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# DP: ppc64el, fix ELFv2 homogeneous float aggregate ABI bug
Subject: [PATCH, rs6000, 4.8/4.9] Fix ELFv2 homogeneous float aggregate ABI bug
Hello,
this is the variant intended for the 4.8/4.9 branches of the patch:
https://gcc.gnu.org/ml/gcc-patches/2014-07/msg00994.html
As discussed, it does *not* actually change ABI, but only warn when
encountering a situation where the ABI will change in a future GCC.
(Avoiding the specific term "GCC 4.10" here since I'm not certain
whether the next GCC release will in fact be called that ...)
Tested on powerpc64-linux and powerpc64le-linux; also verified using
the ABI compat suite (against an unpatched GCC) that this patch does
not change the ABI.
OK for 4.8/4.9 once the mainline patch is in?
Bye,
Ulrich
gcc/ChangeLog:
* config/rs6000/rs6000.c (rs6000_function_arg): If a float argument
does not fit fully into floating-point registers, and there is still
space in the register parameter area, issue -Wpsabi note that the ABI
will change in a future GCC release.
gcc/testsuite/ChangeLog:
* gcc.target/powerpc/ppc64-abi-warn-1.c: New test.
--- a/src/gcc/config/rs6000/rs6000.c
+++ b/src/gcc/config/rs6000/rs6000.c
@@ -10225,6 +10225,7 @@ rs6000_function_arg (cumulative_args_t c
rtx r, off;
int i, k = 0;
unsigned long n_fpreg = (GET_MODE_SIZE (elt_mode) + 7) >> 3;
+ int fpr_words;
/* Do we also need to pass this argument in the parameter
save area? */
@@ -10253,6 +10254,37 @@ rs6000_function_arg (cumulative_args_t c
rvec[k++] = gen_rtx_EXPR_LIST (VOIDmode, r, off);
}
+ /* If there were not enough FPRs to hold the argument, the rest
+ usually goes into memory. However, if the current position
+ is still within the register parameter area, a portion may
+ actually have to go into GPRs.
+
+ Note that it may happen that the portion of the argument
+ passed in the first "half" of the first GPR was already
+ passed in the last FPR as well.
+
+ For unnamed arguments, we already set up GPRs to cover the
+ whole argument in rs6000_psave_function_arg, so there is
+ nothing further to do at this point.
+
+ GCC 4.8/4.9 Note: This was implemented incorrectly in earlier
+ GCC releases. To avoid any ABI change on the release branch,
+ we retain that original implementation here, but warn if we
+ encounter a case where the ABI will change in the future. */
+ fpr_words = (i * GET_MODE_SIZE (elt_mode)) / (TARGET_32BIT ? 4 : 8);
+ if (i < n_elts && align_words + fpr_words < GP_ARG_NUM_REG
+ && cum->nargs_prototype > 0)
+ {
+ static bool warned;
+ if (!warned && warn_psabi)
+ {
+ warned = true;
+ inform (input_location,
+ "the ABI of passing homogeneous float aggregates"
+ " will change in a future GCC release");
+ }
+ }
+
return rs6000_finish_function_arg (mode, rvec, k);
}
else if (align_words < GP_ARG_NUM_REG)
--- /dev/null
+++ b/src/gcc/testsuite/gcc.target/powerpc/ppc64-abi-warn-1.c
@@ -0,0 +1,12 @@
+/* { dg-do compile { target { powerpc*-*-linux* && lp64 } } } */
+/* { dg-options "-mabi=elfv2" } */
+
+struct f8
+ {
+ float x[8];
+ };
+
+void test (struct f8 a, struct f8 b) /* { dg-message "note: the ABI of passing homogeneous float aggregates will change" } */
+{
+}
+
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