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cmd/compile: use NOT pseudo-instruction for riscv64 Slicemask

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Change-Id: Idefb6669d54929065f57e3bd767c91451dc3a375
Reviewed-on: https://go-review.googlesource.com/c/go/+/223562
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Joel Sing 2020-03-16 03:29:19 +11:00
parent 2f54081adf
commit 0e44c692c2
2 changed files with 3 additions and 4 deletions
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2
src/cmd/compile/internal/ssa/gen/RISCV64.rules
View File

@ -143,7 +143,7 @@
// For positive x, bit 63 of x-1 is always 0, so the result is -1.
// For zero x, bit 63 of x-1 is 1, so the result is 0.
//
(Slicemask <t> x) -> (XORI [-1] (SRAI <t> [63] (ADDI <t> [-1] x)))
(Slicemask <t> x) -> (NOT (SRAI <t> [63] (ADDI <t> [-1] x)))
// Truncations
// We ignore the unused high parts of registers, so truncates are just copies.

5
src/cmd/compile/internal/ssa/rewriteRISCV64.go
View File

@ -4309,12 +4309,11 @@ func rewriteValueRISCV64_OpSlicemask(v *Value) bool {
v_0 := v.Args[0]
b := v.Block
// match: (Slicemask <t> x)
// result: (XORI [-1] (SRAI <t> [63] (ADDI <t> [-1] x)))
// result: (NOT (SRAI <t> [63] (ADDI <t> [-1] x)))
for {
t := v.Type
x := v_0
v.reset(OpRISCV64XORI)
v.AuxInt = -1
v.reset(OpRISCV64NOT)
v0 := b.NewValue0(v.Pos, OpRISCV64SRAI, t)
v0.AuxInt = 63
v1 := b.NewValue0(v.Pos, OpRISCV64ADDI, t)