From 934104630291d3bb8b1023e44fe06687e1c0b9c8 Mon Sep 17 00:00:00 2001
From: Jayanth Krishnamurthy <jayanth.krishnamurthy@ibm.com>
Date: Wed, 1 Nov 2023 14:43:42 -0500
Subject: [PATCH] cmd/compile: adding rule to eliminate ANDCCconst

For example, the Slicemask rule in PPC64 generates a sequence wherein there is andi operation, after an  sradi, which can be replaced by srdi. This new rule eliminates ANDCCconst.

Change-Id: I27aaadf76b9c749a60bcdc5e87b1ebb8167d2fd4
Reviewed-on: https://go-review.googlesource.com/c/go/+/539055
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>
Reviewed-by: Jayanth Krishnamurthy <jayanth.krishnamurthy@ibm.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Heschi Kreinick <heschi@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
---
 src/cmd/compile/internal/ssa/_gen/PPC64.rules |  1 +
 src/cmd/compile/internal/ssa/rewritePPC64.go  | 20 +++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/src/cmd/compile/internal/ssa/_gen/PPC64.rules b/src/cmd/compile/internal/ssa/_gen/PPC64.rules
index 5780260c24..c9cd34b9a6 100644
--- a/src/cmd/compile/internal/ssa/_gen/PPC64.rules
+++ b/src/cmd/compile/internal/ssa/_gen/PPC64.rules
@@ -800,6 +800,7 @@
 (AtomicOr(8|32)   ...) => (LoweredAtomicOr(8|32)   ...)
 
 (Slicemask <t> x) => (SRADconst (NEG <t> x) [63])
+(Select0 (ANDCCconst [1] z:(SRADconst [63] x))) && z.Uses == 1  => (SRDconst [63] x)
 
 // Note that MOV??reg returns a 64-bit int, x is not necessarily that wide
 // This may interact with other patterns in the future. (Compare with arm64)
diff --git a/src/cmd/compile/internal/ssa/rewritePPC64.go b/src/cmd/compile/internal/ssa/rewritePPC64.go
index 7ec6bb4e46..473a8ff9d9 100644
--- a/src/cmd/compile/internal/ssa/rewritePPC64.go
+++ b/src/cmd/compile/internal/ssa/rewritePPC64.go
@@ -14552,6 +14552,26 @@ func rewriteValuePPC64_OpSelect0(v *Value) bool {
 		v.AddArg(v0)
 		return true
 	}
+	// match: (Select0 (ANDCCconst [1] z:(SRADconst [63] x)))
+	// cond: z.Uses == 1
+	// result: (SRDconst [63] x)
+	for {
+		if v_0.Op != OpPPC64ANDCCconst || auxIntToInt64(v_0.AuxInt) != 1 {
+			break
+		}
+		z := v_0.Args[0]
+		if z.Op != OpPPC64SRADconst || auxIntToInt64(z.AuxInt) != 63 {
+			break
+		}
+		x := z.Args[0]
+		if !(z.Uses == 1) {
+			break
+		}
+		v.reset(OpPPC64SRDconst)
+		v.AuxInt = int64ToAuxInt(63)
+		v.AddArg(x)
+		return true
+	}
 	return false
 }
 func rewriteValuePPC64_OpSelect1(v *Value) bool {
-- 
2.44.0