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[ARM] Lower llvm.ctlz.i32 to a libcall when clz is not available. 

The inline sequence is very long (about 70 bytes on Thumb1), so it's
not really a good idea to inline it, especially when optimizing for
size.

Differential Revision: https://reviews.llvm.org/D47917

llvm-svn: 340458
This commit is contained in:
Eli Friedman 2018-08-22 21:47:14 +00:00
parent 20f9cd8821
commit 96e3cd85bd
4 changed files with 26 additions and 4 deletions
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3
llvm/include/llvm/IR/RuntimeLibcalls.def
View File

@ -83,6 +83,9 @@ HANDLE_LIBCALL(UDIVREM_I64, nullptr)
HANDLE_LIBCALL(UDIVREM_I128, nullptr)
HANDLE_LIBCALL(NEG_I32, "__negsi2")
HANDLE_LIBCALL(NEG_I64, "__negdi2")
HANDLE_LIBCALL(CTLZ_I32, "__clzsi2")
HANDLE_LIBCALL(CTLZ_I64, "__clzdi2")
HANDLE_LIBCALL(CTLZ_I128, "__clzti2")
// Floating-point
HANDLE_LIBCALL(ADD_F32, "__addsf3")

15
llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
View File

@ -4262,6 +4262,21 @@ void SelectionDAGLegalize::ConvertNodeToLibcall(SDNode *Node) {
RTLIB::MUL_I16, RTLIB::MUL_I32,
RTLIB::MUL_I64, RTLIB::MUL_I128));
break;
case ISD::CTLZ_ZERO_UNDEF:
switch (Node->getSimpleValueType(0).SimpleTy) {
default:
llvm_unreachable("LibCall explicitly requested, but not available");
case MVT::i32:
Results.push_back(ExpandLibCall(RTLIB::CTLZ_I32, Node, false));
break;
case MVT::i64:
Results.push_back(ExpandLibCall(RTLIB::CTLZ_I64, Node, false));
break;
case MVT::i128:
Results.push_back(ExpandLibCall(RTLIB::CTLZ_I128, Node, false));
break;
}
break;
}
// Replace the original node with the legalized result.

4
llvm/lib/Target/ARM/ARMISelLowering.cpp
View File

@ -850,8 +850,10 @@ ARMTargetLowering::ARMTargetLowering(const TargetMachine &TM,
}
setOperationAction(ISD::CTTZ, MVT::i32, Custom);
setOperationAction(ISD::CTPOP, MVT::i32, Expand);
if (!Subtarget->hasV5TOps() || Subtarget->isThumb1Only())
if (!Subtarget->hasV5TOps() || Subtarget->isThumb1Only()) {
setOperationAction(ISD::CTLZ, MVT::i32, Expand);
setOperationAction(ISD::CTLZ_ZERO_UNDEF, MVT::i32, LibCall);
}
// @llvm.readcyclecounter requires the Performance Monitors extension.
// Default to the 0 expansion on unsupported platforms.

8
llvm/test/CodeGen/ARM/clz.ll
View File

@ -1,10 +1,12 @@
; RUN: llc -mtriple=arm-eabi -mattr=+v5t %s -o - | FileCheck %s
; RUN: llc -mtriple=arm-eabi -mattr=+v5t %s -o - | FileCheck %s -check-prefixes=CHECK,INLINE
; RUN: llc -mtriple=arm-eabi %s -o - | FileCheck %s -check-prefixes=CHECK,LIBCALL
declare i32 @llvm.ctlz.i32(i32, i1)
define i32 @test(i32 %x) {
; CHECK: test
; CHECK: clz r0, r0
; CHECK-LABEL: test
; INLINE: clz r0, r0
; LIBCALL: b __clzsi2
%tmp.1 = call i32 @llvm.ctlz.i32( i32 %x, i1 true )
ret i32 %tmp.1
}