cmd/compile: Improve const shifts in PPC64.rules

This change updates PPC64.rules to recognize constant shift
counts and generate more efficient code sequences in those cases.

Fixes #17336

Change-Id: I8a7b812408d7a68388df41e42bad045dd214be17
Reviewed-on: https://go-review.googlesource.com/30310
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

src/cmd/compile/internal/ssa/gen/PPC64.rules

@@ -75,6 +75,85 @@
 
 (Sqrt x) -> (FSQRT x)
 
+// Lowering constants
+(Const8   [val]) -> (MOVDconst [val])
+(Const16  [val]) -> (MOVDconst [val])
+(Const32  [val]) -> (MOVDconst [val])
+(Const64  [val]) -> (MOVDconst [val])
+(Const32F [val]) -> (FMOVSconst [val])
+(Const64F [val]) -> (FMOVDconst [val])
+(ConstNil) -> (MOVDconst [0])
+(ConstBool [b]) -> (MOVDconst [b])
+
+(Lsh64x64  x (Const64 [c])) && uint64(c) < 64 -> (SLDconst x [c])
+(Rsh64x64  x (Const64 [c])) && uint64(c) < 64 -> (SRADconst x [c])
+(Rsh64Ux64 x (Const64 [c])) && uint64(c) < 64 -> (SRDconst x [c])
+(Lsh32x64  x (Const64 [c])) && uint64(c) < 32 -> (SLWconst x [c])
+(Rsh32x64  x (Const64 [c])) && uint64(c) < 32 -> (SRAWconst x [c])
+(Rsh32Ux64 x (Const64 [c])) && uint64(c) < 32 -> (SRWconst x [c])
+(Lsh16x64  x (Const64 [c])) && uint64(c) < 16 -> (SLWconst x [c])
+(Rsh16x64  x (Const64 [c])) && uint64(c) < 16 -> (SRAWconst (SignExt16to32 x) [c])
+(Rsh16Ux64 x (Const64 [c])) && uint64(c) < 16 -> (SRWconst (ZeroExt16to32 x) [c])
+(Lsh8x64   x (Const64 [c])) && uint64(c) < 8  -> (SLWconst x [c])
+(Rsh8x64   x (Const64 [c])) && uint64(c) < 8  -> (SRAWconst (SignExt8to32  x) [c])
+(Rsh8Ux64  x (Const64 [c])) && uint64(c) < 8  -> (SRWconst (ZeroExt8to32  x) [c])
+
+(Lsh64x32  x (Const64 [c])) && uint32(c) < 64 -> (SLDconst x [c])
+(Rsh64x32  x (Const64 [c])) && uint32(c) < 64 -> (SRADconst x [c])
+(Rsh64Ux32 x (Const64 [c])) && uint32(c) < 64 -> (SRDconst x [c])
+(Lsh32x32  x (Const64 [c])) && uint32(c) < 32 -> (SLWconst x [c])
+(Rsh32x32  x (Const64 [c])) && uint32(c) < 32 -> (SRAWconst x [c])
+(Rsh32Ux32 x (Const64 [c])) && uint32(c) < 32 -> (SRWconst x [c])
+(Lsh16x32  x (Const64 [c])) && uint32(c) < 16 -> (SLWconst x [c])
+(Rsh16x32  x (Const64 [c])) && uint32(c) < 16 -> (SRAWconst (SignExt16to32 x) [c])
+(Rsh16Ux32 x (Const64 [c])) && uint32(c) < 16 -> (SRWconst (ZeroExt16to32 x) [c])
+(Lsh8x32   x (Const64 [c])) && uint32(c) < 8  -> (SLWconst x [c])
+(Rsh8x32   x (Const64 [c])) && uint32(c) < 8  -> (SRAWconst (SignExt8to32  x) [c])
+(Rsh8Ux32  x (Const64 [c])) && uint32(c) < 8  -> (SRWconst (ZeroExt8to32  x) [c])
+
+// large constant shifts
+(Lsh64x64  _ (Const64 [c])) && uint64(c) >= 64 -> (MOVDconst [0])
+(Rsh64Ux64 _ (Const64 [c])) && uint64(c) >= 64 -> (MOVDconst [0])
+(Lsh32x64  _ (Const64 [c])) && uint64(c) >= 32 -> (MOVDconst [0])
+(Rsh32Ux64 _ (Const64 [c])) && uint64(c) >= 32 -> (MOVDconst [0])
+(Lsh16x64  _ (Const64 [c])) && uint64(c) >= 16 -> (MOVDconst [0])
+(Rsh16Ux64 _ (Const64 [c])) && uint64(c) >= 16 -> (MOVDconst [0])
+(Lsh8x64   _ (Const64 [c])) && uint64(c) >= 8  -> (MOVDconst [0])
+(Rsh8Ux64  _ (Const64 [c])) && uint64(c) >= 8  -> (MOVDconst [0])
+
+// large constant signed right shift, we leave the sign bit
+(Rsh64x64 x (Const64 [c])) && uint64(c) >= 64 -> (SRADconst x [63])
+(Rsh32x64 x (Const64 [c])) && uint64(c) >= 32 -> (SRAWconst x [63])
+(Rsh16x64 x (Const64 [c])) && uint64(c) >= 16 -> (SRAWconst (SignExt16to32 x) [63])
+(Rsh8x64  x (Const64 [c])) && uint64(c) >= 8  -> (SRAWconst (SignExt8to32  x) [63])
+
+// constant shifts
+(Lsh64x64  x (MOVDconst [c])) && uint64(c) < 64 -> (SLDconst x [c])
+(Rsh64x64  x (MOVDconst [c])) && uint64(c) < 64 -> (SRADconst x [c])
+(Rsh64Ux64 x (MOVDconst [c])) && uint64(c) < 64 -> (SRDconst x [c])
+(Lsh32x64  x (MOVDconst [c])) && uint64(c) < 32 -> (SLWconst x [c])
+(Rsh32x64  x (MOVDconst [c])) && uint64(c) < 32 -> (SRAWconst x [c])
+(Rsh32Ux64 x (MOVDconst [c])) && uint64(c) < 32 -> (SRWconst x [c])
+(Lsh16x64  x (MOVDconst [c])) && uint64(c) < 16 -> (SLWconst x [c])
+(Rsh16x64  x (MOVDconst [c])) && uint64(c) < 16 -> (SRAWconst (SignExt16to32 x) [c])
+(Rsh16Ux64 x (MOVDconst [c])) && uint64(c) < 16 -> (SRWconst (ZeroExt16to32 x) [c])
+(Lsh8x64   x (MOVDconst [c])) && uint64(c) < 8  -> (SLWconst x [c])
+(Rsh8x64   x (MOVDconst [c])) && uint64(c) < 8  -> (SRAWconst (SignExt8to32  x) [c])
+(Rsh8Ux64  x (MOVDconst [c])) && uint64(c) < 8  -> (SRWconst (ZeroExt8to32  x) [c])
+
+(Lsh64x32  x (MOVDconst [c])) && uint32(c) < 64 -> (SLDconst x [c])
+(Rsh64x32  x (MOVDconst [c])) && uint32(c) < 64 -> (SRADconst x [c])
+(Rsh64Ux32 x (MOVDconst [c])) && uint32(c) < 64 -> (SRDconst x [c])
+(Lsh32x32  x (MOVDconst [c])) && uint32(c) < 32 -> (SLWconst x [c])
+(Rsh32x32  x (MOVDconst [c])) && uint32(c) < 32 -> (SRAWconst x [c])
+(Rsh32Ux32 x (MOVDconst [c])) && uint32(c) < 32 -> (SRWconst x [c])
+(Lsh16x32  x (MOVDconst [c])) && uint32(c) < 16 -> (SLWconst x [c])
+(Rsh16x32  x (MOVDconst [c])) && uint32(c) < 16 -> (SRAWconst (SignExt16to32 x) [c])
+(Rsh16Ux32 x (MOVDconst [c])) && uint32(c) < 16 -> (SRWconst (ZeroExt16to32 x) [c])
+(Lsh8x32   x (MOVDconst [c])) && uint32(c) < 8  -> (SLWconst x [c])
+(Rsh8x32   x (MOVDconst [c])) && uint32(c) < 8  -> (SRAWconst (SignExt8to32  x) [c])
+(Rsh8Ux32  x (MOVDconst [c])) && uint32(c) < 8  -> (SRWconst (ZeroExt8to32  x) [c])
+
 (Rsh64x64 x y)  -> (SRAD x (ORN y <config.fe.TypeInt64()> (MaskIfNotCarry (ADDconstForCarry [-64] y))))
 (Rsh64Ux64 x y) -> (SRD  x (ORN y <config.fe.TypeInt64()> (MaskIfNotCarry (ADDconstForCarry [-64] y))))
 (Lsh64x64 x y)  -> (SLD  x (ORN y <config.fe.TypeInt64()> (MaskIfNotCarry (ADDconstForCarry [-64] y))))
@@ -148,16 +227,6 @@
 // (MaskIfNotCarry CarrySet) -> 0
 // (MaskIfNotCarry CarrySet) -> -1
 
-// Lowering constants
-(Const8   [val]) -> (MOVDconst [val])
-(Const16  [val]) -> (MOVDconst [val])
-(Const32  [val]) -> (MOVDconst [val])
-(Const64  [val]) -> (MOVDconst [val])
-(Const32F [val]) -> (FMOVSconst [val])
-(Const64F [val]) -> (FMOVDconst [val])
-(ConstNil) -> (MOVDconst [0])
-(ConstBool [b]) -> (MOVDconst [b])
-
 (Addr {sym} base) -> (MOVDaddr {sym} base)
 // (Addr {sym} base) -> (ADDconst {sym} base)
 (OffPtr [off] ptr) -> (ADD (MOVDconst <config.Frontend().TypeInt64()> [off]) ptr)