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If fast-isel fails, remove dead instructions generated during the failed
attempt. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145425 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -381,6 +381,10 @@ private:
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/// hasTrivialKill - Test whether the given value has exactly one use.
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bool hasTrivialKill(const Value *V) const;
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/// removeDeadCode - Remove all dead instructions between the I and E.
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void removeDeadCode(MachineBasicBlock::iterator I,
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MachineBasicBlock::iterator E);
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};
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}
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@ -66,6 +66,7 @@ STATISTIC(NumFastIselSuccessIndependent, "Number of insts selected by "
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"target-independent selector");
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STATISTIC(NumFastIselSuccessTarget, "Number of insts selected by "
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"target-specific selector");
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STATISTIC(NumFastIselDead, "Number of dead insts removed on failure");
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/// startNewBlock - Set the current block to which generated machine
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/// instructions will be appended, and clear the local CSE map.
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@ -309,6 +310,18 @@ void FastISel::recomputeInsertPt() {
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++FuncInfo.InsertPt;
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}
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void FastISel::removeDeadCode(MachineBasicBlock::iterator I,
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MachineBasicBlock::iterator E) {
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assert (I && E && std::distance(I, E) > 0 && "Invalid iterator!");
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while (I != E) {
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MachineInstr *Dead = &*I;
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++I;
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Dead->eraseFromParent();
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++NumFastIselDead;
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}
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recomputeInsertPt();
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}
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FastISel::SavePoint FastISel::enterLocalValueArea() {
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MachineBasicBlock::iterator OldInsertPt = FuncInfo.InsertPt;
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DebugLoc OldDL = DL;
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@ -794,19 +807,33 @@ FastISel::SelectInstruction(const Instruction *I) {
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DL = I->getDebugLoc();
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MachineBasicBlock::iterator SavedInsertPt = FuncInfo.InsertPt;
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// First, try doing target-independent selection.
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if (SelectOperator(I, I->getOpcode())) {
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++NumFastIselSuccessIndependent;
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DL = DebugLoc();
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return true;
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}
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// Remove dead code. However, ignore call instructions since we've flushed
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// the local value map and recomputed the insert point.
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if (!isa<CallInst>(I)) {
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recomputeInsertPt();
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if (SavedInsertPt != FuncInfo.InsertPt)
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removeDeadCode(FuncInfo.InsertPt, SavedInsertPt);
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}
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// Next, try calling the target to attempt to handle the instruction.
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SavedInsertPt = FuncInfo.InsertPt;
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if (TargetSelectInstruction(I)) {
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++NumFastIselSuccessTarget;
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DL = DebugLoc();
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return true;
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}
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// Check for dead code and remove as necessary.
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recomputeInsertPt();
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if (SavedInsertPt != FuncInfo.InsertPt)
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removeDeadCode(FuncInfo.InsertPt, SavedInsertPt);
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DL = DebugLoc();
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return false;
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23
test/CodeGen/ARM/fast-isel-deadcode.ll
Normal file
23
test/CodeGen/ARM/fast-isel-deadcode.ll
Normal file
@ -0,0 +1,23 @@
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; RUN: llc < %s -O0 -relocation-model=dynamic-no-pic -mtriple=thumbv7-apple-darwin | FileCheck %s --check-prefix=THUMB
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; Target-specific selector can't properly handle the double because it isn't
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; being passed via a register, so the materialized arguments become dead code.
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define i32 @main(i32 %argc, i8** %argv) nounwind {
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entry:
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; THUMB: main
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call void @printArgsNoRet(i32 1, float 0x4000CCCCC0000000, i8 signext 99, double 4.100000e+00)
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; THUMB: blx _printArgsNoRet
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; THUMB-NOT: ldr
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; THUMB-NOT: vldr
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; THUMB-NOT: vmov
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; THUMB-NOT: ldr
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; THUMB-NOT: sxtb
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; THUMB: movs r0, #0
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; THUMB: movt r0, #0
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; THUMB: add sp, #32
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; THUMb: pop {r7, pc}
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ret i32 0
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}
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declare void @printArgsNoRet(i32 %a1, float %a2, i8 signext %a3, double %a4)
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