Run tests on ppc64le machines

Thanks to small string optimization, storing a short string to std::string
is usually more efficient than referring it from std::string_view.

elf/arch-riscv.cc

@@ -939,11 +939,13 @@ i64 riscv_resize_sections(Context<E> &ctx) {
 // identified by name. Some extensions are of single-letter alphabet such
 // as "m" or "q". Newer extension names start with "z" followed by one or
 // more alphabets (i.e. "zicsr"). "s" and "x" prefixes are reserved
-// for supervisor- level extensions and private extensions, respectively.
+// for supervisor-level extensions and private extensions, respectively.
 //
 // Each extension consists of a name, a major version and a minor version.
 // For example, "m2p0" indicates the "m" extension of version 2.0. "p" is
-// just a separator.
+// just a separator. Versions are often omitted in documents, but they are
+// mandatory in .riscv.attributes. Likewise, abbreviations as "g" (which
+// is short for "IMAFD") are not allowed in .riscv.attributes.
 //
 // Each RISC-V object file contains an ISA string enumerating extensions
 // used by the object file. We need to merge input objects' ISA strings
@@ -955,7 +957,7 @@ i64 riscv_resize_sections(Context<E> &ctx) {
 // The following functions takes care of ISA strings.
 
 struct Extn {
-  std::string_view name;
+  std::string name;
   i64 major;
   i64 minor;
 };
@@ -1082,12 +1084,12 @@ static std::vector<Extn> merge_extensions(std::span<Extn> x, std::span<Extn> y)
 }
 
 static std::string to_string(std::span<Extn> v) {
-  std::string str = std::string(v[0].name) + std::to_string(v[0].major) +
-                    "p" + std::to_string(v[0].minor);
+  std::string str = v[0].name + std::to_string(v[0].major) + "p" +
+                    std::to_string(v[0].minor);
 
   for (i64 i = 1; i < v.size(); i++)
-    str += "_" + std::string(v[i].name) + std::to_string(v[i].major) +
-           "p" + std::to_string(v[i].minor);
+    str += "_" + v[i].name + std::to_string(v[i].major) + "p" +
+           std::to_string(v[i].minor);
   return str;
 }
 

elf/output-chunks.cc

@@ -355,7 +355,8 @@ static std::vector<ElfPhdr<E>> create_phdr(Context<E> &ctx) {
 
   // Create a PT_RISCV_ATTRIBUTES
   if constexpr (is_riscv<E>)
-    define(PT_RISCV_ATTRIBUTES, PF_R, 1, ctx.extra.riscv_attributes);
+    if (ctx.extra.riscv_attributes->shdr.sh_size)
+      define(PT_RISCV_ATTRIBUTES, PF_R, 1, ctx.extra.riscv_attributes);
 
   // Create a PT_OPENBSD_RANDOMIZE
   for (Chunk<E> *chunk : ctx.chunks)

test/elf/CMakeLists.txt

@@ -11,6 +11,8 @@ function(add_target TRIPLE)
     set(HOST arm)
   elseif(${HOST} STREQUAL "ppc64")
     set(HOST powerpc64)
+  elseif(${HOST} STREQUAL "ppc64le")
+    set(HOST powerpc64le)
   endif()
 
   if(${TRIPLE} MATCHES "${HOST}-.*")

test/elf/riscv64_attributes.sh

@@ -5,6 +5,9 @@ cat <<EOF | $CC -march=rv64imafd_xfoo1p5 -o $t/a.o -c -xc -
 void foo() {}
 EOF
 
+# The compiler might not create .riscv.attributes
+readelf --sections $t/a.o | grep -Fq .riscv.attributes || skip
+
 cat <<EOF | $CC -march=rv64imafd_xfoo2p0 -o $t/b.o -c -xc -
 void bar() {}
 EOF

test/elf/riscv64_attributes2.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+. $(dirname $0)/common.inc
+
+cat <<EOF | $CC -o $t/a.o -c -xc -
+void _start() {}
+EOF
+
+$STRIP --remove-section=.riscv.attributes $t/a.o
+
+$CC -B. -nostdlib -o $t/exe $t/a.o
+
+readelf -W --segments --sections $t/exe > $t/log
+! grep -F .riscv.attributes $t/log || false
+! grep -F RISCV_ATTR $t/log || false