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[RISCV] Implement mayBeEmittedAsTailCall for tail call optimization

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Implement TargetLowering callback mayBeEmittedAsTailCall for riscv in CodeGenPrepare,
which will duplicate return instructions to enable tailcall optimization.

Differential Revision: https://reviews.llvm.org/D73699
This commit is contained in:
Andrew Wei 2020-02-18 23:53:26 +08:00
parent 04e619f3c1
commit 2d085cde30
3 changed files with 49 additions and 0 deletions
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4
lib/Target/RISCV/RISCVISelLowering.cpp
View File

@ -2494,6 +2494,10 @@ void RISCVTargetLowering::validateCCReservedRegs(
F, "Argument register required, but has been reserved."});
}
bool RISCVTargetLowering::mayBeEmittedAsTailCall(const CallInst *CI) const {
return CI->isTailCall();
}
const char *RISCVTargetLowering::getTargetNodeName(unsigned Opcode) const {
switch ((RISCVISD::NodeType)Opcode) {
case RISCVISD::FIRST_NUMBER:

1
lib/Target/RISCV/RISCVISelLowering.h
View File

@ -181,6 +181,7 @@ private:
Type *Ty) const override {
return true;
}
bool mayBeEmittedAsTailCall(const CallInst *CI) const override;
template <class NodeTy>
SDValue getAddr(NodeTy *N, SelectionDAG &DAG, bool IsLocal = true) const;

44
test/CodeGen/RISCV/tail-calls.ll
View File

@ -168,6 +168,50 @@ entry:
ret i32 %rv
}
; Duplicate returns to enable tail call optimizations.
declare i32 @test()
declare i32 @test1()
declare i32 @test2()
declare i32 @test3()
define i32 @duplicate_returns(i32 %a, i32 %b) nounwind {
; CHECK-LABEL: duplicate_returns:
; CHECK: tail test2
; CHECK: tail test
; CHECK: tail test1
; CHECK: tail test3
entry:
%cmp = icmp eq i32 %a, 0
br i1 %cmp, label %if.then, label %if.else
if.then: ; preds = %entry
%call = tail call i32 @test()
br label %return
if.else: ; preds = %entry
%cmp1 = icmp eq i32 %b, 0
br i1 %cmp1, label %if.then2, label %if.else4
if.then2: ; preds = %if.else
%call3 = tail call i32 @test1()
br label %return
if.else4: ; preds = %if.else
%cmp5 = icmp sgt i32 %a, %b
br i1 %cmp5, label %if.then6, label %if.else8
if.then6: ; preds = %if.else4
%call7 = tail call i32 @test2()
br label %return
if.else8: ; preds = %if.else4
%call9 = tail call i32 @test3()
br label %return
return: ; preds = %if.else8, %if.then6, %if.then2, %if.then
%retval = phi i32 [ %call, %if.then ], [ %call3, %if.then2 ], [ %call7, %if.then6 ], [ %call9, %if.else8 ]
ret i32 %retval
}
!llvm.module.flags = !{!0}
!0 = !{i32 1, !"ProfileSummary", !1}
!1 = !{!2, !3, !4, !5, !6, !7, !8, !9}