cmd/compile: emit OffPtr for first field in SSA'd structs

Given

  (Store [c] (OffPtr <T1> [0] (Addr <T> _)) _
    (Store [c] (Addr <T> _) _ _))

dead store elimination doesn't eliminate the inner
Store, because it addresses a type of a different width
than the first store.

When decomposing StructMake operations, always generate
an OffPtr to address struct fields so that dead stores to
the first field of the struct can be optimized away.

benchmarks affected on darwin/amd64:
HTTPClientServer-8        73.2µs ± 1%    72.7µs ± 1%  -0.69%  (p=0.022 n=9+10)
TimeParse-8                304ns ± 1%     300ns ± 0%  -1.61%  (p=0.000 n=9+9)
RegexpMatchEasy1_32-8     80.1ns ± 0%    79.5ns ± 1%  -0.84%  (p=0.000 n=8+9)
GobDecode-8               6.78ms ± 0%    6.81ms ± 1%  +0.46%  (p=0.000 n=9+10)
Gunzip-8                  36.1ms ± 1%    36.2ms ± 0%  +0.37%  (p=0.019 n=10+10)
JSONEncode-8              15.6ms ± 0%    15.7ms ± 0%  +0.69%  (p=0.000 n=9+10)

Change-Id: Ia80d73fd047f9400c616ca64fdee4f438a0e7f21
Reviewed-on: https://go-review.googlesource.com/37769
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

diff --git a/src/cmd/compile/internal/ssa/gen/generic.rules b/src/cmd/compile/internal/ssa/gen/generic.rules
index 00103babe5153c8f95299bcf84440d777c294c52..a81d2826d8b67bbb561ee29e88d2cff8a412a842 100644 (file)
--- a/src/cmd/compile/internal/ssa/gen/generic.rules
+++ b/src/cmd/compile/internal/ssa/gen/generic.rules
@@ -772,19 +772,19 @@
   (StructMake0)
 (Load <t> ptr mem) && t.IsStruct() && t.NumFields() == 1 && config.fe.CanSSA(t) ->
   (StructMake1
-    (Load <t.FieldType(0)> ptr mem))
+    (Load <t.FieldType(0)> (OffPtr <t.FieldType(0).PtrTo()> [0] ptr) mem))
 (Load <t> ptr mem) && t.IsStruct() && t.NumFields() == 2 && config.fe.CanSSA(t) ->
   (StructMake2
-    (Load <t.FieldType(0)> ptr mem)
+    (Load <t.FieldType(0)> (OffPtr <t.FieldType(0).PtrTo()> [0]             ptr) mem)
     (Load <t.FieldType(1)> (OffPtr <t.FieldType(1).PtrTo()> [t.FieldOff(1)] ptr) mem))
 (Load <t> ptr mem) && t.IsStruct() && t.NumFields() == 3 && config.fe.CanSSA(t) ->
   (StructMake3
-    (Load <t.FieldType(0)> ptr mem)
+    (Load <t.FieldType(0)> (OffPtr <t.FieldType(0).PtrTo()> [0]             ptr) mem)
     (Load <t.FieldType(1)> (OffPtr <t.FieldType(1).PtrTo()> [t.FieldOff(1)] ptr) mem)
     (Load <t.FieldType(2)> (OffPtr <t.FieldType(2).PtrTo()> [t.FieldOff(2)] ptr) mem))
 (Load <t> ptr mem) && t.IsStruct() && t.NumFields() == 4 && config.fe.CanSSA(t) ->
   (StructMake4
-    (Load <t.FieldType(0)> ptr mem)
+    (Load <t.FieldType(0)> (OffPtr <t.FieldType(0).PtrTo()> [0]             ptr) mem)
     (Load <t.FieldType(1)> (OffPtr <t.FieldType(1).PtrTo()> [t.FieldOff(1)] ptr) mem)
     (Load <t.FieldType(2)> (OffPtr <t.FieldType(2).PtrTo()> [t.FieldOff(2)] ptr) mem)
     (Load <t.FieldType(3)> (OffPtr <t.FieldType(3).PtrTo()> [t.FieldOff(3)] ptr) mem))
@@ -794,12 +794,14 @@
 
 (Store _ (StructMake0) mem) -> mem
 (Store dst (StructMake1 <t> f0) mem) ->
-  (Store [t.FieldType(0).Size()] dst f0 mem)
+  (Store [t.FieldType(0).Size()] (OffPtr <t.FieldType(0).PtrTo()> [0] dst) f0 mem)
 (Store dst (StructMake2 <t> f0 f1) mem) ->
   (Store [t.FieldType(1).Size()]
     (OffPtr <t.FieldType(1).PtrTo()> [t.FieldOff(1)] dst)
     f1
-    (Store [t.FieldType(0).Size()] dst f0 mem))
+    (Store [t.FieldType(0).Size()]
+      (OffPtr <t.FieldType(0)> [0] dst)
+        f0 mem))
 (Store dst (StructMake3 <t> f0 f1 f2) mem) ->
   (Store [t.FieldType(2).Size()]
     (OffPtr <t.FieldType(2).PtrTo()> [t.FieldOff(2)] dst)
@@ -807,7 +809,9 @@
     (Store [t.FieldType(1).Size()]
       (OffPtr <t.FieldType(1).PtrTo()> [t.FieldOff(1)] dst)
       f1
-      (Store [t.FieldType(0).Size()] dst f0 mem)))
+      (Store [t.FieldType(0).Size()]
+        (OffPtr <t.FieldType(0).PtrTo()> [0] dst)
+          f0 mem)))
 (Store dst (StructMake4 <t> f0 f1 f2 f3) mem) ->
   (Store [t.FieldType(3).Size()]
     (OffPtr <t.FieldType(3).PtrTo()> [t.FieldOff(3)] dst)
@@ -818,7 +822,9 @@
       (Store [t.FieldType(1).Size()]
         (OffPtr <t.FieldType(1).PtrTo()> [t.FieldOff(1)] dst)
         f1
-        (Store [t.FieldType(0).Size()] dst f0 mem))))
+        (Store [t.FieldType(0).Size()]
+          (OffPtr <t.FieldType(0).PtrTo()> [0] dst)
+            f0 mem))))
 
 // Putting struct{*byte} and similar into direct interfaces.
 (IMake typ (StructMake1 val)) -> (IMake typ val)

diff --git a/src/cmd/compile/internal/ssa/rewritegeneric.go b/src/cmd/compile/internal/ssa/rewritegeneric.go
index 5c09ea03f4a65e093e4be11260a01eb479f82f0f..7690e73d41c5ac5ecc098265f0f3f6332a84a257 100644 (file)
--- a/src/cmd/compile/internal/ssa/rewritegeneric.go
+++ b/src/cmd/compile/internal/ssa/rewritegeneric.go
@@ -6733,7 +6733,7 @@ func rewriteValuegeneric_OpLoad(v *Value, config *Config) bool {
        }
        // match: (Load <t> ptr mem)
        // cond: t.IsStruct() && t.NumFields() == 1 && config.fe.CanSSA(t)
-       // result: (StructMake1     (Load <t.FieldType(0)> ptr mem))
+       // result: (StructMake1     (Load <t.FieldType(0)> (OffPtr <t.FieldType(0).PtrTo()> [0] ptr) mem))
        for {
                t := v.Type
                ptr := v.Args[0]
@@ -6743,14 +6743,17 @@ func rewriteValuegeneric_OpLoad(v *Value, config *Config) bool {
                }
                v.reset(OpStructMake1)
                v0 := b.NewValue0(v.Pos, OpLoad, t.FieldType(0))
-               v0.AddArg(ptr)
+               v1 := b.NewValue0(v.Pos, OpOffPtr, t.FieldType(0).PtrTo())
+               v1.AuxInt = 0
+               v1.AddArg(ptr)
+               v0.AddArg(v1)
                v0.AddArg(mem)
                v.AddArg(v0)
                return true
        }
        // match: (Load <t> ptr mem)
        // cond: t.IsStruct() && t.NumFields() == 2 && config.fe.CanSSA(t)
-       // result: (StructMake2     (Load <t.FieldType(0)> ptr mem)     (Load <t.FieldType(1)> (OffPtr <t.FieldType(1).PtrTo()> [t.FieldOff(1)] ptr) mem))
+       // result: (StructMake2     (Load <t.FieldType(0)> (OffPtr <t.FieldType(0).PtrTo()> [0]             ptr) mem)     (Load <t.FieldType(1)> (OffPtr <t.FieldType(1).PtrTo()> [t.FieldOff(1)] ptr) mem))
        for {
                t := v.Type
                ptr := v.Args[0]
@@ -6760,21 +6763,24 @@ func rewriteValuegeneric_OpLoad(v *Value, config *Config) bool {
                }
                v.reset(OpStructMake2)
                v0 := b.NewValue0(v.Pos, OpLoad, t.FieldType(0))
-               v0.AddArg(ptr)
+               v1 := b.NewValue0(v.Pos, OpOffPtr, t.FieldType(0).PtrTo())
+               v1.AuxInt = 0
+               v1.AddArg(ptr)
+               v0.AddArg(v1)
                v0.AddArg(mem)
                v.AddArg(v0)
-               v1 := b.NewValue0(v.Pos, OpLoad, t.FieldType(1))
-               v2 := b.NewValue0(v.Pos, OpOffPtr, t.FieldType(1).PtrTo())
-               v2.AuxInt = t.FieldOff(1)
-               v2.AddArg(ptr)
-               v1.AddArg(v2)
-               v1.AddArg(mem)
-               v.AddArg(v1)
+               v2 := b.NewValue0(v.Pos, OpLoad, t.FieldType(1))
+               v3 := b.NewValue0(v.Pos, OpOffPtr, t.FieldType(1).PtrTo())
+               v3.AuxInt = t.FieldOff(1)
+               v3.AddArg(ptr)
+               v2.AddArg(v3)
+               v2.AddArg(mem)
+               v.AddArg(v2)
                return true
        }
        // match: (Load <t> ptr mem)
        // cond: t.IsStruct() && t.NumFields() == 3 && config.fe.CanSSA(t)
-       // result: (StructMake3     (Load <t.FieldType(0)> ptr mem)     (Load <t.FieldType(1)> (OffPtr <t.FieldType(1).PtrTo()> [t.FieldOff(1)] ptr) mem)     (Load <t.FieldType(2)> (OffPtr <t.FieldType(2).PtrTo()> [t.FieldOff(2)] ptr) mem))
+       // result: (StructMake3     (Load <t.FieldType(0)> (OffPtr <t.FieldType(0).PtrTo()> [0]             ptr) mem)     (Load <t.FieldType(1)> (OffPtr <t.FieldType(1).PtrTo()> [t.FieldOff(1)] ptr) mem)     (Load <t.FieldType(2)> (OffPtr <t.FieldType(2).PtrTo()> [t.FieldOff(2)] ptr) mem))
        for {
                t := v.Type
                ptr := v.Args[0]
@@ -6784,28 +6790,31 @@ func rewriteValuegeneric_OpLoad(v *Value, config *Config) bool {
                }
                v.reset(OpStructMake3)
                v0 := b.NewValue0(v.Pos, OpLoad, t.FieldType(0))
-               v0.AddArg(ptr)
+               v1 := b.NewValue0(v.Pos, OpOffPtr, t.FieldType(0).PtrTo())
+               v1.AuxInt = 0
+               v1.AddArg(ptr)
+               v0.AddArg(v1)
                v0.AddArg(mem)
                v.AddArg(v0)
-               v1 := b.NewValue0(v.Pos, OpLoad, t.FieldType(1))
-               v2 := b.NewValue0(v.Pos, OpOffPtr, t.FieldType(1).PtrTo())
-               v2.AuxInt = t.FieldOff(1)
-               v2.AddArg(ptr)
-               v1.AddArg(v2)
-               v1.AddArg(mem)
-               v.AddArg(v1)
-               v3 := b.NewValue0(v.Pos, OpLoad, t.FieldType(2))
-               v4 := b.NewValue0(v.Pos, OpOffPtr, t.FieldType(2).PtrTo())
-               v4.AuxInt = t.FieldOff(2)
-               v4.AddArg(ptr)
-               v3.AddArg(v4)
-               v3.AddArg(mem)
-               v.AddArg(v3)
+               v2 := b.NewValue0(v.Pos, OpLoad, t.FieldType(1))
+               v3 := b.NewValue0(v.Pos, OpOffPtr, t.FieldType(1).PtrTo())
+               v3.AuxInt = t.FieldOff(1)
+               v3.AddArg(ptr)
+               v2.AddArg(v3)
+               v2.AddArg(mem)
+               v.AddArg(v2)
+               v4 := b.NewValue0(v.Pos, OpLoad, t.FieldType(2))
+               v5 := b.NewValue0(v.Pos, OpOffPtr, t.FieldType(2).PtrTo())
+               v5.AuxInt = t.FieldOff(2)
+               v5.AddArg(ptr)
+               v4.AddArg(v5)
+               v4.AddArg(mem)
+               v.AddArg(v4)
                return true
        }
        // match: (Load <t> ptr mem)
        // cond: t.IsStruct() && t.NumFields() == 4 && config.fe.CanSSA(t)
-       // result: (StructMake4     (Load <t.FieldType(0)> ptr mem)     (Load <t.FieldType(1)> (OffPtr <t.FieldType(1).PtrTo()> [t.FieldOff(1)] ptr) mem)     (Load <t.FieldType(2)> (OffPtr <t.FieldType(2).PtrTo()> [t.FieldOff(2)] ptr) mem)     (Load <t.FieldType(3)> (OffPtr <t.FieldType(3).PtrTo()> [t.FieldOff(3)] ptr) mem))
+       // result: (StructMake4     (Load <t.FieldType(0)> (OffPtr <t.FieldType(0).PtrTo()> [0]             ptr) mem)     (Load <t.FieldType(1)> (OffPtr <t.FieldType(1).PtrTo()> [t.FieldOff(1)] ptr) mem)     (Load <t.FieldType(2)> (OffPtr <t.FieldType(2).PtrTo()> [t.FieldOff(2)] ptr) mem)     (Load <t.FieldType(3)> (OffPtr <t.FieldType(3).PtrTo()> [t.FieldOff(3)] ptr) mem))
        for {
                t := v.Type
                ptr := v.Args[0]
@@ -6815,30 +6824,33 @@ func rewriteValuegeneric_OpLoad(v *Value, config *Config) bool {
                }
                v.reset(OpStructMake4)
                v0 := b.NewValue0(v.Pos, OpLoad, t.FieldType(0))
-               v0.AddArg(ptr)
+               v1 := b.NewValue0(v.Pos, OpOffPtr, t.FieldType(0).PtrTo())
+               v1.AuxInt = 0
+               v1.AddArg(ptr)
+               v0.AddArg(v1)
                v0.AddArg(mem)
                v.AddArg(v0)
-               v1 := b.NewValue0(v.Pos, OpLoad, t.FieldType(1))
-               v2 := b.NewValue0(v.Pos, OpOffPtr, t.FieldType(1).PtrTo())
-               v2.AuxInt = t.FieldOff(1)
-               v2.AddArg(ptr)
-               v1.AddArg(v2)
-               v1.AddArg(mem)
-               v.AddArg(v1)
-               v3 := b.NewValue0(v.Pos, OpLoad, t.FieldType(2))
-               v4 := b.NewValue0(v.Pos, OpOffPtr, t.FieldType(2).PtrTo())
-               v4.AuxInt = t.FieldOff(2)
-               v4.AddArg(ptr)
-               v3.AddArg(v4)
-               v3.AddArg(mem)
-               v.AddArg(v3)
-               v5 := b.NewValue0(v.Pos, OpLoad, t.FieldType(3))
-               v6 := b.NewValue0(v.Pos, OpOffPtr, t.FieldType(3).PtrTo())
-               v6.AuxInt = t.FieldOff(3)
-               v6.AddArg(ptr)
-               v5.AddArg(v6)
-               v5.AddArg(mem)
-               v.AddArg(v5)
+               v2 := b.NewValue0(v.Pos, OpLoad, t.FieldType(1))
+               v3 := b.NewValue0(v.Pos, OpOffPtr, t.FieldType(1).PtrTo())
+               v3.AuxInt = t.FieldOff(1)
+               v3.AddArg(ptr)
+               v2.AddArg(v3)
+               v2.AddArg(mem)
+               v.AddArg(v2)
+               v4 := b.NewValue0(v.Pos, OpLoad, t.FieldType(2))
+               v5 := b.NewValue0(v.Pos, OpOffPtr, t.FieldType(2).PtrTo())
+               v5.AuxInt = t.FieldOff(2)
+               v5.AddArg(ptr)
+               v4.AddArg(v5)
+               v4.AddArg(mem)
+               v.AddArg(v4)
+               v6 := b.NewValue0(v.Pos, OpLoad, t.FieldType(3))
+               v7 := b.NewValue0(v.Pos, OpOffPtr, t.FieldType(3).PtrTo())
+               v7.AuxInt = t.FieldOff(3)
+               v7.AddArg(ptr)
+               v6.AddArg(v7)
+               v6.AddArg(mem)
+               v.AddArg(v6)
                return true
        }
        // match: (Load <t> _ _)
@@ -14671,7 +14683,7 @@ func rewriteValuegeneric_OpStore(v *Value, config *Config) bool {
        }
        // match: (Store dst (StructMake1 <t> f0) mem)
        // cond:
-       // result: (Store [t.FieldType(0).Size()] dst f0 mem)
+       // result: (Store [t.FieldType(0).Size()] (OffPtr <t.FieldType(0).PtrTo()> [0] dst) f0 mem)
        for {
                dst := v.Args[0]
                v_1 := v.Args[1]
@@ -14683,14 +14695,17 @@ func rewriteValuegeneric_OpStore(v *Value, config *Config) bool {
                mem := v.Args[2]
                v.reset(OpStore)
                v.AuxInt = t.FieldType(0).Size()
-               v.AddArg(dst)
+               v0 := b.NewValue0(v.Pos, OpOffPtr, t.FieldType(0).PtrTo())
+               v0.AuxInt = 0
+               v0.AddArg(dst)
+               v.AddArg(v0)
                v.AddArg(f0)
                v.AddArg(mem)
                return true
        }
        // match: (Store dst (StructMake2 <t> f0 f1) mem)
        // cond:
-       // result: (Store [t.FieldType(1).Size()]     (OffPtr <t.FieldType(1).PtrTo()> [t.FieldOff(1)] dst)     f1     (Store [t.FieldType(0).Size()] dst f0 mem))
+       // result: (Store [t.FieldType(1).Size()]     (OffPtr <t.FieldType(1).PtrTo()> [t.FieldOff(1)] dst)     f1     (Store [t.FieldType(0).Size()]       (OffPtr <t.FieldType(0)> [0] dst)         f0 mem))
        for {
                dst := v.Args[0]
                v_1 := v.Args[1]
@@ -14710,7 +14725,10 @@ func rewriteValuegeneric_OpStore(v *Value, config *Config) bool {
                v.AddArg(f1)
                v1 := b.NewValue0(v.Pos, OpStore, TypeMem)
                v1.AuxInt = t.FieldType(0).Size()
-               v1.AddArg(dst)
+               v2 := b.NewValue0(v.Pos, OpOffPtr, t.FieldType(0))
+               v2.AuxInt = 0
+               v2.AddArg(dst)
+               v1.AddArg(v2)
                v1.AddArg(f0)
                v1.AddArg(mem)
                v.AddArg(v1)
@@ -14718,7 +14736,7 @@ func rewriteValuegeneric_OpStore(v *Value, config *Config) bool {
        }
        // match: (Store dst (StructMake3 <t> f0 f1 f2) mem)
        // cond:
-       // result: (Store [t.FieldType(2).Size()]     (OffPtr <t.FieldType(2).PtrTo()> [t.FieldOff(2)] dst)     f2     (Store [t.FieldType(1).Size()]       (OffPtr <t.FieldType(1).PtrTo()> [t.FieldOff(1)] dst)       f1       (Store [t.FieldType(0).Size()] dst f0 mem)))
+       // result: (Store [t.FieldType(2).Size()]     (OffPtr <t.FieldType(2).PtrTo()> [t.FieldOff(2)] dst)     f2     (Store [t.FieldType(1).Size()]       (OffPtr <t.FieldType(1).PtrTo()> [t.FieldOff(1)] dst)       f1       (Store [t.FieldType(0).Size()]         (OffPtr <t.FieldType(0).PtrTo()> [0] dst)           f0 mem)))
        for {
                dst := v.Args[0]
                v_1 := v.Args[1]
@@ -14746,7 +14764,10 @@ func rewriteValuegeneric_OpStore(v *Value, config *Config) bool {
                v1.AddArg(f1)
                v3 := b.NewValue0(v.Pos, OpStore, TypeMem)
                v3.AuxInt = t.FieldType(0).Size()
-               v3.AddArg(dst)
+               v4 := b.NewValue0(v.Pos, OpOffPtr, t.FieldType(0).PtrTo())
+               v4.AuxInt = 0
+               v4.AddArg(dst)
+               v3.AddArg(v4)
                v3.AddArg(f0)
                v3.AddArg(mem)
                v1.AddArg(v3)
@@ -14755,7 +14776,7 @@ func rewriteValuegeneric_OpStore(v *Value, config *Config) bool {
        }
        // match: (Store dst (StructMake4 <t> f0 f1 f2 f3) mem)
        // cond:
-       // result: (Store [t.FieldType(3).Size()]     (OffPtr <t.FieldType(3).PtrTo()> [t.FieldOff(3)] dst)     f3     (Store [t.FieldType(2).Size()]       (OffPtr <t.FieldType(2).PtrTo()> [t.FieldOff(2)] dst)       f2       (Store [t.FieldType(1).Size()]         (OffPtr <t.FieldType(1).PtrTo()> [t.FieldOff(1)] dst)         f1         (Store [t.FieldType(0).Size()] dst f0 mem))))
+       // result: (Store [t.FieldType(3).Size()]     (OffPtr <t.FieldType(3).PtrTo()> [t.FieldOff(3)] dst)     f3     (Store [t.FieldType(2).Size()]       (OffPtr <t.FieldType(2).PtrTo()> [t.FieldOff(2)] dst)       f2       (Store [t.FieldType(1).Size()]         (OffPtr <t.FieldType(1).PtrTo()> [t.FieldOff(1)] dst)         f1         (Store [t.FieldType(0).Size()]           (OffPtr <t.FieldType(0).PtrTo()> [0] dst)             f0 mem))))
        for {
                dst := v.Args[0]
                v_1 := v.Args[1]
@@ -14791,7 +14812,10 @@ func rewriteValuegeneric_OpStore(v *Value, config *Config) bool {
                v3.AddArg(f1)
                v5 := b.NewValue0(v.Pos, OpStore, TypeMem)
                v5.AuxInt = t.FieldType(0).Size()
-               v5.AddArg(dst)
+               v6 := b.NewValue0(v.Pos, OpOffPtr, t.FieldType(0).PtrTo())
+               v6.AuxInt = 0
+               v6.AddArg(dst)
+               v5.AddArg(v6)
                v5.AddArg(f0)
                v5.AddArg(mem)
                v3.AddArg(v5)