cmd/compile: use SEQZ pseudo instruction in RISCV64 boolean rules

This makes the intent clearer, allows for another ellipsis and will aid
in future rewriting. While here, document boolean loads to explain register
contents.

Change-Id: I933db2813826d88819366191fbbea8fcee5e4dda
Reviewed-on: https://go-review.googlesource.com/c/go/+/230120
Reviewed-by: Keith Randall <khr@golang.org>

diff --git a/src/cmd/compile/internal/ssa/gen/RISCV64.rules b/src/cmd/compile/internal/ssa/gen/RISCV64.rules
index 845ca58b6ed5d4a95d76275f20d01debc9392d85..fbd87360ac839047ddded22e3679af35dd6268d6 100644 (file)
--- a/src/cmd/compile/internal/ssa/gen/RISCV64.rules
+++ b/src/cmd/compile/internal/ssa/gen/RISCV64.rules
@@ -414,9 +414,9 @@
 // Boolean ops; 0=false, 1=true
 (AndB ...) => (AND ...)
 (OrB  ...) => (OR  ...)
-(EqB  x y) => (XORI [1] (XOR <typ.Bool> x y))
+(EqB  x y) => (SEQZ (XOR <typ.Bool> x y))
 (NeqB ...) => (XOR ...)
-(Not  x)   => (XORI [1] x)
+(Not  ...) => (SEQZ ...)
 
 // Lowering pointer arithmetic
 // TODO: Special handling for SP offsets, like ARM

diff --git a/src/cmd/compile/internal/ssa/gen/RISCV64Ops.go b/src/cmd/compile/internal/ssa/gen/RISCV64Ops.go
index 8bdb35f95af4bd1376e2b6af10b7bc707e66a213..8ab4abe04a073e9c4fa9843e714a06e58ed6e4a3 100644 (file)
--- a/src/cmd/compile/internal/ssa/gen/RISCV64Ops.go
+++ b/src/cmd/compile/internal/ssa/gen/RISCV64Ops.go
@@ -10,6 +10,9 @@ import (
        "fmt"
 )
 
+// Notes:
+//  - Boolean types occupy the entire register. 0=false, 1=true.
+
 // Suffixes encode the bit width of various instructions:
 //
 // D (double word) = 64 bit int

diff --git a/src/cmd/compile/internal/ssa/rewriteRISCV64.go b/src/cmd/compile/internal/ssa/rewriteRISCV64.go
index db9f529bae0b0061949cd3cac262c79d9388630a..6b91c08628b544399da4782144257dfd1ccb1bfc 100644 (file)
--- a/src/cmd/compile/internal/ssa/rewriteRISCV64.go
+++ b/src/cmd/compile/internal/ssa/rewriteRISCV64.go
@@ -391,7 +391,8 @@ func rewriteValueRISCV64(v *Value) bool {
                v.Op = OpRISCV64LoweredNilCheck
                return true
        case OpNot:
-               return rewriteValueRISCV64_OpNot(v)
+               v.Op = OpRISCV64SEQZ
+               return true
        case OpOffPtr:
                return rewriteValueRISCV64_OpOffPtr(v)
        case OpOr16:
@@ -913,12 +914,11 @@ func rewriteValueRISCV64_OpEqB(v *Value) bool {
        b := v.Block
        typ := &b.Func.Config.Types
        // match: (EqB x y)
-       // result: (XORI [1] (XOR <typ.Bool> x y))
+       // result: (SEQZ (XOR <typ.Bool> x y))
        for {
                x := v_0
                y := v_1
-               v.reset(OpRISCV64XORI)
-               v.AuxInt = int64ToAuxInt(1)
+               v.reset(OpRISCV64SEQZ)
                v0 := b.NewValue0(v.Pos, OpRISCV64XOR, typ.Bool)
                v0.AddArg2(x, y)
                v.AddArg(v0)
@@ -2132,18 +2132,6 @@ func rewriteValueRISCV64_OpNeqPtr(v *Value) bool {
                return true
        }
 }
-func rewriteValueRISCV64_OpNot(v *Value) bool {
-       v_0 := v.Args[0]
-       // match: (Not x)
-       // result: (XORI [1] x)
-       for {
-               x := v_0
-               v.reset(OpRISCV64XORI)
-               v.AuxInt = int64ToAuxInt(1)
-               v.AddArg(x)
-               return true
-       }
-}
 func rewriteValueRISCV64_OpOffPtr(v *Value) bool {
        v_0 := v.Args[0]
        b := v.Block