[llvm] r180121 - LoopVectorizer: Fix 15830. When scalarizing and unrolling stores make sure that the order in which the elements are scalarized is the same as the original order.

[Nadav Rotem]

Author: nadav
Date: Tue Apr 23 12:12:42 2013
New Revision: 180121

URL: http://llvm.org/viewvc/llvm-project?rev=180121&view=rev
Log:
LoopVectorizer: Fix 15830. When scalarizing and unrolling stores make sure that the order in which the elements are scalarized is the same as the original order.
This fixes a miscompilation in FreeBSD's regex library.


Added:
    llvm/trunk/test/Transforms/LoopVectorize/bsd_regex.ll
Modified:
    llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp

Modified: llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp?rev=180121&r1=180120&r2=180121&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp (original)
+++ llvm/trunk/lib/Transforms/Vectorize/LoopVectorize.cpp Tue Apr 23 12:12:42 2013
@@ -1085,10 +1085,10 @@ void InnerLoopVectorizer::scalarizeInstr
   // Create a new entry in the WidenMap and initialize it to Undef or Null.
   VectorParts &VecResults = WidenMap.splat(Instr, UndefVec);
 
-  // For each scalar that we create:
-  for (unsigned Width = 0; Width < VF; ++Width) {
-    // For each vector unroll 'part':
-    for (unsigned Part = 0; Part < UF; ++Part) {
+  // For each vector unroll 'part':
+  for (unsigned Part = 0; Part < UF; ++Part) {
+    // For each scalar that we create:
+    for (unsigned Width = 0; Width < VF; ++Width) {
       Instruction *Cloned = Instr->clone();
       if (!IsVoidRetTy)
         Cloned->setName(Instr->getName() + ".cloned");

Added: llvm/trunk/test/Transforms/LoopVectorize/bsd_regex.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopVectorize/bsd_regex.ll?rev=180121&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/LoopVectorize/bsd_regex.ll (added)
+++ llvm/trunk/test/Transforms/LoopVectorize/bsd_regex.ll Tue Apr 23 12:12:42 2013
@@ -0,0 +1,36 @@
+; RUN: opt -S -loop-vectorize -dce -instcombine -force-vector-width=2 -force-vector-unroll=2 < %s | FileCheck %s
+
+;PR 15830.
+
+;CHECK: foo
+; When scalarizing stores we need to preserve the original order.
+; Make sure that we are extracting in the correct order (0101, and not 0011).
+;CHECK: extractelement <2 x i64> {{.*}}, i32 0
+;CHECK: extractelement <2 x i64> {{.*}}, i32 1
+;CHECK: extractelement <2 x i64> {{.*}}, i32 0
+;CHECK: extractelement <2 x i64> {{.*}}, i32 1
+;CHECK: store
+;CHECK: store
+;CHECK: store
+;CHECK: store
+;CHECK: ret
+
+define i32 @foo(i32* nocapture %A) {
+entry:
+  br label %for.body
+
+for.body:
+  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+  %0 = shl nsw i64 %indvars.iv, 2
+  %arrayidx = getelementptr inbounds i32* %A, i64 %0
+  store i32 4, i32* %arrayidx, align 4
+  %indvars.iv.next = add i64 %indvars.iv, 1
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+  %exitcond = icmp eq i32 %lftr.wideiv, 10000
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:
+  ret i32 undef
+}
+
+