Commit 5e1b9055 authored by Hans Wennborg's avatar Hans Wennborg
Browse files

Merging r244448: 

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r244448 | fcormack | 2015-08-10 07:48:47 -0700 (Mon, 10 Aug 2015) | 12 lines

Prevent the scalarizer from caching incorrect entries

The scalarizer can cache incorrect entries when walking up a chain of
insertelement instructions. This occurs when it encounters more than one
instruction that it is not actively searching for, as it unconditionally caches
every element it finds. The fix is to only cache the first element that it
isn't searching for so we don't overwrite correct entries.

Reviewers: hfinkel

Differential Revision: http://reviews.llvm.org/D11559

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llvm-svn: 245457
parent 55418e10

llvm/lib/Transforms/Scalar/Scalarizer.cpp

+8 −2
Original line number Diff line number Diff line
@@ -227,10 +227,16 @@ Value *Scatterer::operator[](unsigned I) { 
      if (!Idx)

        break;

      unsigned J = Idx->getZExtValue();

      CV[J] = Insert->getOperand(1);

      V = Insert->getOperand(0);

      if (I == J)

      if (I == J) {

        CV[J] = Insert->getOperand(1);

        return CV[J];

      } else if (!CV[J]) {

        // Only cache the first entry we find for each index we're not actively

        // searching for. This prevents us from going too far up the chain and

        // caching incorrect entries.

        CV[J] = Insert->getOperand(1);

      }

    }

    CV[I] = Builder.CreateExtractElement(V, Builder.getInt32(I),

                                         V->getName() + ".i" + Twine(I));

llvm/test/Transforms/Scalarizer/cache-bug.ll

0 → 100644
+30 −0
Original line number Diff line number Diff line 
; RUN: opt -scalarizer -S < %s | FileCheck %s

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"





; Check that vector element 1 is scalarized correctly from a chain of

; insertelement instructions

define void @func(i32 %x) {

; CHECK-LABEL: @func(

; CHECK-NOT: phi i32 [ %x, %entry ], [ %inc.pos.y, %loop ]

; CHECK:     phi i32 [ %inc, %entry ], [ %inc.pos.y, %loop ]

; CHECK:   ret void

entry:

  %vecinit = insertelement <2 x i32> <i32 0, i32 0>, i32 %x, i32 1

  %inc = add i32 %x, 1

  %0 = insertelement <2 x i32> %vecinit, i32 %inc, i32 1

  br label %loop



loop:

  %pos = phi <2 x i32> [ %0, %entry ], [ %new.pos.y, %loop ]

  %i = phi i32 [ 0, %entry ], [ %new.i, %loop ]

  %pos.y = extractelement <2 x i32> %pos, i32 1

  %inc.pos.y = add i32 %pos.y, 1

  %new.pos.y = insertelement <2 x i32> %pos, i32 %inc.pos.y, i32 1

  %new.i = add i32 %i, 1

  %cmp2 = icmp slt i32 %new.i, 1

  br i1 %cmp2, label %loop, label %exit



exit:

  ret void

}