http://llvm.org/bugs/show_bug.cgi?id=3474
Summary: x86-32: clang could avoid byval in more cases
Product: clang
Version: unspecified
Platform: All
OS/Version: All
Status: NEW
Severity: normal
Priority: P2
Component: LLVM Codegen
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected]
clang currently passes some structures byval even when they will be passed in
an integer register. clang should avoid using byval in such cases to give the
LLVM optimizers the most freedom to hack on the type.
For example,
--
ddun...@67-218-102-230:single-args$ cat t.c
struct s { short a, b, c, d; } f0(struct s x) {
return x;
}
ddun...@67-218-102-230:single-args$ xcc -emit-llvm -S -o - t.c -m32
; ModuleID = 't.c'
target datalayout =
"e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
target triple = "i386-apple-darwin10.0"
%struct.s = type <{ i16, i16, i16, i16 }>
define i64 @f0(%struct.s* byval %x) nounwind {
entry:
%retval = alloca %struct.s ; <%struct.s*> [#uses=2]
%tmp = bitcast %struct.s* %retval to i8* ; <i8*>
[#uses=1]
%tmp1 = bitcast %struct.s* %x to i8* ; <i8*> [#uses=1]
call void @llvm.memmove.i32(i8* %tmp, i8* %tmp1, i32 8, i32 2)
%0 = bitcast %struct.s* %retval to i64* ; <i64*> [#uses=1]
%1 = load i64* %0 ; <i64> [#uses=1]
ret i64 %1
}
declare void @llvm.memmove.i32(i8* nocapture, i8* nocapture, i32, i32) nounwind
--
This should be easy to fix since return arguments already get coerced to avoid
sret.
--
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