[dev.ssa] cmd/compile: handle floating point on ARM

Machine supports (or the runtime simulates in soft float mode)
(u)int32<->float conversions. The frontend rewrites int64<->float
conversions to call to runtime function.

For int64->float32 conversion, the frontend generates

.   .   AS u(100) l(10) tc(1)
.   .   .   NAME-main.~r1 u(1) a(true) g(1) l(9) x(8+0) class(PPARAMOUT) f(1) float32
.   .   .   CALLFUNC u(100) l(10) tc(1) float32
.   .   .   .   NAME-runtime.int64tofloat64 u(1) a(true) x(0+0) class(PFUNC) tc(1) used(true) FUNC-func(int64) float64

The CALLFUNC node has type float32, whereas runtime.int64tofloat64
returns float64. The legacy backend implicitly makes a float64->float32
conversion. The SSA backend does not do implicit conversion, so we
insert an explicit CONV here.

All cmd/compile/internal/gc/testdata/*_ssa.go tests passed.

Progress on SSA for ARM. Still not complete.

Update #15365.

Change-Id: I30937c8ff977271246b068f48224693776804339
Reviewed-on: https://go-review.googlesource.com/23652
Reviewed-by: Keith Randall <khr@golang.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/ssa/decompose.go b/src/cmd/compile/internal/ssa/decompose.go
index 0ee5f53291..08cc1b9dee 100644
--- a/src/cmd/compile/internal/ssa/decompose.go
+++ b/src/cmd/compile/internal/ssa/decompose.go
@@ -94,6 +94,8 @@ func decomposeBuiltIn(f *Func) {
 				f.NamedValues[dataName] = append(f.NamedValues[dataName], data)
 			}
 			delete(f.NamedValues, name)
+		case t.IsFloat():
+			// floats are never decomposed, even ones bigger than IntSize
 		case t.Size() > f.Config.IntSize:
 			f.Unimplementedf("undecomposed named type %s %s", name, t)
 		default:
@@ -115,6 +117,8 @@ func decomposeBuiltInPhi(v *Value) {
 		decomposeSlicePhi(v)
 	case v.Type.IsInterface():
 		decomposeInterfacePhi(v)
+	case v.Type.IsFloat():
+		// floats are never decomposed, even ones bigger than IntSize
 	case v.Type.Size() > v.Block.Func.Config.IntSize:
 		v.Unimplementedf("undecomposed type %s", v.Type)
 	}