SLPVectorizer: Fix invalid iterator errors

Update iterator when the SLP vectorizer changes the instructions in the basic
block by restarting the traversal of the basic block.

Patch by Yi Jiang!

Fixes PR 16899.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188832 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Vectorize/SLPVectorizer.cpp b/lib/Transforms/Vectorize/SLPVectorizer.cpp
index ee9c5f2de7d5c76294817db07b6e84bc011bbe78..3c24af8d8b676b6d0afa464c066e3563295ac441 100644 (file)
--- a/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -1875,6 +1875,8 @@ bool SLPVectorizer::tryToVectorize(BinaryOperator *V, BoUpSLP &R) {
 bool SLPVectorizer::vectorizeChainsInBlock(BasicBlock *BB, BoUpSLP &R) {
   bool Changed = false;
   SmallVector<Value *, 4> Incoming;
+  SmallSet<Instruction *, 16> VisitedInstrs;
+
   // Collect the incoming values from the PHIs.
   for (BasicBlock::iterator instr = BB->begin(), ie = BB->end(); instr != ie;
        ++instr) {
@@ -1883,9 +1885,21 @@ bool SLPVectorizer::vectorizeChainsInBlock(BasicBlock *BB, BoUpSLP &R) {
     if (!P)
       break;
 
+    // We may go through BB multiple times so skip the one we have checked.
+    if (VisitedInstrs.count(instr))
+      continue;
+    VisitedInstrs.insert(instr);
+
     // Stop constructing the list when you reach a different type.
     if (Incoming.size() && P->getType() != Incoming[0]->getType()) {
-      Changed |= tryToVectorizeList(Incoming, R);
+      if (tryToVectorizeList(Incoming, R)) {
+        // We would like to start over since some instructions are deleted
+        // and the iterator may become invalid value.
+        Changed = true;
+        instr = BB->begin();
+        ie = BB->end();
+      }
+
       Incoming.clear();
     }
 
@@ -1895,14 +1909,20 @@ bool SLPVectorizer::vectorizeChainsInBlock(BasicBlock *BB, BoUpSLP &R) {
   if (Incoming.size() > 1)
     Changed |= tryToVectorizeList(Incoming, R);
 
-  llvm::Instruction *I;
-  for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e;) {
-    I = it++;
-    if (isa<DbgInfoIntrinsic>(I))
+  VisitedInstrs.clear();
+
+  for (BasicBlock::iterator it = BB->begin(), e = BB->end(); it != e; it++) {
+
+    // We may go through BB multiple times so skip the one we have checked.
+    if (VisitedInstrs.count(it))
+      continue;
+    VisitedInstrs.insert(it);
+
+    if (isa<DbgInfoIntrinsic>(it))
       continue;
 
     // Try to vectorize reductions that use PHINodes.
-    if (PHINode *P = dyn_cast<PHINode>(I)) {
+    if (PHINode *P = dyn_cast<PHINode>(it)) {
       // Check that the PHI is a reduction PHI.
       if (P->getNumIncomingValues() != 2)
         return Changed;
@@ -1919,20 +1939,38 @@ bool SLPVectorizer::vectorizeChainsInBlock(BasicBlock *BB, BoUpSLP &R) {
       if (Inst == P)
         Inst = BI->getOperand(1);
 
-      Changed |= tryToVectorize(dyn_cast<BinaryOperator>(Inst), R);
+      if (tryToVectorize(dyn_cast<BinaryOperator>(Inst), R)) {
+        // We would like to start over since some instructions are deleted
+        // and the iterator may become invalid value.
+        Changed = true;
+        it = BB->begin();
+        e = BB->end();
+      }
       continue;
     }
 
     // Try to vectorize trees that start at compare instructions.
-    if (CmpInst *CI = dyn_cast<CmpInst>(I)) {
+    if (CmpInst *CI = dyn_cast<CmpInst>(it)) {
       if (tryToVectorizePair(CI->getOperand(0), CI->getOperand(1), R)) {
-        Changed |= true;
+        Changed = true;
+        // We would like to start over since some instructions are deleted
+        // and the iterator may become invalid value.
+        it = BB->begin();
+        e = BB->end();
         continue;
       }
-      for (int i = 0; i < 2; ++i)
-        if (BinaryOperator *BI = dyn_cast<BinaryOperator>(CI->getOperand(i)))
-          Changed |=
-              tryToVectorizePair(BI->getOperand(0), BI->getOperand(1), R);
+
+      for (int i = 0; i < 2; ++i) {
+         if (BinaryOperator *BI = dyn_cast<BinaryOperator>(CI->getOperand(i))) {
+            if (tryToVectorizePair(BI->getOperand(0), BI->getOperand(1), R)) {
+              Changed = true;
+              // We would like to start over since some instructions are deleted
+              // and the iterator may become invalid value.
+              it = BB->begin();
+              e = BB->end();
+            }
+         }
+      }
       continue;
     }
   }

diff --git a/test/Transforms/SLPVectorizer/X86/pr16899.ll b/test/Transforms/SLPVectorizer/X86/pr16899.ll
new file mode 100644 (file)
index 0000000..d715239
--- /dev/null
+++ b/test/Transforms/SLPVectorizer/X86/pr16899.ll
@@ -0,0 +1,30 @@
+; RUN: opt < %s  -slp-vectorizer -S -mtriple=i386--netbsd -mcpu=i486
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32-S128"
+target triple = "i386--netbsd"
+
+@a = common global i32* null, align 4
+
+; Function Attrs: noreturn nounwind readonly
+define i32 @fn1() #0 {
+entry:
+  %0 = load i32** @a, align 4, !tbaa !0
+  %1 = load i32* %0, align 4, !tbaa !3
+  %arrayidx1 = getelementptr inbounds i32* %0, i32 1
+  %2 = load i32* %arrayidx1, align 4, !tbaa !3
+  br label %do.body
+
+do.body:                                          ; preds = %do.body, %entry
+  %c.0 = phi i32 [ %2, %entry ], [ %add2, %do.body ]
+  %b.0 = phi i32 [ %1, %entry ], [ %add, %do.body ]
+  %add = add nsw i32 %b.0, %c.0
+  %add2 = add nsw i32 %add, 1
+  br label %do.body
+}
+
+attributes #0 = { noreturn nounwind readonly "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf"="true" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!0 = metadata !{metadata !"any pointer", metadata !1}
+!1 = metadata !{metadata !"omnipotent char", metadata !2}
+!2 = metadata !{metadata !"Simple C/C++ TBAA"}
+!3 = metadata !{metadata !"int", metadata !1}
+