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69 lines
3.2 KiB
Diff
69 lines
3.2 KiB
Diff
commit eb5698897c52702498938592d7f76e67d126451f
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Author: Eric Botcazou <ebotcazou@adacore.com>
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Date: Wed May 5 22:48:51 2021 +0200
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Fix PR target/100402
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This is a regression for 64-bit Windows present from mainline down to the 9
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branch and introduced by the fix for PR target/99234. Again SEH, but with
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a twist related to the way MinGW implements setjmp/longjmp, which turns out
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to be piggybacked on SEH with recent versions of MinGW, i.e. the longjmp
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performs a bona-fide unwinding of the stack, because it calls RtlUnwindEx
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with the second argument initially passed to setjmp, which is the result of
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__builtin_frame_address (0) in the MinGW header file:
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define setjmp(BUF) _setjmp((BUF), __builtin_frame_address (0))
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This means that we directly expose the frame pointer to the SEH machinery
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here (unlike with regular exception handling where we use an intermediate
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CFA) and thus that we cannot do whatever we want with it. The old code
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would leave it unaligned, i.e. not multiple of 16, whereas the new code
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aligns it, but this breaks for some reason; at least it appears that a
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.seh_setframe directive with 0 as second argument always works, so the
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fix aligns it this way.
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gcc/
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PR target/100402
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* config/i386/i386.c (ix86_compute_frame_layout): For a SEH target,
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always return the establisher frame for __builtin_frame_address (0).
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gcc/testsuite/
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* gcc.c-torture/execute/20210505-1.c: New test.
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diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
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index 2f838840e96..06ad1b2274e 100644
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--- a/gcc/config/i386/i386.c
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+++ b/gcc/config/i386/i386.c
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@@ -6356,12 +6356,29 @@ ix86_compute_frame_layout (void)
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area, see the SEH code in config/i386/winnt.c for the rationale. */
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frame->hard_frame_pointer_offset = frame->sse_reg_save_offset;
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- /* If we can leave the frame pointer where it is, do so. Also, return
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+ /* If we can leave the frame pointer where it is, do so; however return
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the establisher frame for __builtin_frame_address (0) or else if the
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- frame overflows the SEH maximum frame size. */
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+ frame overflows the SEH maximum frame size.
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+
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+ Note that the value returned by __builtin_frame_address (0) is quite
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+ constrained, because setjmp is piggybacked on the SEH machinery with
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+ recent versions of MinGW:
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+
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+ # elif defined(__SEH__)
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+ # if defined(__aarch64__) || defined(_ARM64_)
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+ # define setjmp(BUF) _setjmp((BUF), __builtin_sponentry())
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+ # elif (__MINGW_GCC_VERSION < 40702)
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+ # define setjmp(BUF) _setjmp((BUF), mingw_getsp())
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+ # else
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+ # define setjmp(BUF) _setjmp((BUF), __builtin_frame_address (0))
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+ # endif
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+
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+ and the second argument passed to _setjmp, if not null, is forwarded
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+ to the TargetFrame parameter of RtlUnwindEx by longjmp (after it has
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+ built an ExceptionRecord on the fly describing the setjmp buffer). */
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const HOST_WIDE_INT diff
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= frame->stack_pointer_offset - frame->hard_frame_pointer_offset;
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- if (diff <= 255)
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+ if (diff <= 255 && !crtl->accesses_prior_frames)
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{
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/* The resulting diff will be a multiple of 16 lower than 255,
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i.e. at most 240 as required by the unwind data structure. */
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