cmd/compile: define starting block before opening html writer

Opening the html writer can fail, and the failure printer wants
to use the entry block's line number. So make sure we set up
the entry block first.

Fixes #40919

Change-Id: I4ffa2839b45a721bbaf04ff84418e8108fa1cc37
Reviewed-on: https://go-review.googlesource.com/c/go/+/249497
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index 5d0098b4e6fa11d14cf778db40cd7fdf64127942..4124655b791411eaeef03ebd13a8131d78e0786a 100644 (file)
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -338,6 +338,10 @@ func buildssa(fn *Node, worker int) *ssa.Func {
        s.panics = map[funcLine]*ssa.Block{}
        s.softFloat = s.config.SoftFloat
 
+       // Allocate starting block
+       s.f.Entry = s.f.NewBlock(ssa.BlockPlain)
+       s.f.Entry.Pos = fn.Pos
+
        if printssa {
                s.f.HTMLWriter = ssa.NewHTMLWriter(ssaDumpFile, s.f, ssaDumpCFG)
                // TODO: generate and print a mapping from nodes to values and blocks
@@ -345,9 +349,6 @@ func buildssa(fn *Node, worker int) *ssa.Func {
                s.f.HTMLWriter.WriteAST("AST", astBuf)
        }
 
-       // Allocate starting block
-       s.f.Entry = s.f.NewBlock(ssa.BlockPlain)
-
        // Allocate starting values
        s.labels = map[string]*ssaLabel{}
        s.labeledNodes = map[*Node]*ssaLabel{}