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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.

llvm-svn: 212922
This commit is contained in:
Bill Wendling 2014-07-14 06:22:36 +00:00
parent 5c40508457
commit 151b44d653
2 changed files with 41 additions and 10 deletions
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20
llvm/lib/CodeGen/SjLjEHPrepare.cpp
View File

@ -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);
// 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);
// Set the operand of the instructions back to the AllocaInst.
EI->setOperand(0, AI);
NI->setOperand(0, AI);
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

31
llvm/test/CodeGen/ARM/sjljehprepare-lower-empty-struct.ll Normal file
View File

@ -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(...)