> +
> +; Function Attrs: nounwind readonly uwtable
> +define i32 @vect() {
> +; CHECK: LV: Checking a loop in "vect"
> +entry:
> +  br label %for.body
> +
> +for.body:                                         ; preds = %for.body, %entry
> +; We need to make sure we did vectorize the loop
> +; CHECK: LV: Found a loop: for.body
> +; CHECK: LV: We can vectorize this loop!
> +  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
> +  %red.05 = phi i32 [ 0, %entry ], [ %add, %for.body ]
> +  %arrayidx = getelementptr inbounds [255 x i32]* @a, i64 0, i64 %indvars.iv
> +  %0 = load i32* %arrayidx, align 4
> +  %add = add nsw i32 %0, %red.05
> +  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
> +  %exitcond = icmp eq i64 %indvars.iv.next, 255
> +  br i1 %exitcond, label %for.end, label %for.body
> +
> +; If it did, we have two loops:
> +; CHECK: vector.body:
> +; CHECK: br {{.*}} label %vector.body, !llvm.loop [[vect:![0-9]+]]
> +; CHECK: for.body:
> +; CHECK: br {{.*}} label %for.body, !llvm.loop [[scalar:![0-9]+]]
> +
> +for.end:                                          ; preds = %for.body
> +  ret i32 %add
> +}
> +
> +; Now, we check for the Hint metadata
> +; CHECK: [[vect]] = metadata !{metadata [[vect]], metadata [[width:![0-9]+]], metadata [[unroll:![0-9]+]]}
> +; CHECK: [[width]] = metadata !{metadata !"llvm.vectorizer.width", i32 1}
> +; CHECK: [[unroll]] = metadata !{metadata !"llvm.vectorizer.unroll", i32 1}
> +; CHECK: [[scalar]] = metadata !{metadata [[scalar]], metadata [[width]], metadata [[unroll]]}
> +
> Index: test/Transforms/LoopVectorize/vectorize-once.ll
> ===================================================================
> --- test/Transforms/LoopVectorize/vectorize-once.ll
> +++ test/Transforms/LoopVectorize/vectorize-once.ll
> @@ -68,9 +68,10 @@
> 
> attributes #0 = { nounwind readonly ssp uwtable "fp-contract-model"="standard" "no-frame-pointer-elim" "no-frame-pointer-elim-non-leaf" "realign-stack" "relocation-model"="pic" "ssp-buffers-size"="8" }
> 
> -; CHECK: !0 = metadata !{metadata !0, metadata !1}
> +; CHECK: !0 = metadata !{metadata !0, metadata !1, metadata !2}
> ; CHECK: !1 = metadata !{metadata !"llvm.vectorizer.width", i32 1}
> -; CHECK: !2 = metadata !{metadata !2, metadata !1}
> +; CHECK: !2 = metadata !{metadata !"llvm.vectorizer.unroll", i32 1}
> +; CHECK: !3 = metadata !{metadata !3, metadata !1, metadata !2}
> 
> !0 = metadata !{metadata !0, metadata !1}
> !1 = metadata !{metadata !"llvm.vectorizer.width", i32 1}
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