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authorBjörn Gustavsson <[email protected]>2018-02-06 06:28:05 +0100
committerBjörn Gustavsson <[email protected]>2018-03-14 11:28:57 +0100
commitc896f08f5c028b1e31290e6a5502597401acd39f (patch)
treec8709d66de1d66d74f3f728f075a1e37a035bb98
parent64859cc36efde18483f3a9116c85c2e73ecb304d (diff)
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v3_kernel: Stop ensuring one return value in #k_try{}
For unclear reasons, v3_kernel attempts to guarantee that #k_try{} always has at least one return value, even if it will never be used. I said "attempts", because the handler block that is executed when an exception is caught does not have the same guarantee. That means that if an exception is thrown, the return value will not actually be set. In practice, however, this is not a problem for the existing code generator (v3_codegen). The generated code will still be safe. If we are to rewrite the code generator to generate an SSA-based intermediate format, this inconsistency *will* cause problems when creating phi nodes. While at it, also remove an unecessary creation of new variables in generation of #k_try_enter{}.
-rw-r--r--lib/compiler/src/v3_kernel.erl13
1 files changed, 5 insertions, 8 deletions
diff --git a/lib/compiler/src/v3_kernel.erl b/lib/compiler/src/v3_kernel.erl
index fd73e5a7dc..dfe8d26afb 100644
--- a/lib/compiler/src/v3_kernel.erl
+++ b/lib/compiler/src/v3_kernel.erl
@@ -2377,12 +2377,11 @@ uexpr(#k_try{anno=A,arg=A0,vars=Vs,body=B0,evars=Evs,handler=H0},
{A1,Au,St2} = ubody(A0, {break,Avs}, St1),
{B1,Bu,St3} = ubody(B0, Br, St2),
{H1,Hu,St4} = ubody(H0, Br, St3),
- {Rs1,St5} = ensure_return_vars(Rs0, St4),
Used = union([Au,subtract(Bu, lit_list_vars(Vs)),
subtract(Hu, lit_list_vars(Evs))]),
- {#k_try{anno=#k{us=Used,ns=lit_list_vars(Rs1),a=A},
- arg=A1,vars=Vs,body=B1,evars=Evs,handler=H1,ret=Rs1},
- Used,St5}
+ {#k_try{anno=#k{us=Used,ns=lit_list_vars(Rs0),a=A},
+ arg=A1,vars=Vs,body=B1,evars=Evs,handler=H1,ret=Rs0},
+ Used,St4}
end;
uexpr(#k_try{anno=A,arg=A0,vars=Vs,body=B0,evars=Evs,handler=H0},
return, St0) ->
@@ -2390,13 +2389,11 @@ uexpr(#k_try{anno=A,arg=A0,vars=Vs,body=B0,evars=Evs,handler=H0},
{A1,Au,St2} = ubody(A0, {break,Avs}, St1), %Must break to clean up here!
{B1,Bu,St3} = ubody(B0, return, St2),
{H1,Hu,St4} = ubody(H0, return, St3),
- NumNew = 1,
- {Ns,St5} = new_vars(NumNew, St4),
Used = union([Au,subtract(Bu, lit_list_vars(Vs)),
subtract(Hu, lit_list_vars(Evs))]),
- {#k_try_enter{anno=#k{us=Used,ns=Ns,a=A},
+ {#k_try_enter{anno=#k{us=Used,ns=[],a=A},
arg=A1,vars=Vs,body=B1,evars=Evs,handler=H1},
- Used,St5};
+ Used,St4};
uexpr(#k_catch{anno=A,body=B0}, {break,Rs0}, St0) ->
{Rb,St1} = new_var(St0),
{B1,Bu,St2} = ubody(B0, {break,[Rb]}, St1),