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add a new @llvm.donothing intrinsic that, well, does nothing, and teach CodeGen to ignore calls to it

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159383 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nuno Lopes 2012-06-28 22:30:12 +00:00
parent 926dc168c8
commit 85b408991a
3 changed files with 42 additions and 1 deletions
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3
include/llvm/Intrinsics.td
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@ -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]>,

9
lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
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@ -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;
}
}

31
test/CodeGen/Generic/donothing.ll Normal file
View File

@ -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
}