From: Joel Sing <joel@sing.id.au>
Date: Mon, 26 Oct 2020 07:35:40 +0000 (+1100)
Subject: cmd/compile: avoid unnecessary sign/zero extension for consts on riscv64
X-Git-Tag: go1.16beta1~371
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=12a2e72065105a7c167d7f41500b5a80547f14d0;p=gostls13.git

cmd/compile: avoid unnecessary sign/zero extension for consts on riscv64

Sign extension for consts is unnecessary and zero extension for consts can be avoided
via casts. This removes over 16,000 instructions from the Go binary, in part because it
allows for better zero const absorbtion in blocks - for example,
`(BEQ (MOVBU (MOVBconst [0])) cond yes no)` now becomes `(BEQZ cond yes no)` when
this change is combined with existing rules.

Change-Id: I27e791bfa84869639db653af6119f6e10369ba3d
Reviewed-on: https://go-review.googlesource.com/c/go/+/265041
Trust: Joel Sing <joel@sing.id.au>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
---

diff --git a/src/cmd/compile/internal/ssa/gen/RISCV64.rules b/src/cmd/compile/internal/ssa/gen/RISCV64.rules
index 306103c7b6..449f3cad03 100644
--- a/src/cmd/compile/internal/ssa/gen/RISCV64.rules
+++ b/src/cmd/compile/internal/ssa/gen/RISCV64.rules
@@ -430,6 +430,8 @@
 (OffPtr [off] ptr) && is32Bit(off) => (ADDI [off] ptr)
 (OffPtr [off] ptr) => (ADD (MOVDconst [off]) ptr)
 
+// TODO(jsing): Check if we actually need MOV{B,H,W}const as most platforms
+// use a single MOVDconst op.
 (Const8 ...) => (MOVBconst ...)
 (Const16 ...) => (MOVHconst ...)
 (Const32 ...) => (MOVWconst ...)
@@ -507,6 +509,20 @@
 (MOVWstore [off] {sym} ptr (MOVWconst [0]) mem) => (MOVWstorezero [off] {sym} ptr mem)
 (MOVDstore [off] {sym} ptr (MOVDconst [0]) mem) => (MOVDstorezero [off] {sym} ptr mem)
 
+// Avoid sign/zero extension for consts.
+(MOVBreg  (MOVBconst [c])) => (MOVDconst [int64(c)])
+(MOVHreg  (MOVBconst [c])) => (MOVDconst [int64(c)])
+(MOVHreg  (MOVHconst [c])) => (MOVDconst [int64(c)])
+(MOVWreg  (MOVBconst [c])) => (MOVDconst [int64(c)])
+(MOVWreg  (MOVHconst [c])) => (MOVDconst [int64(c)])
+(MOVWreg  (MOVWconst [c])) => (MOVDconst [int64(c)])
+(MOVBUreg (MOVBconst [c])) => (MOVDconst [int64(uint8(c))])
+(MOVHUreg (MOVBconst [c])) => (MOVDconst [int64(uint16(c))])
+(MOVHUreg (MOVHconst [c])) => (MOVDconst [int64(uint16(c))])
+(MOVWUreg (MOVBconst [c])) => (MOVDconst [int64(uint32(c))])
+(MOVWUreg (MOVHconst [c])) => (MOVDconst [int64(uint32(c))])
+(MOVWUreg (MOVWconst [c])) => (MOVDconst [int64(uint32(c))])
+
 // Avoid sign/zero extension after properly typed load.
 (MOVBreg  x:(MOVBload  _ _)) => (MOVDreg x)
 (MOVHreg  x:(MOVBload  _ _)) => (MOVDreg x)
diff --git a/src/cmd/compile/internal/ssa/rewriteRISCV64.go b/src/cmd/compile/internal/ssa/rewriteRISCV64.go
index 67d3ecf2cc..a91e8428ef 100644
--- a/src/cmd/compile/internal/ssa/rewriteRISCV64.go
+++ b/src/cmd/compile/internal/ssa/rewriteRISCV64.go
@@ -2512,6 +2512,17 @@ func rewriteValueRISCV64_OpRISCV64MOVBUload(v *Value) bool {
 func rewriteValueRISCV64_OpRISCV64MOVBUreg(v *Value) bool {
 	v_0 := v.Args[0]
 	b := v.Block
+	// match: (MOVBUreg (MOVBconst [c]))
+	// result: (MOVDconst [int64(uint8(c))])
+	for {
+		if v_0.Op != OpRISCV64MOVBconst {
+			break
+		}
+		c := auxIntToInt8(v_0.AuxInt)
+		v.reset(OpRISCV64MOVDconst)
+		v.AuxInt = int64ToAuxInt(int64(uint8(c)))
+		return true
+	}
 	// match: (MOVBUreg x:(MOVBUload _ _))
 	// result: (MOVDreg x)
 	for {
@@ -2611,6 +2622,17 @@ func rewriteValueRISCV64_OpRISCV64MOVBload(v *Value) bool {
 func rewriteValueRISCV64_OpRISCV64MOVBreg(v *Value) bool {
 	v_0 := v.Args[0]
 	b := v.Block
+	// match: (MOVBreg (MOVBconst [c]))
+	// result: (MOVDconst [int64(c)])
+	for {
+		if v_0.Op != OpRISCV64MOVBconst {
+			break
+		}
+		c := auxIntToInt8(v_0.AuxInt)
+		v.reset(OpRISCV64MOVDconst)
+		v.AuxInt = int64ToAuxInt(int64(c))
+		return true
+	}
 	// match: (MOVBreg x:(MOVBload _ _))
 	// result: (MOVDreg x)
 	for {
@@ -3151,6 +3173,28 @@ func rewriteValueRISCV64_OpRISCV64MOVHUload(v *Value) bool {
 func rewriteValueRISCV64_OpRISCV64MOVHUreg(v *Value) bool {
 	v_0 := v.Args[0]
 	b := v.Block
+	// match: (MOVHUreg (MOVBconst [c]))
+	// result: (MOVDconst [int64(uint16(c))])
+	for {
+		if v_0.Op != OpRISCV64MOVBconst {
+			break
+		}
+		c := auxIntToInt8(v_0.AuxInt)
+		v.reset(OpRISCV64MOVDconst)
+		v.AuxInt = int64ToAuxInt(int64(uint16(c)))
+		return true
+	}
+	// match: (MOVHUreg (MOVHconst [c]))
+	// result: (MOVDconst [int64(uint16(c))])
+	for {
+		if v_0.Op != OpRISCV64MOVHconst {
+			break
+		}
+		c := auxIntToInt16(v_0.AuxInt)
+		v.reset(OpRISCV64MOVDconst)
+		v.AuxInt = int64ToAuxInt(int64(uint16(c)))
+		return true
+	}
 	// match: (MOVHUreg x:(MOVBUload _ _))
 	// result: (MOVDreg x)
 	for {
@@ -3272,6 +3316,28 @@ func rewriteValueRISCV64_OpRISCV64MOVHload(v *Value) bool {
 func rewriteValueRISCV64_OpRISCV64MOVHreg(v *Value) bool {
 	v_0 := v.Args[0]
 	b := v.Block
+	// match: (MOVHreg (MOVBconst [c]))
+	// result: (MOVDconst [int64(c)])
+	for {
+		if v_0.Op != OpRISCV64MOVBconst {
+			break
+		}
+		c := auxIntToInt8(v_0.AuxInt)
+		v.reset(OpRISCV64MOVDconst)
+		v.AuxInt = int64ToAuxInt(int64(c))
+		return true
+	}
+	// match: (MOVHreg (MOVHconst [c]))
+	// result: (MOVDconst [int64(c)])
+	for {
+		if v_0.Op != OpRISCV64MOVHconst {
+			break
+		}
+		c := auxIntToInt16(v_0.AuxInt)
+		v.reset(OpRISCV64MOVDconst)
+		v.AuxInt = int64ToAuxInt(int64(c))
+		return true
+	}
 	// match: (MOVHreg x:(MOVBload _ _))
 	// result: (MOVDreg x)
 	for {
@@ -3598,6 +3664,39 @@ func rewriteValueRISCV64_OpRISCV64MOVWUload(v *Value) bool {
 func rewriteValueRISCV64_OpRISCV64MOVWUreg(v *Value) bool {
 	v_0 := v.Args[0]
 	b := v.Block
+	// match: (MOVWUreg (MOVBconst [c]))
+	// result: (MOVDconst [int64(uint32(c))])
+	for {
+		if v_0.Op != OpRISCV64MOVBconst {
+			break
+		}
+		c := auxIntToInt8(v_0.AuxInt)
+		v.reset(OpRISCV64MOVDconst)
+		v.AuxInt = int64ToAuxInt(int64(uint32(c)))
+		return true
+	}
+	// match: (MOVWUreg (MOVHconst [c]))
+	// result: (MOVDconst [int64(uint32(c))])
+	for {
+		if v_0.Op != OpRISCV64MOVHconst {
+			break
+		}
+		c := auxIntToInt16(v_0.AuxInt)
+		v.reset(OpRISCV64MOVDconst)
+		v.AuxInt = int64ToAuxInt(int64(uint32(c)))
+		return true
+	}
+	// match: (MOVWUreg (MOVWconst [c]))
+	// result: (MOVDconst [int64(uint32(c))])
+	for {
+		if v_0.Op != OpRISCV64MOVWconst {
+			break
+		}
+		c := auxIntToInt32(v_0.AuxInt)
+		v.reset(OpRISCV64MOVDconst)
+		v.AuxInt = int64ToAuxInt(int64(uint32(c)))
+		return true
+	}
 	// match: (MOVWUreg x:(MOVBUload _ _))
 	// result: (MOVDreg x)
 	for {
@@ -3741,6 +3840,39 @@ func rewriteValueRISCV64_OpRISCV64MOVWload(v *Value) bool {
 func rewriteValueRISCV64_OpRISCV64MOVWreg(v *Value) bool {
 	v_0 := v.Args[0]
 	b := v.Block
+	// match: (MOVWreg (MOVBconst [c]))
+	// result: (MOVDconst [int64(c)])
+	for {
+		if v_0.Op != OpRISCV64MOVBconst {
+			break
+		}
+		c := auxIntToInt8(v_0.AuxInt)
+		v.reset(OpRISCV64MOVDconst)
+		v.AuxInt = int64ToAuxInt(int64(c))
+		return true
+	}
+	// match: (MOVWreg (MOVHconst [c]))
+	// result: (MOVDconst [int64(c)])
+	for {
+		if v_0.Op != OpRISCV64MOVHconst {
+			break
+		}
+		c := auxIntToInt16(v_0.AuxInt)
+		v.reset(OpRISCV64MOVDconst)
+		v.AuxInt = int64ToAuxInt(int64(c))
+		return true
+	}
+	// match: (MOVWreg (MOVWconst [c]))
+	// result: (MOVDconst [int64(c)])
+	for {
+		if v_0.Op != OpRISCV64MOVWconst {
+			break
+		}
+		c := auxIntToInt32(v_0.AuxInt)
+		v.reset(OpRISCV64MOVDconst)
+		v.AuxInt = int64ToAuxInt(int64(c))
+		return true
+	}
 	// match: (MOVWreg x:(MOVBload _ _))
 	// result: (MOVDreg x)
 	for {