cmd/compile: clean up equality generation

We're using sort.SliceStable, so no need to keep track of indexes as well.

Use a more robust test for whether a node is a call.

Add a test that we're actually reordering comparisons. This test fails
without the alg.go changes in this CL because eqstring uses OCALLFUNC
instead of OCALL for its data comparisons.

Update #8606

Change-Id: Ieeec33434c72e3aa328deb11cc415cfda05632e2
Reviewed-on: https://go-review.googlesource.com/c/go/+/237921
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

1 files changed, 12 insertions, 19 deletions

diff --git a/src/cmd/compile/internal/gc/alg.go b/src/cmd/compile/internal/gc/alg.go
index e2e2374717..2b63700569 100644
--- a/src/cmd/compile/internal/gc/alg.go
+++ b/src/cmd/compile/internal/gc/alg.go
@@ -646,17 +646,11 @@ func geneq(t *types.Type) *obj.LSym {
 		// Build a list of conditions to satisfy.
 		// The conditions are a list-of-lists. Conditions are reorderable
 		// within each inner list. The outer lists must be evaluated in order.
-		// Even within each inner list, track their order so that we can preserve
-		// aspects of that order. (TODO: latter part needed?)
-		type nodeIdx struct {
-			n   *Node
-			idx int
-		}
-		var conds [][]nodeIdx
-		conds = append(conds, []nodeIdx{})
+		var conds [][]*Node
+		conds = append(conds, []*Node{})
 		and := func(n *Node) {
 			i := len(conds) - 1
-			conds[i] = append(conds[i], nodeIdx{n: n, idx: len(conds[i])})
+			conds[i] = append(conds[i], n)
 		}
 
 		// Walk the struct using memequal for runs of AMEM
@@ -674,7 +668,7 @@ func geneq(t *types.Type) *obj.LSym {
 			if !IsRegularMemory(f.Type) {
 				if EqCanPanic(f.Type) {
 					// Enforce ordering by starting a new set of reorderable conditions.
-					conds = append(conds, []nodeIdx{})
+					conds = append(conds, []*Node{})
 				}
 				p := nodSym(OXDOT, np, f.Sym)
 				q := nodSym(OXDOT, nq, f.Sym)
@@ -688,7 +682,7 @@ func geneq(t *types.Type) *obj.LSym {
 				}
 				if EqCanPanic(f.Type) {
 					// Also enforce ordering after something that can panic.
-					conds = append(conds, []nodeIdx{})
+					conds = append(conds, []*Node{})
 				}
 				i++
 				continue
@@ -713,14 +707,13 @@ func geneq(t *types.Type) *obj.LSym {
 
 		// Sort conditions to put runtime calls last.
 		// Preserve the rest of the ordering.
-		var flatConds []nodeIdx
+		var flatConds []*Node
 		for _, c := range conds {
+			isCall := func(n *Node) bool {
+				return n.Op == OCALL || n.Op == OCALLFUNC
+			}
 			sort.SliceStable(c, func(i, j int) bool {
-				x, y := c[i], c[j]
-				if (x.n.Op != OCALL) == (y.n.Op != OCALL) {
-					return x.idx < y.idx
-				}
-				return x.n.Op != OCALL
+				return !isCall(c[i]) && isCall(c[j])
 			})
 			flatConds = append(flatConds, c...)
 		}
@@ -729,9 +722,9 @@ func geneq(t *types.Type) *obj.LSym {
 		if len(flatConds) == 0 {
 			cond = nodbool(true)
 		} else {
-			cond = flatConds[0].n
+			cond = flatConds[0]
 			for _, c := range flatConds[1:] {
-				cond = nod(OANDAND, cond, c.n)
+				cond = nod(OANDAND, cond, c)
 			}
 		}