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add a new @llvm.donothing intrinsic that, well, does nothing, and tea…

…ch CodeGen to ignore calls to it

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159383 91177308-0d34-0410-b5e6-96231b3b80d8
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1 parent 992c9c9 commit c57595eda28b86f64400519246313bb3e1eb364b @nunoplopes nunoplopes committed Jun 28, 2012
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3 include/llvm/Intrinsics.td
@@ -412,6 +412,9 @@ def int_trap : Intrinsic<[], [], [IntrNoReturn]>,
def int_debugtrap : Intrinsic<[]>,
GCCBuiltin<"__builtin_debugtrap">;
+// NOP: calls/invokes to this intrinsic are removed by codegen
+def int_donothing : Intrinsic<[], [], [IntrNoMem]>;
+
// Intrisics to support half precision floating point format
let Properties = [IntrNoMem] in {
def int_convert_to_fp16 : Intrinsic<[llvm_i16_ty], [llvm_float_ty]>,
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9 lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -1828,9 +1828,13 @@ void SelectionDAGBuilder::visitInvoke(const InvokeInst &I) {
MachineBasicBlock *LandingPad = FuncInfo.MBBMap[I.getSuccessor(1)];
const Value *Callee(I.getCalledValue());
+ const Function *Fn = dyn_cast<Function>(Callee);
if (isa<InlineAsm>(Callee))
visitInlineAsm(&I);
- else
+ else if (Fn && Fn->isIntrinsic()) {
+ assert(Fn->getIntrinsicID() == Intrinsic::donothing);
+ return; // ignore invokes to @llvm.donothing
+ } else
LowerCallTo(&I, getValue(Callee), false, LandingPad);
// If the value of the invoke is used outside of its defining block, make it
@@ -5178,6 +5182,9 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
case Intrinsic::lifetime_end:
// Discard region information.
return 0;
+ case Intrinsic::donothing:
+ // ignore
+ return 0;
}
}
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31 test/CodeGen/Generic/donothing.ll
@@ -0,0 +1,31 @@
+; RUN: llc < %s | FileCheck %s
+
+declare i32 @__gxx_personality_v0(...)
+declare void @__cxa_call_unexpected(i8*)
+declare void @llvm.donothing() readnone
+
+; CHECK: f1
+define void @f1() nounwind uwtable ssp {
+entry:
+; CHECK-NOT donothing
+ invoke void @llvm.donothing()
+ to label %invoke.cont unwind label %lpad
+
+invoke.cont:
+ ret void
+
+lpad:
+ %0 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+ filter [0 x i8*] zeroinitializer
+ %1 = extractvalue { i8*, i32 } %0, 0
+ tail call void @__cxa_call_unexpected(i8* %1) noreturn nounwind
+ unreachable
+}
+
+; CHECK: f2
+define void @f2() nounwind {
+entry:
+; CHECK-NOT donothing
+ call void @llvm.donothing()
+ ret void
+}

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