Support lowering of empty aggregates.

This crash was pretty common while compiling Rust for iOS (armv7). Reason -
SjLj preparation step was lowering aggregate arguments as ExtractValue +
InsertValue. ExtractValue has assertion which checks that there is some data in
value, which is not true in case of empty (no fields) structures. Rust uses
them quite extensively so this patch uses a 'select true, %val, undef'
instruction to lower the argument.

Patch by Valerii Hiora.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212922 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SjLjEHPrepare.cpp b/lib/CodeGen/SjLjEHPrepare.cpp
index d2f395594860740ea888c5d533a590c8ed0a4245..f53408a0f12476801b647a6828c8094ff82abda1 100644 (file)
--- a/lib/CodeGen/SjLjEHPrepare.cpp
+++ b/lib/CodeGen/SjLjEHPrepare.cpp
@@ -249,18 +249,18 @@ void SjLjEHPrepare::lowerIncomingArguments(Function &F) {
        ++AI) {
     Type *Ty = AI->getType();
 
-    // Aggregate types can't be cast, but are legal argument types, so we have
-    // to handle them differently. We use an extract/insert pair as a
-    // lightweight method to achieve the same goal.
     if (isa<StructType>(Ty) || isa<ArrayType>(Ty)) {
-      Instruction *EI = ExtractValueInst::Create(AI, 0, "", AfterAllocaInsPt);
-      Instruction *NI = InsertValueInst::Create(AI, EI, 0);
-      NI->insertAfter(EI);
-      AI->replaceAllUsesWith(NI);
-
-      // Set the operand of the instructions back to the AllocaInst.
-      EI->setOperand(0, AI);
-      NI->setOperand(0, AI);
+      // Aggregate types can't be cast, but are legal argument types,
+      // so we have to handle them differently.  We use
+      // select i8 true, %arg, undef to achieve the same goal
+      Value *TrueValue = ConstantInt::getTrue(F.getContext());
+      Value *UndefValue = UndefValue::get(Ty);
+      Instruction *SI = SelectInst::Create(TrueValue, AI, UndefValue,
+                                           AI->getName() + ".tmp",
+                                           AfterAllocaInsPt);
+      AI->replaceAllUsesWith(SI);
+
+      SI->setOperand(1, AI);
     } else {
       // This is always a no-op cast because we're casting AI to AI->getType()
       // so src and destination types are identical. BitCast is the only

diff --git a/test/CodeGen/ARM/sjljehprepare-lower-empty-struct.ll b/test/CodeGen/ARM/sjljehprepare-lower-empty-struct.ll
new file mode 100644 (file)
index 0000000..e26f635
--- /dev/null
+++ b/test/CodeGen/ARM/sjljehprepare-lower-empty-struct.ll
@@ -0,0 +1,31 @@
+; RUN: llc -mtriple=armv7-apple-ios -O0 < %s | FileCheck %s
+; RUN: llc -mtriple=armv7-apple-ios -O1 < %s | FileCheck %s
+; RUN: llc -mtriple=armv7-apple-ios -O2 < %s | FileCheck %s
+; RUN: llc -mtriple=armv7-apple-ios -O3 < %s | FileCheck %s
+
+; SjLjEHPrepare shouldn't crash when lowering empty structs.
+;
+; Checks that between in case of empty structs used as arguments
+; nothing happens, i.e. there are no instructions between
+; __Unwind_SjLj_Register and actual @bar invocation
+
+
+define i8* @foo({} %c) {
+entry:
+; CHECK: bl __Unwind_SjLj_Register
+; CHECK-NEXT: {{[A-Z][a-zA-Z0-9]*}}:
+; CHECK-NEXT: bl _bar
+  invoke void @bar ()
+    to label %unreachable unwind label %handler
+
+unreachable:
+  unreachable
+
+handler:
+  %tmp = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @baz to i8*)
+  cleanup
+  resume { i8*, i32 } undef
+}
+
+declare void @bar()
+declare i32 @baz(...)