compiler, runtime: check len/cap for append(s, make(T, l)...)

The overflow checks done in growslice always reported an error for the
capacity argument, even if it was the length argument that overflowed.
This change lets the code pass the current issue4085b.go test.

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/273806

4 files changed, 28 insertions, 25 deletions

diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index e8cf468..eec3d07 100644
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-be1738f1fff0e817d921ed568791f9b0585a6982
+84506e0f6bf282765856cb5aeb17124222f73042
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
diff --git a/gcc/go/gofrontend/expressions.cc b/gcc/go/gofrontend/expressions.cc
index d154630..23caf61 100644
--- a/gcc/go/gofrontend/expressions.cc
+++ b/gcc/go/gofrontend/expressions.cc
@@ -8893,8 +8893,8 @@ Builtin_call_expression::flatten_append(Gogo* gogo, Named_object* function,
           // We will optimize this to directly zeroing the tail,
           // instead of allocating a new slice then copy.
 
-          // Retrieve the length. Cannot reference s2 as we will remove
-          // the makeslice call.
+          // Retrieve the length and capacity. Cannot reference s2 as
+          // we will remove the makeslice call.
           Expression* len_arg = makecall->args()->at(1);
           len_arg = Expression::make_cast(int_type, len_arg, loc);
           l2tmp = Statement::make_temporary(int_type, len_arg, loc);
@@ -8907,28 +8907,19 @@ Builtin_call_expression::flatten_append(Gogo* gogo, Named_object* function,
           inserter->insert(c2tmp);
 
           // Check bad len/cap here.
-          // if len2 < 0 { panicmakeslicelen(); }
+	  // checkmakeslice(type, len, cap)
+	  // (Note that if len and cap are constants, we won't see a
+	  // makeslice call here, as it will be rewritten to a stack
+	  // allocated array by Mark_address_taken::expression.)
+	  Expression* elem = Expression::make_type_descriptor(element_type,
+							      loc);
           len2 = Expression::make_temporary_reference(l2tmp, loc);
-          Expression* zero = Expression::make_integer_ul(0, int_type, loc);
-          Expression* cond = Expression::make_binary(OPERATOR_LT, len2,
-                                                     zero, loc);
-	  Expression* call = Runtime::make_call(Runtime::PANIC_MAKE_SLICE_LEN,
-						loc, 0);
-          cond = Expression::make_conditional(cond, call, zero->copy(), loc);
-          gogo->lower_expression(function, inserter, &cond);
-          gogo->flatten_expression(function, inserter, &cond);
-          Statement* s = Statement::make_statement(cond, false);
-          inserter->insert(s);
-
-          // if cap2 < 0 { panicmakeslicecap(); }
           Expression* cap2 = Expression::make_temporary_reference(c2tmp, loc);
-          cond = Expression::make_binary(OPERATOR_LT, cap2,
-                                         zero->copy(), loc);
-	  call = Runtime::make_call(Runtime::PANIC_MAKE_SLICE_CAP, loc, 0);
-          cond = Expression::make_conditional(cond, call, zero->copy(), loc);
-          gogo->lower_expression(function, inserter, &cond);
-          gogo->flatten_expression(function, inserter, &cond);
-          s = Statement::make_statement(cond, false);
+	  Expression* check = Runtime::make_call(Runtime::CHECK_MAKE_SLICE,
+						 loc, 3, elem, len2, cap2);
+          gogo->lower_expression(function, inserter, &check);
+          gogo->flatten_expression(function, inserter, &check);
+          Statement* s = Statement::make_statement(check, false);
           inserter->insert(s);
 
           // Remove the original makeslice call.
diff --git a/gcc/go/gofrontend/runtime.def b/gcc/go/gofrontend/runtime.def
index b608766..9a3c680 100644
--- a/gcc/go/gofrontend/runtime.def
+++ b/gcc/go/gofrontend/runtime.def
@@ -265,6 +265,11 @@ DEF_GO_RUNTIME(GROWSLICE, "runtime.growslice",
                P5(TYPE, POINTER, INT, INT, INT), R1(SLICE))
 
 
+// Check the length and cap passed to make, without making a slice.
+// This is used for apend(s, make([]T, len)...).
+DEF_GO_RUNTIME(CHECK_MAKE_SLICE, "runtime.checkMakeSlice", P3(TYPE, INT, INT),
+	       R1(UINTPTR))
+
 // Register roots (global variables) for the garbage collector.
 DEF_GO_RUNTIME(REGISTER_GC_ROOTS, "runtime.registerGCRoots", P1(POINTER), R0())
 
diff --git a/libgo/go/runtime/slice.go b/libgo/go/runtime/slice.go
index 97b2659..ddd588e 100644
--- a/libgo/go/runtime/slice.go
+++ b/libgo/go/runtime/slice.go
@@ -15,6 +15,7 @@ import (
 //go:linkname panicmakeslicelen
 //go:linkname panicmakeslicecap
 //go:linkname makeslice
+//go:linkname checkMakeSlice
 //go:linkname makeslice64
 //go:linkname growslice
 //go:linkname slicecopy
@@ -91,6 +92,13 @@ func makeslicecopy(et *_type, tolen int, fromlen int, from unsafe.Pointer) unsaf
 }
 
 func makeslice(et *_type, len, cap int) unsafe.Pointer {
+	mem := checkMakeSlice(et, len, cap)
+	return mallocgc(mem, et, true)
+}
+
+// checkMakeSlice is called for append(s, make([]T, len, cap)...) to check
+// the values of len and cap.
+func checkMakeSlice(et *_type, len, cap int) uintptr {
 	mem, overflow := math.MulUintptr(et.size, uintptr(cap))
 	if overflow || mem > maxAlloc || len < 0 || len > cap {
 		// NOTE: Produce a 'len out of range' error instead of a
@@ -104,8 +112,7 @@ func makeslice(et *_type, len, cap int) unsafe.Pointer {
 		}
 		panicmakeslicecap()
 	}
-
-	return mallocgc(mem, et, true)
+	return mem
 }
 
 func makeslice64(et *_type, len64, cap64 int64) unsafe.Pointer {