Add llvm patch corresponding to r275635.

2014-12-09 20:05:05 +00:00 · 2014-12-09 20:05:05 +00:00 · 55681de413
commit 55681de413
parent 3d89bd48fb
1 changed files with 75 additions and 0 deletions
--- a/contrib/llvm/patches/patch-21-llvm-r223171-fix-vectorizer.diff
+++ b/contrib/llvm/patches/patch-21-llvm-r223171-fix-vectorizer.diff
@ -0,0 +1,75 @@
+Pull in r223171 from upstream llvm trunk (by Michael Zolotukhin):
+
+  PR21302. Vectorize only bottom-tested loops.
+
+  rdar://problem/18886083
+
+This fixes a bug in the llvm vectorizer, which could sometimes cause
+vectorized loops to perform an additional iteration, leading to possible
+buffer overruns.  Symptoms of this, which are usually segfaults, were
+first noticed when building gcc ports, here:
+
+https://lists.freebsd.org/pipermail/freebsd-ports/2014-September/095466.html
+https://lists.freebsd.org/pipermail/freebsd-toolchain/2014-September/001211.html
+
+Note: because this is applied on top of llvm/clang 3.5.0, this fix is
+slightly different from the one just checked into head in r275633.
+
+Introduced here: http://svnweb.freebsd.org/changeset/base/275635
+
+Index: lib/Transforms/Vectorize/LoopVectorize.cpp
+===================================================================
+--- lib/Transforms/Vectorize/LoopVectorize.cpp	(revision 21)
+++ lib/Transforms/Vectorize/LoopVectorize.cpp	(revision 22)
+@@ -3466,6 +3466,15 @@ bool LoopVectorizationLegality::canVectorize() {
+     return false;
+   }
+ 
+  // We only handle bottom-tested loops, i.e. loop in which the condition is
+  // checked at the end of each iteration. With that we can assume that all
+  // instructions in the loop are executed the same number of times.
+  if (TheLoop->getExitingBlock() != TheLoop->getLoopLatch()) {
+    emitAnalysis(
+        Report() << "loop control flow is not understood by vectorizer");
+    return false;
+  }
+
+   // We need to have a loop header.
+   DEBUG(dbgs() << "LV: Found a loop: " <<
+         TheLoop->getHeader()->getName() << '\n');
+Index: test/Transforms/LoopVectorize/loop-form.ll
+===================================================================
+--- test/Transforms/LoopVectorize/loop-form.ll	(revision 0)
+++ test/Transforms/LoopVectorize/loop-form.ll	(revision 22)
+@@ -0,0 +1,31 @@
+; RUN: opt -S -loop-vectorize < %s | FileCheck %s
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+
+; Check that we vectorize only bottom-tested loops.
+; This is a reduced testcase from PR21302.
+;
+; rdar://problem/18886083
+
+%struct.X = type { i32, i16 }
+; CHECK-LABEL: @foo(
+; CHECK-NOT: vector.body
+
+define void @foo(i32 %n) {
+entry:
+  br label %for.cond
+
+for.cond:
+  %i = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %cmp = icmp slt i32 %i, %n
+  br i1 %cmp, label %for.body, label %if.end
+
+for.body:
+  %iprom = sext i32 %i to i64
+  %b = getelementptr inbounds %struct.X* undef, i64 %iprom, i32 1
+  store i16 0, i16* %b, align 4
+  %inc = add nsw i32 %i, 1
+  br label %for.cond
+
+if.end:
+  ret void
+}