builder: build SSA before compiling packages

builder/build.go

@@ -24,6 +24,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"sync"
 
 	"github.com/gofrs/flock"
 	"github.com/tinygo-org/tinygo/compileopts"
@@ -269,6 +270,7 @@ func Build(pkgName, outpath, tmpdir string, config *compileopts.Config) (BuildRe
 	// Create the *ssa.Program. This does not yet build the entire SSA of the
 	// program so it's pretty fast and doesn't need to be parallelized.
 	program := lprogram.LoadSSA()
+	buildProgram := sync.OnceFunc(program.Build)
 
 	// Add jobs to compile each package.
 	// Packages that have a cache hit will not be compiled again.
@@ -398,8 +400,13 @@ func Build(pkgName, outpath, tmpdir string, config *compileopts.Config) (BuildRe
 					return nil
 				}
 
-				// Compile AST to IR. The compiler.CompilePackage function will
-				// build the SSA as needed.
+				// SSA package builds may run concurrently, but the resulting
+				// functions cannot be inspected until all builds have finished:
+				// generic instances and wrappers can be shared across packages.
+				// Build the whole program once before compiling any package.
+				buildProgram()
+
+				// Compile AST to IR.
 				mod, errs := compiler.CompilePackage(pkg.ImportPath, pkg, program.Package(pkg.Pkg), machine, compilerConfig, config.DumpSSA())
 				defer mod.Context().Dispose()
 				defer mod.Dispose()