IRgen/ABI/x86_64: Avoid passing small structs using byval sometimes.
- We do this when it is easy to determine that the backend will pass them on
the stack properly by itself.
Currently LLVM codegen is really bad in some cases with byval, for example, on
the test case here (which is derived from Sema code, which likes to pass
SourceLocations around)::
struct s47 { unsigned a; };
void f47(int,int,int,int,int,int,struct s47);
void test47(int a, struct s47 b) { f47(a, a, a, a, a, a, b); }
we used to emit code like this::
...
movl %esi, -8(%rbp)
movl -8(%rbp), %ecx
movl %ecx, (%rsp)
...
to handle moving the struct onto the stack, which is just appalling.
Now we generate::
movl %esi, (%rsp)
which seems better, no?
llvm-svn: 152462
2012-03-10 09:03:58 +08:00
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// RUN: %clang_cc1 -emit-llvm %s -o %t -triple=x86_64-apple-darwin10
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// RUN: FileCheck < %t %s
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2011-06-16 02:26:32 +08:00
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IRgen/ABI/x86_64: Avoid passing small structs using byval sometimes.
- We do this when it is easy to determine that the backend will pass them on
the stack properly by itself.
Currently LLVM codegen is really bad in some cases with byval, for example, on
the test case here (which is derived from Sema code, which likes to pass
SourceLocations around)::
struct s47 { unsigned a; };
void f47(int,int,int,int,int,int,struct s47);
void test47(int a, struct s47 b) { f47(a, a, a, a, a, a, b); }
we used to emit code like this::
...
movl %esi, -8(%rbp)
movl -8(%rbp), %ecx
movl %ecx, (%rsp)
...
to handle moving the struct onto the stack, which is just appalling.
Now we generate::
movl %esi, (%rsp)
which seems better, no?
llvm-svn: 152462
2012-03-10 09:03:58 +08:00
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// Make sure this doesn't crash. We used to generate a byval here and wanted to
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// verify a valid alignment, but we now realize we can use an i16 and let the
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// backend guarantee the alignment.
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2011-06-16 02:26:32 +08:00
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void a(int,int,int,int,int,int,__complex__ char);
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void b(__complex__ char *y) { a(0,0,0,0,0,0,*y); }
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2013-08-15 14:47:53 +08:00
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// CHECK-LABEL: define void @b
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2011-07-10 01:41:47 +08:00
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// CHECK: alloca { i8, i8 }*, align 8
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IRgen/ABI/x86_64: Avoid passing small structs using byval sometimes.
- We do this when it is easy to determine that the backend will pass them on
the stack properly by itself.
Currently LLVM codegen is really bad in some cases with byval, for example, on
the test case here (which is derived from Sema code, which likes to pass
SourceLocations around)::
struct s47 { unsigned a; };
void f47(int,int,int,int,int,int,struct s47);
void test47(int a, struct s47 b) { f47(a, a, a, a, a, a, b); }
we used to emit code like this::
...
movl %esi, -8(%rbp)
movl -8(%rbp), %ecx
movl %ecx, (%rsp)
...
to handle moving the struct onto the stack, which is just appalling.
Now we generate::
movl %esi, (%rsp)
which seems better, no?
llvm-svn: 152462
2012-03-10 09:03:58 +08:00
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// CHECK: call void @a(i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i16 {{.*}})
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