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author | Chad Rosier <mcrosier@apple.com> | 2012-12-11 00:18:02 +0000 |
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committer | Chad Rosier <mcrosier@apple.com> | 2012-12-11 00:18:02 +0000 |
commit | 425e951734c3a0615e22ec94ffa51cc16ce6e483 (patch) | |
tree | 498b09ecb92c4701f5626d07a50ac1c0d5401830 | |
parent | 0e3e9b79f6e471b46438251249f18121408e5189 (diff) | |
download | external_llvm-425e951734c3a0615e22ec94ffa51cc16ce6e483.zip external_llvm-425e951734c3a0615e22ec94ffa51cc16ce6e483.tar.gz external_llvm-425e951734c3a0615e22ec94ffa51cc16ce6e483.tar.bz2 |
Fall back to the selection dag isel to select tail calls.
This shouldn't affect codegen for -O0 compiles as tail call markers are not
emitted in unoptimized compiles. Testing with the external/internal nightly
test suite reveals no change in compile time performance. Testing with -O1,
-O2 and -O3 with fast-isel enabled did not cause any compile-time or
execution-time failures. All tests were performed on my x86 machine.
I'll monitor our arm testers to ensure no regressions occur there.
In an upcoming clang patch I will be marking the objc_autoreleaseReturnValue
and objc_retainAutoreleaseReturnValue as tail calls unconditionally. While
it's theoretically true that this is just an optimization, it's an
optimization that we very much want to happen even at -O0, or else ARC
applications become substantially harder to debug.
Part of rdar://12553082
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169796 91177308-0d34-0410-b5e6-96231b3b80d8
-rw-r--r-- | include/llvm/CodeGen/FastISel.h | 8 | ||||
-rw-r--r-- | lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp | 5 | ||||
-rw-r--r-- | lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp | 12 | ||||
-rw-r--r-- | lib/Target/ARM/ARMFastISel.cpp | 3 | ||||
-rw-r--r-- | lib/Target/X86/X86FastISel.cpp | 4 | ||||
-rw-r--r-- | test/CodeGen/X86/tailcall-fastisel.ll | 5 |
6 files changed, 20 insertions, 17 deletions
diff --git a/include/llvm/CodeGen/FastISel.h b/include/llvm/CodeGen/FastISel.h index 5c872b1..0561905 100644 --- a/include/llvm/CodeGen/FastISel.h +++ b/include/llvm/CodeGen/FastISel.h @@ -131,6 +131,10 @@ public: /// into the current block. void recomputeInsertPt(); + /// removeDeadCode - Remove all dead instructions between the I and E. + void removeDeadCode(MachineBasicBlock::iterator I, + MachineBasicBlock::iterator E); + struct SavePoint { MachineBasicBlock::iterator InsertPt; DebugLoc DL; @@ -395,10 +399,6 @@ private: /// hasTrivialKill - Test whether the given value has exactly one use. bool hasTrivialKill(const Value *V) const; - - /// removeDeadCode - Remove all dead instructions between the I and E. - void removeDeadCode(MachineBasicBlock::iterator I, - MachineBasicBlock::iterator E); }; } diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp index 97d975e..ee8f272 100644 --- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp +++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp @@ -5273,11 +5273,6 @@ void SelectionDAGBuilder::LowerCallTo(ImmutableCallSite CS, SDValue Callee, !isInTailCallPosition(CS, CS.getAttributes().getRetAttributes(), TLI)) isTailCall = false; - // If there's a possibility that fast-isel has already selected some amount - // of the current basic block, don't emit a tail call. - if (isTailCall && TM.Options.EnableFastISel) - isTailCall = false; - TargetLowering:: CallLoweringInfo CLI(getRoot(), RetTy, FTy, isTailCall, Callee, Args, DAG, getCurDebugLoc(), CS); diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp index ca25274..c755d72 100644 --- a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp +++ b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp @@ -1113,19 +1113,21 @@ void SelectionDAGISel::SelectAllBasicBlocks(const Function &Fn) { } bool HadTailCall = false; + MachineBasicBlock::iterator SavedInsertPt = FuncInfo->InsertPt; SelectBasicBlock(Inst, BI, HadTailCall); - // Recompute NumFastIselRemaining as Selection DAG instruction - // selection may have handled the call, input args, etc. - unsigned RemainingNow = std::distance(Begin, BI); - NumFastIselFailures += NumFastIselRemaining - RemainingNow; - // If the call was emitted as a tail call, we're done with the block. + // We also need to delete any previously emitted instructions. if (HadTailCall) { + FastIS->removeDeadCode(SavedInsertPt, FuncInfo->MBB->end()); --BI; break; } + // Recompute NumFastIselRemaining as Selection DAG instruction + // selection may have handled the call, input args, etc. + unsigned RemainingNow = std::distance(Begin, BI); + NumFastIselFailures += NumFastIselRemaining - RemainingNow; NumFastIselRemaining = RemainingNow; continue; } diff --git a/lib/Target/ARM/ARMFastISel.cpp b/lib/Target/ARM/ARMFastISel.cpp index 21bb147..c3a5e64 100644 --- a/lib/Target/ARM/ARMFastISel.cpp +++ b/lib/Target/ARM/ARMFastISel.cpp @@ -2284,6 +2284,9 @@ bool ARMFastISel::SelectCall(const Instruction *I, // Can't handle inline asm. if (isa<InlineAsm>(Callee)) return false; + // Allow SelectionDAG isel to handle tail calls. + if (CI->isTailCall()) return false; + // Check the calling convention. ImmutableCallSite CS(CI); CallingConv::ID CC = CS.getCallingConv(); diff --git a/lib/Target/X86/X86FastISel.cpp b/lib/Target/X86/X86FastISel.cpp index b26b9d7..3e78b4c 100644 --- a/lib/Target/X86/X86FastISel.cpp +++ b/lib/Target/X86/X86FastISel.cpp @@ -1529,6 +1529,10 @@ bool X86FastISel::X86SelectCall(const Instruction *I) { if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI)) return X86VisitIntrinsicCall(*II); + // Allow SelectionDAG isel to handle tail calls. + if (cast<CallInst>(I)->isTailCall()) + return false; + return DoSelectCall(I, 0); } diff --git a/test/CodeGen/X86/tailcall-fastisel.ll b/test/CodeGen/X86/tailcall-fastisel.ll index 7f92af4..9962d71 100644 --- a/test/CodeGen/X86/tailcall-fastisel.ll +++ b/test/CodeGen/X86/tailcall-fastisel.ll @@ -1,12 +1,11 @@ -; RUN: llc < %s -march=x86-64 -tailcallopt -fast-isel | not grep TAILCALL - -; Fast-isel shouldn't attempt to cope with tail calls. +; RUN: llc < %s -march=x86-64 -tailcallopt -fast-isel -fast-isel-abort | FileCheck %s %0 = type { i64, i32, i8* } define fastcc i8* @"visit_array_aux<`Reference>"(%0 %arg, i32 %arg1) nounwind { fail: ; preds = %entry %tmp20 = tail call fastcc i8* @"visit_array_aux<`Reference>"(%0 %arg, i32 undef) ; <i8*> [#uses=1] +; CHECK: jmp "_visit_array_aux<`Reference>" ## TAILCALL ret i8* %tmp20 } |