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42d43351b2
parameters. Examples of these are:
struct { } a;
union { } b[256];
int a[0];
An empty aggregate has an address, although dereferencing that address is
pointless. When passed as a parameter, an empty aggregate does not consume
a protocol register, nor does it consume a doubleword in the parameter save
area. Passing an empty aggregate by reference passes an address just as
for any other aggregate. Returning an empty aggregate uses GPR3 as a hidden
address of the return value location, just as for any other aggregate.
The patch modifies PPCTargetLowering::LowerFormalArguments_64SVR4 and
PPCTargetLowering::LowerCall_64SVR4 to properly skip empty aggregate
parameters passed by value. The handling of return values and by-reference
parameters was already correct.
Built on powerpc64-unknown-linux-gnu and tested with no new regressions.
A test case is included to test proper handling of empty aggregate
parameters on both sides of the function call protocol.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167090 91177308-0d34-0410-b5e6-96231b3b80d8
52 lines
1.9 KiB
LLVM
52 lines
1.9 KiB
LLVM
; RUN: llc -mcpu=pwr7 -O0 < %s | FileCheck %s
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; This tests correct handling of empty aggregate parameters and return values.
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; An empty parameter passed by value does not consume a protocol register or
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; a parameter save area doubleword. An empty parameter passed by reference
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; is treated as any other pointer parameter. An empty aggregate return value
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; is treated as any other aggregate return value, passed via address as a
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; hidden parameter in GPR3. In this example, GPR3 contains the return value
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; address, GPR4 contains the address of e2, and e1 and e3 are not passed or
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; received.
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target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f128:128:128-v128:128:128-n32:64"
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target triple = "powerpc64-unknown-linux-gnu"
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%struct.empty = type {}
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define void @callee(%struct.empty* noalias sret %agg.result, %struct.empty* byval %a1, %struct.empty* %a2, %struct.empty* byval %a3) nounwind {
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entry:
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%a2.addr = alloca %struct.empty*, align 8
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store %struct.empty* %a2, %struct.empty** %a2.addr, align 8
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%0 = load %struct.empty** %a2.addr, align 8
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%1 = bitcast %struct.empty* %agg.result to i8*
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%2 = bitcast %struct.empty* %0 to i8*
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call void @llvm.memcpy.p0i8.p0i8.i64(i8* %1, i8* %2, i64 0, i32 1, i1 false)
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ret void
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}
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; CHECK: callee:
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; CHECK: std 4,
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; CHECK: std 3,
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; CHECK-NOT: std 5,
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; CHECK-NOT: std 6,
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; CHECK: blr
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declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture, i64, i32, i1) nounwind
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define void @caller(%struct.empty* noalias sret %agg.result) nounwind {
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entry:
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%e1 = alloca %struct.empty, align 1
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%e2 = alloca %struct.empty, align 1
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%e3 = alloca %struct.empty, align 1
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call void @callee(%struct.empty* sret %agg.result, %struct.empty* byval %e1, %struct.empty* %e2, %struct.empty* byval %e3)
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ret void
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}
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; CHECK: caller:
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; CHECK: addi 4,
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; CHECK: std 3,
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; CHECK-NOT: std 5,
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; CHECK-NOT: std 6,
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; CHECK: bl callee
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