cmd/compile: fix conditional move rule on PPC64

Similar to CL 456556 but for ppc64 instead of arm64.

Change docs about how booleans are stored in registers for ppc64.
We now don't promise to keep the upper bits zeroed; they might be junk.

To test, I changed the boolean generation instructions (MOVBZload* and ISEL*
with boolean type) to OR in 0x100 to the result. all.bash still passed,
so I think nothing else is depending on the upper bits of booleans.

Update #57184

Change-Id: Ie66f8934a0dafa34d0a8c2a37324868d959a852c
Reviewed-on: https://go-review.googlesource.com/c/go/+/456437
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Keith Randall <khr@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: KAMPANAT THUMWONG (KONG PC) <1992kongpc.kth@gmail.com>
Run-TryBot: Archana Ravindar <aravind5@in.ibm.com>

diff --git a/src/cmd/compile/internal/ssa/_gen/PPC64.rules b/src/cmd/compile/internal/ssa/_gen/PPC64.rules
index aee53d4f0fa206860cbec11564d86b926d2a770d..5a68de0ca4dadff18c19b4c37b09094998b9ecee 100644 (file)
--- a/src/cmd/compile/internal/ssa/_gen/PPC64.rules
+++ b/src/cmd/compile/internal/ssa/_gen/PPC64.rules
@@ -409,9 +409,9 @@
 ((EQ|NE|LT|LE|GT|GE) (CMPconst [0] z:(XOR x y)) yes no) && z.Uses == 1 => ((EQ|NE|LT|LE|GT|GE) (Select1 <types.TypeFlags> (XORCC x y)) yes no)
 
 // Only lower after bool is lowered. It should always lower. This helps ensure the folding below happens reliably.
-(CondSelect x y bool) && flagArg(bool) == nil => (ISEL [6] x y (CMPWconst [0] bool))
+(CondSelect x y bool) && flagArg(bool) == nil => (ISEL [6] x y (Select1 <types.TypeFlags> (ANDCCconst [1] bool)))
 // Fold any CR -> GPR -> CR transfers when applying the above rule.
-(ISEL [6] x y (CMPWconst [0] (ISELB [c] one cmp))) => (ISEL [c] x y cmp)
+(ISEL [6] x y (Select1 (ANDCCconst [1] (ISELB [c] one cmp)))) => (ISEL [c] x y cmp)
 
 // Lowering loads
 (Load <t> ptr mem) && (is64BitInt(t) || isPtr(t)) => (MOVDload ptr mem)

diff --git a/src/cmd/compile/internal/ssa/_gen/PPC64Ops.go b/src/cmd/compile/internal/ssa/_gen/PPC64Ops.go
index baa783e30b7515aba4e5eb4edfdfd782ccfec3bd..2d651dd780332eb885ec20ef7ac33b926fdacbf5 100644 (file)
--- a/src/cmd/compile/internal/ssa/_gen/PPC64Ops.go
+++ b/src/cmd/compile/internal/ssa/_gen/PPC64Ops.go
@@ -8,8 +8,8 @@ import "strings"
 
 // Notes:
 //  - Less-than-64-bit integer types live in the low portion of registers.
-//    For now, the upper portion is junk; sign/zero-extension might be optimized in the future, but not yet.
-//  - Boolean types are zero or 1; stored in a byte, but loaded with AMOVBZ so the upper bytes of a register are zero.
+//    The upper portion is junk.
+//  - Boolean types are zero or 1; stored in a byte, with upper bytes of the register containing junk.
 //  - *const instructions may use a constant larger than the instruction can encode.
 //    In this case the assembler expands to multiple instructions and uses tmp
 //    register (R31).

diff --git a/src/cmd/compile/internal/ssa/rewritePPC64.go b/src/cmd/compile/internal/ssa/rewritePPC64.go
index 8b5ea14757afc8eefa8d2b0167f6290735c12c56..bc593128daf4ca6d1149f2700a2e952427e79895 100644 (file)
--- a/src/cmd/compile/internal/ssa/rewritePPC64.go
+++ b/src/cmd/compile/internal/ssa/rewritePPC64.go
@@ -1172,9 +1172,10 @@ func rewriteValuePPC64_OpCondSelect(v *Value) bool {
        v_1 := v.Args[1]
        v_0 := v.Args[0]
        b := v.Block
+       typ := &b.Func.Config.Types
        // match: (CondSelect x y bool)
        // cond: flagArg(bool) == nil
-       // result: (ISEL [6] x y (CMPWconst [0] bool))
+       // result: (ISEL [6] x y (Select1 <types.TypeFlags> (ANDCCconst [1] bool)))
        for {
                x := v_0
                y := v_1
@@ -1184,9 +1185,11 @@ func rewriteValuePPC64_OpCondSelect(v *Value) bool {
                }
                v.reset(OpPPC64ISEL)
                v.AuxInt = int32ToAuxInt(6)
-               v0 := b.NewValue0(v.Pos, OpPPC64CMPWconst, types.TypeFlags)
-               v0.AuxInt = int32ToAuxInt(0)
-               v0.AddArg(bool)
+               v0 := b.NewValue0(v.Pos, OpSelect1, types.TypeFlags)
+               v1 := b.NewValue0(v.Pos, OpPPC64ANDCCconst, types.NewTuple(typ.Int, types.TypeFlags))
+               v1.AuxInt = int64ToAuxInt(1)
+               v1.AddArg(bool)
+               v0.AddArg(v1)
                v.AddArg3(x, y, v0)
                return true
        }
@@ -5355,7 +5358,7 @@ func rewriteValuePPC64_OpPPC64ISEL(v *Value) bool {
                v.AddArg(v0)
                return true
        }
-       // match: (ISEL [6] x y (CMPWconst [0] (ISELB [c] one cmp)))
+       // match: (ISEL [6] x y (Select1 (ANDCCconst [1] (ISELB [c] one cmp))))
        // result: (ISEL [c] x y cmp)
        for {
                if auxIntToInt32(v.AuxInt) != 6 {
@@ -5363,15 +5366,19 @@ func rewriteValuePPC64_OpPPC64ISEL(v *Value) bool {
                }
                x := v_0
                y := v_1
-               if v_2.Op != OpPPC64CMPWconst || auxIntToInt32(v_2.AuxInt) != 0 {
+               if v_2.Op != OpSelect1 {
                        break
                }
                v_2_0 := v_2.Args[0]
-               if v_2_0.Op != OpPPC64ISELB {
+               if v_2_0.Op != OpPPC64ANDCCconst || auxIntToInt64(v_2_0.AuxInt) != 1 {
+                       break
+               }
+               v_2_0_0 := v_2_0.Args[0]
+               if v_2_0_0.Op != OpPPC64ISELB {
                        break
                }
-               c := auxIntToInt32(v_2_0.AuxInt)
-               cmp := v_2_0.Args[1]
+               c := auxIntToInt32(v_2_0_0.AuxInt)
+               cmp := v_2_0_0.Args[1]
                v.reset(OpPPC64ISEL)
                v.AuxInt = int32ToAuxInt(c)
                v.AddArg3(x, y, cmp)