8 files changed, 74 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/ssa/gen/386.rules b/src/cmd/compile/internal/ssa/gen/386.rules
index 537705c681..fbc12fd672 100644
--- a/src/cmd/compile/internal/ssa/gen/386.rules
+++ b/src/cmd/compile/internal/ssa/gen/386.rules
@@ -531,6 +531,7 @@
 // fold ADDL into LEAL
 (ADDLconst [c] (LEAL [d] {s} x)) && is32Bit(int64(c)+int64(d)) => (LEAL [c+d] {s} x)
 (LEAL [c] {s} (ADDLconst [d] x)) && is32Bit(int64(c)+int64(d)) => (LEAL [c+d] {s} x)
+(ADDLconst [c] x:(SP)) => (LEAL [c] x) // so it is rematerializeable
 (LEAL [c] {s} (ADDL x y)) && x.Op != OpSB && y.Op != OpSB => (LEAL1 [c] {s} x y)
 (ADDL x (LEAL [c] {s} y)) && x.Op != OpSB && y.Op != OpSB => (LEAL1 [c] {s} x y)
 
diff --git a/src/cmd/compile/internal/ssa/gen/PPC64.rules b/src/cmd/compile/internal/ssa/gen/PPC64.rules
index 31b186d167..c064046172 100644
--- a/src/cmd/compile/internal/ssa/gen/PPC64.rules
+++ b/src/cmd/compile/internal/ssa/gen/PPC64.rules
@@ -845,6 +845,7 @@
 (SUB x (MOVDconst [c])) && is32Bit(-c) => (ADDconst [-c] x)
 
 (ADDconst [c] (MOVDaddr [d] {sym} x)) && is32Bit(c+int64(d)) => (MOVDaddr [int32(c+int64(d))] {sym} x)
+(ADDconst [c] x:(SP)) && is32Bit(c) => (MOVDaddr [int32(c)] x) // so it is rematerializeable
 
 (MULL(W|D) x (MOVDconst [c])) && is16Bit(c) => (MULL(W|D)const [int32(c)] x)
 
diff --git a/src/cmd/compile/internal/ssa/gen/Wasm.rules b/src/cmd/compile/internal/ssa/gen/Wasm.rules
index ea12c5d617..fc45cd3ed5 100644
--- a/src/cmd/compile/internal/ssa/gen/Wasm.rules
+++ b/src/cmd/compile/internal/ssa/gen/Wasm.rules
@@ -399,6 +399,7 @@
 // folding offset into address
 (I64AddConst [off] (LoweredAddr {sym} [off2] base)) && isU32Bit(off+int64(off2)) =>
 	(LoweredAddr {sym} [int32(off)+off2] base)
+(I64AddConst [off] x:(SP)) && isU32Bit(off) => (LoweredAddr [int32(off)] x) // so it is rematerializeable
 
 // transforming readonly globals into constants
 (I64Load [off] (LoweredAddr {sym} [off2] (SB)) _) && symIsRO(sym) && isU32Bit(off+int64(off2)) => (I64Const [int64(read64(sym, off+int64(off2), config.ctxt.Arch.ByteOrder))])
diff --git a/src/cmd/compile/internal/ssa/rewrite386.go b/src/cmd/compile/internal/ssa/rewrite386.go
index eca4817b9b..2acdccd568 100644
--- a/src/cmd/compile/internal/ssa/rewrite386.go
+++ b/src/cmd/compile/internal/ssa/rewrite386.go
@@ -1027,6 +1027,19 @@ func rewriteValue386_Op386ADDLconst(v *Value) bool {
 		v.AddArg(x)
 		return true
 	}
+	// match: (ADDLconst [c] x:(SP))
+	// result: (LEAL [c] x)
+	for {
+		c := auxIntToInt32(v.AuxInt)
+		x := v_0
+		if x.Op != OpSP {
+			break
+		}
+		v.reset(Op386LEAL)
+		v.AuxInt = int32ToAuxInt(c)
+		v.AddArg(x)
+		return true
+	}
 	// match: (ADDLconst [c] (LEAL1 [d] {s} x y))
 	// cond: is32Bit(int64(c)+int64(d))
 	// result: (LEAL1 [c+d] {s} x y)
diff --git a/src/cmd/compile/internal/ssa/rewritePPC64.go b/src/cmd/compile/internal/ssa/rewritePPC64.go
index 7d4cf73fd8..455f9b1388 100644
--- a/src/cmd/compile/internal/ssa/rewritePPC64.go
+++ b/src/cmd/compile/internal/ssa/rewritePPC64.go
@@ -4195,6 +4195,20 @@ func rewriteValuePPC64_OpPPC64ADDconst(v *Value) bool {
 		v.AddArg(x)
 		return true
 	}
+	// match: (ADDconst [c] x:(SP))
+	// cond: is32Bit(c)
+	// result: (MOVDaddr [int32(c)] x)
+	for {
+		c := auxIntToInt64(v.AuxInt)
+		x := v_0
+		if x.Op != OpSP || !(is32Bit(c)) {
+			break
+		}
+		v.reset(OpPPC64MOVDaddr)
+		v.AuxInt = int32ToAuxInt(int32(c))
+		v.AddArg(x)
+		return true
+	}
 	// match: (ADDconst [c] (SUBFCconst [d] x))
 	// cond: is32Bit(c+d)
 	// result: (SUBFCconst [c+d] x)
diff --git a/src/cmd/compile/internal/ssa/rewriteWasm.go b/src/cmd/compile/internal/ssa/rewriteWasm.go
index 52b6f6bfc7..c8ecefc736 100644
--- a/src/cmd/compile/internal/ssa/rewriteWasm.go
+++ b/src/cmd/compile/internal/ssa/rewriteWasm.go
@@ -3693,6 +3693,20 @@ func rewriteValueWasm_OpWasmI64AddConst(v *Value) bool {
 		v.AddArg(base)
 		return true
 	}
+	// match: (I64AddConst [off] x:(SP))
+	// cond: isU32Bit(off)
+	// result: (LoweredAddr [int32(off)] x)
+	for {
+		off := auxIntToInt64(v.AuxInt)
+		x := v_0
+		if x.Op != OpSP || !(isU32Bit(off)) {
+			break
+		}
+		v.reset(OpWasmLoweredAddr)
+		v.AuxInt = int32ToAuxInt(int32(off))
+		v.AddArg(x)
+		return true
+	}
 	return false
 }
 func rewriteValueWasm_OpWasmI64And(v *Value) bool {
diff --git a/src/cmd/compile/internal/wasm/ssa.go b/src/cmd/compile/internal/wasm/ssa.go
index a36fbca4e0..9c9f6edc5f 100644
--- a/src/cmd/compile/internal/wasm/ssa.go
+++ b/src/cmd/compile/internal/wasm/ssa.go
@@ -230,6 +230,12 @@ func ssaGenValueOnStack(s *gc.SSAGenState, v *ssa.Value, extend bool) {
 		}
 
 	case ssa.OpWasmLoweredAddr:
+		if v.Aux == nil { // address of off(SP), no symbol
+			getValue64(s, v.Args[0])
+			i64Const(s, v.AuxInt)
+			s.Prog(wasm.AI64Add)
+			break
+		}
 		p := s.Prog(wasm.AGet)
 		p.From.Type = obj.TYPE_ADDR
 		switch v.Aux.(type) {
diff --git a/test/fixedbugs/issue42944.go b/test/fixedbugs/issue42944.go
new file mode 100644
index 0000000000..bb947bc609
--- /dev/null
+++ b/test/fixedbugs/issue42944.go
@@ -0,0 +1,24 @@
+// errorcheck -0 -live
+
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Issue 42944: address of callee args area should only be short-lived
+// and never across a call.
+
+package p
+
+type T [10]int // trigger DUFFCOPY when passing by value, so it uses the address
+
+func F() {
+	var x T
+	var i int
+	for {
+		x = G(i) // no autotmp live at this and next calls
+		H(i, x)
+	}
+}
+
+func G(int) T
+func H(int, T)