compiler: use builtin memcmp directly

    
    Instead of going through a C function __go_memcmp, we can just
    use __builtin_memcmp directly. This allows more optimizations in
    the compiler backend.
    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/183537

From-SVN: r272620

gcc/go/gofrontend/MERGE

-1232eef628227ef855c5fa6d94b31778b2e74a85
+338e4baf88a4ae676205dff601dbef2d31b19d2d
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

gcc/go/gofrontend/expressions.cc

@@ -6199,7 +6199,8 @@ Binary_expression::lower_compare_to_memcmp(Gogo*, Statement_inserter* inserter)
 					       TYPE_INFO_SIZE);
 
   Expression* call = Runtime::make_call(Runtime::MEMCMP, loc, 3, a1, a2, len);
-  Expression* zero = Expression::make_integer_ul(0, NULL, loc);
+  Type* int32_type = Type::lookup_integer_type("int32");
+  Expression* zero = Expression::make_integer_ul(0, int32_type, loc);
   return Expression::make_binary(this->op_, call, zero, loc);
 }
 

gcc/go/gofrontend/runtime.def

@@ -29,7 +29,7 @@
 // result types.
 
 // The standard C memcmp function, used for struct comparisons.
-DEF_GO_RUNTIME(MEMCMP, "__go_memcmp", P3(POINTER, POINTER, UINTPTR), R1(INT))
+DEF_GO_RUNTIME(MEMCMP, "__builtin_memcmp", P3(POINTER, POINTER, UINTPTR), R1(INT32))
 
 // Decode a non-ASCII rune from a string.
 DEF_GO_RUNTIME(DECODERUNE, "runtime.decoderune", P2(STRING, INT),

libgo/Makefile.am

@@ -459,7 +459,6 @@ runtime_files = \
 	runtime/go-fieldtrack.c \
 	runtime/go-matherr.c \
 	runtime/go-memclr.c \
-	runtime/go-memcmp.c \
 	runtime/go-memequal.c \
 	runtime/go-nanotime.c \
 	runtime/go-now.c \

libgo/Makefile.in

@@ -244,8 +244,8 @@ am__objects_3 = runtime/aeshash.lo runtime/go-assert.lo \
 	runtime/go-cgo.lo runtime/go-construct-map.lo \
 	runtime/go-ffi.lo runtime/go-fieldtrack.lo \
 	runtime/go-matherr.lo runtime/go-memclr.lo \
-	runtime/go-memcmp.lo runtime/go-memequal.lo \
-	runtime/go-nanotime.lo runtime/go-now.lo runtime/go-nosys.lo \
+	runtime/go-memequal.lo runtime/go-nanotime.lo \
+	runtime/go-now.lo runtime/go-nosys.lo \
 	runtime/go-reflect-call.lo runtime/go-runtime-error.lo \
 	runtime/go-setenv.lo runtime/go-signal.lo \
 	runtime/go-unsafe-pointer.lo runtime/go-unsetenv.lo \
@@ -892,7 +892,6 @@ runtime_files = \
 	runtime/go-fieldtrack.c \
 	runtime/go-matherr.c \
 	runtime/go-memclr.c \
-	runtime/go-memcmp.c \
 	runtime/go-memequal.c \
 	runtime/go-nanotime.c \
 	runtime/go-now.c \
@@ -1343,8 +1342,6 @@ runtime/go-matherr.lo: runtime/$(am__dirstamp) \
 	runtime/$(DEPDIR)/$(am__dirstamp)
 runtime/go-memclr.lo: runtime/$(am__dirstamp) \
 	runtime/$(DEPDIR)/$(am__dirstamp)
-runtime/go-memcmp.lo: runtime/$(am__dirstamp) \
-	runtime/$(DEPDIR)/$(am__dirstamp)
 runtime/go-memequal.lo: runtime/$(am__dirstamp) \
 	runtime/$(DEPDIR)/$(am__dirstamp)
 runtime/go-nanotime.lo: runtime/$(am__dirstamp) \
@@ -1436,7 +1433,6 @@ distclean-compile:
 @AMDEP_TRUE@@am__include@ @am__quote@runtime/$(DEPDIR)/go-fieldtrack.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@runtime/$(DEPDIR)/go-matherr.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@runtime/$(DEPDIR)/go-memclr.Plo@am__quote@
-@AMDEP_TRUE@@am__include@ @am__quote@runtime/$(DEPDIR)/go-memcmp.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@runtime/$(DEPDIR)/go-memequal.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@runtime/$(DEPDIR)/go-nanotime.Plo@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@runtime/$(DEPDIR)/go-nosys.Plo@am__quote@

libgo/runtime/go-memcmp.c

-/* go-memcmp.c -- the go memory comparison function.
-
-   Copyright 2012 The Go Authors. All rights reserved.
-   Use of this source code is governed by a BSD-style
-   license that can be found in the LICENSE file.  */
-
-#include "runtime.h"
-
-intgo
-__go_memcmp (const void *p1, const void *p2, uintptr len)
-{
-  return __builtin_memcmp (p1, p2, len);
-}