[llvm] r193891 - LoopVectorizer: Perform redundancy elimination on induction variables
Nadav Rotem
nrotem at apple.com
Fri Nov 1 16:12:01 PDT 2013
Arnold, can you please extract this code into its own function ?
On Nov 1, 2013, at 3:18 PM, Arnold Schwaighofer <aschwaighofer at apple.com> wrote:
> Author: arnolds
> Date: Fri Nov 1 17:18:19 2013
> New Revision: 193891
>
> URL: http://llvm.org/viewvc/llvm-project?rev=193891&view=rev
> Log:
> LoopVectorizer: Perform redundancy elimination on induction variables
>
> When the loop vectorizer was part of the SCC inliner pass manager gvn would
> run after the loop vectorizer followed by instcombine. This way redundancy
> (multiple uses) were removed and instcombine could perform scalarization on the
> induction variables. Having moved the loop vectorizer to later we no longer run
> any form of redundancy elimination before we perform instcombine. This caused
> vectorized induction variables to survive that did not before.
>
> On a recent iMac this helps linpack back from 6000Mflops to 7000Mflops.
>
> This should also help lpbench and paq8p.
>
> I ran a Release (without Asserts) build over the test-suite and did not see any
> negative impact on compile time.
>
> radar://15339680
>
> Modified:
> llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
> llvm/trunk/test/Transforms/LoopVectorize/global_alias.ll
> llvm/trunk/test/Transforms/LoopVectorize/induction.ll
> llvm/trunk/test/Transforms/LoopVectorize/induction_plus.ll
>
> Modified: llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp?rev=193891&r1=193890&r2=193891&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp (original)
> +++ llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp Fri Nov 1 17:18:19 2013
> @@ -2272,8 +2272,41 @@ InnerLoopVectorizer::vectorizeLoop(LoopV
> (RdxPhi)->setIncomingValue(SelfEdgeBlockIdx, ReducedPartRdx);
> (RdxPhi)->setIncomingValue(IncomingEdgeBlockIdx, RdxDesc.LoopExitInstr);
> }// end of for each redux variable.
> -
> +
> fixLCSSAPHIs();
> +
> + // Perform simple cse.
> + SmallPtrSet<Instruction*, 16> Visited;
> + SmallVector<Instruction*, 16> ToRemove;
> + for (BasicBlock::iterator I = LoopVectorBody->begin(),
> + E = LoopVectorBody->end(); I != E; ++I) {
> + Instruction *In = I;
> +
> + if (!isa<InsertElementInst>(In) && !isa<ExtractElementInst>(In) &&
> + !isa<ShuffleVectorInst>(In) && !isa<GetElementPtrInst>(In))
> + continue;
> +
> + // Check if we can replace this instruction with any of the
> + // visited instructions.
> + for (SmallPtrSet<Instruction*, 16>::iterator v = Visited.begin(),
> + ve = Visited.end(); v != ve; ++v) {
> + if (In->isIdenticalTo(*v)) {
> + In->replaceAllUsesWith(*v);
> + ToRemove.push_back(In);
> + In = 0;
> + break;
> + }
> + }
> + if (In)
> + Visited.insert(In);
> +
> + }
> + // Erase all of the instructions that we RAUWed.
> + for (SmallVectorImpl<Instruction *>::iterator v = ToRemove.begin(),
> + ve = ToRemove.end(); v != ve; ++v) {
> + assert((*v)->getNumUses() == 0 && "Can't remove instructions with uses");
> + (*v)->eraseFromParent();
> + }
> }
>
> void InnerLoopVectorizer::fixLCSSAPHIs() {
>
> Modified: llvm/trunk/test/Transforms/LoopVectorize/global_alias.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopVectorize/global_alias.ll?rev=193891&r1=193890&r2=193891&view=diff
> ==============================================================================
> --- llvm/trunk/test/Transforms/LoopVectorize/global_alias.ll (original)
> +++ llvm/trunk/test/Transforms/LoopVectorize/global_alias.ll Fri Nov 1 17:18:19 2013
> @@ -336,9 +336,8 @@ for.end:
> ; return Foo.A[a];
> ; }
> ; CHECK-LABEL: define i32 @noAlias07(
> -; CHECK: sub nsw <4 x i32>
> +; CHECK: store <4 x i32>
> ; CHECK: ret
> -
> define i32 @noAlias07(i32 %a) #0 {
> entry:
> %a.addr = alloca i32, align 4
> @@ -552,7 +551,7 @@ for.end:
> ; return Bar.A[N][a];
> ; }
> ; CHECK-LABEL: define i32 @noAlias11(
> -; CHECK: sub nsw <4 x i32>
> +; CHECK: store <4 x i32>
> ; CHECK: ret
>
> define i32 @noAlias11(i32 %a) #0 {
> @@ -612,7 +611,7 @@ for.end:
> ; return Bar.A[N][a];
> ; }
> ; CHECK-LABEL: define i32 @noAlias12(
> -; CHECK: sub nsw <4 x i32>
> +; CHECK: store <4 x i32>
> ; CHECK: ret
>
> define i32 @noAlias12(i32 %a) #0 {
>
> Modified: llvm/trunk/test/Transforms/LoopVectorize/induction.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopVectorize/induction.ll?rev=193891&r1=193890&r2=193891&view=diff
> ==============================================================================
> --- llvm/trunk/test/Transforms/LoopVectorize/induction.ll (original)
> +++ llvm/trunk/test/Transforms/LoopVectorize/induction.ll Fri Nov 1 17:18:19 2013
> @@ -28,3 +28,41 @@ for.end:
> ret void
> }
>
> +; RUN: opt < %s -loop-vectorize -force-vector-unroll=1 -force-vector-width=2 -instcombine -S | FileCheck %s --check-prefix=IND
> +
> +; Make sure we remove unneeded vectorization of induction variables.
> +; In order for instcombine to cleanup the vectorized induction variables that we
> +; create in the loop vectorizer we need to perform some form of redundancy
> +; elimination to get rid of multiple uses.
> +
> +; IND-LABEL: scalar_use
> +
> +; IND: br label %vector.body
> +; IND: vector.body:
> +; Vectorized induction variable.
> +; IND-NOT: insertelement <2 x i64>
> +; IND-NOT: shufflevector <2 x i64>
> +; IND: br {{.*}}, label %vector.body
> +
> +define void @scalar_use(float* %a, float %b, i64 %offset, i64 %offset2, i64 %n) {
> +entry:
> + br label %for.body
> +
> +for.body:
> + %iv = phi i64 [ 0, %entry ], [ %iv.next, %for.body ]
> + %ind.sum = add i64 %iv, %offset
> + %arr.idx = getelementptr inbounds float* %a, i64 %ind.sum
> + %l1 = load float* %arr.idx, align 4
> + %ind.sum2 = add i64 %iv, %offset2
> + %arr.idx2 = getelementptr inbounds float* %a, i64 %ind.sum2
> + %l2 = load float* %arr.idx2, align 4
> + %m = fmul fast float %b, %l2
> + %ad = fadd fast float %l1, %m
> + store float %ad, float* %arr.idx, align 4
> + %iv.next = add nuw nsw i64 %iv, 1
> + %exitcond = icmp eq i64 %iv.next, %n
> + br i1 %exitcond, label %loopexit, label %for.body
> +
> +loopexit:
> + ret void
> +}
>
> Modified: llvm/trunk/test/Transforms/LoopVectorize/induction_plus.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopVectorize/induction_plus.ll?rev=193891&r1=193890&r2=193891&view=diff
> ==============================================================================
> --- llvm/trunk/test/Transforms/LoopVectorize/induction_plus.ll (original)
> +++ llvm/trunk/test/Transforms/LoopVectorize/induction_plus.ll Fri Nov 1 17:18:19 2013
> @@ -6,8 +6,8 @@ target triple = "x86_64-apple-macosx10.8
> @array = common global [1024 x i32] zeroinitializer, align 16
>
> ;CHECK-LABEL: @array_at_plus_one(
> -;CHECK: trunc i64
> ;CHECK: add i64 %index, 12
> +;CHECK: trunc i64
> ;CHECK: ret i32
> define i32 @array_at_plus_one(i32 %n) nounwind uwtable ssp {
> %1 = icmp sgt i32 %n, 0
>
>
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