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Stop putting operations after a tail call.

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This prevents the emission of DAG-generated vreg definitions after a
tail call be dropping them entirely (on the grounds that nothing could
use them anyway, and they interfere with O0 CodeGen).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185754 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Tim Northover 2013-07-06 12:58:45 +00:00
parent 8064628379
commit e5a81a130f
2 changed files with 20 additions and 0 deletions
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4
lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
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@ -5357,6 +5357,10 @@ void SelectionDAGBuilder::LowerCallTo(ImmutableCallSite CS, SDValue Callee,
// As a special case, a null chain means that a tail call has been emitted and
// the DAG root is already updated.
HasTailCall = true;
// Since there's no actual continuation from this block, nothing can be
// relying on us setting vregs for them.
PendingExports.clear();
} else {
DAG.setRoot(Result.second);
}

16
test/CodeGen/ARM/fast-tail-call.ll Normal file
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@ -0,0 +1,16 @@
; RUN: llc -mtriple=thumbv7-linux-gnueabi -O0 -arm-tail-calls < %s | FileCheck %s
; Primarily a non-crash test: Thumbv7 Linux does not have FastISel support,
; which led (via a convoluted route) to DAG nodes after a TC_RETURN that
; couldn't possibly work.
declare i8* @g(i8*)
define i8* @f(i8* %a) {
entry:
%0 = tail call i8* @g(i8* %a)
ret i8* %0
; CHECK: b g
; CHECK-NOT: ldr
; CHECK-NOT: str
}