[SimplifyCFG] Allow some switch optimizations early in the pipeline #158242
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This was referenced Sep 12, 2025
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While we do not want to form actual lookup tables early, we do want to perform some optimizations, as they may enable inlining of the much simpler form. Builds on llvm#156477, which originally included this change as well.
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@llvm/pr-subscribers-llvm-transforms Author: Nikita Popov (nikic) ChangesWhile we do not want to form actual lookup tables early, we do want to perform some optimizations, as they may enable inlining of the much simpler form. Builds on #156477, which originally included this change as well. This PR makes two changes on top of it:
Patch is 20.06 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/158242.diff 9 Files Affected:
diff --git a/llvm/include/llvm/Transforms/Utils/SimplifyCFGOptions.h b/llvm/include/llvm/Transforms/Utils/SimplifyCFGOptions.h
index ee3cc950cdb50..2d0f95741077f 100644
--- a/llvm/include/llvm/Transforms/Utils/SimplifyCFGOptions.h
+++ b/llvm/include/llvm/Transforms/Utils/SimplifyCFGOptions.h
@@ -24,6 +24,7 @@ struct SimplifyCFGOptions {
int BonusInstThreshold = 1;
bool ForwardSwitchCondToPhi = false;
bool ConvertSwitchRangeToICmp = false;
+ bool ConvertSwitchToArithmetic = false;
bool ConvertSwitchToLookupTable = false;
bool NeedCanonicalLoop = true;
bool HoistCommonInsts = false;
@@ -48,6 +49,10 @@ struct SimplifyCFGOptions {
ConvertSwitchRangeToICmp = B;
return *this;
}
+ SimplifyCFGOptions &convertSwitchToArithmetic(bool B) {
+ ConvertSwitchToArithmetic = B;
+ return *this;
+ }
SimplifyCFGOptions &convertSwitchToLookupTable(bool B) {
ConvertSwitchToLookupTable = B;
return *this;
diff --git a/llvm/lib/Passes/PassBuilder.cpp b/llvm/lib/Passes/PassBuilder.cpp
index 20dcde8fff0d4..53cf0046bd858 100644
--- a/llvm/lib/Passes/PassBuilder.cpp
+++ b/llvm/lib/Passes/PassBuilder.cpp
@@ -1111,6 +1111,8 @@ Expected<SimplifyCFGOptions> parseSimplifyCFGOptions(StringRef Params) {
Result.forwardSwitchCondToPhi(Enable);
} else if (ParamName == "switch-range-to-icmp") {
Result.convertSwitchRangeToICmp(Enable);
+ } else if (ParamName == "switch-to-arithmetic") {
+ Result.convertSwitchToArithmetic(Enable);
} else if (ParamName == "switch-to-lookup") {
Result.convertSwitchToLookupTable(Enable);
} else if (ParamName == "keep-loops") {
diff --git a/llvm/lib/Passes/PassBuilderPipelines.cpp b/llvm/lib/Passes/PassBuilderPipelines.cpp
index 119caead6e8bf..fea0d255cc91a 100644
--- a/llvm/lib/Passes/PassBuilderPipelines.cpp
+++ b/llvm/lib/Passes/PassBuilderPipelines.cpp
@@ -781,6 +781,7 @@ PassBuilder::buildFunctionSimplificationPipeline(OptimizationLevel Level,
FPM.addPass(SimplifyCFGPass(SimplifyCFGOptions()
.convertSwitchRangeToICmp(true)
+ .convertSwitchToArithmetic(true)
.hoistCommonInsts(true)
.sinkCommonInsts(true)));
FPM.addPass(InstCombinePass());
@@ -1377,6 +1378,7 @@ void PassBuilder::addVectorPasses(OptimizationLevel Level,
FPM.addPass(SimplifyCFGPass(SimplifyCFGOptions()
.forwardSwitchCondToPhi(true)
.convertSwitchRangeToICmp(true)
+ .convertSwitchToArithmetic(true)
.convertSwitchToLookupTable(true)
.needCanonicalLoops(false)
.hoistCommonInsts(true)
@@ -1603,6 +1605,7 @@ PassBuilder::buildModuleOptimizationPipeline(OptimizationLevel Level,
OptimizePM.addPass(
SimplifyCFGPass(SimplifyCFGOptions()
.convertSwitchRangeToICmp(true)
+ .convertSwitchToArithmetic(true)
.speculateUnpredictables(true)
.hoistLoadsStoresWithCondFaulting(true)));
@@ -2187,6 +2190,7 @@ PassBuilder::buildLTODefaultPipeline(OptimizationLevel Level,
// Delete basic blocks, which optimization passes may have killed.
LateFPM.addPass(SimplifyCFGPass(SimplifyCFGOptions()
.convertSwitchRangeToICmp(true)
+ .convertSwitchToArithmetic(true)
.hoistCommonInsts(true)
.speculateUnpredictables(true)));
MPM.addPass(createModuleToFunctionPassAdaptor(std::move(LateFPM)));
diff --git a/llvm/lib/Passes/PassRegistry.def b/llvm/lib/Passes/PassRegistry.def
index c5c0d643d1498..1b1652555cd28 100644
--- a/llvm/lib/Passes/PassRegistry.def
+++ b/llvm/lib/Passes/PassRegistry.def
@@ -687,8 +687,9 @@ FUNCTION_PASS_WITH_PARAMS(
parseSimplifyCFGOptions,
"no-speculate-blocks;speculate-blocks;no-simplify-cond-branch;"
"simplify-cond-branch;no-forward-switch-cond;forward-switch-cond;"
- "no-switch-range-to-icmp;switch-range-to-icmp;no-switch-to-lookup;"
- "switch-to-lookup;no-keep-loops;keep-loops;no-hoist-common-insts;"
+ "no-switch-range-to-icmp;switch-range-to-icmp;no-switch-to-arithmetic;"
+ "switch-to-arithmetic;no-switch-to-lookup;switch-to-lookup;"
+ "no-keep-loops;keep-loops;no-hoist-common-insts;"
"hoist-common-insts;no-hoist-loads-stores-with-cond-faulting;"
"hoist-loads-stores-with-cond-faulting;no-sink-common-insts;"
"sink-common-insts;no-speculate-unpredictables;speculate-unpredictables;"
diff --git a/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp b/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
index 60e5df08c6efd..7ffccf73bd39d 100644
--- a/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
+++ b/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
@@ -355,6 +355,8 @@ void SimplifyCFGPass::printPipeline(
OS << (Options.ForwardSwitchCondToPhi ? "" : "no-") << "forward-switch-cond;";
OS << (Options.ConvertSwitchRangeToICmp ? "" : "no-")
<< "switch-range-to-icmp;";
+ OS << (Options.ConvertSwitchToArithmetic ? "" : "no-")
+ << "switch-to-arithmetic;";
OS << (Options.ConvertSwitchToLookupTable ? "" : "no-")
<< "switch-to-lookup;";
OS << (Options.NeedCanonicalLoop ? "" : "no-") << "keep-loops;";
diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index b8cfe3a8a941d..2cc795dfa7958 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -6642,6 +6642,9 @@ class SwitchReplacement {
/// Return true if the replacement is a lookup table.
bool isLookupTable();
+ /// Return true if the replacement is a bit map.
+ bool isBitMap();
+
private:
// Depending on the switch, there are different alternatives.
enum {
@@ -6932,6 +6935,8 @@ Constant *SwitchReplacement::getDefaultValue() { return DefaultValue; }
bool SwitchReplacement::isLookupTable() { return Kind == LookupTableKind; }
+bool SwitchReplacement::isBitMap() { return Kind == BitMapKind; }
+
static bool isSwitchDense(uint64_t NumCases, uint64_t CaseRange) {
// 40% is the default density for building a jump table in optsize/minsize
// mode. See also TargetLoweringBase::isSuitableForJumpTable(), which this
@@ -7097,7 +7102,8 @@ static void reuseTableCompare(
/// lookup tables.
static bool simplifySwitchLookup(SwitchInst *SI, IRBuilder<> &Builder,
DomTreeUpdater *DTU, const DataLayout &DL,
- const TargetTransformInfo &TTI) {
+ const TargetTransformInfo &TTI,
+ bool ConvertSwitchToLookupTable) {
assert(SI->getNumCases() > 1 && "Degenerate switch?");
BasicBlock *BB = SI->getParent();
@@ -7262,6 +7268,8 @@ static bool simplifySwitchLookup(SwitchInst *SI, IRBuilder<> &Builder,
bool AnyLookupTables = any_of(
PhiToReplacementMap, [](auto &KV) { return KV.second.isLookupTable(); });
+ bool AnyBitMaps = any_of(PhiToReplacementMap,
+ [](auto &KV) { return KV.second.isBitMap(); });
// A few conditions prevent the generation of lookup tables:
// 1. The target does not support lookup tables.
@@ -7274,6 +7282,12 @@ static bool simplifySwitchLookup(SwitchInst *SI, IRBuilder<> &Builder,
Fn->getFnAttribute("no-jump-tables").getValueAsBool()))
return false;
+ // In the early optimization pipeline, disable formation of lookup tables,
+ // bit maps and mask checks, as they may inhibit further optimization.
+ if (!ConvertSwitchToLookupTable &&
+ (AnyLookupTables || AnyBitMaps || NeedMask))
+ return false;
+
Builder.SetInsertPoint(SI);
// TableIndex is the switch condition - TableIndexOffset if we don't
// use the condition directly
@@ -7929,14 +7943,10 @@ bool SimplifyCFGOpt::simplifySwitch(SwitchInst *SI, IRBuilder<> &Builder) {
if (Options.ForwardSwitchCondToPhi && forwardSwitchConditionToPHI(SI))
return requestResimplify();
- // The conversion from switch to lookup tables results in difficult-to-analyze
- // code and makes pruning branches much harder. This is a problem if the
- // switch expression itself can still be restricted as a result of inlining or
- // CVP. Therefore, only apply this transformation during late stages of the
- // optimisation pipeline.
- if (Options.ConvertSwitchToLookupTable &&
- simplifySwitchLookup(SI, Builder, DTU, DL, TTI))
- return requestResimplify();
+ if (Options.ConvertSwitchToArithmetic || Options.ConvertSwitchToLookupTable)
+ if (simplifySwitchLookup(SI, Builder, DTU, DL, TTI,
+ Options.ConvertSwitchToLookupTable))
+ return requestResimplify();
if (simplifySwitchOfPowersOfTwo(SI, Builder, DL, TTI))
return requestResimplify();
diff --git a/llvm/test/Other/new-pm-print-pipeline.ll b/llvm/test/Other/new-pm-print-pipeline.ll
index 6fa57f17174e9..3536932f4432e 100644
--- a/llvm/test/Other/new-pm-print-pipeline.ll
+++ b/llvm/test/Other/new-pm-print-pipeline.ll
@@ -50,7 +50,7 @@
; CHECK-17: function(print<stack-lifetime><may>,print<stack-lifetime><must>)
; RUN: opt -disable-output -disable-verify -print-pipeline-passes -passes='function(simplifycfg<bonus-inst-threshold=5;forward-switch-cond;switch-to-lookup;keep-loops;hoist-common-insts;hoist-loads-stores-with-cond-faulting;sink-common-insts;speculate-blocks;simplify-cond-branch;speculate-unpredictables>,simplifycfg<bonus-inst-threshold=7;no-forward-switch-cond;no-switch-to-lookup;no-keep-loops;no-hoist-common-insts;no-hoist-loads-stores-with-cond-faulting;no-sink-common-insts;no-speculate-blocks;no-simplify-cond-branch;no-speculate-unpredictables>)' < %s | FileCheck %s --match-full-lines --check-prefixes=CHECK-18
-; CHECK-18: function(simplifycfg<bonus-inst-threshold=5;forward-switch-cond;no-switch-range-to-icmp;switch-to-lookup;keep-loops;hoist-common-insts;hoist-loads-stores-with-cond-faulting;sink-common-insts;speculate-blocks;simplify-cond-branch;speculate-unpredictables>,simplifycfg<bonus-inst-threshold=7;no-forward-switch-cond;no-switch-range-to-icmp;no-switch-to-lookup;no-keep-loops;no-hoist-common-insts;no-hoist-loads-stores-with-cond-faulting;no-sink-common-insts;no-speculate-blocks;no-simplify-cond-branch;no-speculate-unpredictables>)
+; CHECK-18: function(simplifycfg<bonus-inst-threshold=5;forward-switch-cond;no-switch-range-to-icmp;no-switch-to-arithmetic;switch-to-lookup;keep-loops;hoist-common-insts;hoist-loads-stores-with-cond-faulting;sink-common-insts;speculate-blocks;simplify-cond-branch;speculate-unpredictables>,simplifycfg<bonus-inst-threshold=7;no-forward-switch-cond;no-switch-range-to-icmp;no-switch-to-arithmetic;no-switch-to-lookup;no-keep-loops;no-hoist-common-insts;no-hoist-loads-stores-with-cond-faulting;no-sink-common-insts;no-speculate-blocks;no-simplify-cond-branch;no-speculate-unpredictables>)
; RUN: opt -disable-output -disable-verify -print-pipeline-passes -passes='function(loop-vectorize<no-interleave-forced-only;no-vectorize-forced-only>,loop-vectorize<interleave-forced-only;vectorize-forced-only>)' < %s | FileCheck %s --match-full-lines --check-prefixes=CHECK-19
; CHECK-19: function(loop-vectorize<no-interleave-forced-only;no-vectorize-forced-only;>,loop-vectorize<interleave-forced-only;vectorize-forced-only;>)
diff --git a/llvm/test/Transforms/PhaseOrdering/switch-to-arithmetic-inlining.ll b/llvm/test/Transforms/PhaseOrdering/switch-to-arithmetic-inlining.ll
index caf7a801dfc51..7c9888fb12a7c 100644
--- a/llvm/test/Transforms/PhaseOrdering/switch-to-arithmetic-inlining.ll
+++ b/llvm/test/Transforms/PhaseOrdering/switch-to-arithmetic-inlining.ll
@@ -436,10 +436,11 @@ bb104: ; preds = %bb102
br label %bb105
}
+; Make sure the call is inlined.
define i8 @test2(i8 %x) {
; CHECK-LABEL: define range(i8 0, 53) i8 @test2(
; CHECK-SAME: i8 [[X:%.*]]) local_unnamed_addr #[[ATTR0]] {
-; CHECK-NEXT: [[CALL:%.*]] = tail call i8 @test(i8 [[X]])
+; CHECK-NEXT: [[CALL:%.*]] = tail call range(i8 0, 53) i8 @llvm.umin.i8(i8 [[X]], i8 52)
; CHECK-NEXT: ret i8 [[CALL]]
;
%call = call i8 @test(i8 %x)
diff --git a/llvm/test/Transforms/SimplifyCFG/switch-transformations-no-lut.ll b/llvm/test/Transforms/SimplifyCFG/switch-transformations-no-lut.ll
index c9063d3ec26ff..25267dcc6dbcb 100644
--- a/llvm/test/Transforms/SimplifyCFG/switch-transformations-no-lut.ll
+++ b/llvm/test/Transforms/SimplifyCFG/switch-transformations-no-lut.ll
@@ -1,5 +1,5 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
-; RUN: opt -S -passes='simplifycfg' < %s | FileCheck %s --check-prefix=OPTNOLUT
+; RUN: opt -S -passes='simplifycfg<switch-to-arithmetic>' < %s | FileCheck %s --check-prefix=OPTNOLUT
; RUN: %if amdgpu-registered-target %{ opt -mtriple=amdgcn--amdpal -S -passes='simplifycfg<switch-to-lookup>' < %s | FileCheck %s --check-prefix=TTINOLUT %}
;
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
@@ -7,23 +7,11 @@ target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
define i32 @linear_transform_with_default(i32 %x) {
; OPTNOLUT-LABEL: define i32 @linear_transform_with_default(
; OPTNOLUT-SAME: i32 [[X:%.*]]) {
-; OPTNOLUT-NEXT: [[ENTRY:.*]]:
-; OPTNOLUT-NEXT: switch i32 [[X]], label %[[END:.*]] [
-; OPTNOLUT-NEXT: i32 0, label %[[CASE0:.*]]
-; OPTNOLUT-NEXT: i32 1, label %[[CASE1:.*]]
-; OPTNOLUT-NEXT: i32 2, label %[[CASE2:.*]]
-; OPTNOLUT-NEXT: i32 3, label %[[CASE3:.*]]
-; OPTNOLUT-NEXT: ]
-; OPTNOLUT: [[CASE0]]:
-; OPTNOLUT-NEXT: br label %[[END]]
-; OPTNOLUT: [[CASE1]]:
-; OPTNOLUT-NEXT: br label %[[END]]
-; OPTNOLUT: [[CASE2]]:
-; OPTNOLUT-NEXT: br label %[[END]]
-; OPTNOLUT: [[CASE3]]:
-; OPTNOLUT-NEXT: br label %[[END]]
-; OPTNOLUT: [[END]]:
-; OPTNOLUT-NEXT: [[IDX:%.*]] = phi i32 [ 1, %[[CASE0]] ], [ 4, %[[CASE1]] ], [ 7, %[[CASE2]] ], [ 10, %[[CASE3]] ], [ 13, %[[ENTRY]] ]
+; OPTNOLUT-NEXT: [[ENTRY:.*:]]
+; OPTNOLUT-NEXT: [[TMP0:%.*]] = icmp ult i32 [[X]], 4
+; OPTNOLUT-NEXT: [[SWITCH_IDX_MULT:%.*]] = mul nsw i32 [[X]], 3
+; OPTNOLUT-NEXT: [[SWITCH_OFFSET:%.*]] = add nsw i32 [[SWITCH_IDX_MULT]], 1
+; OPTNOLUT-NEXT: [[IDX:%.*]] = select i1 [[TMP0]], i32 [[SWITCH_OFFSET]], i32 13
; OPTNOLUT-NEXT: ret i32 [[IDX]]
;
; TTINOLUT-LABEL: define i32 @linear_transform_with_default(
@@ -138,26 +126,8 @@ end:
define i32 @linear_transform_no_default(i32 %x) {
; OPTNOLUT-LABEL: define i32 @linear_transform_no_default(
; OPTNOLUT-SAME: i32 [[X:%.*]]) {
-; OPTNOLUT-NEXT: [[ENTRY:.*]]:
-; OPTNOLUT-NEXT: switch i32 [[X]], label %[[DEFAULT:.*]] [
-; OPTNOLUT-NEXT: i32 0, label %[[END:.*]]
-; OPTNOLUT-NEXT: i32 1, label %[[CASE1:.*]]
-; OPTNOLUT-NEXT: i32 2, label %[[CASE2:.*]]
-; OPTNOLUT-NEXT: i32 3, label %[[CASE3:.*]]
-; OPTNOLUT-NEXT: i32 4, label %[[CASE4:.*]]
-; OPTNOLUT-NEXT: ]
-; OPTNOLUT: [[CASE1]]:
-; OPTNOLUT-NEXT: br label %[[END]]
-; OPTNOLUT: [[CASE2]]:
-; OPTNOLUT-NEXT: br label %[[END]]
-; OPTNOLUT: [[CASE3]]:
-; OPTNOLUT-NEXT: br label %[[END]]
-; OPTNOLUT: [[CASE4]]:
-; OPTNOLUT-NEXT: br label %[[END]]
-; OPTNOLUT: [[DEFAULT]]:
-; OPTNOLUT-NEXT: unreachable
-; OPTNOLUT: [[END]]:
-; OPTNOLUT-NEXT: [[SWITCH_IDX_MULT:%.*]] = phi i32 [ 3, %[[CASE1]] ], [ 6, %[[CASE2]] ], [ 9, %[[CASE3]] ], [ 12, %[[CASE4]] ], [ 0, %[[ENTRY]] ]
+; OPTNOLUT-NEXT: [[ENTRY:.*:]]
+; OPTNOLUT-NEXT: [[SWITCH_IDX_MULT:%.*]] = mul nsw i32 [[X]], 3
; OPTNOLUT-NEXT: ret i32 [[SWITCH_IDX_MULT]]
;
; TTINOLUT-LABEL: define i32 @linear_transform_no_default(
@@ -350,18 +320,9 @@ end:
define i32 @single_value_withdefault(i32 %x) {
; OPTNOLUT-LABEL: define i32 @single_value_withdefault(
; OPTNOLUT-SAME: i32 [[X:%.*]]) {
-; OPTNOLUT-NEXT: [[ENTRY:.*]]:
-; OPTNOLUT-NEXT: switch i32 [[X]], label %[[DEFAULT:.*]] [
-; OPTNOLUT-NEXT: i32 0, label %[[END:.*]]
-; OPTNOLUT-NEXT: i32 1, label %[[END]]
-; OPTNOLUT-NEXT: i32 2, label %[[END]]
-; OPTNOLUT-NEXT: i32 3, label %[[END]]
-; OPTNOLUT-NEXT: i32 4, label %[[END]]
-; OPTNOLUT-NEXT: ]
-; OPTNOLUT: [[DEFAULT]]:
-; OPTNOLUT-NEXT: br label %[[END]]
-; OPTNOLUT: [[END]]:
-; OPTNOLUT-NEXT: [[DOT:%.*]] = phi i32 [ 3, %[[DEFAULT]] ], [ 2, %[[ENTRY]] ], [ 2, %[[ENTRY]] ], [ 2, %[[ENTRY]] ], [ 2, %[[ENTRY]] ], [ 2, %[[ENTRY]] ]
+; OPTNOLUT-NEXT: [[ENTRY:.*:]]
+; OPTNOLUT-NEXT: [[TMP0:%.*]] = icmp ult i32 [[X]], 5
+; OPTNOLUT-NEXT: [[DOT:%.*]] = select i1 [[TMP0]], i32 2, i32 3
; OPTNOLUT-NEXT: ret i32 [[DOT]]
;
; TTINOLUT-LABEL: define i32 @single_value_withdefault(
@@ -401,18 +362,9 @@ end:
define i32 @single_value_no_jump_tables(i32 %x) "no-jump-tables"="true" {
; OPTNOLUT-LABEL: define i32 @single_value_no_jump_tables(
; OPTNOLUT-SAME: i32 [[X:%.*]]) #[[ATTR0:[0-9]+]] {
-; OPTNOLUT-NEXT: [[ENTRY:.*]]:
-; OPTNOLUT-NEXT: switch i32 [[X]], label %[[DEFAULT:.*]] [
-; OPTNOLUT-NEXT: i32 0, label %[[END:.*]]
-; OPTNOLUT-NEXT: i32 1, label %[[END]]
-; OPTNOLUT-NEXT: i32 2, label %[[END]]
-; OPTNOLUT-NEXT: i32 3, label %[[END]]
-; OPTNOLUT-NEXT: i32 4, label %[[END]]
-; OPTNOLUT-NEXT: ]
-; OPTNOLUT: [[DEFAULT]]:
-; OPTNOLUT-NEXT: br label %[[END]]
-; OPTNOLUT: [[END]]:
-; OPTNOLUT-NEXT: [[IDX:%.*]] = phi i32 [ 3, %[[DEFAULT]] ], [ 2, %[[ENTRY]] ], [ 2, %[[ENTRY]] ], [ 2, %[[ENTRY]] ], [ 2, %[[ENTRY]] ], [ 2, %[[ENTRY]] ]
+; OPTNOLUT-NEXT: [[ENTRY:.*:]]
+; OPTNOLUT-NEXT: [[TMP0:%.*]] = icmp ult i32 [[X]], 5
+; OPTNOLUT-NEXT: [[IDX:%.*]] = select i1 [[TMP0]], i32 2, i32 3
; OPTNOLUT-NEXT: ret i32 [[IDX]]
;
; TTINOLUT-LABEL: define i32 @single_value_no_jump_tables(
@@ -449,6 +401,60 @@ end:
ret i32 %idx
}
+define i1 @single_value_with_mask(i32 %x) {
+; OPTNOLUT-LABEL: define i1 @single_value_with_mask(
+; OPTNOLUT-SAME: i32 [[X:%.*]]) {
+; OPTNOLUT-NEXT: [[ENTRY:.*]]:
+; OPTNOLUT-NEXT: switch i32 [[X]], label %[[DEFAULT:.*]] [
+; OPTNOLUT-NEXT: i32 18, label %[[END:.*]]
+; OPTNOLUT-NEXT: i32 21, label %[[END]]
+; OPTNOLUT-NEXT: i32 48, label %[[END]]
+; OPTNOLUT-NEXT: i32 16, label %[[END]]
+; OPTNOLUT-NEXT: ]
+; OPTNOLUT: [[DEFAULT]]:
+; OPTNOLUT-NEXT: [[CMP:%.*]] = icmp eq i32 [[X]], 80
+; OPTNOLUT-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i1 false, i1 true
+; OPTNOLUT-NEXT: br label %[[END]]
+; OPTNOLUT: [[END]]:
+; OPTNOLUT-NEXT: [[RES:%.*]] = phi i1 [ false, %[[ENTRY]] ], [ false, %[[ENTRY]] ], [ false, %[[ENTRY]] ], [ false, %[[ENTRY]] ], [ [[SEL]], %[[DEFAULT]] ]
+; OPTNOLUT-NEXT: ret i1 [[RES]]
+;
+; TTINOLUT-LABEL: define i1 @single_value_with_mask(
+; TTINOLUT-SAME: i32 [[X:%.*]]) {
+; TTINOLUT-NEXT: [[ENTRY:.*]]:
+; TTINOLUT-NEXT: [[SWITCH_TABLEIDX:%.*]] = sub i32 [[X]], 16
+; TTINOLUT-NEXT: [[TMP0:%.*]] = icmp ult i32 [[SWITCH_TABLEIDX]], 33
+; TTINOLUT-NEXT: [[SWITCH_MASKINDEX:%.*]] = zext i32 [[SWITCH_TABLEIDX]] to i64
+; TTINOLUT-NEXT: [[SWITCH_SHIFTED:%.*]] = lshr i64 4294967333, [[SWITCH_MASKINDEX]]
+; TTINOLUT-NEXT: [[SWITCH_LOBIT:%.*]] = trunc i64 [[SWITCH_SHIFTED]] to i1
+; TTINOLUT-NEXT: [[OR_COND:%.*]] = select i1 [[TMP0]], i1 [[SWITCH_LOBIT]], i1 false
+; TTINOLUT-NEXT: br i1 [[OR_COND]], label %[[END:.*]], label %[[DEFAULT:.*]]
+; TTINOLUT: [[DEFAULT]]:
+; TTINOLUT-NEXT: [[CMP:%.*]] = icmp eq i32 [[X]], 80
+; TTINOLUT-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i1 false, i1 true
+; TTINOLUT-NEXT: br label %[[END]]
+; TTINOLUT: [[END]]:
+; TTINOLUT-NEXT: [[RES:%.*]] = phi i1 [ [[SEL]], %[[DEFAULT]] ], [ false, %[[ENTRY]] ]
+; TTINOLUT-NEXT: ret i1 [[RES]]
+;
+entry:
+ switch i32 %x, label %default [
+ i32 18, label %end
+ i32 21, label %end
+ i32 48, label %end
+ i32 16, label %end
+ ]
+
+default:
+ %cmp = icmp eq i32 %x, 80
+ %sel = select i1 %cmp, i1 false, i1 true
+ br label %end
+
+end:
+ %res = phi i1 [ false, %entry ], [ false, %entry ], [ false, %entry ], [ false, %entry ], [ %sel, %default ]
+ ret i1 %res
+}
+
define i32 @lookup_table(i32 %x) {
; OPTNOLUT-LAB...
[truncated]
|
| if (Options.ConvertSwitchToLookupTable && | ||
| simplifySwitchLookup(SI, Builder, DTU, DL, TTI)) | ||
| return requestResimplify(); | ||
| if (Options.ConvertSwitchToArithmetic || Options.ConvertSwitchToLookupTable) |
There was a problem hiding this comment.
Would it be reasonable to refine the comment instead of dropping it (at least, the final heuristic part)? The premise should still apply.
dianqk
approved these changes
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I agree with @antoniofrighetto about the comment, but looks good otherwise. Thank you for finding a good solution!
svkeerthy
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…158242) While we do not want to form actual lookup tables early, we do want to perform some optimizations, as they may enable inlining of the much simpler form. Builds on #156477, which originally included this change as well. This PR makes two changes on top of it: * Do not perform the optimization early if it requires adding a mask check. These make the resulting IR less analyzable. * Add a new SimplifyCFG option that controls switch-to-arithmetic conversion separately from switch-to-lookup conversion. Enable the new flag at the end of the function simplification pipeline. This means that we attempt the arithmetic conversion before inlining, but avoid it in the early pipeline, where it may lose information.
clingfei
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…lvm#158242) While we do not want to form actual lookup tables early, we do want to perform some optimizations, as they may enable inlining of the much simpler form. Builds on llvm#156477, which originally included this change as well. This PR makes two changes on top of it: * Do not perform the optimization early if it requires adding a mask check. These make the resulting IR less analyzable. * Add a new SimplifyCFG option that controls switch-to-arithmetic conversion separately from switch-to-lookup conversion. Enable the new flag at the end of the function simplification pipeline. This means that we attempt the arithmetic conversion before inlining, but avoid it in the early pipeline, where it may lose information.
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While we do not want to form actual lookup tables early, we do want to perform some optimizations, as they may enable inlining of the much simpler form.
Builds on #156477, which originally included this change as well. This PR makes two changes on top of it: