gcc: Add uncommitted patch.

pkgs/development/compilers/gcc/7/riscv-no-relax.patch

@@ -0,0 +1,109 @@
+commit e7c570f37384d824cb9725f237920e9691e57269
+gpg: Signature made Tue 06 Mar 2018 04:52:46 PM PST
+gpg:                using RSA key 00CE76D1834960DFCE886DF8EF4CA1502CCBAB41
+gpg:                issuer "palmer@dabbelt.com"
+gpg: Good signature from "Palmer Dabbelt <palmer@dabbelt.com>" [ultimate]
+gpg:                 aka "Palmer Dabbelt <palmer@sifive.com>" [ultimate]
+Author: Palmer Dabbelt <palmer@sifive.com>
+Date:   Thu Mar 1 12:01:06 2018 -0800
+
+    RISC-V: Add and document the "-mno-relax" option
+
+    RISC-V relies on aggressive linker relaxation to get good code size.  As
+    a result no text symbol addresses can be known until link time, which
+    means that alignment must be handled during the link.  This alignment
+    pass is essentially just another linker relaxation, so this has the
+    unfortunate side effect that linker relaxation is required for
+    correctness on many RISC-V targets.
+
+    The RISC-V assembler has supported an ".option norelax" for a long time
+    because there are situations in which linker relaxation is a bad idea --
+    the canonical example is when trying to materialize the initial value of
+    the global pointer into a register, which would otherwise be relaxed to
+    a NOP.  We've been relying on users who want to disable relaxation for
+    an entire link to pass "-Wl,--no-relax", but that still relies on the
+    linker relaxing R_RISCV_ALIGN to handle alignment despite it not being
+    strictly necessary.
+
+    This patch adds a GCC option, "-mno-relax", that disable linker
+    relaxation by adding ".option norelax" to the top of every generated
+    assembly file.  The assembler is smart enough to handle alignment at
+    assemble time for files that have never emitted a relaxable relocation,
+    so this is sufficient to really disable all relaxations in the linker,
+    which results in significantly faster link times for large objects.
+
+    This also has the side effect of allowing toolchains that don't support
+    linker relaxation (LLVM and the Linux module loader) to function
+    correctly.  Toolchains that don't support linker relaxation should
+    default to "-mno-relax" and error when presented with any R_RISCV_ALIGN
+    relocation as those need to be handled for correctness.
+
+    gcc/ChangeLog
+
+    2018-03-01  Palmer Dabbelt  <palmer@sifive.com>
+
+            * config/riscv/riscv.opt (mrelax): New option.
+            * config/riscv/riscv.c (riscv_file_start): Emit ".option
+            "norelax" when riscv_mrelax is disabled.
+            * doc/invoke.texi (RISC-V): Document "-mrelax" and "-mno-relax".
+
+diff --git a/gcc/config/riscv/riscv.c b/gcc/config/riscv/riscv.c
+index c38f6c394d54..3e81874de232 100644
+--- a/gcc/config/riscv/riscv.c
++++ b/gcc/config/riscv/riscv.c
+@@ -3979,6 +3979,11 @@ riscv_file_start (void)
+
+   /* Instruct GAS to generate position-[in]dependent code.  */
+   fprintf (asm_out_file, "\t.option %spic\n", (flag_pic ? "" : "no"));
++
++  /* If the user specifies "-mno-relax" on the command line then disable linker
++     relaxation in the assembler.  */
++  if (! riscv_mrelax)
++    fprintf (asm_out_file, "\t.option norelax\n");
+ }
+
+ /* Implement TARGET_ASM_OUTPUT_MI_THUNK.  Generate rtl rather than asm text
+diff --git a/gcc/config/riscv/riscv.opt b/gcc/config/riscv/riscv.opt
+index 581a26bb5c1e..b37ac75d9bb4 100644
+--- a/gcc/config/riscv/riscv.opt
++++ b/gcc/config/riscv/riscv.opt
+@@ -106,6 +106,11 @@ mexplicit-relocs
+ Target Report Mask(EXPLICIT_RELOCS)
+ Use %reloc() operators, rather than assembly macros, to load addresses.
+
++mrelax
++Target Bool Var(riscv_mrelax) Init(1)
++Take advantage of linker relaxations to reduce the number of instructions
++required to materialize symbol addresses.
++
+ Mask(64BIT)
+
+ Mask(MUL)
+diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
+index 8d366c626bae..deb48af2ecad 100644
+--- a/gcc/doc/invoke.texi
++++ b/gcc/doc/invoke.texi
+@@ -1042,7 +1042,8 @@ See RS/6000 and PowerPC Options.
+ -msave-restore  -mno-save-restore @gol
+ -mstrict-align -mno-strict-align @gol
+ -mcmodel=medlow -mcmodel=medany @gol
+--mexplicit-relocs  -mno-explicit-relocs @gol}
++-mexplicit-relocs  -mno-explicit-relocs @gol
++-mrelax -mno-relax @gol}
+
+ @emph{RL78 Options}
+ @gccoptlist{-msim  -mmul=none  -mmul=g13  -mmul=g14  -mallregs @gol
+@@ -23102,6 +23103,12 @@ Use or do not use assembler relocation operators when dealing with symbolic
+ addresses.  The alternative is to use assembler macros instead, which may
+ limit optimization.
+
++@item -mrelax
++@itemx -mno-relax
++Take advantage of linker relaxations to reduce the number of instructions
++required to materialize symbol addresses. The default is to take advantage of
++linker relaxations.
++
+ @end table
+
+ @node RL78 Options
+