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[AArch64] Implement the isTruncateFree API.

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In AArch64 i64 to i32 truncate operation is a subregister access.

This allows more opportunities for LSR optmization to eliminate
variables of different types (i32 and i64).

llvm-svn: 205925
This commit is contained in:
Chad Rosier 2014-04-09 20:43:40 +00:00
parent 95c5120626
commit b6bf098390
3 changed files with 63 additions and 0 deletions
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21
lib/Target/AArch64/AArch64ISelLowering.cpp
View File

@ -5368,3 +5368,24 @@ bool AArch64TargetLowering::getTgtMemIntrinsic(IntrinsicInfo &Info,
return false;
}
// Truncations from 64-bit GPR to 32-bit GPR is free.
bool AArch64TargetLowering::isTruncateFree(Type *Ty1, Type *Ty2) const {
if (!Ty1->isIntegerTy() || !Ty2->isIntegerTy())
return false;
unsigned NumBits1 = Ty1->getPrimitiveSizeInBits();
unsigned NumBits2 = Ty2->getPrimitiveSizeInBits();
if (NumBits1 <= NumBits2)
return false;
return true;
}
bool AArch64TargetLowering::isTruncateFree(EVT VT1, EVT VT2) const {
if (!VT1.isInteger() || !VT2.isInteger())
return false;
unsigned NumBits1 = VT1.getSizeInBits();
unsigned NumBits2 = VT2.getSizeInBits();
if (NumBits1 <= NumBits2)
return false;
return true;
}

4
lib/Target/AArch64/AArch64ISelLowering.h
View File

@ -277,6 +277,10 @@ public:
SDValue LowerOperation(SDValue Op, SelectionDAG &DAG) const;
bool isLegalICmpImmediate(int64_t Val) const;
bool isTruncateFree(Type *Ty1, Type *Ty2) const override;
bool isTruncateFree(EVT VT1, EVT VT2) const override;
SDValue getSelectableIntSetCC(SDValue LHS, SDValue RHS, ISD::CondCode CC,
SDValue &A64cc, SelectionDAG &DAG, SDLoc &dl) const;

38
test/CodeGen/AArch64/eliminate-trunc.ll Normal file
View File

@ -0,0 +1,38 @@
; RUN: llc -verify-machineinstrs < %s -mtriple=aarch64-none-linux-gnu | FileCheck %s
; Check trunc i64 operation is translated as a subregister access
; eliminating an i32 induction varible.
; CHECK: add {{x[0-9]+}}, {{x[0-9]+}}, #1
; CHECK-NOT: add {{w[0-9]+}}, {{w[0-9]+}}, #1
; CHECK-NEXT: cmp {{w[0-9]+}}, {{w[0-9]+}}, uxtw
define void @test1_signed([8 x i8]* nocapture %a, i8* nocapture readonly %box, i8 %limit) {
entry:
%conv = zext i8 %limit to i32
%cmp223 = icmp eq i8 %limit, 0
br i1 %cmp223, label %for.end15, label %for.body4.lr.ph.us
for.body4.us:
%indvars.iv = phi i64 [ 0, %for.body4.lr.ph.us ], [ %indvars.iv.next, %for.body4.us ]
%arrayidx6.us = getelementptr inbounds [8 x i8]* %a, i64 %indvars.iv26, i64 %indvars.iv
%0 = load i8* %arrayidx6.us, align 1
%idxprom7.us = zext i8 %0 to i64
%arrayidx8.us = getelementptr inbounds i8* %box, i64 %idxprom7.us
%1 = load i8* %arrayidx8.us, align 1
store i8 %1, i8* %arrayidx6.us, align 1
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
%2 = trunc i64 %indvars.iv.next to i32
%cmp2.us = icmp slt i32 %2, %conv
br i1 %cmp2.us, label %for.body4.us, label %for.cond1.for.inc13_crit_edge.us
for.body4.lr.ph.us:
%indvars.iv26 = phi i64 [ %indvars.iv.next27, %for.cond1.for.inc13_crit_edge.us ], [ 0, %entry ]
br label %for.body4.us
for.cond1.for.inc13_crit_edge.us:
%indvars.iv.next27 = add nuw nsw i64 %indvars.iv26, 1
%exitcond28 = icmp eq i64 %indvars.iv26, 3
br i1 %exitcond28, label %for.end15, label %for.body4.lr.ph.us
for.end15:
ret void
}