Hello,
In gcc 9.0 r266355 there was change in ABI for mingw-w64 (64-bit) target --
"Return AX_REG instead of FIRST_SSE_REG for 4 or 8 byte modes". It is wrong --
now function return double in rax instead of xmm0 register. This patch shows
how to change return register from xmm0 to eax/rax (which is cool).
There are 2 problems:
1) r266355 broke 64-bit gcc 9 for mingw-w64 target
2) gcc could/should return aggregate types of up to 8 bytes via EAX register
(not st(0) or xmm0)
I've prepared patches to gcc (branches 7 and 8 + trunk 9) that checks if type
is not aggregate of up to 8 bytes before it returns in st(0)/xmm0 -- now it
should be like in C++ from MSVC. (svn patches -- please apply with -p0 option)
I think this is not new problem so if there are some hints/opinion -- please
share.
My questions are:
are the patches OK?
are the changes really needed (return struct with float in eax)?
Now (with patches) it works like this:
$ cat t.cpp
float fun1(void)
{
return 4.14f;
}
typedef struct {float x;} Float;
Float fun2(void)
{
Float v;
v.x = 4.14f;
return v;
}
double fun3(void)
{
return 3.13;
}
typedef struct {double x;} Double;
Double fun4(void)
{
Double v;
v.x = 3.13;
return v;
}
Mateusz@Mateusz-i7 /c/temp
$ g++ -c -Wall -O2 -o t.o t.cpp
Mateusz@Mateusz-i7 /c/temp
$ objdump -dr t.o
t.o: file format pe-x86-64
Disassembly of section .text:
0000000000000000 <_Z4fun1v>:
0: f3 0f 10 05 00 00 00 movss 0x0(%rip),%xmm0 # 8 <_Z4fun1v+0x8>
7: 00
4: R_X86_64_PC32 .rdata
8: c3 retq
9: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)
0000000000000010 <_Z4fun2v>:
10: 8b 05 00 00 00 00 mov 0x0(%rip),%eax # 16 <_Z4fun2v+0x6>
12: R_X86_64_PC32 .rdata
16: c3 retq
17: 66 0f 1f 84 00 00 00 nopw 0x0(%rax,%rax,1)
1e: 00 00
0000000000000020 <_Z4fun3v>:
20: f2 0f 10 05 08 00 00 movsd 0x8(%rip),%xmm0 # 30 <_Z4fun4v>
27: 00
24: R_X86_64_PC32 .rdata
28: c3 retq
29: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)
0000000000000030 <_Z4fun4v>:
30: 48 8b 05 08 00 00 00 mov 0x8(%rip),%rax # 3f <_Z4fun4v+0xf>
33: R_X86_64_PC32 .rdata
37: c3 retq
38: 90 nop
39: 90 nop
3a: 90 nop
3b: 90 nop
3c: 90 nop
3d: 90 nop
3e: 90 nop
3f: 90 nop
Mateusz@Mateusz-i7 /c/temp
$ m32- 900
Mateusz@Mateusz-i7 /c/temp
$ g++ -c -Wall -O2 -o t32.o t.cpp
Mateusz@Mateusz-i7 /c/temp
$ objdump -dr t32.o
t32.o: file format pe-i386
Disassembly of section .text:
00000000 <__Z4fun1v>:
0: d9 05 00 00 00 00 flds 0x0
2: dir32 .rdata
6: c3 ret
7: 8d b4 26 00 00 00 00 lea 0x0(%esi,%eiz,1),%esi
e: 66 90 xchg %ax,%ax
00000010 <__Z4fun2v>:
10: a1 00 00 00 00 mov 0x0,%eax
11: dir32 .rdata
15: c3 ret
16: 8d b4 26 00 00 00 00 lea 0x0(%esi,%eiz,1),%esi
1d: 8d 76 00 lea 0x0(%esi),%esi
00000020 <__Z4fun3v>:
20: dd 05 08 00 00 00 fldl 0x8
22: dir32 .rdata
26: c3 ret
27: 8d b4 26 00 00 00 00 lea 0x0(%esi,%eiz,1),%esi
2e: 66 90 xchg %ax,%ax
00000030 <__Z4fun4v>:
30: b8 0a d7 a3 70 mov $0x70a3d70a,%eax
35: ba 3d 0a 09 40 mov $0x40090a3d,%edx
3a: c3 ret
3b: 90 nop
3c: 90 nop
3d: 90 nop
3e: 90 nop
3f: 90 nop
Regards,
Mateusz
Index: gcc/config/i386/i386.c
===================================================================
--- gcc/config/i386/i386.c (revision 267306)
+++ gcc/config/i386/i386.c (working copy)
@@ -10553,6 +10553,66 @@
}
static rtx
+function_value_ms_32 (machine_mode orig_mode, machine_mode mode,
+ const_tree fntype, const_tree fn, const_tree valtype)
+{
+ unsigned int regno;
+
+ /* 8-byte vector modes in %mm0. See ix86_return_in_memory for where
+ we normally prevent this case when mmx is not available. However
+ some ABIs may require the result to be returned like DImode. */
+ if (VECTOR_MODE_P (mode) && GET_MODE_SIZE (mode) == 8)
+ regno = FIRST_MMX_REG;
+
+ /* 16-byte vector modes in %xmm0. See ix86_return_in_memory for where
+ we prevent this case when sse is not available. However some ABIs
+ may require the result to be returned like integer TImode. */
+ else if (mode == TImode
+ || (VECTOR_MODE_P (mode) && GET_MODE_SIZE (mode) == 16))
+ regno = FIRST_SSE_REG;
+
+ /* 32-byte vector modes in %ymm0. */
+ else if (VECTOR_MODE_P (mode) && GET_MODE_SIZE (mode) == 32)
+ regno = FIRST_SSE_REG;
+
+ /* 64-byte vector modes in %zmm0. */
+ else if (VECTOR_MODE_P (mode) && GET_MODE_SIZE (mode) == 64)
+ regno = FIRST_SSE_REG;
+
+ /* Floating point return values in %st(0)
+ (unless -mno-fp-ret-in-387 or aggregate type of up to 8 bytes). */
+ else if (X87_FLOAT_MODE_P (mode) && TARGET_FLOAT_RETURNS_IN_80387
+ && (GET_MODE_SIZE (mode) > 8
+ || valtype == NULL_TREE || !AGGREGATE_TYPE_P (valtype)))
+ regno = FIRST_FLOAT_REG;
+ else
+ /* Most things go in %eax. */
+ regno = AX_REG;
+
+ /* Override FP return register with %xmm0 for local functions when
+ SSE math is enabled or for functions with sseregparm attribute. */
+ if ((fn || fntype) && (mode == SFmode || mode == DFmode))
+ {
+ int sse_level = ix86_function_sseregparm (fntype, fn, false);
+ if (sse_level == -1)
+ {
+ error ("calling %qD with SSE calling convention without "
+ "SSE/SSE2 enabled", fn);
+ sorry ("this is a GCC bug that can be worked around by adding "
+ "attribute used to function called");
+ }
+ else if ((sse_level >= 1 && mode == SFmode)
+ || (sse_level == 2 && mode == DFmode))
+ regno = FIRST_SSE_REG;
+ }
+
+ /* OImode shouldn't be used directly. */
+ gcc_assert (mode != OImode);
+
+ return gen_rtx_REG (orig_mode, regno);
+}
+
+static rtx
function_value_64 (machine_mode orig_mode, machine_mode mode,
const_tree valtype)
{
@@ -10628,6 +10688,8 @@
break;
case 8:
case 4:
+ if (valtype != NULL_TREE && AGGREGATE_TYPE_P (valtype))
+ break;
if (mode == SFmode || mode == DFmode)
regno = FIRST_SSE_REG;
break;
@@ -10652,8 +10714,13 @@
if ((valtype && POINTER_BOUNDS_TYPE_P (valtype))
|| POINTER_BOUNDS_MODE_P (mode))
return gen_rtx_REG (BNDmode, FIRST_BND_REG);
- else if (TARGET_64BIT && ix86_function_type_abi (fntype) == MS_ABI)
- return function_value_ms_64 (orig_mode, mode, valtype);
+ else if (ix86_function_type_abi (fntype) == MS_ABI)
+ {
+ if (TARGET_64BIT)
+ return function_value_ms_64 (orig_mode, mode, valtype);
+ else
+ return function_value_ms_32 (orig_mode, mode, fntype, fn, valtype);
+ }
else if (TARGET_64BIT)
return function_value_64 (orig_mode, mode, valtype);
else
Index: gcc/config/i386/i386.c
===================================================================
--- gcc/config/i386/i386.c (revision 267306)
+++ gcc/config/i386/i386.c (working copy)
@@ -8990,6 +8990,66 @@
}
static rtx
+function_value_ms_32 (machine_mode orig_mode, machine_mode mode,
+ const_tree fntype, const_tree fn, const_tree valtype)
+{
+ unsigned int regno;
+
+ /* 8-byte vector modes in %mm0. See ix86_return_in_memory for where
+ we normally prevent this case when mmx is not available. However
+ some ABIs may require the result to be returned like DImode. */
+ if (VECTOR_MODE_P (mode) && GET_MODE_SIZE (mode) == 8)
+ regno = FIRST_MMX_REG;
+
+ /* 16-byte vector modes in %xmm0. See ix86_return_in_memory for where
+ we prevent this case when sse is not available. However some ABIs
+ may require the result to be returned like integer TImode. */
+ else if (mode == TImode
+ || (VECTOR_MODE_P (mode) && GET_MODE_SIZE (mode) == 16))
+ regno = FIRST_SSE_REG;
+
+ /* 32-byte vector modes in %ymm0. */
+ else if (VECTOR_MODE_P (mode) && GET_MODE_SIZE (mode) == 32)
+ regno = FIRST_SSE_REG;
+
+ /* 64-byte vector modes in %zmm0. */
+ else if (VECTOR_MODE_P (mode) && GET_MODE_SIZE (mode) == 64)
+ regno = FIRST_SSE_REG;
+
+ /* Floating point return values in %st(0)
+ (unless -mno-fp-ret-in-387 or aggregate type of up to 8 bytes). */
+ else if (X87_FLOAT_MODE_P (mode) && TARGET_FLOAT_RETURNS_IN_80387
+ && (GET_MODE_SIZE (mode) > 8
+ || valtype == NULL_TREE || !AGGREGATE_TYPE_P (valtype)))
+ regno = FIRST_FLOAT_REG;
+ else
+ /* Most things go in %eax. */
+ regno = AX_REG;
+
+ /* Override FP return register with %xmm0 for local functions when
+ SSE math is enabled or for functions with sseregparm attribute. */
+ if ((fn || fntype) && (mode == SFmode || mode == DFmode))
+ {
+ int sse_level = ix86_function_sseregparm (fntype, fn, false);
+ if (sse_level == -1)
+ {
+ error ("calling %qD with SSE calling convention without "
+ "SSE/SSE2 enabled", fn);
+ sorry ("this is a GCC bug that can be worked around by adding "
+ "attribute used to function called");
+ }
+ else if ((sse_level >= 1 && mode == SFmode)
+ || (sse_level == 2 && mode == DFmode))
+ regno = FIRST_SSE_REG;
+ }
+
+ /* OImode shouldn't be used directly. */
+ gcc_assert (mode != OImode);
+
+ return gen_rtx_REG (orig_mode, regno);
+}
+
+static rtx
function_value_64 (machine_mode orig_mode, machine_mode mode,
const_tree valtype)
{
@@ -9063,6 +9123,13 @@
&& !COMPLEX_MODE_P (mode))
regno = FIRST_SSE_REG;
break;
+ case 8:
+ case 4:
+ if (valtype != NULL_TREE && AGGREGATE_TYPE_P (valtype))
+ break;
+ if (mode == SFmode || mode == DFmode)
+ regno = FIRST_SSE_REG;
+ break;
default:
break;
}
@@ -9081,8 +9148,13 @@
fn = fntype_or_decl;
fntype = fn ? TREE_TYPE (fn) : fntype_or_decl;
- if (TARGET_64BIT && ix86_function_type_abi (fntype) == MS_ABI)
- return function_value_ms_64 (orig_mode, mode, valtype);
+ if (ix86_function_type_abi (fntype) == MS_ABI)
+ {
+ if (TARGET_64BIT)
+ return function_value_ms_64 (orig_mode, mode, valtype);
+ else
+ return function_value_ms_32 (orig_mode, mode, fntype, fn, valtype);
+ }
else if (TARGET_64BIT)
return function_value_64 (orig_mode, mode, valtype);
else
Index: gcc/config/i386/i386.c
===================================================================
--- gcc/config/i386/i386.c (revision 267306)
+++ gcc/config/i386/i386.c (working copy)
@@ -9314,6 +9314,66 @@
}
static rtx
+function_value_ms_32 (machine_mode orig_mode, machine_mode mode,
+ const_tree fntype, const_tree fn, const_tree valtype)
+{
+ unsigned int regno;
+
+ /* 8-byte vector modes in %mm0. See ix86_return_in_memory for where
+ we normally prevent this case when mmx is not available. However
+ some ABIs may require the result to be returned like DImode. */
+ if (VECTOR_MODE_P (mode) && GET_MODE_SIZE (mode) == 8)
+ regno = FIRST_MMX_REG;
+
+ /* 16-byte vector modes in %xmm0. See ix86_return_in_memory for where
+ we prevent this case when sse is not available. However some ABIs
+ may require the result to be returned like integer TImode. */
+ else if (mode == TImode
+ || (VECTOR_MODE_P (mode) && GET_MODE_SIZE (mode) == 16))
+ regno = FIRST_SSE_REG;
+
+ /* 32-byte vector modes in %ymm0. */
+ else if (VECTOR_MODE_P (mode) && GET_MODE_SIZE (mode) == 32)
+ regno = FIRST_SSE_REG;
+
+ /* 64-byte vector modes in %zmm0. */
+ else if (VECTOR_MODE_P (mode) && GET_MODE_SIZE (mode) == 64)
+ regno = FIRST_SSE_REG;
+
+ /* Floating point return values in %st(0)
+ (unless -mno-fp-ret-in-387 or aggregate type of up to 8 bytes). */
+ else if (X87_FLOAT_MODE_P (mode) && TARGET_FLOAT_RETURNS_IN_80387
+ && (GET_MODE_SIZE (mode) > 8
+ || valtype == NULL_TREE || !AGGREGATE_TYPE_P (valtype)))
+ regno = FIRST_FLOAT_REG;
+ else
+ /* Most things go in %eax. */
+ regno = AX_REG;
+
+ /* Override FP return register with %xmm0 for local functions when
+ SSE math is enabled or for functions with sseregparm attribute. */
+ if ((fn || fntype) && (mode == SFmode || mode == DFmode))
+ {
+ int sse_level = ix86_function_sseregparm (fntype, fn, false);
+ if (sse_level == -1)
+ {
+ error ("calling %qD with SSE calling convention without "
+ "SSE/SSE2 enabled", fn);
+ sorry ("this is a GCC bug that can be worked around by adding "
+ "attribute used to function called");
+ }
+ else if ((sse_level >= 1 && mode == SFmode)
+ || (sse_level == 2 && mode == DFmode))
+ regno = FIRST_SSE_REG;
+ }
+
+ /* OImode shouldn't be used directly. */
+ gcc_assert (mode != OImode);
+
+ return gen_rtx_REG (orig_mode, regno);
+}
+
+static rtx
function_value_64 (machine_mode orig_mode, machine_mode mode,
const_tree valtype)
{
@@ -9389,6 +9449,8 @@
break;
case 8:
case 4:
+ if (valtype != NULL_TREE && AGGREGATE_TYPE_P (valtype))
+ break;
if (mode == SFmode || mode == DFmode)
regno = FIRST_SSE_REG;
break;
@@ -9413,8 +9475,13 @@
if ((valtype && POINTER_BOUNDS_TYPE_P (valtype))
|| POINTER_BOUNDS_MODE_P (mode))
return gen_rtx_REG (BNDmode, FIRST_BND_REG);
- else if (TARGET_64BIT && ix86_function_type_abi (fntype) == MS_ABI)
- return function_value_ms_64 (orig_mode, mode, valtype);
+ else if (ix86_function_type_abi (fntype) == MS_ABI)
+ {
+ if (TARGET_64BIT)
+ return function_value_ms_64 (orig_mode, mode, valtype);
+ else
+ return function_value_ms_32 (orig_mode, mode, fntype, fn, valtype);
+ }
else if (TARGET_64BIT)
return function_value_64 (orig_mode, mode, valtype);
else
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