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Only use length-based dispatch optimization under /optimize+ (#70680)
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@jcouv
jcouv authored Nov 3, 2023
1 parent c054f18 commit c446628
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Showing 2 changed files with 260 additions and 1 deletion.
1 change: 1 addition & 0 deletions src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter.DecisionDagRewriter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -758,6 +758,7 @@ private void LowerSwitchDispatchNode(ValueDispatchNode.SwitchDispatch node, Boun
var stringPatternInput = isStringInput ? StringPatternInput.String : (isSpanInput ? StringPatternInput.SpanChar : StringPatternInput.ReadOnlySpanChar);

if (!this._localRewriter._compilation.FeatureDisableLengthBasedSwitch &&
this._factory.Compilation.Options.OptimizationLevel == OptimizationLevel.Release &&
LengthBasedStringSwitchData.Create(node.Cases) is var lengthBasedDispatch &&
lengthBasedDispatch.ShouldGenerateLengthBasedSwitch(node.Cases.Length) &&
hasLengthBasedDispatchRequiredMembers(stringPatternInput))
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260 changes: 259 additions & 1 deletion src/Compilers/CSharp/Test/Emit2/CodeGen/CodeGenLengthBasedSwitchTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -268,8 +268,9 @@ .locals init (string V_0,
comp.VerifyDiagnostics();
verifier = CompileAndVerify(comp, expectedOutput: "RAN");
verifier.VerifyMemberInIL(PrivateImplementationDetails.SynthesizedStringHashFunctionName + "(string)", expected: true);

verifier.VerifyIL("C.M", """
{
{
// Code size 786 (0x312)
.maxstack 2
.locals init (string V_0,
Expand Down Expand Up @@ -499,6 +500,263 @@ .locals init (string V_0,
IL_0310: ldloc.0
IL_0311: ret
}
""");

comp = CreateCompilation(source, options: TestOptions.DebugExe);
comp.VerifyDiagnostics();
verifier = CompileAndVerify(comp, expectedOutput: "RAN");
verifier.VerifyIL("C.M", """
{
// Code size 819 (0x333)
.maxstack 2
.locals init (string V_0,
uint V_1,
string V_2)
IL_0000: nop
IL_0001: ldc.i4.1
IL_0002: brtrue.s IL_0005
IL_0004: nop
IL_0005: ldarg.0
IL_0006: call "ComputeStringHash(string)"
IL_000b: stloc.1
IL_000c: ldloc.1
IL_000d: ldc.i4 0x62366ffa
IL_0012: bgt.un IL_00a3
IL_0017: ldloc.1
IL_0018: ldc.i4 0x3ec721c0
IL_001d: bgt.un.s IL_0061
IL_001f: ldloc.1
IL_0020: ldc.i4 0x2f69f5a5
IL_0025: bgt.un.s IL_0044
IL_0027: ldloc.1
IL_0028: ldc.i4 0x242602e6
IL_002d: beq IL_0215
IL_0032: br.s IL_0034
IL_0034: ldloc.1
IL_0035: ldc.i4 0x2f69f5a5
IL_003a: beq IL_01ac
IL_003f: br IL_0321
IL_0044: ldloc.1
IL_0045: ldc.i4 0x3448ae58
IL_004a: beq IL_0200
IL_004f: br.s IL_0051
IL_0051: ldloc.1
IL_0052: ldc.i4 0x3ec721c0
IL_0057: beq IL_0269
IL_005c: br IL_0321
IL_0061: ldloc.1
IL_0062: ldc.i4 0x4f9f2cab
IL_0067: bgt.un.s IL_0086
IL_0069: ldloc.1
IL_006a: ldc.i4 0x4e9f3590
IL_006f: beq IL_0197
IL_0074: br.s IL_0076
IL_0076: ldloc.1
IL_0077: ldc.i4 0x4f9f2cab
IL_007c: beq IL_01eb
IL_0081: br IL_0321
IL_0086: ldloc.1
IL_0087: ldc.i4 0x5cb7aa8a
IL_008c: beq IL_027e
IL_0091: br.s IL_0093
IL_0093: ldloc.1
IL_0094: ldc.i4 0x62366ffa
IL_0099: beq IL_0182
IL_009e: br IL_0321
IL_00a3: ldloc.1
IL_00a4: ldc.i4 0xb51d04ba
IL_00a9: bgt.un.s IL_00ea
IL_00ab: ldloc.1
IL_00ac: ldc.i4 0x811c9dc5
IL_00b1: bgt.un.s IL_00cd
IL_00b3: ldloc.1
IL_00b4: ldc.i4 0x63cb5a27
IL_00b9: beq IL_0254
IL_00be: br.s IL_00c0
IL_00c0: ldloc.1
IL_00c1: ldc.i4 0x811c9dc5
IL_00c6: beq.s IL_0130
IL_00c8: br IL_0321
IL_00cd: ldloc.1
IL_00ce: ldc.i4 0x872213e7
IL_00d3: beq IL_01c1
IL_00d8: br.s IL_00da
IL_00da: ldloc.1
IL_00db: ldc.i4 0xb51d04ba
IL_00e0: beq IL_022a
IL_00e5: br IL_0321
IL_00ea: ldloc.1
IL_00eb: ldc.i4 0xe60c2c52
IL_00f0: bgt.un.s IL_0109
IL_00f2: ldloc.1
IL_00f3: ldc.i4 0xe40c292c
IL_00f8: beq.s IL_0143
IL_00fa: br.s IL_00fc
IL_00fc: ldloc.1
IL_00fd: ldc.i4 0xe60c2c52
IL_0102: beq.s IL_016d
IL_0104: br IL_0321
IL_0109: ldloc.1
IL_010a: ldc.i4 0xe6e5718f
IL_010f: beq IL_023f
IL_0114: br.s IL_0116
IL_0116: ldloc.1
IL_0117: ldc.i4 0xe70c2de5
IL_011c: beq.s IL_0158
IL_011e: br.s IL_0120
IL_0120: ldloc.1
IL_0121: ldc.i4 0xf76b8c8e
IL_0126: beq IL_01d6
IL_012b: br IL_0321
IL_0130: ldarg.0
IL_0131: brfalse.s IL_013e
IL_0133: ldarg.0
IL_0134: call "int string.Length.get"
IL_0139: brfalse IL_0293
IL_013e: br IL_0321
IL_0143: ldarg.0
IL_0144: ldstr "a"
IL_0149: call "bool string.op_Equality(string, string)"
IL_014e: brtrue IL_029e
IL_0153: br IL_0321
IL_0158: ldarg.0
IL_0159: ldstr "b"
IL_015e: call "bool string.op_Equality(string, string)"
IL_0163: brtrue IL_02a9
IL_0168: br IL_0321
IL_016d: ldarg.0
IL_016e: ldstr "c"
IL_0173: call "bool string.op_Equality(string, string)"
IL_0178: brtrue IL_02b1
IL_017d: br IL_0321
IL_0182: ldarg.0
IL_0183: ldstr "no"
IL_0188: call "bool string.op_Equality(string, string)"
IL_018d: brtrue IL_02b9
IL_0192: br IL_0321
IL_0197: ldarg.0
IL_0198: ldstr "yes"
IL_019d: call "bool string.op_Equality(string, string)"
IL_01a2: brtrue IL_02c1
IL_01a7: br IL_0321
IL_01ac: ldarg.0
IL_01ad: ldstr "four"
IL_01b2: call "bool string.op_Equality(string, string)"
IL_01b7: brtrue IL_02c9
IL_01bc: br IL_0321
IL_01c1: ldarg.0
IL_01c2: ldstr "alice"
IL_01c7: call "bool string.op_Equality(string, string)"
IL_01cc: brtrue IL_02d1
IL_01d1: br IL_0321
IL_01d6: ldarg.0
IL_01d7: ldstr "blurb"
IL_01dc: call "bool string.op_Equality(string, string)"
IL_01e1: brtrue IL_02d9
IL_01e6: br IL_0321
IL_01eb: ldarg.0
IL_01ec: ldstr "hello"
IL_01f1: call "bool string.op_Equality(string, string)"
IL_01f6: brtrue IL_02e1
IL_01fb: br IL_0321
IL_0200: ldarg.0
IL_0201: ldstr "lamps"
IL_0206: call "bool string.op_Equality(string, string)"
IL_020b: brtrue IL_02e9
IL_0210: br IL_0321
IL_0215: ldarg.0
IL_0216: ldstr "lambs"
IL_021b: call "bool string.op_Equality(string, string)"
IL_0220: brtrue IL_02f1
IL_0225: br IL_0321
IL_022a: ldarg.0
IL_022b: ldstr "lower"
IL_0230: call "bool string.op_Equality(string, string)"
IL_0235: brtrue IL_02f9
IL_023a: br IL_0321
IL_023f: ldarg.0
IL_0240: ldstr "names"
IL_0245: call "bool string.op_Equality(string, string)"
IL_024a: brtrue IL_0301
IL_024f: br IL_0321
IL_0254: ldarg.0
IL_0255: ldstr "slurp"
IL_025a: call "bool string.op_Equality(string, string)"
IL_025f: brtrue IL_0309
IL_0264: br IL_0321
IL_0269: ldarg.0
IL_026a: ldstr "towed"
IL_026f: call "bool string.op_Equality(string, string)"
IL_0274: brtrue IL_0311
IL_0279: br IL_0321
IL_027e: ldarg.0
IL_027f: ldstr "words"
IL_0284: call "bool string.op_Equality(string, string)"
IL_0289: brtrue IL_0319
IL_028e: br IL_0321
IL_0293: ldstr "blank"
IL_0298: stloc.0
IL_0299: br IL_0329
IL_029e: ldstr "a"
IL_02a3: stloc.0
IL_02a4: br IL_0329
IL_02a9: ldstr "b"
IL_02ae: stloc.0
IL_02af: br.s IL_0329
IL_02b1: ldstr "c"
IL_02b6: stloc.0
IL_02b7: br.s IL_0329
IL_02b9: ldstr "no"
IL_02be: stloc.0
IL_02bf: br.s IL_0329
IL_02c1: ldstr "yes"
IL_02c6: stloc.0
IL_02c7: br.s IL_0329
IL_02c9: ldstr "four"
IL_02ce: stloc.0
IL_02cf: br.s IL_0329
IL_02d1: ldstr "alice"
IL_02d6: stloc.0
IL_02d7: br.s IL_0329
IL_02d9: ldstr "blurb"
IL_02de: stloc.0
IL_02df: br.s IL_0329
IL_02e1: ldstr "hello"
IL_02e6: stloc.0
IL_02e7: br.s IL_0329
IL_02e9: ldstr "lamps"
IL_02ee: stloc.0
IL_02ef: br.s IL_0329
IL_02f1: ldstr "lambs"
IL_02f6: stloc.0
IL_02f7: br.s IL_0329
IL_02f9: ldstr "lower"
IL_02fe: stloc.0
IL_02ff: br.s IL_0329
IL_0301: ldstr "names"
IL_0306: stloc.0
IL_0307: br.s IL_0329
IL_0309: ldstr "slurp"
IL_030e: stloc.0
IL_030f: br.s IL_0329
IL_0311: ldstr "towed"
IL_0316: stloc.0
IL_0317: br.s IL_0329
IL_0319: ldstr "words"
IL_031e: stloc.0
IL_031f: br.s IL_0329
IL_0321: ldstr "default"
IL_0326: stloc.0
IL_0327: br.s IL_0329
IL_0329: ldc.i4.1
IL_032a: brtrue.s IL_032d
IL_032c: nop
IL_032d: ldloc.0
IL_032e: stloc.2
IL_032f: br.s IL_0331
IL_0331: ldloc.2
IL_0332: ret
}
""");
}

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