Fix bug 25440: GVN assertion after coercing loads

Optimizations like LoadPRE in GVN will insert new instructions.
If the insertion point is in a already processed BB, they should
get a value number explicitly. If the insertion point is after
current instruction, then just leave it. However, current GVN framework
has no support for it.
In this patch, we just bail out if a VN can't be found.

Dfferential Revision: http://reviews.llvm.org/D14670

A    test/Transforms/GVN/pr25440.ll
M    lib/Transforms/Scalar/GVN.cpp


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@253536 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Scalar/GVN.cpp

@@ -129,6 +129,7 @@ namespace {
     uint32_t lookup(Value *V) const;
     uint32_t lookup_or_add_cmp(unsigned Opcode, CmpInst::Predicate Pred,
                                Value *LHS, Value *RHS);
+    bool exists(Value *V) const;
     void add(Value *V, uint32_t num);
     void clear();
     void erase(Value *v);
@@ -389,6 +390,9 @@ uint32_t ValueTable::lookup_or_add_call(CallInst *C) {
   }
 }
 
+/// Returns true if a value number exists for the specified value.
+bool ValueTable::exists(Value *V) const { return valueNumbering.count(V) != 0; }
+
 /// lookup_or_add - Returns the value number for the specified value, assigning
 /// it a new number if it did not have one before.
 uint32_t ValueTable::lookup_or_add(Value *V) {
@@ -2534,7 +2538,14 @@ bool GVN::performScalarPREInsertion(Instruction *Instr, BasicBlock *Pred,
     Value *Op = Instr->getOperand(i);
     if (isa<Argument>(Op) || isa<Constant>(Op) || isa<GlobalValue>(Op))
       continue;
-
+    // This could be a newly inserted instruction, in which case, we won't
+    // find a value number, and should give up before we hurt ourselves.
+    // FIXME: Rewrite the infrastructure to let it easier to value number
+    // and process newly inserted instructions.
+    if (!VN.exists(Op)) {
+      success = false;
+      break;
+    }
     if (Value *V = findLeader(Pred, VN.lookup(Op))) {
       Instr->setOperand(i, V);
     } else {

test/Transforms/GVN/pr25440.ll

@@ -0,0 +1,108 @@
+;RUN: opt -gvn -S < %s | FileCheck %s
+
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n8:16:32-S64"
+target triple = "thumbv7--linux-gnueabi"
+
+%struct.a = type { i16, i16, [1 x %union.a] }
+%union.a = type { i32 }
+
+@length = external global [0 x i32], align 4
+
+; Function Attrs: nounwind
+define fastcc void @foo(%struct.a* nocapture readonly %x) {
+;CHECK-LABEL: foo
+entry:
+  br label %bb0
+
+bb0:                                      ; preds = %land.lhs.true, %entry
+;CHECK: bb0:
+  %x.tr = phi %struct.a* [ %x, %entry ], [ null, %land.lhs.true ]
+  %code1 = getelementptr inbounds %struct.a, %struct.a* %x.tr, i32 0, i32 0
+  %0 = load i16, i16* %code1, align 4
+; CHECK: load i32, i32*
+  %conv = zext i16 %0 to i32
+  switch i32 %conv, label %if.end.50 [
+    i32 43, label %cleanup
+    i32 52, label %if.then.5
+  ]
+
+if.then.5:                                        ; preds = %bb0
+  br i1 undef, label %land.lhs.true, label %if.then.26
+
+land.lhs.true:                                    ; preds = %if.then.5
+  br i1 undef, label %cleanup, label %bb0
+
+if.then.26:                                       ; preds = %if.then.5
+  %x.tr.lcssa163 = phi %struct.a* [ %x.tr, %if.then.5 ]
+  br i1 undef, label %cond.end, label %cond.false
+
+cond.false:                                       ; preds = %if.then.26
+; CHECK: cond.false:
+; CHECK-NOT: load
+  %mode = getelementptr inbounds %struct.a, %struct.a* %x.tr.lcssa163, i32 0, i32 1
+  %bf.load = load i16, i16* %mode, align 2
+  %bf.shl = shl i16 %bf.load, 8
+  br label %cond.end
+
+cond.end:                                         ; preds = %cond.false, %if.then.26
+  br i1 undef, label %if.then.44, label %cleanup
+
+if.then.44:                                       ; preds = %cond.end
+  unreachable
+
+if.end.50:                                        ; preds = %bb0
+;%CHECK: if.end.50:
+  %conv.lcssa = phi i32 [ %conv, %bb0 ]
+  %arrayidx52 = getelementptr inbounds [0 x i32], [0 x i32]* @length, i32 0, i32 %conv.lcssa
+  %1 = load i32, i32* %arrayidx52, align 4
+  br i1 undef, label %for.body.57, label %cleanup
+
+for.body.57:                                      ; preds = %if.end.50
+  %i.2157 = add nsw i32 %1, -1
+  unreachable
+
+cleanup:                                          ; preds = %if.end.50, %cond.end, %land.lhs.true, %bb0
+  ret void
+}
+
+@yy_c_buf_p = external unnamed_addr global i8*, align 4
+@dfg_text = external global i8*, align 4
+
+define void @dfg_lex() {
+;CHECK-LABEL: dfg_lex
+entry:
+  br label %while.bodythread-pre-split
+
+while.bodythread-pre-split:                       ; preds = %while.end, %while.end, %entry
+  br i1 undef, label %if.then.14, label %if.end.15
+
+if.then.14:                                       ; preds = %while.end, %while.bodythread-pre-split
+  %v1 = load i32, i32* bitcast (i8** @dfg_text to i32*), align 4
+  %sub.ptr.sub = sub i32 undef, %v1
+  br label %if.end.15
+
+if.end.15:                                        ; preds = %if.then.14, %while.bodythread-pre-split
+  %v2 = load i8*, i8** @yy_c_buf_p, align 4
+  br label %while.cond.16
+
+while.cond.16:                                    ; preds = %while.cond.16, %if.end.15
+  br i1 undef, label %while.cond.16, label %while.end
+
+while.end:                                        ; preds = %while.cond.16
+  %add.ptr = getelementptr inbounds i8, i8* %v2, i32 undef
+  store i8* %add.ptr, i8** @dfg_text, align 4
+  %sub.ptr.rhs.cast25 = ptrtoint i8* %add.ptr to i32
+  %sub.ptr.sub26 = sub i32 0, %sub.ptr.rhs.cast25
+  switch i32 undef, label %sw.default [
+    i32 65, label %while.bodythread-pre-split
+    i32 3, label %return
+    i32 57, label %while.bodythread-pre-split
+    i32 60, label %if.then.14
+  ]
+
+sw.default:                                       ; preds = %while.end
+  unreachable
+
+return:                                           ; preds = %while.end
+  ret void
+}