ppc64asm: cleanup objdump comparison tests

The objdump comparison test compares the instructions encoded
in decode.txt with a ppc64 objdump.  We can reduce the number
of exceptions (cases where objdump and golang disagree) to those
which are contained in decode.txt.

With ISA 3.1 many of the more exotic instructions which never
appeared in go have been removed.  Likewise, we may consider
removing this test as the additional generated tests for ISA 3.1
cover all instructions and do not require a ppc64 gnu objdump.

Change-Id: Ica84c3e8f977da2e9df2c138456ea5b791aaec9f
Reviewed-on: https://go-review.googlesource.com/c/arch/+/295194
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Lynn Boger <laboger@linux.vnet.ibm.com>

ppc64/ppc64asm/objdump_test.go

@@ -17,7 +17,7 @@ func TestObjdumpPowerManual(t *testing.T)   { testObjdump(t, hexCases(t, objdump
 // generates lots of ppc64x instructions not possible with golang so not worth supporting..
 //func TestObjdumpPowerRandom(t *testing.T)   { testObjdump(t, randomCases(t)) }
 
-// objdumpManualTests holds test cases that will be run by TestObjdumpARMManual.
+// objdumpManualTests holds test cases that will be run by TestObjdumpPowerManual.
 // If you are debugging a few cases that turned up in a longer run, it can be useful
 // to list them here and then use -run=Manual, particularly with tracing enabled.
 // Note that these are byte sequences, so they must be reversed from the usual
@@ -31,38 +31,19 @@ var objdumpManualTests = `
 // allowedMismatchObjdump reports whether the mismatch between text and dec
 // should be allowed by the test.
 func allowedMismatchObjdump(text string, size int, inst *Inst, dec ExtInst) bool {
-	if hasPrefix(dec.text, deleted...) {
-		return true
-	}
-
 	// we support more instructions than binutils
 	if strings.Contains(dec.text, ".long") {
 		return true
 	}
 
-	if hasPrefix(text, "error:") {
-		if hasPrefix(dec.text, unsupported...) {
-			return true
-		}
-	}
-
 	switch inst.Op {
-	case BC, BCA, BL, BLA, BCL, BCLA, TDI, TWI, TW, TD:
-		return true // TODO(minux): we lack the support for extended opcodes here
-	case RLWNM, RLWNMCC, RLDICL, RLDICLCC, RLWINM, RLWINMCC, RLDCL, RLDCLCC:
-		return true // TODO(minux): we lack the support for extended opcodes here
-	case DCBTST, DCBT:
-		return true // objdump uses the embedded argument order, we use the server argument order
-	case MTFSF, MTFSFCC: // objdump doesn't show the last two arguments
+	case BC: // We don't print PC relative branches the same way.
 		return true
-	case VSPLTB, VSPLTH, VSPLTW: // objdump generates unreasonable result "vspltw v6,v19,4" for 10c49a8c, the last 4 should be 0.
+	case DCBF, DCBT: // We only support extended mnemonics, and may not print 0 where R0 == 0.
 		return true
 	case MTVSRWA, MTVSRWZ, MFVSRWZ, MFVSRD, MTVSRD: // We don't support extended mnemonics using VRs or FPRs
 		return true
 	}
-	if hasPrefix(text, "evm", "evl", "efs") { // objdump will disassemble them wrong (e.g. evmhoumia as vsldoi)
-		return true
-	}
 
 	if len(dec.enc) >= 4 {
 		_ = binary.BigEndian.Uint32(dec.enc[:4])
@@ -70,66 +51,3 @@ func allowedMismatchObjdump(text string, size int, inst *Inst, dec ExtInst) bool
 
 	return false
 }
-
-// Instructions known to libopcodes (or xed) but not to us.
-// TODO(minux): those single precision instructions are missing from ppc64.csv
-// those data cache instructions are deprecated, but must be treated as no-ops, see 4.3.2.1 pg. 774.
-var unsupported = strings.Fields(`
-fmsubs
-fmsubs.
-fnmadds
-fnmadds.
-fnmsubs
-fnmsubs.
-fmuls
-fmuls.
-fdivs
-fdivs.
-fadds
-fadds.
-fsubs
-fsubs.
-dst
-dstst
-dssall
-`)
-
-// Instructions explicitly dropped in Power ISA that were in POWER architecture.
-// See A.30 Deleted Instructions and A.31 Discontiued Opcodes
-var deleted = strings.Fields(`
-abs
-clcs
-clf
-cli
-dclst
-div
-divs
-doz
-dozi
-lscbx
-maskg
-maskir
-mfsri
-mul
-nabs
-rac
-rfi
-rfsvc
-rlmi
-rrib
-sle
-sleq
-sliq
-slliq
-sllq
-slq
-sraiq
-sraq
-sre
-srea
-sreq
-sriq
-srliq
-srlq
-srq
-maskg`)