[release-branch.go1.21] Revert "cmd/compile: omit redundant sign/unsign extension on arm64"

This reverts CL 427454.

Reason for revert: causes incorrect generated code in some rare cases

We'll fix-forward at tip, so the revert just needs to be done for 1.21.

Fixes #62143

Change-Id: Id242230481ff4d4ba5f58236c6d8237729fc3b80
Reviewed-on: https://go-review.googlesource.com/c/go/+/520976
Run-TryBot: Keith Randall <[email protected]>
Reviewed-by: Ruinan Sun <[email protected]>
Reviewed-by: Keith Randall <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>

Author: randall77

src/cmd/compile/internal/ssa/_gen/ARM64.rules

@@ -1571,14 +1571,6 @@
 // zero upper bit of the register; no need to zero-extend
 (MOVBUreg x:((Equal|NotEqual|LessThan|LessThanU|LessThanF|LessEqual|LessEqualU|LessEqualF|GreaterThan|GreaterThanU|GreaterThanF|GreaterEqual|GreaterEqualU|GreaterEqualF) _)) => (MOVDreg x)
 
-// omit unsign extension
-(MOVWUreg x) && zeroUpper32Bits(x, 3) => x
-
-// omit sign extension
-(MOVWreg <t> (ANDconst x [c])) && uint64(c) & uint64(0xffffffff80000000) == 0 => (ANDconst <t> x [c])
-(MOVHreg <t> (ANDconst x [c])) && uint64(c) & uint64(0xffffffffffff8000) == 0 => (ANDconst <t> x [c])
-(MOVBreg <t> (ANDconst x [c])) && uint64(c) & uint64(0xffffffffffffff80) == 0 => (ANDconst <t> x [c])
-
 // absorb flag constants into conditional instructions
 (CSEL  [cc] x _ flag) && ccARM64Eval(cc, flag) > 0 => x
 (CSEL  [cc] _ y flag) && ccARM64Eval(cc, flag) < 0 => y

src/cmd/compile/internal/ssa/_gen/ARM64Ops.go

@@ -13,7 +13,6 @@ import "strings"
 //  - *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 (R27).
-//  - All 32-bit Ops will zero the upper 32 bits of the destination register.
 
 // Suffixes encode the bit width of various instructions.
 // D (double word) = 64 bit

src/cmd/compile/internal/ssa/rewrite.go

@@ -1281,10 +1281,6 @@ func zeroUpper32Bits(x *Value, depth int) bool {
 		OpAMD64SHRL, OpAMD64SHRLconst, OpAMD64SARL, OpAMD64SARLconst,
 		OpAMD64SHLL, OpAMD64SHLLconst:
 		return true
-	case OpARM64REV16W, OpARM64REVW, OpARM64RBITW, OpARM64CLZW, OpARM64EXTRWconst,
-		OpARM64MULW, OpARM64MNEGW, OpARM64UDIVW, OpARM64DIVW, OpARM64UMODW,
-		OpARM64MADDW, OpARM64MSUBW, OpARM64RORW, OpARM64RORWconst:
-		return true
 	case OpArg:
 		return x.Type.Size() == 4
 	case OpPhi, OpSelect0, OpSelect1:

src/cmd/compile/internal/ssa/rewriteARM64.go

@@ -6,8 +6,6 @@
 
 package codegen
 
-import "math/bits"
-
 var sval64 [8]int64
 var sval32 [8]int32
 var sval16 [8]int16
@@ -187,95 +185,3 @@ func cmp64(u8 *uint8, x16 *int16, u16 *uint16, x32 *int32, u32 *uint32) bool {
 	}
 	return false
 }
-
-// no unsign extension following 32 bits ops
-
-func noUnsignEXT(t1, t2, t3, t4 uint32, k int64) uint64 {
-	var ret uint64
-
-	// arm64:"RORW",-"MOVWU"
-	ret += uint64(bits.RotateLeft32(t1, 7))
-
-	// arm64:"MULW",-"MOVWU"
-	ret *= uint64(t1 * t2)
-
-	// arm64:"MNEGW",-"MOVWU"
-	ret += uint64(-t1 * t3)
-
-	// arm64:"UDIVW",-"MOVWU"
-	ret += uint64(t1 / t4)
-
-	// arm64:-"MOVWU"
-	ret += uint64(t2 % t3)
-
-	// arm64:"MSUBW",-"MOVWU"
-	ret += uint64(t1 - t2*t3)
-
-	// arm64:"MADDW",-"MOVWU"
-	ret += uint64(t3*t4 + t2)
-
-	// arm64:"REVW",-"MOVWU"
-	ret += uint64(bits.ReverseBytes32(t1))
-
-	// arm64:"RBITW",-"MOVWU"
-	ret += uint64(bits.Reverse32(t1))
-
-	// arm64:"CLZW",-"MOVWU"
-	ret += uint64(bits.LeadingZeros32(t1))
-
-	// arm64:"REV16W",-"MOVWU"
-	ret += uint64(((t1 & 0xff00ff00) >> 8) | ((t1 & 0x00ff00ff) << 8))
-
-	// arm64:"EXTRW",-"MOVWU"
-	ret += uint64((t1 << 25) | (t2 >> 7))
-
-	return ret
-}
-
-// no sign extension when the upper bits of the result are zero
-
-func noSignEXT(x int) int64 {
-	t1 := int32(x)
-
-	var ret int64
-
-	// arm64:-"MOVW"
-	ret += int64(t1 & 1)
-
-	// arm64:-"MOVW"
-	ret += int64(int32(x & 0x7fffffff))
-
-	// arm64:-"MOVH"
-	ret += int64(int16(x & 0x7fff))
-
-	// arm64:-"MOVB"
-	ret += int64(int8(x & 0x7f))
-
-	return ret
-}
-
-// corner cases that sign extension must not be omitted
-
-func shouldSignEXT(x int) int64 {
-	t1 := int32(x)
-
-	var ret int64
-
-	// arm64:"MOVW"
-	ret += int64(t1 & (-1))
-
-	// arm64:"MOVW"
-	ret += int64(int32(x & 0x80000000))
-
-	// arm64:"MOVW"
-	ret += int64(int32(x & 0x1100000011111111))
-
-	// arm64:"MOVH"
-	ret += int64(int16(x & 0x1100000000001111))
-
-	// arm64:"MOVB"
-	ret += int64(int8(x & 0x1100000000000011))
-
-	return ret
-
-}