Jeff Law writes:
> On 01/06/2017 09:08 AM, Mikael Pettersson wrote:
> > This fixes / works-around the wrong-code PR57583 on M68K, caused by
> > overflowing the 16-bit jump table offsets the backend uses.
> >
> > Ideally the backend should define CASE_VECTOR_SHORTEN_MODE, but that
> > AFAIK needs insn length attributes, which the backend only has for CF
> > but not for classic M68K.
> >
> > Instead this patch adds an -mlong-jump-table-offsets option, and adjusts
> > the code for emitting and using jump table offsets to handle both short
> > and long offsets. As long as the option is not selected, the backend
> > behaves exactly as before.
> >
> > John Paul Adrian Glaubitz tested this patch by compiling "mednafen"
> > with it, which previously failed; I also tested earlier versions.
> >
> > Is this Ok for trunk?
> >
> > /Mikael
> >
> >
> > gcc/
> >
> > 2017-01-06 Mikael Pettersson <mikpeli...@gmail.com>
> >
> > PR target/57583
> > * config/m68k/m68k.opt (LONG_JUMP_TABLE_OFFSETS): New option.
> > * config/m68k/linux.h (ASM_RETURN_CASE_JUMP): Handle
> > TARGET_LONG_JUMP_TABLE_OFFSETS.
> > * config/m68k/m68kelf.h (ASM_RETURN_CASE_JUMP): Likewise.
> > * config/m68k/netbsd-elf.h (ASM_RETURN_CASE_JUMP): Likewise.
> > * config/m68k/m68k.h (CASE_VECTOR_MODE): Likewise.
> > (ASM_OUTPUT_ADDR_DIFF_ELF): Likewise.
> > * config/m68k/m68k.md (tablejump expander): Likewise.
> > (*tablejump_pcrel_hi): Renamed from unnamed insn, reject
> > TARGET_LONG_JUMP_TABLE_OFFSETS.
> > (*tablejump_pcrel_si): New insn, handle TARGET_LONG_JUMP_TABLE_OFFSETS.
> > * doc/invoke.texi (M68K options): Add -mlong-jump-table-offsets.
> Can't tablejump_pcrel_si be simplified? Isn't the output pattern just:
>
> #ifdef ASM_RETURN_CASE_JUMP
> ASM_RETURN_CASE_JUMP;
> #else
> return MOTOROLA ? "jmp (2,pc,%0.l)" : "jmp pc@(2,%0:l)";
> #endif
>
> With that simplification I think this will be fine.
>
> jeff
Indeed, good catch. Revised patch below. /Mikael
gcc/
2017-01-06 Mikael Pettersson <mikpeli...@gmail.com>
PR target/57583
* config/m68k/m68k.opt (LONG_JUMP_TABLE_OFFSETS): New option.
* config/m68k/linux.h (ASM_RETURN_CASE_JUMP): Handle
TARGET_LONG_JUMP_TABLE_OFFSETS.
* config/m68k/m68kelf.h (ASM_RETURN_CASE_JUMP): Likewise.
* config/m68k/netbsd-elf.h (ASM_RETURN_CASE_JUMP): Likewise.
* config/m68k/m68k.h (CASE_VECTOR_MODE): Likewise.
(ASM_OUTPUT_ADDR_DIFF_ELF): Likewise.
* config/m68k/m68k.md (tablejump expander): Likewise.
(*tablejump_pcrel_hi): Renamed from unnamed insn, reject
TARGET_LONG_JUMP_TABLE_OFFSETS.
(*tablejump_pcrel_si): New insn, handle TARGET_LONG_JUMP_TABLE_OFFSETS.
* doc/invoke.texi (M68K options): Add -mlong-jump-table-offsets.
--- gcc-7-20170101/gcc/config/m68k/linux.h.~1~ 2017-01-01 13:07:43.000000000
+0100
+++ gcc-7-20170101/gcc/config/m68k/linux.h 2017-01-06 20:16:25.278132607
+0100
@@ -98,9 +98,13 @@ along with GCC; see the file COPYING3.
{ \
if (ADDRESS_REG_P (operands[0])) \
return "jmp %%pc@(2,%0:l)"; \
+ else if (TARGET_LONG_JUMP_TABLE_OFFSETS) \
+ return "jmp %%pc@(2,%0:l)"; \
else \
return "ext%.l %0\n\tjmp %%pc@(2,%0:l)"; \
} \
+ else if (TARGET_LONG_JUMP_TABLE_OFFSETS) \
+ return "jmp %%pc@(2,%0:l)"; \
else \
return "jmp %%pc@(2,%0:w)"; \
} while (0)
--- gcc-7-20170101/gcc/config/m68k/m68k.h.~1~ 2017-01-01 13:07:43.000000000
+0100
+++ gcc-7-20170101/gcc/config/m68k/m68k.h 2017-01-06 20:16:25.278132607
+0100
@@ -675,7 +675,7 @@ __transfer_from_trampoline ()
\
/* This address is OK as it stands. */
#define PIC_CASE_VECTOR_ADDRESS(index) index
-#define CASE_VECTOR_MODE HImode
+#define CASE_VECTOR_MODE (TARGET_LONG_JUMP_TABLE_OFFSETS ? SImode : HImode)
#define CASE_VECTOR_PC_RELATIVE 1
#define DEFAULT_SIGNED_CHAR 1
@@ -857,7 +857,11 @@ do { if (cc_prev_status.flags & CC_IN_68
asm_fprintf (FILE, "\t.long %LL%d\n", VALUE)
#define ASM_OUTPUT_ADDR_DIFF_ELT(FILE, BODY, VALUE, REL) \
- asm_fprintf (FILE, "\t.word %LL%d-%LL%d\n", VALUE, REL)
+ asm_fprintf (FILE, \
+ TARGET_LONG_JUMP_TABLE_OFFSETS \
+ ? "\t.long %LL%d-%LL%d\n" \
+ : "\t.word %LL%d-%LL%d\n", \
+ VALUE, REL)
/* We don't have a way to align to more than a two-byte boundary, so do the
best we can and don't complain. */
--- gcc-7-20170101/gcc/config/m68k/m68k.md.~1~ 2017-01-01 13:07:43.000000000
+0100
+++ gcc-7-20170101/gcc/config/m68k/m68k.md 2017-01-06 20:21:32.677641812
+0100
@@ -6695,7 +6695,9 @@ (define_expand "tablejump"
{
#if CASE_VECTOR_PC_RELATIVE
operands[0] = gen_rtx_PLUS (SImode, pc_rtx,
- gen_rtx_SIGN_EXTEND (SImode, operands[0]));
+ TARGET_LONG_JUMP_TABLE_OFFSETS
+ ? operands[0]
+ : gen_rtx_SIGN_EXTEND (SImode, operands[0]));
#endif
})
@@ -6710,12 +6712,26 @@ (define_insn "*tablejump_internal"
[(set_attr "type" "jmp")])
;; Jump to variable address from dispatch table of relative addresses.
-(define_insn ""
+(define_insn "*tablejump_pcrel_si"
+ [(set (pc)
+ (plus:SI (pc)
+ (match_operand:SI 0 "register_operand" "r")))
+ (use (label_ref (match_operand 1 "" "")))]
+ "TARGET_LONG_JUMP_TABLE_OFFSETS"
+{
+#ifdef ASM_RETURN_CASE_JUMP
+ ASM_RETURN_CASE_JUMP;
+#else
+ return MOTOROLA ? "jmp (2,pc,%0.l)" : "jmp pc@(2,%0:l)";
+#endif
+})
+
+(define_insn "*tablejump_pcrel_hi"
[(set (pc)
(plus:SI (pc)
(sign_extend:SI (match_operand:HI 0 "register_operand" "r"))))
(use (label_ref (match_operand 1 "" "")))]
- ""
+ "!TARGET_LONG_JUMP_TABLE_OFFSETS"
{
#ifdef ASM_RETURN_CASE_JUMP
ASM_RETURN_CASE_JUMP;
--- gcc-7-20170101/gcc/config/m68k/m68k.opt.~1~ 2017-01-01 13:07:43.000000000
+0100
+++ gcc-7-20170101/gcc/config/m68k/m68k.opt 2017-01-06 20:16:25.278132607
+0100
@@ -142,6 +142,10 @@ mid-shared-library
Target Report Mask(ID_SHARED_LIBRARY)
Enable ID based shared library.
+mlong-jump-table-offsets
+Target Report RejectNegative Mask(LONG_JUMP_TABLE_OFFSETS)
+Use 32-bit offsets in jump tables rather than 16-bit offsets.
+
mnobitfield
Target RejectNegative InverseMask(BITFIELD)
Do not use the bit-field instructions.
--- gcc-7-20170101/gcc/config/m68k/m68kelf.h.~1~ 2017-01-01
13:07:43.000000000 +0100
+++ gcc-7-20170101/gcc/config/m68k/m68kelf.h 2017-01-06 20:16:25.278132607
+0100
@@ -58,9 +58,13 @@ along with GCC; see the file COPYING3.
{ \
if (ADDRESS_REG_P (operands[0])) \
return "jmp %%pc@(2,%0:l)"; \
+ else if (TARGET_LONG_JUMP_TABLE_OFFSETS) \
+ return "jmp %%pc@(2,%0:l)"; \
else \
return "ext%.l %0\n\tjmp %%pc@(2,%0:l)"; \
} \
+ else if (TARGET_LONG_JUMP_TABLE_OFFSETS) \
+ return "jmp %%pc@(2,%0:l)"; \
else \
return "jmp %%pc@(2,%0:w)"; \
} while (0)
--- gcc-7-20170101/gcc/config/m68k/netbsd-elf.h.~1~ 2017-01-01
13:07:43.000000000 +0100
+++ gcc-7-20170101/gcc/config/m68k/netbsd-elf.h 2017-01-06 20:16:25.278132607
+0100
@@ -136,9 +136,13 @@ while (0)
{ \
if (ADDRESS_REG_P (operands[0])) \
return "jmp %%pc@(2,%0:l)"; \
+ else if (TARGET_LONG_JUMP_TABLE_OFFSETS) \
+ return "jmp %%pc@(2,%0:l)"; \
else \
return "ext%.l %0\n\tjmp %%pc@(2,%0:l)"; \
} \
+ else if (TARGET_LONG_JUMP_TABLE_OFFSETS) \
+ return "jmp %%pc@(2,%0:l)"; \
else \
return "jmp %%pc@(2,%0:w)"; \
} while (0)
--- gcc-7-20170101/gcc/doc/invoke.texi.~1~ 2017-01-01 13:07:43.000000000
+0100
+++ gcc-7-20170101/gcc/doc/invoke.texi 2017-01-06 20:16:25.278132607 +0100
@@ -837,7 +837,7 @@ Objective-C and Objective-C++ Dialects}.
-mno-short -mhard-float -m68881 -msoft-float -mpcrel @gol
-malign-int -mstrict-align -msep-data -mno-sep-data @gol
-mshared-library-id=n -mid-shared-library -mno-id-shared-library @gol
--mxgot -mno-xgot}
+-mxgot -mno-xgot -mlong-jump-table-offsets}
@emph{MCore Options}
@gccoptlist{-mhardlit -mno-hardlit -mdiv -mno-div -mrelax-immediates @gol
@@ -18460,6 +18460,11 @@ object file that accesses more than 8192
These options have no effect unless GCC is generating
position-independent code.
+@item -mlong-jump-table-offsets
+@opindex mlong-jump-table-offsets
+Use 32-bit offsets in @code{switch} tables. The default is to use
+16-bit offsets.
+
@end table
@node MCore Options
