commit d4a95e78fa176e02a19cd94c9c273743f3a983c1
author Alexandru Moșoi <mosoi@google.com> Wed Feb 03 19:43:46 2016 +0100
committer Keith Randall <khr@golang.org> Thu Feb 04 16:00:19 2016 +0000
tree 80deb85aa9fdd65907e129f29be5639a534c47d2
parent c58c20f30f5b34af6b36b21b1348a5d8011612ac

[dev.ssa] cmd/compile/internal/ssa: simplify comparisons with constants

* Simplify comparisons of form a + const1 == const2 or a + const1 != const2.
* Canonicalize Eq, Neq, Add, Sub to have a constant as first argument.
Needed for the above new rules and helps constant folding.

Change-Id: I8078702a5daa706da57106073a3e9f640a67f486
Reviewed-on: https://go-review.googlesource.com/19192
Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/compile/internal/ssa/gen/generic.rules

diff --git a/src/cmd/compile/internal/ssa/gen/generic.rules b/src/cmd/compile/internal/ssa/gen/generic.rules
index 3b7209a..658d78c 100644
--- a/src/cmd/compile/internal/ssa/gen/generic.rules
+++ b/src/cmd/compile/internal/ssa/gen/generic.rules
@@ -48,6 +48,37 @@
 (Neq16 x x) -> (ConstBool [0])
 (Neq8 x x) -> (ConstBool [0])
 
+(Eq64 (Const64 <t> [c]) (Add64 (Const64 <t> [d]) x)) -> (Eq64 (Const64 <t> [c-d]) x)
+(Eq32 (Const32 <t> [c]) (Add32 (Const32 <t> [d]) x)) -> (Eq32 (Const32 <t> [c-d]) x)
+(Eq16 (Const16 <t> [c]) (Add16 (Const16 <t> [d]) x)) -> (Eq16 (Const16 <t> [c-d]) x)
+(Eq8 (Const8 <t> [c]) (Add8 (Const8 <t> [d]) x)) -> (Eq8 (Const8 <t> [c-d]) x)
+
+(Neq64 (Const64 <t> [c]) (Add64 (Const64 <t> [d]) x)) -> (Neq64 (Const64 <t> [c-d]) x)
+(Neq32 (Const32 <t> [c]) (Add32 (Const32 <t> [d]) x)) -> (Neq32 (Const32 <t> [c-d]) x)
+(Neq16 (Const16 <t> [c]) (Add16 (Const16 <t> [d]) x)) -> (Neq16 (Const16 <t> [c-d]) x)
+(Neq8 (Const8 <t> [c]) (Add8 (Const8 <t> [d]) x)) -> (Neq8 (Const8 <t> [c-d]) x)
+
+// canonicalize: swap arguments for commutative opertions when one argument is a constant.
+(Eq64 x (Const64 <t> [c])) && x.Op != OpConst64 -> (Eq64 (Const64 <t> [c]) x)
+(Eq32 x (Const32 <t> [c])) && x.Op != OpConst32 -> (Eq32 (Const32 <t> [c]) x)
+(Eq16 x (Const16 <t> [c])) && x.Op != OpConst16 -> (Eq16 (Const16 <t> [c]) x)
+(Eq8 x (Const8 <t> [c])) && x.Op != OpConst8 -> (Eq8 (Const8 <t> [c]) x)
+
+(Neq64 x (Const64 <t> [c])) && x.Op != OpConst64 -> (Neq64 (Const64 <t> [c]) x)
+(Neq32 x (Const32 <t> [c])) && x.Op != OpConst32 -> (Neq32 (Const32 <t> [c]) x)
+(Neq16 x (Const16 <t> [c])) && x.Op != OpConst16 -> (Neq16 (Const16 <t> [c]) x)
+(Neq8 x (Const8 <t> [c])) && x.Op != OpConst8 -> (Neq8 (Const8 <t> [c]) x)
+
+(Add64 x (Const64 <t> [c])) && x.Op != OpConst64 -> (Add64 (Const64 <t> [c]) x)
+(Add32 x (Const32 <t> [c])) && x.Op != OpConst32 -> (Add32 (Const32 <t> [c]) x)
+(Add16 x (Const16 <t> [c])) && x.Op != OpConst16 -> (Add16 (Const16 <t> [c]) x)
+(Add8 x (Const8 <t> [c])) && x.Op != OpConst8 -> (Add8 (Const8 <t> [c]) x)
+
+(Sub64 x (Const64 <t> [c])) && x.Op != OpConst64 -> (Add64 (Const64 <t> [-c]) x)
+(Sub32 x (Const32 <t> [c])) && x.Op != OpConst32 -> (Add32 (Const32 <t> [-c]) x)
+(Sub16 x (Const16 <t> [c])) && x.Op != OpConst16 -> (Add16 (Const16 <t> [-c]) x)
+(Sub8 x (Const8 <t> [c])) && x.Op != OpConst8 -> (Add8 (Const8 <t> [-c]) x)
+
 // constant comparisons
 (Eq64 (Const64 [c]) (Const64 [d])) -> (ConstBool [b2i(int64(c) == int64(d))])
 (Eq32 (Const32 [c]) (Const32 [d])) -> (ConstBool [b2i(int32(c) == int32(d))])