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TRE: make TRE a bit more aggressive

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Make tail recursion elimination a bit more aggressive.  This allows us to get
tail recursion on functions that are just branches to a different function.  The
fact that the function takes a byval argument does not restrict it from being
optimised into just a tail call.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219899 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Saleem Abdulrasool 2014-10-16 03:27:30 +00:00
parent 608d59f535
commit ebe6584c32
4 changed files with 39 additions and 10 deletions
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10
lib/Transforms/Scalar/TailRecursionElimination.cpp
View File

@ -249,12 +249,7 @@ bool TailCallElim::markTails(Function &F, bool &AllCallsAreTailCalls) {
return false;
AllCallsAreTailCalls = true;
// The local stack holds all alloca instructions and all byval arguments.
AllocaDerivedValueTracker Tracker;
for (Argument &Arg : F.args()) {
if (Arg.hasByValAttr())
Tracker.walk(&Arg);
}
for (auto &BB : F) {
for (auto &I : BB)
if (AllocaInst *AI = dyn_cast<AllocaInst>(&I))
@ -310,9 +305,8 @@ bool TailCallElim::markTails(Function &F, bool &AllCallsAreTailCalls) {
for (auto &Arg : CI->arg_operands()) {
if (isa<Constant>(Arg.getUser()))
continue;
if (Argument *A = dyn_cast<Argument>(Arg.getUser()))
if (!A->hasByValAttr())
continue;
if (isa<Argument>(Arg.getUser()))
continue;
SafeToTail = false;
break;
}

3
test/Transforms/Inline/byval-tail-call.ll
View File

@ -27,10 +27,11 @@ define internal void @qux(i32* byval %x) {
tail call void @ext(i32* null)
ret void
}
define void @frob(i32* %x) {
; CHECK-LABEL: define void @frob(
; CHECK: alloca i32
; CHECK: {{^ *}}call void @ext(
; CHECK: {{^ *}}tail call void @ext(
; CHECK: tail call void @ext(i32* null)
; CHECK: ret void
tail call void @qux(i32* byval %x)

2
test/Transforms/TailCallElim/basic.ll
View File

@ -147,7 +147,7 @@ cond_false:
; Don't tail call if a byval arg is captured.
define void @test9(i32* byval %a) {
; CHECK-LABEL: define void @test9(
; CHECK: {{^ *}}call void @use(
; CHECK: {{^ *}}tail call void @use(
call void @use(i32* %a)
ret void
}

34
test/Transforms/TailCallElim/byval.ll Normal file
View File

@ -0,0 +1,34 @@
; RUN: opt -mtriple i386 -Os -S %s -o - | FileCheck %s
; RUN: opt -mtriple x86_64 -Os -S %s -o - | FileCheck %s
; RUN: opt -mtriple armv7 -Os -S %s -o - | FileCheck %s
%struct.D16 = type { [16 x double] }
declare void @_Z2OpP3D16PKS_S2_(%struct.D16*, %struct.D16*, %struct.D16*)
define void @_Z7TestRefRK3D16S1_(%struct.D16* noalias sret %agg.result, %struct.D16* %RHS, %struct.D16* %LHS) {
%1 = alloca %struct.D16*, align 8
%2 = alloca %struct.D16*, align 8
store %struct.D16* %RHS, %struct.D16** %1, align 8
store %struct.D16* %LHS, %struct.D16** %2, align 8
%3 = load %struct.D16** %1, align 8
%4 = load %struct.D16** %2, align 8
call void @_Z2OpP3D16PKS_S2_(%struct.D16* %agg.result, %struct.D16* %3, %struct.D16* %4)
ret void
}
; CHECK: define void @_Z7TestRefRK3D16S1_({{.*}}) {
; CHECK: tail call void @_Z2OpP3D16PKS_S2_(%struct.D16* %agg.result, %struct.D16* %RHS, %struct.D16* %LHS)
; CHECK: ret void
; CHECK: }
define void @_Z7TestVal3D16S_(%struct.D16* noalias sret %agg.result, %struct.D16* byval align 8 %RHS, %struct.D16* byval align 8 %LHS) {
call void @_Z2OpP3D16PKS_S2_(%struct.D16* %agg.result, %struct.D16* %RHS, %struct.D16* %LHS)
ret void
}
; CHECK: define void @_Z7TestVal3D16S_({{.*}}) {
; CHECK: tail call void @_Z2OpP3D16PKS_S2_(%struct.D16* %agg.result, %struct.D16* %RHS, %struct.D16* %LHS)
; CHECK: ret void
; CHECK: }