ISel: We need to notify FastIS of the IMPLICIT_DEF we created in createSwiftErrorEntriesInEntryBlock

Otherwise, it will insert instructions before it.

rdar://30536186

llvm-svn: 296395

2 files changed, 34 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 5a16f4afc1a..d980c4d019a 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -1306,6 +1306,7 @@ static void setupSwiftErrorVals(const Function &Fn, const TargetLowering *TLI,
 }
 
 static void createSwiftErrorEntriesInEntryBlock(FunctionLoweringInfo *FuncInfo,
+                                                FastISel *FastIS,
                                                 const TargetLowering *TLI,
                                                 const TargetInstrInfo *TII,
                                                 SelectionDAGBuilder *SDB) {
@@ -1332,6 +1333,11 @@ static void createSwiftErrorEntriesInEntryBlock(FunctionLoweringInfo *FuncInfo,
     BuildMI(*FuncInfo->MBB, FuncInfo->MBB->getFirstNonPHI(),
             SDB->getCurDebugLoc(), TII->get(TargetOpcode::IMPLICIT_DEF),
             VReg);
+
+    // Keep FastIS informed about the value we just inserted.
+    if (FastIS)
+      FastIS->setLastLocalValue(&*std::prev(FuncInfo->InsertPt));
+
     FuncInfo->setCurrentSwiftErrorVReg(FuncInfo->MBB, SwiftErrorVal, VReg);
   }
 }
@@ -1501,7 +1507,7 @@ void SelectionDAGISel::SelectAllBasicBlocks(const Function &Fn) {
     else
       FastIS->setLastLocalValue(nullptr);
   }
-  createSwiftErrorEntriesInEntryBlock(FuncInfo, TLI, TII, SDB);
+  createSwiftErrorEntriesInEntryBlock(FuncInfo, FastIS, TLI, TII, SDB);
 
   // Iterate over all basic blocks in the function.
   for (const BasicBlock *LLVMBB : RPOT) {
diff --git a/llvm/test/CodeGen/X86/swifterror.ll b/llvm/test/CodeGen/X86/swifterror.ll
index 86e0221c201..5704d191998 100644
--- a/llvm/test/CodeGen/X86/swifterror.ll
+++ b/llvm/test/CodeGen/X86/swifterror.ll
@@ -685,3 +685,30 @@ entry:
   tail call void @acallee(i8* null)
   ret void
 }
+
+; Make sure we don't crash on this function during -O0.
+; We used to crash because we would insert an IMPLICIT_DEF for the swifterror at
+; beginning of the machine basic block but did not inform FastISel of the
+; inserted instruction. When computing the InsertPoint in the entry block
+; FastISel would choose an insertion point before the IMPLICIT_DEF causing a
+; crash later on.
+declare hidden swiftcc i8* @testFunA()
+
+%TSb = type <{ i1 }>
+
+define swiftcc void @dontCrash()  {
+entry:
+  %swifterror = alloca swifterror %swift_error*, align 8
+  store %swift_error* null, %swift_error** %swifterror, align 8
+  %a = call i8* @testFunA()
+  %b = bitcast i8* %a to %TSb*
+  %._value = getelementptr inbounds %TSb, %TSb* %b, i32 0, i32 0
+  %c = load i1, i1* %._value, align 1
+  br i1 %c, label %trueBB, label %falseBB
+
+trueBB:
+  ret void
+
+falseBB:
+  ret void
+}