This is the test case.
________________________________________
From: Hatanaka, Akira
Sent: Wednesday, January 04, 2012 11:21 AM
To: Eli Friedman
Cc: [email protected]
Subject: RE: [cfe-commits] r143596 - /cfe/trunk/lib/CodeGen/TargetInfo.cpp
So I finally came up with a way to fix the alignment issue.
Please review the attached patch & test case.
The idea is to add a parameter to ABIArgInfo::getDirect that is used to set the
size of a padding inserted before a byval aggregate. The test case shows
padding is inserted before the first element of a 16-byte aligned byval
structure when the first element is not aligned to a 16-byte boundary.
________________________________________
From: Eli Friedman [[email protected]]
Sent: Monday, November 07, 2011 8:04 PM
To: Hatanaka, Akira
Cc: [email protected]
Subject: Re: [cfe-commits] r143596 - /cfe/trunk/lib/CodeGen/TargetInfo.cpp
On Mon, Nov 7, 2011 at 7:27 PM, Hatanaka, Akira <[email protected]> wrote:
> Just to add to my previous email,
>
> tail call void @callee(i32 3, double %0, i64 %1, i64 %2, i64 %3) nounwind
>
> Without alignment information attached to "double %0", this is how the
> backend will pass arguments in registers, when the function above is lowered:
> i32 3 => 1st integer register
> double %0 => 2nd FP register
> i64 %1 => 3rd integer register
> i64 %2, i64 %3 => 4th and 5th integer register
>
> The correct way to pass arguments is the following:
> i32 3 => 1st integer register
> double %0 => 3rd FP register
> i64 %1 => 4th integer register
> i64 %2, i64 %3 => 5th and 6th integer register
As you've figured out, you can't attach alignment to scalars. IIRC,
x86 doesn't run into this issue. Something like "tail call void
@callee(i32 3, i32 undef, double %0, i64 %1, i64 %2, i64 %3) nounwind"
probably does what you want. I'm not entirely sure how you would
convince clang to emit that, though; it might require extending the
ABI interface a bit.
-Eli
// RUN: %clang -ccc-host-triple mips64el-unknown-linux -ccc-clang-archs mips64el -O3 -S -mabi=n64 -o - -emit-llvm %s | FileCheck %s
typedef struct {
double d;
long double ld;
} S0;
// CHECK: define void @foo1(i32 %a0, i64, double %a1.coerce0, i64 %a1.coerce1, i64 %a1.coerce2, i64 %a1.coerce3, double %a2.coerce0, i64 %a2.coerce1, i64 %a2.coerce2, i64 %a2.coerce3, i32 %b, i64, double %a3.coerce0, i64 %a3.coerce1, i64 %a3.coerce2, i64 %a3.coerce3)
// CHECK: tail call void @foo2(i32 1, i32 2, i32 %a0, i64 undef, double %a1.coerce0, i64 %a1.coerce1, i64 %a1.coerce2, i64 %a1.coerce3, double %a2.coerce0, i64 %a2.coerce1, i64 %a2.coerce2, i64 %a2.coerce3, i32 3, i64 undef, double %a3.coerce0, i64 %a3.coerce1, i64 %a3.coerce2, i64 %a3.coerce3)
// CHECK: declare void @foo2(i32, i32, i32, i64, double, i64, i64, i64, double, i64, i64, i64, i32, i64, double, i64, i64, i64)
extern void foo2(int, int, int, S0, S0, int, S0);
void foo1(int a0, S0 a1, S0 a2, int b, S0 a3) {
foo2(1, 2, a0, a1, a2, 3, a3);
}
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