From: Gustavo Romero <gromero@br.ibm.com>
From: Jakub Jirutka <jakub@jirutka.cz>
Date: Mon, 28 Mar 2017 01:51:00 +0200
Subject: [PATCH] Fix compilation on PPC when libc musl is used instead of glibc

Musl on Power does not define regs member as a pt_regs pointer type,
hence it's necessary to use member gp_regs instead.

Ported to nodejs 7.7.4 (jirutka)

--- a/deps/v8/src/libsampler/sampler.cc
+++ b/deps/v8/src/libsampler/sampler.cc
@@ -450,11 +450,19 @@
   state->sp = reinterpret_cast<void*>(mcontext.gregs[29]);
   state->fp = reinterpret_cast<void*>(mcontext.gregs[30]);
 #elif V8_HOST_ARCH_PPC
+#if V8_LIBC_GLIBC
   state->pc = reinterpret_cast<void*>(ucontext->uc_mcontext.regs->nip);
   state->sp =
       reinterpret_cast<void*>(ucontext->uc_mcontext.regs->gpr[PT_R1]);
   state->fp =
       reinterpret_cast<void*>(ucontext->uc_mcontext.regs->gpr[PT_R31]);
+#else
+  // Some C libraries, notably Musl, define the regs member as a void pointer,
+  // hence we use the gp_regs member instead.
+  state.pc = reinterpret_cast<void*>(ucontext->uc_mcontext.gp_regs[32]);
+  state.sp = reinterpret_cast<void*>(ucontext->uc_mcontext.gp_regs[1]);
+  state.fp = reinterpret_cast<void*>(ucontext->uc_mcontext.gp_regs[31]);
+#endif
 #elif V8_HOST_ARCH_S390
 #if V8_TARGET_ARCH_32_BIT
   // 31-bit target will have bit 0 (MSB) of the PSW set to denote addressing