compiler,runtime: pass only ptr and len to some runtime calls

This ports https://golang.org/cl/227163 to the Go frontend.
This is a step toward moving up to the go1.15rc1 release.

Original CL description:

    cmd/compile,runtime: pass only ptr and len to some runtime calls

    Some runtime calls accept a slice, but only use ptr and len.
    This change modifies most such routines to accept only ptr and len.

    After this change, the only runtime calls that accept an unnecessary
    cap arg are concatstrings and slicerunetostring.
    Neither is particularly common, and both are complicated to modify.

    Negligible compiler performance impact. Shrinks binaries a little.
    There are only a few regressions; the one I investigated was
    due to register allocation fluctuation.

    Passes 'go test -race std cmd', modulo golang/go#38265 and golang/go#38266.
    Wow, does that take a long time to run.

    file      before    after     Δ       %
    compile   19655024  19655152  +128    +0.001%
    cover     5244840   5236648   -8192   -0.156%
    dist      3662376   3658280   -4096   -0.112%
    link      6680056   6675960   -4096   -0.061%
    pprof     14789844  14777556  -12288  -0.083%
    test2json 2824744   2820648   -4096   -0.145%
    trace     11647876  11639684  -8192   -0.070%
    vet       8260472   8256376   -4096   -0.050%
    total     115163736 115118808 -44928  -0.039%

For golang/go#36890

Change-Id: I1dc1424ccb092a9ad70472e560a743c35dd27bfc
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/245099
Reviewed-by: Cherry Zhang <[email protected]>

Author: ianlancetaylor

go/expressions.cc

@@ -4157,45 +4157,43 @@ Type_conversion_expression::do_get_backend(Translate_context* context)
       go_assert(e->integer_type() != NULL);
       go_assert(this->expr_->is_variable());
 
-      Runtime::Function code;
+      Expression* buf;
+      if (this->no_escape_ && !this->no_copy_)
+        {
+          Type* byte_type = Type::lookup_integer_type("uint8");
+          Expression* buflen =
+            Expression::make_integer_ul(tmp_string_buf_size, NULL, loc);
+          Type* array_type = Type::make_array_type(byte_type, buflen);
+          buf = Expression::make_allocation(array_type, loc);
+          buf->allocation_expression()->set_allocate_on_stack();
+          buf->allocation_expression()->set_no_zero();
+        }
+      else
+        buf = Expression::make_nil(loc);
+
       if (e->integer_type()->is_byte())
         {
+	  Expression* ptr =
+	    Expression::make_slice_info(this->expr_, SLICE_INFO_VALUE_POINTER,
+					loc);
+	  Expression* len =
+	    Expression::make_slice_info(this->expr_, SLICE_INFO_LENGTH, loc);
           if (this->no_copy_)
             {
               if (gogo->debug_optimization())
                 go_debug(loc, "no copy string([]byte)");
-              Expression* ptr = Expression::make_slice_info(this->expr_,
-                                                            SLICE_INFO_VALUE_POINTER,
-                                                            loc);
-              Expression* len = Expression::make_slice_info(this->expr_,
-                                                            SLICE_INFO_LENGTH,
-                                                            loc);
               Expression* str = Expression::make_string_value(ptr, len, loc);
               return str->get_backend(context);
             }
-          code = Runtime::SLICEBYTETOSTRING;
+	  return Runtime::make_call(Runtime::SLICEBYTETOSTRING, loc, 3, buf,
+				    ptr, len)->get_backend(context);
         }
       else
         {
           go_assert(e->integer_type()->is_rune());
-          code = Runtime::SLICERUNETOSTRING;
-        }
-
-      Expression* buf;
-      if (this->no_escape_)
-        {
-          Type* byte_type = Type::lookup_integer_type("uint8");
-          Expression* buflen =
-            Expression::make_integer_ul(tmp_string_buf_size, NULL, loc);
-          Type* array_type = Type::make_array_type(byte_type, buflen);
-          buf = Expression::make_allocation(array_type, loc);
-          buf->allocation_expression()->set_allocate_on_stack();
-          buf->allocation_expression()->set_no_zero();
-        }
-      else
-        buf = Expression::make_nil(loc);
-      return Runtime::make_call(code, loc, 2, buf,
-				this->expr_)->get_backend(context);
+	  return Runtime::make_call(Runtime::SLICERUNETOSTRING, loc, 2, buf,
+				    this->expr_)->get_backend(context);
+	}
     }
   else if (type->is_slice_type() && expr_type->is_string_type())
     {
@@ -8397,8 +8395,16 @@ Builtin_call_expression::do_flatten(Gogo* gogo, Named_object* function,
         if (et->has_pointer())
           {
             Expression* td = Expression::make_type_descriptor(et, loc);
+	    Expression* pd =
+	      Expression::make_slice_info(arg1, SLICE_INFO_VALUE_POINTER, loc);
+	    Expression* ld =
+	      Expression::make_slice_info(arg1, SLICE_INFO_LENGTH, loc);
+	    Expression* ps =
+	      Expression::make_slice_info(arg2, SLICE_INFO_VALUE_POINTER, loc);
+	    Expression* ls =
+	      Expression::make_slice_info(arg2, SLICE_INFO_LENGTH, loc);
             ret = Runtime::make_call(Runtime::TYPEDSLICECOPY, loc,
-                                     3, td, arg1, arg2);
+                                     5, td, pd, ld, ps, ls);
           }
         else
           {

go/runtime.def

@@ -47,7 +47,7 @@ DEF_GO_RUNTIME(INTSTRING, "runtime.intstring", P2(POINTER, INT64), R1(STRING))
 
 // Convert a []byte to a string.
 DEF_GO_RUNTIME(SLICEBYTETOSTRING, "runtime.slicebytetostring",
-	       P2(POINTER, SLICE), R1(STRING))
+	       P3(POINTER, POINTER, INT), R1(STRING))
 
 // Convert a []rune to a string.
 DEF_GO_RUNTIME(SLICERUNETOSTRING, "runtime.slicerunetostring",
@@ -249,17 +249,16 @@ DEF_GO_RUNTIME(CLOSE, "runtime.closechan", P1(CHAN), R0())
 
 
 // Copy.
-DEF_GO_RUNTIME(SLICECOPY, "runtime.slicecopy", P3(SLICE, SLICE, UINTPTR),
-	       R1(INT))
+DEF_GO_RUNTIME(SLICECOPY, "runtime.slicecopy",
+	       P5(POINTER, INT, POINTER, INT, UINTPTR), R1(INT))
 
 // Copy from string.
-DEF_GO_RUNTIME(SLICESTRINGCOPY, "runtime.slicestringcopy", P2(SLICE, STRING),
-	       R1(INT))
+DEF_GO_RUNTIME(SLICESTRINGCOPY, "runtime.slicestringcopy",
+	       P3(POINTER, INT, STRING), R1(INT))
 
 // Copy of value containing pointers.
 DEF_GO_RUNTIME(TYPEDSLICECOPY, "runtime.typedslicecopy",
-	       P3(TYPE, SLICE, SLICE), R1(INT))
-
+	       P5(TYPE, POINTER, INT, POINTER, INT), R1(INT))
 
 // Grow a slice for append.
 DEF_GO_RUNTIME(GROWSLICE, "runtime.growslice",

libgo/go/runtime/cgocheck.go

@@ -76,23 +76,24 @@ func cgoCheckMemmove(typ *_type, dst, src unsafe.Pointer, off, size uintptr) {
 	cgoCheckTypedBlock(typ, src, off, size)
 }
 
-// cgoCheckSliceCopy is called when copying n elements of a slice from
-// src to dst.  typ is the element type of the slice.
+// cgoCheckSliceCopy is called when copying n elements of a slice.
+// src and dst are pointers to the first element of the slice.
+// typ is the element type of the slice.
 // It throws if the program is copying slice elements that contain Go pointers
 // into non-Go memory.
 //go:nosplit
 //go:nowritebarrier
-func cgoCheckSliceCopy(typ *_type, dst, src slice, n int) {
+func cgoCheckSliceCopy(typ *_type, dst, src unsafe.Pointer, n int) {
 	if typ.ptrdata == 0 {
 		return
 	}
-	if !cgoIsGoPointer(src.array) {
+	if !cgoIsGoPointer(src) {
 		return
 	}
-	if cgoIsGoPointer(dst.array) {
+	if cgoIsGoPointer(dst) {
 		return
 	}
-	p := src.array
+	p := src
 	for i := 0; i < n; i++ {
 		cgoCheckTypedBlock(typ, p, 0, typ.size)
 		p = add(p, typ.size)

libgo/go/runtime/mbarrier.go

@@ -219,16 +219,14 @@ func reflect_typedmemmovepartial(typ *_type, dst, src unsafe.Pointer, off, size
 }
 
 //go:nosplit
-func typedslicecopy(typ *_type, dst, src slice) int {
-	n := dst.len
-	if n > src.len {
-		n = src.len
+func typedslicecopy(typ *_type, dstPtr unsafe.Pointer, dstLen int, srcPtr unsafe.Pointer, srcLen int) int {
+	n := dstLen
+	if n > srcLen {
+		n = srcLen
 	}
 	if n == 0 {
 		return 0
 	}
-	dstp := dst.array
-	srcp := src.array
 
 	// The compiler emits calls to typedslicecopy before
 	// instrumentation runs, so unlike the other copying and
@@ -237,19 +235,19 @@ func typedslicecopy(typ *_type, dst, src slice) int {
 	if raceenabled {
 		callerpc := getcallerpc()
 		pc := funcPC(slicecopy)
-		racewriterangepc(dstp, uintptr(n)*typ.size, callerpc, pc)
-		racereadrangepc(srcp, uintptr(n)*typ.size, callerpc, pc)
+		racewriterangepc(dstPtr, uintptr(n)*typ.size, callerpc, pc)
+		racereadrangepc(srcPtr, uintptr(n)*typ.size, callerpc, pc)
 	}
 	if msanenabled {
-		msanwrite(dstp, uintptr(n)*typ.size)
-		msanread(srcp, uintptr(n)*typ.size)
+		msanwrite(dstPtr, uintptr(n)*typ.size)
+		msanread(srcPtr, uintptr(n)*typ.size)
 	}
 
 	if writeBarrier.cgo {
-		cgoCheckSliceCopy(typ, dst, src, n)
+		cgoCheckSliceCopy(typ, dstPtr, srcPtr, n)
 	}
 
-	if dstp == srcp {
+	if dstPtr == srcPtr {
 		return n
 	}
 
@@ -259,11 +257,11 @@ func typedslicecopy(typ *_type, dst, src slice) int {
 	// before calling typedslicecopy.
 	size := uintptr(n) * typ.size
 	if writeBarrier.needed {
-		bulkBarrierPreWrite(uintptr(dstp), uintptr(srcp), size)
+		bulkBarrierPreWrite(uintptr(dstPtr), uintptr(srcPtr), size)
 	}
 	// See typedmemmove for a discussion of the race between the
 	// barrier and memmove.
-	memmove(dstp, srcp, size)
+	memmove(dstPtr, srcPtr, size)
 	return n
 }
 
@@ -293,7 +291,7 @@ func reflect_typedslicecopy(elemType *_type, dst, src slice) int {
 		memmove(dst.array, src.array, size)
 		return n
 	}
-	return typedslicecopy(elemType, dst, src)
+	return typedslicecopy(elemType, dst.array, dst.len, src.array, src.len)
 }
 
 // typedmemclr clears the typed memory at ptr with type typ. The

libgo/go/runtime/os_linux.go

@@ -207,13 +207,14 @@ func getHugePageSize() uintptr {
 	if fd < 0 {
 		return 0
 	}
-	n := read(fd, noescape(unsafe.Pointer(&numbuf[0])), int32(len(numbuf)))
+	ptr := noescape(unsafe.Pointer(&numbuf[0]))
+	n := read(fd, ptr, int32(len(numbuf)))
 	closefd(fd)
 	if n <= 0 {
 		return 0
 	}
-	l := n - 1 // remove trailing newline
-	v, ok := atoi(slicebytetostringtmp(numbuf[:l]))
+	n-- // remove trailing newline
+	v, ok := atoi(slicebytetostringtmp((*byte)(ptr), int(n)))
 	if !ok || v < 0 {
 		v = 0
 	}

libgo/go/runtime/slice.go

@@ -199,14 +199,14 @@ func isPowerOfTwo(x uintptr) bool {
 	return x&(x-1) == 0
 }
 
-func slicecopy(to, fm slice, width uintptr) int {
-	if fm.len == 0 || to.len == 0 {
+func slicecopy(toPtr unsafe.Pointer, toLen int, fmPtr unsafe.Pointer, fmLen int, width uintptr) int {
+	if fmLen == 0 || toLen == 0 {
 		return 0
 	}
 
-	n := fm.len
-	if to.len < n {
-		n = to.len
+	n := fmLen
+	if toLen < n {
+		n = toLen
 	}
 
 	if width == 0 {
@@ -216,43 +216,43 @@ func slicecopy(to, fm slice, width uintptr) int {
 	if raceenabled {
 		callerpc := getcallerpc()
 		pc := funcPC(slicecopy)
-		racewriterangepc(to.array, uintptr(n*int(width)), callerpc, pc)
-		racereadrangepc(fm.array, uintptr(n*int(width)), callerpc, pc)
+		racewriterangepc(toPtr, uintptr(n*int(width)), callerpc, pc)
+		racereadrangepc(fmPtr, uintptr(n*int(width)), callerpc, pc)
 	}
 	if msanenabled {
-		msanwrite(to.array, uintptr(n*int(width)))
-		msanread(fm.array, uintptr(n*int(width)))
+		msanwrite(toPtr, uintptr(n*int(width)))
+		msanread(fmPtr, uintptr(n*int(width)))
 	}
 
 	size := uintptr(n) * width
 	if size == 1 { // common case worth about 2x to do here
 		// TODO: is this still worth it with new memmove impl?
-		*(*byte)(to.array) = *(*byte)(fm.array) // known to be a byte pointer
+		*(*byte)(toPtr) = *(*byte)(fmPtr) // known to be a byte pointer
 	} else {
-		memmove(to.array, fm.array, size)
+		memmove(toPtr, fmPtr, size)
 	}
 	return n
 }
 
-func slicestringcopy(to []byte, fm string) int {
-	if len(fm) == 0 || len(to) == 0 {
+func slicestringcopy(toPtr *byte, toLen int, fm string) int {
+	if len(fm) == 0 || toLen == 0 {
 		return 0
 	}
 
 	n := len(fm)
-	if len(to) < n {
-		n = len(to)
+	if toLen < n {
+		n = toLen
 	}
 
 	if raceenabled {
 		callerpc := getcallerpc()
 		pc := funcPC(slicestringcopy)
-		racewriterangepc(unsafe.Pointer(&to[0]), uintptr(n), callerpc, pc)
+		racewriterangepc(unsafe.Pointer(toPtr), uintptr(n), callerpc, pc)
 	}
 	if msanenabled {
-		msanwrite(unsafe.Pointer(&to[0]), uintptr(n))
+		msanwrite(unsafe.Pointer(toPtr), uintptr(n))
 	}
 
-	memmove(unsafe.Pointer(&to[0]), stringStructOf(&fm).str, uintptr(n))
+	memmove(unsafe.Pointer(toPtr), stringStructOf(&fm).str, uintptr(n))
 	return n
 }