Re: [PATCH] i386: Add "Ws" constraint for symbolic address/label reference [PR105576]
On Tue, Jan 16, 2024 at 11:47 PM Uros Bizjak wrote: > > On Thu, Jan 11, 2024 at 7:24 PM Fangrui Song wrote: > > > > Printing the raw symbol is useful in inline asm (e.g. in C++ to get the > > mangled name). Similar constraints are available in other targets (e.g. > > "S" for aarch64/riscv, "Cs" for m68k). > > > > There isn't a good way for x86 yet, e.g. "i" doesn't work for > > PIC/-mcmodel=large. This patch adds "Ws". Here are possible use cases: > > > > ``` > > namespace ns { extern int var; } > > asm (".pushsection .xxx,\"aw\"; .dc.a %0; .popsection" :: "Ws"(&var)); > > asm (".reloc ., BFD_RELOC_NONE, %0" :: "Ws"(&var)); > > ``` > > > > gcc/ChangeLog: > > > > PR target/105576 > > * config/i386/constraints.md: Define constraint "Ws". > > * doc/md.texi: Document it. > > > > gcc/testsuite/ChangeLog: > > > > * gcc.target/i386/asm-raw-symbol.c: New testcase. > > OK. Hi Fangrui, I pushed it for you with indentation changes in the commit log. Thanks. > Thanks, > Uros. > > > > > --- > > > > This obsoletes > > https://gcc.gnu.org/pipermail/gcc-patches/2024-January/642580.html > > I initially tried 'z', but Uros requested that a W prefix is used. > > --- > > gcc/config/i386/constraints.md | 4 > > gcc/doc/md.texi| 4 > > gcc/testsuite/gcc.target/i386/asm-raw-symbol.c | 13 + > > 3 files changed, 21 insertions(+) > > create mode 100644 gcc/testsuite/gcc.target/i386/asm-raw-symbol.c > > > > diff --git a/gcc/config/i386/constraints.md b/gcc/config/i386/constraints.md > > index 0c6e662df25..280e4c8e36c 100644 > > --- a/gcc/config/i386/constraints.md > > +++ b/gcc/config/i386/constraints.md > > @@ -348,6 +348,10 @@ (define_constraint "Wf" > > to double word size." > >(match_operand 0 "x86_64_dwzext_immediate_operand")) > > > > +(define_constraint "Ws" > > + "A symbolic reference or label reference." > > + (match_code "const,symbol_ref,label_ref")) > > + > > (define_constraint "Z" > >"32-bit unsigned integer constant, or a symbolic reference known > > to fit that range (for immediate operands in zero-extending x86-64 > > diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi > > index 47a87d6ceec..b0c61925120 100644 > > --- a/gcc/doc/md.texi > > +++ b/gcc/doc/md.texi > > @@ -4275,6 +4275,10 @@ require non-@code{VOIDmode} immediate operands). > > 128-bit integer constant where both the high and low 64-bit word > > satisfy the @code{e} constraint. > > > > +@item Ws > > +A symbolic reference or label reference. > > +You can use the @code{%p} modifier to print the raw symbol. > > + > > @item Z > > 32-bit unsigned integer constant, or a symbolic reference known > > to fit that range (for immediate operands in zero-extending x86-64 > > diff --git a/gcc/testsuite/gcc.target/i386/asm-raw-symbol.c > > b/gcc/testsuite/gcc.target/i386/asm-raw-symbol.c > > new file mode 100644 > > index 000..b7854567dd9 > > --- /dev/null > > +++ b/gcc/testsuite/gcc.target/i386/asm-raw-symbol.c > > @@ -0,0 +1,13 @@ > > +/* { dg-do compile } */ > > + > > +extern int var; > > + > > +void > > +func (void) > > +{ > > + __asm__ ("@ %p0" : : "Ws" (func)); > > + __asm__ ("@ %p0" : : "Ws" (&var + 1)); > > +} > > + > > +/* { dg-final { scan-assembler "@ func" } } */ > > +/* { dg-final { scan-assembler "@ var\\+4" } } */ > > -- > > 2.43.0.275.g3460e3d667-goog > > -- H.J.
Re: [PATCH] i386: Add "Ws" constraint for symbolic address/label reference [PR105576]
On Thu, Jan 11, 2024 at 7:24 PM Fangrui Song wrote: > > Printing the raw symbol is useful in inline asm (e.g. in C++ to get the > mangled name). Similar constraints are available in other targets (e.g. > "S" for aarch64/riscv, "Cs" for m68k). > > There isn't a good way for x86 yet, e.g. "i" doesn't work for > PIC/-mcmodel=large. This patch adds "Ws". Here are possible use cases: > > ``` > namespace ns { extern int var; } > asm (".pushsection .xxx,\"aw\"; .dc.a %0; .popsection" :: "Ws"(&var)); > asm (".reloc ., BFD_RELOC_NONE, %0" :: "Ws"(&var)); > ``` > > gcc/ChangeLog: > > PR target/105576 > * config/i386/constraints.md: Define constraint "Ws". > * doc/md.texi: Document it. > > gcc/testsuite/ChangeLog: > > * gcc.target/i386/asm-raw-symbol.c: New testcase. OK. Thanks, Uros. > > --- > > This obsoletes > https://gcc.gnu.org/pipermail/gcc-patches/2024-January/642580.html > I initially tried 'z', but Uros requested that a W prefix is used. > --- > gcc/config/i386/constraints.md | 4 > gcc/doc/md.texi| 4 > gcc/testsuite/gcc.target/i386/asm-raw-symbol.c | 13 + > 3 files changed, 21 insertions(+) > create mode 100644 gcc/testsuite/gcc.target/i386/asm-raw-symbol.c > > diff --git a/gcc/config/i386/constraints.md b/gcc/config/i386/constraints.md > index 0c6e662df25..280e4c8e36c 100644 > --- a/gcc/config/i386/constraints.md > +++ b/gcc/config/i386/constraints.md > @@ -348,6 +348,10 @@ (define_constraint "Wf" > to double word size." >(match_operand 0 "x86_64_dwzext_immediate_operand")) > > +(define_constraint "Ws" > + "A symbolic reference or label reference." > + (match_code "const,symbol_ref,label_ref")) > + > (define_constraint "Z" >"32-bit unsigned integer constant, or a symbolic reference known > to fit that range (for immediate operands in zero-extending x86-64 > diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi > index 47a87d6ceec..b0c61925120 100644 > --- a/gcc/doc/md.texi > +++ b/gcc/doc/md.texi > @@ -4275,6 +4275,10 @@ require non-@code{VOIDmode} immediate operands). > 128-bit integer constant where both the high and low 64-bit word > satisfy the @code{e} constraint. > > +@item Ws > +A symbolic reference or label reference. > +You can use the @code{%p} modifier to print the raw symbol. > + > @item Z > 32-bit unsigned integer constant, or a symbolic reference known > to fit that range (for immediate operands in zero-extending x86-64 > diff --git a/gcc/testsuite/gcc.target/i386/asm-raw-symbol.c > b/gcc/testsuite/gcc.target/i386/asm-raw-symbol.c > new file mode 100644 > index 000..b7854567dd9 > --- /dev/null > +++ b/gcc/testsuite/gcc.target/i386/asm-raw-symbol.c > @@ -0,0 +1,13 @@ > +/* { dg-do compile } */ > + > +extern int var; > + > +void > +func (void) > +{ > + __asm__ ("@ %p0" : : "Ws" (func)); > + __asm__ ("@ %p0" : : "Ws" (&var + 1)); > +} > + > +/* { dg-final { scan-assembler "@ func" } } */ > +/* { dg-final { scan-assembler "@ var\\+4" } } */ > -- > 2.43.0.275.g3460e3d667-goog >
Re: [PATCH] i386: Add "Ws" constraint for symbolic address/label reference [PR105576]
On Thu, Jan 11, 2024 at 10:24 AM Fangrui Song wrote: > > Printing the raw symbol is useful in inline asm (e.g. in C++ to get the > mangled name). Similar constraints are available in other targets (e.g. > "S" for aarch64/riscv, "Cs" for m68k). > > There isn't a good way for x86 yet, e.g. "i" doesn't work for > PIC/-mcmodel=large. This patch adds "Ws". Here are possible use cases: > > ``` > namespace ns { extern int var; } > asm (".pushsection .xxx,\"aw\"; .dc.a %0; .popsection" :: "Ws"(&var)); > asm (".reloc ., BFD_RELOC_NONE, %0" :: "Ws"(&var)); > ``` > > gcc/ChangeLog: > > PR target/105576 > * config/i386/constraints.md: Define constraint "Ws". > * doc/md.texi: Document it. > > gcc/testsuite/ChangeLog: > > * gcc.target/i386/asm-raw-symbol.c: New testcase. > > --- > > This obsoletes > https://gcc.gnu.org/pipermail/gcc-patches/2024-January/642580.html > I initially tried 'z', but Uros requested that a W prefix is used. > --- > gcc/config/i386/constraints.md | 4 > gcc/doc/md.texi| 4 > gcc/testsuite/gcc.target/i386/asm-raw-symbol.c | 13 + > 3 files changed, 21 insertions(+) > create mode 100644 gcc/testsuite/gcc.target/i386/asm-raw-symbol.c Thanks to Uros for "W" prefix suggestion. If "Ws" sounds a good choice, I'll go ahead with my Clang patch adding "Ws", even if the GCC patch is still pending:) https://github.com/protocolbuffers/protobuf/blob/1fe463ce71b6acc60b3aef65d51185e3704cac8b/src/google/protobuf/stubs/common.h // Strongly references the given variable such that the linker will be forced // to pull in this variable's translation unit. template void StrongReference(const T& var) { auto volatile unused = &var; (void)&unused; // Use address to avoid an extra load of "unused". } is an example that "Ws" constraint (which expands to no instruction) works better than the volatile address-taken operation. I am not so familiar with the mechanism, but StrongReference is used to establish a dependency edge so that the ld --gc-sections will not garbage `var`. -- 宋方睿
[PATCH] i386: Add "Ws" constraint for symbolic address/label reference [PR105576]
Printing the raw symbol is useful in inline asm (e.g. in C++ to get the mangled name). Similar constraints are available in other targets (e.g. "S" for aarch64/riscv, "Cs" for m68k). There isn't a good way for x86 yet, e.g. "i" doesn't work for PIC/-mcmodel=large. This patch adds "Ws". Here are possible use cases: ``` namespace ns { extern int var; } asm (".pushsection .xxx,\"aw\"; .dc.a %0; .popsection" :: "Ws"(&var)); asm (".reloc ., BFD_RELOC_NONE, %0" :: "Ws"(&var)); ``` gcc/ChangeLog: PR target/105576 * config/i386/constraints.md: Define constraint "Ws". * doc/md.texi: Document it. gcc/testsuite/ChangeLog: * gcc.target/i386/asm-raw-symbol.c: New testcase. --- This obsoletes https://gcc.gnu.org/pipermail/gcc-patches/2024-January/642580.html I initially tried 'z', but Uros requested that a W prefix is used. --- gcc/config/i386/constraints.md | 4 gcc/doc/md.texi| 4 gcc/testsuite/gcc.target/i386/asm-raw-symbol.c | 13 + 3 files changed, 21 insertions(+) create mode 100644 gcc/testsuite/gcc.target/i386/asm-raw-symbol.c diff --git a/gcc/config/i386/constraints.md b/gcc/config/i386/constraints.md index 0c6e662df25..280e4c8e36c 100644 --- a/gcc/config/i386/constraints.md +++ b/gcc/config/i386/constraints.md @@ -348,6 +348,10 @@ (define_constraint "Wf" to double word size." (match_operand 0 "x86_64_dwzext_immediate_operand")) +(define_constraint "Ws" + "A symbolic reference or label reference." + (match_code "const,symbol_ref,label_ref")) + (define_constraint "Z" "32-bit unsigned integer constant, or a symbolic reference known to fit that range (for immediate operands in zero-extending x86-64 diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi index 47a87d6ceec..b0c61925120 100644 --- a/gcc/doc/md.texi +++ b/gcc/doc/md.texi @@ -4275,6 +4275,10 @@ require non-@code{VOIDmode} immediate operands). 128-bit integer constant where both the high and low 64-bit word satisfy the @code{e} constraint. +@item Ws +A symbolic reference or label reference. +You can use the @code{%p} modifier to print the raw symbol. + @item Z 32-bit unsigned integer constant, or a symbolic reference known to fit that range (for immediate operands in zero-extending x86-64 diff --git a/gcc/testsuite/gcc.target/i386/asm-raw-symbol.c b/gcc/testsuite/gcc.target/i386/asm-raw-symbol.c new file mode 100644 index 000..b7854567dd9 --- /dev/null +++ b/gcc/testsuite/gcc.target/i386/asm-raw-symbol.c @@ -0,0 +1,13 @@ +/* { dg-do compile } */ + +extern int var; + +void +func (void) +{ + __asm__ ("@ %p0" : : "Ws" (func)); + __asm__ ("@ %p0" : : "Ws" (&var + 1)); +} + +/* { dg-final { scan-assembler "@ func" } } */ +/* { dg-final { scan-assembler "@ var\\+4" } } */ -- 2.43.0.275.g3460e3d667-goog