From: Alan Modra <amodra@gmail.com>
Date: Mon, 28 Sep 2020 06:53:01 +0000 (+0930)
Subject: [RS6000] -mno-minimal-toc vs. power10 pcrelative
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=c6be439b37702f6ac4c2fc447c6f3ed1042b80a3;p=gcc.git

[RS6000] -mno-minimal-toc vs. power10 pcrelative

We've had this hack in the libgcc config to build libgcc with
-mcmodel=small for powerpc64 for a long time.  It wouldn't be a bad
thing if someone who knows the multilib machinery well could arrange
for -mcmodel=small to be passed just for ppc64 when building for
earlier than power10.  But for now, make -mno-minimal-toc do nothing
when pcrel.  Which will do the right thing for any project that has
copied libgcc's trick.

We want this if configuring using --with-cpu=power10 to build a
power10 pcrel libgcc.  --mcmodel=small turns off pcrel.

gcc/
	* config/rs6000/linux64.h (SUBSUBTARGET_OVERRIDE_OPTIONS): Don't
	set -mcmodel=small for -mno-minimal-toc when pcrel.
libgcc/
	* config/rs6000/t-linux: Document purpose of -mno-minimal-toc.
---

diff --git a/gcc/config/rs6000/linux64.h b/gcc/config/rs6000/linux64.h
index 2ded3301282..5c9f8e3d7af 100644
--- a/gcc/config/rs6000/linux64.h
+++ b/gcc/config/rs6000/linux64.h
@@ -132,20 +132,29 @@ extern int dot_symbols;
 	  if ((rs6000_isa_flags & OPTION_MASK_POWERPC64) == 0)	\
 	    {							\
 	      rs6000_isa_flags |= OPTION_MASK_POWERPC64;	\
-	      error ("%<-m64%> requires a PowerPC64 cpu");		\
+	      error ("%<-m64%> requires a PowerPC64 cpu");	\
 	    }							\
+	  if (!global_options_set.x_rs6000_current_cmodel)	\
+	    SET_CMODEL (CMODEL_MEDIUM);				\
 	  if ((rs6000_isa_flags_explicit			\
 	       & OPTION_MASK_MINIMAL_TOC) != 0)			\
 	    {							\
 	      if (global_options_set.x_rs6000_current_cmodel	\
 		  && rs6000_current_cmodel != CMODEL_SMALL)	\
 		error ("%<-mcmodel incompatible with other toc options%>"); \
-	      SET_CMODEL (CMODEL_SMALL);			\
+	      if (TARGET_MINIMAL_TOC)				\
+		SET_CMODEL (CMODEL_SMALL);			\
+	      else if (TARGET_PCREL				\
+		       || (PCREL_SUPPORTED_BY_OS		\
+			   && (rs6000_isa_flags_explicit	\
+			       & OPTION_MASK_PCREL) == 0))	\
+		/* Ignore -mno-minimal-toc.  */			\
+		;						\
+	      else						\
+		SET_CMODEL (CMODEL_SMALL);			\
 	    }							\
 	  else							\
 	    {							\
-	      if (!global_options_set.x_rs6000_current_cmodel)	\
-		SET_CMODEL (CMODEL_MEDIUM);			\
 	      if (rs6000_current_cmodel != CMODEL_SMALL)	\
 		{						\
 		  if (!global_options_set.x_TARGET_NO_FP_IN_TOC) \
diff --git a/libgcc/config/rs6000/t-linux b/libgcc/config/rs6000/t-linux
index 4f6d4c4a4d2..ed821947b66 100644
--- a/libgcc/config/rs6000/t-linux
+++ b/libgcc/config/rs6000/t-linux
@@ -1,3 +1,8 @@
 SHLIB_MAPFILES += $(srcdir)/config/rs6000/libgcc-glibc.ver
 
-HOST_LIBGCC2_CFLAGS += -mlong-double-128 -mno-minimal-toc
+HOST_LIBGCC2_CFLAGS += -mlong-double-128
+
+# This is a way of selecting -mcmodel=small for ppc64, which gives
+# smaller and faster libgcc code.  Directly specifying -mcmodel=small
+# would need to take into account targets for which -mcmodel is invalid.
+HOST_LIBGCC2_CFLAGS += -mno-minimal-toc