Ignore dbg intrinsics while folding switch instruction.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@63802 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Utils/SimplifyCFG.cpp

@@ -1330,6 +1330,20 @@ static bool FoldTwoEntryPHINode(PHINode *PN) {
   return true;
 }
 
+/// isTerminatorFirstRelevantInsn - Return true if Term is very first 
+/// instruction ignoring Phi nodes and dbg intrinsics.
+static bool isTerminatorFirstRelevantInsn(BasicBlock *BB, Instruction *Term) {
+  BasicBlock::iterator BBI = Term;
+  while (BBI != BB->begin()) {
+    --BBI;
+    if (!isa<DbgInfoIntrinsic>(BBI))
+      break;
+  }
+  if (isa<PHINode>(BBI) || &*BBI == Term)
+    return true;
+  return false;
+}
+
 /// SimplifyCondBranchToTwoReturns - If we found a conditional branch that goes
 /// to two returning blocks, try to merge them together into one return,
 /// introducing a select if the return values disagree.
@@ -1343,12 +1357,10 @@ static bool SimplifyCondBranchToTwoReturns(BranchInst *BI) {
   // Check to ensure both blocks are empty (just a return) or optionally empty
   // with PHI nodes.  If there are other instructions, merging would cause extra
   // computation on one path or the other.
-  BasicBlock::iterator BBI = TrueRet;
+  if (!isTerminatorFirstRelevantInsn(TrueSucc, TrueRet))
-  if (BBI != TrueSucc->begin() && !isa<PHINode>(--BBI))
+    return false;
-    return false;  // Not empty with optional phi nodes.
+  if (!isTerminatorFirstRelevantInsn(FalseSucc, FalseRet))
-  BBI = FalseRet;
+    return false;
-  if (BBI != FalseSucc->begin() && !isa<PHINode>(--BBI))
-    return false;  // Not empty with optional phi nodes.
 
   // Okay, we found a branch that is going to two return nodes.  If
   // there is no return value for this function, just change the
@@ -1750,8 +1762,7 @@ bool llvm::SimplifyCFG(BasicBlock *BB) {
   // different return values, fold the replace the branch/return with a select
   // and return.
   if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
-    BasicBlock::iterator BBI = BB->getTerminator();
+    if (isTerminatorFirstRelevantInsn(BB, BB->getTerminator())) {
-    if (BBI == BB->begin() || isa<PHINode>(--BBI)) {
       // Find predecessors that end with branches.
       SmallVector<BasicBlock*, 8> UncondBranchPreds;
       SmallVector<BranchInst*, 8> CondBranchPreds;

test/Transforms/SimplifyCFG/2003-08-17-FoldSwitch-dbg.ll

@@ -0,0 +1,58 @@
+; RUN: llvm-as < %s | opt -simplifycfg | llvm-dis | \
+; RUN:   not grep switch
+
+
+        %llvm.dbg.anchor.type = type { i32, i32 }
+        %llvm.dbg.compile_unit.type = type { i32, { }*, i32, i8*, i8*, i8*, i1, i1, i8* }
+
+@llvm.dbg.compile_units = linkonce constant %llvm.dbg.anchor.type { i32 458752, i32 17 }, section "llvm.metadata"		; 
+
+@.str = internal constant [4 x i8] c"a.c\00", section "llvm.metadata"		; <[4 x i8]*> [#uses=1]
+@.str1 = internal constant [6 x i8] c"/tmp/\00", section "llvm.metadata"	; <[6 x i8]*> [#uses=1]
+@.str2 = internal constant [55 x i8] c"4.2.1 (Based on Apple Inc. build 5636) (LLVM build 00)\00", section "llvm.metadata"		; <[55 x i8]*> [#uses=1]
+@llvm.dbg.compile_unit = internal constant %llvm.dbg.compile_unit.type { i32 458769, { }* bitcast (%llvm.dbg.anchor.type* @llvm.dbg.compile_units to { }*), i32 1, i8* getelementptr ([4 x i8]* @.str, i32 0, i32 0), i8* getelementptr ([6 x i8]* @.str1, i32 0, i32 0), i8* getelementptr ([55 x i8]* @.str2, i32 0, i32 0), i1 true, i1 false, i8* null }, section "llvm.metadata"		; <%llvm.dbg.compile_unit.type*> [#uses=1]
+
+declare void @llvm.dbg.stoppoint(i32, i32, { }*) nounwind
+
+; Test folding all to same dest
+define i32 @test3(i1 %C) {
+        br i1 %C, label %Start, label %TheDest
+Start:          ; preds = %0
+call void @llvm.dbg.stoppoint(i32 5, i32 0, { }* bitcast (%llvm.dbg.compile_unit.type* @llvm.dbg.compile_unit to { }*))
+        switch i32 3, label %TheDest [
+                 i32 0, label %TheDest
+                 i32 1, label %TheDest
+                 i32 2, label %TheDest
+                 i32 5, label %TheDest
+        ]
+TheDest:                ; preds = %Start, %Start, %Start, %Start, %Start, %0
+        ret i32 1234
+}
+
+; Test folding switch -> branch
+define i32 @test4(i32 %C) {
+        switch i32 %C, label %L1 [
+                 i32 0, label %L2
+        ]
+L1:             ; preds = %0
+call void @llvm.dbg.stoppoint(i32 5, i32 0, { }* bitcast (%llvm.dbg.compile_unit.type* @llvm.dbg.compile_unit to { }*))
+        ret i32 0
+L2:             ; preds = %0
+call void @llvm.dbg.stoppoint(i32 5, i32 0, { }* bitcast (%llvm.dbg.compile_unit.type* @llvm.dbg.compile_unit to { }*))
+        ret i32 1
+}
+
+; Can fold into a cond branch!
+define i32 @test5(i32 %C) {
+        switch i32 %C, label %L1 [
+                 i32 0, label %L2
+                 i32 123, label %L1
+        ]
+L1:             ; preds = %0, %0
+call void @llvm.dbg.stoppoint(i32 5, i32 0, { }* bitcast (%llvm.dbg.compile_unit.type* @llvm.dbg.compile_unit to { }*))
+        ret i32 0
+L2:             ; preds = %0
+call void @llvm.dbg.stoppoint(i32 5, i32 0, { }* bitcast (%llvm.dbg.compile_unit.type* @llvm.dbg.compile_unit to { }*))
+        ret i32 1
+}
+