daniellansun commented on code in PR #2707:
URL: https://github.com/apache/groovy/pull/2707#discussion_r3604084417
##########
src/test/groovy/org/codehaus/groovy/classgen/asm/PeepholeOptimizingMethodVisitorTest.groovy:
##########
@@ -329,16 +329,91 @@ final class PeepholeOptimizingMethodVisitorTest {
assert opcodeLines(bytecode) == ['IINC 0 1', 'RETURN']
}
+ @Test
+ void removesLoadAndAttachedCheckcastBeforePop() {
+ def bytecode = sequenceFor('(Ljava/lang/Object;)V') {
+ visitVarInsn(Opcodes.ALOAD, 0)
+ visitTypeInsn(Opcodes.CHECKCAST, 'java/lang/String')
+ visitInsn(Opcodes.POP)
+ visitInsn(RETURN)
+ }
+
+ // ALOAD + CHECKCAST are both dead once the value is discarded.
+ assert opcodeLines(bytecode) == ['RETURN']
+ }
+
@Test
void removesStandaloneCheckcastBeforePop() {
def bytecode = sequenceFor('(Ljava/lang/Object;)V') {
visitVarInsn(Opcodes.ALOAD, 0)
+ visitInsn(Opcodes.NOP) // force the load to flush so CHECKCAST is
standalone
visitTypeInsn(Opcodes.CHECKCAST, 'java/lang/String')
visitInsn(Opcodes.POP)
visitInsn(RETURN)
}
- assert opcodeLines(bytecode) == ['ALOAD 0', 'POP', 'RETURN']
+ assert opcodeLines(bytecode) == ['ALOAD 0', 'NOP', 'POP', 'RETURN']
+ }
+
+ @Test
+ void rewritesNullComparisonsAgainstAconstNull() {
+ def nullComparisons = [
+ (Opcodes.IF_ACMPEQ): 'IFNULL',
+ (Opcodes.IF_ACMPNE): 'IFNONNULL',
+ ]
+
+ nullComparisons.each { opcode, expected ->
+ def label = new Label()
+ def bytecode = sequenceFor('(Ljava/lang/Object;)V') {
+ visitVarInsn(Opcodes.ALOAD, 0)
+ visitInsn(Opcodes.ACONST_NULL)
+ visitJumpInsn(opcode, label)
+ visitInsn(RETURN)
+ visitLabel(label)
+ visitInsn(RETURN)
+ }
+ def lines = opcodeLines(bytecode)
+
+ assert lines.size() == 4
+ assert lines[0] == 'ALOAD 0'
+ assert lines[1].startsWith(expected)
+ assert lines[2..3] == ['RETURN', 'RETURN']
+ assert !lines[1].startsWith(Printer.OPCODES[opcode])
+ }
+ }
+
+ @Test
+ void removesBareDupBeforeMatchingPop() {
+ def bytecode = sequenceFor {
+ visitInsn(Opcodes.ICONST_1)
+ visitInsn(Opcodes.DUP)
+ visitInsn(Opcodes.POP)
+ visitLdcInsn(2L)
+ visitInsn(Opcodes.DUP2)
+ visitInsn(Opcodes.POP2)
+ visitInsn(RETURN)
+ }
+
+ assert opcodeLines(bytecode) == [
+ 'ICONST_1',
+ 'LDC 2L',
+ 'RETURN',
Review Comment:
Agreed — once DUP/POP is gone the constants are already flushed out of the
single load window, so a second pass / wider window would be needed to drop
them before void RETURN. Happy as a follow-up; not this PR.
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