/usr/src/gcc-4.6/debian/patches/libffi-powerpc-sysv-without-string-ops.diff is in gcc-4.6-source 4.6.4-6ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 | --- a/src/libffi/src/powerpc/ffi.c
+++ b/src/libffi/src/powerpc/ffi.c
@@ -45,11 +45,6 @@
FLAG_RETURNS_64BITS = 1 << (31-28),
FLAG_RETURNS_128BITS = 1 << (31-27), /* cr6 */
- FLAG_SYSV_SMST_R4 = 1 << (31-26), /* use r4 for FFI_SYSV 8 byte
- structs. */
- FLAG_SYSV_SMST_R3 = 1 << (31-25), /* use r3 for FFI_SYSV 4 byte
- structs. */
- /* Bits (31-24) through (31-19) store shift value for SMST */
FLAG_ARG_NEEDS_COPY = 1 << (31- 7),
#ifndef __NO_FPRS__
@@ -687,37 +682,22 @@
break;
case FFI_TYPE_STRUCT:
- if (cif->abi == FFI_SYSV)
- {
- /* The final SYSV ABI says that structures smaller or equal 8 bytes
- are returned in r3/r4. The FFI_GCC_SYSV ABI instead returns them
- in memory. */
+ /*
+ * The final SYSV ABI says that structures smaller or equal 8 bytes
+ * are returned in r3/r4. The FFI_GCC_SYSV ABI instead returns them
+ * in memory.
+ *
+ * NOTE: The assembly code can safely assume that it just needs to
+ * store both r3 and r4 into a 8-byte word-aligned buffer, as
+ * we allocate a temporary buffer in ffi_call() if this flag is
+ * set.
+ */
+ if (cif->abi == FFI_SYSV && size <= 8)
+ flags |= FLAG_RETURNS_SMST;
- /* Treat structs with size <= 8 bytes. */
- if (size <= 8)
- {
- flags |= FLAG_RETURNS_SMST;
- /* These structs are returned in r3. We pack the type and the
- precalculated shift value (needed in the sysv.S) into flags.
- The same applies for the structs returned in r3/r4. */
- if (size <= 4)
- {
- flags |= FLAG_SYSV_SMST_R3;
- flags |= 8 * (4 - size) << 8;
- break;
- }
- /* These structs are returned in r3 and r4. See above. */
- if (size <= 8)
- {
- flags |= FLAG_SYSV_SMST_R3 | FLAG_SYSV_SMST_R4;
- flags |= 8 * (8 - size) << 8;
- break;
- }
- }
- }
- intarg_count++;
- flags |= FLAG_RETVAL_REFERENCE;
- /* Fall through. */
+ intarg_count++;
+ flags |= FLAG_RETVAL_REFERENCE;
+ /* Fall through. */
case FFI_TYPE_VOID:
flags |= FLAG_RETURNS_NOTHING;
break;
@@ -931,21 +911,30 @@
void
ffi_call(ffi_cif *cif, void (*fn)(void), void *rvalue, void **avalue)
{
+ /*
+ * The final SYSV ABI says that structures smaller or equal 8 bytes
+ * are returned in r3/r4. The FFI_GCC_SYSV ABI instead returns them
+ * in memory.
+ *
+ * Just to keep things simple for the assembly code, we will always
+ * bounce-buffer struct return values less than or equal to 8 bytes.
+ * This allows the ASM to handle SYSV small structures by directly
+ * writing r3 and r4 to memory without worrying about struct size.
+ */
+ unsigned int smst_buffer[2];
extended_cif ecif;
ecif.cif = cif;
ecif.avalue = avalue;
- /* If the return value is a struct and we don't have a return */
- /* value address then we need to make one */
-
- if ((rvalue == NULL) && (cif->rtype->type == FFI_TYPE_STRUCT))
- {
- ecif.rvalue = alloca(cif->rtype->size);
- }
- else
- ecif.rvalue = rvalue;
-
+ /* Ensure that we have a valid struct return value */
+ ecif.rvalue = rvalue;
+ if (cif->rtype->type == FFI_TYPE_STRUCT) {
+ if (cif->rtype->size <= 8)
+ ecif.rvalue = smst_buffer;
+ else if (!rvalue)
+ ecif.rvalue = alloca(cif->rtype->size);
+ }
switch (cif->abi)
{
@@ -967,6 +956,10 @@
FFI_ASSERT (0);
break;
}
+
+ /* Check for a bounce-buffered return value */
+ if (rvalue && ecif.rvalue == smst_buffer)
+ memcpy(rvalue, smst_buffer, cif->rtype->size);
}
--- a/src/libffi/src/powerpc/sysv.S
+++ b/src/libffi/src/powerpc/sysv.S
@@ -142,19 +142,14 @@
#endif
L(small_struct_return_value):
- extrwi %r6,%r31,2,19 /* number of bytes padding = shift/8 */
- mtcrf 0x02,%r31 /* copy flags to cr[24:27] (cr6) */
- extrwi %r5,%r31,5,19 /* r5 <- number of bits of padding */
- subfic %r6,%r6,4 /* r6 <- number of useful bytes in r3 */
- bf- 25,L(done_return_value) /* struct in r3 ? if not, done. */
-/* smst_one_register: */
- slw %r3,%r3,%r5 /* Left-justify value in r3 */
- mtxer %r6 /* move byte count to XER ... */
- stswx %r3,0,%r30 /* ... and store that many bytes */
- bf+ 26,L(done_return_value) /* struct in r3:r4 ? */
- add %r6,%r6,%r30 /* adjust pointer */
- stswi %r4,%r6,4 /* store last four bytes */
- b L(done_return_value)
+ /*
+ * The C code always allocates a properly-aligned 8-byte bounce
+ * buffer to make this assembly code very simple. Just write out
+ * r3 and r4 to the buffer to allow the C code to handle the rest.
+ */
+ stw %r3, 0(%r30)
+ stw %r4, 4(%r30)
+ b L(done_return_value)
.LFE1:
END(ffi_call_SYSV)
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