SLPVectorizer: Implement DCE as part of vectorization.

This is a complete re-write if the bottom-up vectorization class.
Before this commit we scanned the instruction tree 3 times. First in search of merge points for the trees. Second, for estimating the cost. And finally for vectorization.
There was a lot of code duplication and adding the DCE exposed bugs. The new design is simpler and DCE was a part of the design.
In this implementation we build the tree once. After that we estimate the cost by scanning the different entries in the constructed tree (in any order). The vectorization phase also works on the built tree.

llvm-svn: 185774

1 files changed, 53 insertions, 0 deletions

diff --git a/llvm/test/Transforms/SLPVectorizer/X86/crash_mandeltext.ll b/llvm/test/Transforms/SLPVectorizer/X86/crash_mandeltext.ll
new file mode 100644
index 00000000000..b3ca235c2c7
--- /dev/null
+++ b/llvm/test/Transforms/SLPVectorizer/X86/crash_mandeltext.ll
@@ -0,0 +1,53 @@
+; RUN: opt < %s -basicaa -slp-vectorizer -dce -S -mtriple=x86_64-apple-macosx10.8.0 -mcpu=corei7
+
+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-apple-macosx10.8.0"
+
+define void @main() {
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %for.end44, %entry
+  br label %for.cond4.preheader
+
+for.cond4.preheader:                              ; preds = %if.then25, %for.body
+  br label %for.body6
+
+for.body6:                                        ; preds = %for.inc21, %for.cond4.preheader
+  br label %for.body12
+
+for.body12:                                       ; preds = %if.end, %for.body6
+  %fZImg.069 = phi double [ undef, %for.body6 ], [ %add19, %if.end ]
+  %fZReal.068 = phi double [ undef, %for.body6 ], [ %add20, %if.end ]
+  %mul13 = fmul double %fZReal.068, %fZReal.068
+  %mul14 = fmul double %fZImg.069, %fZImg.069
+  %add15 = fadd double %mul13, %mul14
+  %cmp16 = fcmp ogt double %add15, 4.000000e+00
+  br i1 %cmp16, label %for.inc21, label %if.end
+
+if.end:                                           ; preds = %for.body12
+  %mul18 = fmul double undef, %fZImg.069
+  %add19 = fadd double undef, %mul18
+  %sub = fsub double %mul13, %mul14
+  %add20 = fadd double undef, %sub
+  br i1 undef, label %for.body12, label %for.inc21
+
+for.inc21:                                        ; preds = %if.end, %for.body12
+  br i1 undef, label %for.end23, label %for.body6
+
+for.end23:                                        ; preds = %for.inc21
+  br i1 undef, label %if.then25, label %if.then26
+
+if.then25:                                        ; preds = %for.end23
+  br i1 undef, label %for.end44, label %for.cond4.preheader
+
+if.then26:                                        ; preds = %for.end23
+  unreachable
+
+for.end44:                                        ; preds = %if.then25
+  br i1 undef, label %for.end48, label %for.body
+
+for.end48:                                        ; preds = %for.end44
+  ret void
+}
+