[SimplifyCFG] Use icmp eq for one case

Author: dianqk

llvm/lib/Transforms/Utils/SimplifyCFG.cpp

@@ -5877,18 +5877,22 @@ bool SimplifyCFGOpt::turnSwitchRangeIntoICmp(SwitchInst *SI,
   Constant *NumCases = ConstantInt::get(Offset->getType(),
                                         ContiguousCasesMax->getValue() -
                                             ContiguousCasesMin->getValue() + 1);
-
-  Value *Sub = SI->getCondition();
-  if (!Offset->isNullValue())
-    Sub = Builder.CreateAdd(Sub, Offset, Sub->getName() + ".off");
-
-  Value *Cmp;
+  BranchInst *NewBI;
+  if (NumCases->isOneValue()) {
+    assert(ContiguousCasesMax->getValue() == ContiguousCasesMin->getValue());
+    Value *Cmp = Builder.CreateICmpEQ(SI->getCondition(), ContiguousCasesMin);
+    NewBI = Builder.CreateCondBr(Cmp, ContiguousDest, OtherDest);
+  }
   // If NumCases overflowed, then all possible values jump to the successor.
-  if (NumCases->isNullValue() && !ContiguousCases->empty())
-    Cmp = ConstantInt::getTrue(SI->getContext());
-  else
-    Cmp = Builder.CreateICmpULT(Sub, NumCases, "switch");
-  BranchInst *NewBI = Builder.CreateCondBr(Cmp, ContiguousDest, OtherDest);
+  else if (NumCases->isNullValue() && !ContiguousCases->empty()) {
+    NewBI = Builder.CreateBr(ContiguousDest);
+  } else {
+    Value *Sub = SI->getCondition();
+    if (!Offset->isNullValue())
+      Sub = Builder.CreateAdd(Sub, Offset, Sub->getName() + ".off");
+    Value *Cmp = Builder.CreateICmpULT(Sub, NumCases, "switch");
+    NewBI = Builder.CreateCondBr(Cmp, ContiguousDest, OtherDest);
+  }
 
   // Update weight for the newly-created conditional branch.
   if (hasBranchWeightMD(*SI)) {

llvm/test/Transforms/Coroutines/coro-catchswitch-cleanuppad.ll

@@ -80,8 +80,8 @@ cleanup2:
 ; CHECK: cleanup2.corodispatch:
 ; CHECK:   %1 = phi i8 [ 0, %handler2 ], [ 1, %catch.dispatch.2 ]
 ; CHECK:   %2 = cleanuppad within %h1 []
-; CHECK:   %switch = icmp ult i8 %1, 1
-; CHECK:   br i1 %switch, label %cleanup2.from.handler2, label %cleanup2.from.catch.dispatch.2
+; CHECK:   %3 = icmp eq i8 %1, 0
+; CHECK:   br i1 %3, label %cleanup2.from.handler2, label %cleanup2.from.catch.dispatch.2
 
 ; CHECK: cleanup2.from.handler2:
 ; CHECK:   %valueB.reload = load i32, ptr %valueB.spill.addr, align 4

llvm/test/Transforms/SimplifyCFG/switch-dead-default.ll

@@ -7,8 +7,7 @@ declare void @foo(i32)
 define void @test(i1 %a) {
 ; CHECK-LABEL: define void @test(
 ; CHECK-SAME: i1 [[A:%.*]]) {
-; CHECK-NEXT:    [[A_OFF:%.*]] = add i1 [[A]], true
-; CHECK-NEXT:    [[SWITCH:%.*]] = icmp ult i1 [[A_OFF]], true
+; CHECK-NEXT:    [[SWITCH:%.*]] = icmp eq i1 [[A]], true
 ; CHECK-NEXT:    br i1 [[SWITCH]], label [[TRUE:%.*]], label [[FALSE:%.*]]
 ; CHECK:       common.ret:
 ; CHECK-NEXT:    ret void
@@ -209,8 +208,7 @@ define void @test5(i8 %a) {
 ; CHECK-SAME: i8 [[A:%.*]]) {
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i8 [[A]], 2
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[CMP]])
-; CHECK-NEXT:    [[A_OFF:%.*]] = add i8 [[A]], -1
-; CHECK-NEXT:    [[SWITCH:%.*]] = icmp ult i8 [[A_OFF]], 1
+; CHECK-NEXT:    [[SWITCH:%.*]] = icmp eq i8 [[A]], 1
 ; CHECK-NEXT:    br i1 [[SWITCH]], label [[TRUE:%.*]], label [[FALSE:%.*]]
 ; CHECK:       common.ret:
 ; CHECK-NEXT:    ret void
@@ -243,8 +241,7 @@ define void @test6(i8 %a) {
 ; CHECK-NEXT:    [[AND:%.*]] = and i8 [[A]], -2
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i8 [[AND]], -2
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[CMP]])
-; CHECK-NEXT:    [[A_OFF:%.*]] = add i8 [[A]], 1
-; CHECK-NEXT:    [[SWITCH:%.*]] = icmp ult i8 [[A_OFF]], 1
+; CHECK-NEXT:    [[SWITCH:%.*]] = icmp eq i8 [[A]], -1
 ; CHECK-NEXT:    br i1 [[SWITCH]], label [[TRUE:%.*]], label [[FALSE:%.*]]
 ; CHECK:       common.ret:
 ; CHECK-NEXT:    ret void
@@ -279,8 +276,7 @@ define void @test7(i8 %a) {
 ; CHECK-NEXT:    [[AND:%.*]] = and i8 [[A]], -2
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i8 [[AND]], -2
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[CMP]])
-; CHECK-NEXT:    [[A_OFF:%.*]] = add i8 [[A]], 1
-; CHECK-NEXT:    [[SWITCH:%.*]] = icmp ult i8 [[A_OFF]], 1
+; CHECK-NEXT:    [[SWITCH:%.*]] = icmp eq i8 [[A]], -1
 ; CHECK-NEXT:    br i1 [[SWITCH]], label [[TRUE:%.*]], label [[FALSE:%.*]]
 ; CHECK:       common.ret:
 ; CHECK-NEXT:    ret void

llvm/test/Transforms/SimplifyCFG/switch-range-to-icmp.ll

@@ -220,8 +220,7 @@ else:
 
 define i32 @wrapping_known_range_2(i8 range(i8 0, 6) %arg) {
 ; CHECK-LABEL: @wrapping_known_range_2(
-; CHECK-NEXT:    [[ARG_OFF:%.*]] = add i8 [[ARG:%.*]], -1
-; CHECK-NEXT:    [[SWITCH:%.*]] = icmp ult i8 [[ARG_OFF]], 1
+; CHECK-NEXT:    [[SWITCH:%.*]] = icmp eq i8 [[ARG:%.*]], 1
 ; CHECK-NEXT:    br i1 [[SWITCH]], label [[ELSE:%.*]], label [[IF:%.*]]
 ; CHECK:       common.ret:
 ; CHECK-NEXT:    [[COMMON_RET_OP:%.*]] = phi i32 [ [[I0:%.*]], [[IF]] ], [ [[I1:%.*]], [[ELSE]] ]
@@ -338,8 +337,7 @@ else:
 define i32 @one_case_1(i32 %x) {
 ; CHECK-LABEL: @one_case_1(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[X_OFF:%.*]] = add i32 [[X:%.*]], -10
-; CHECK-NEXT:    [[SWITCH:%.*]] = icmp ult i32 [[X_OFF]], 1
+; CHECK-NEXT:    [[SWITCH:%.*]] = icmp eq i32 [[X:%.*]], 10
 ; CHECK-NEXT:    br i1 [[SWITCH]], label [[A:%.*]], label [[B:%.*]]
 ; CHECK:       common.ret:
 ; CHECK-NEXT:    [[COMMON_RET_OP:%.*]] = phi i32 [ [[TMP0:%.*]], [[B]] ], [ [[TMP1:%.*]], [[A]] ]
@@ -372,8 +370,7 @@ b:
 define i32 @one_case_2(i32 %x) {
 ; CHECK-LABEL: @one_case_2(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[X_OFF:%.*]] = add i32 [[X:%.*]], -5
-; CHECK-NEXT:    [[SWITCH:%.*]] = icmp ult i32 [[X_OFF]], 1
+; CHECK-NEXT:    [[SWITCH:%.*]] = icmp eq i32 [[X:%.*]], 5
 ; CHECK-NEXT:    br i1 [[SWITCH]], label [[A:%.*]], label [[B:%.*]]
 ; CHECK:       common.ret:
 ; CHECK-NEXT:    [[COMMON_RET_OP:%.*]] = phi i32 [ [[TMP0:%.*]], [[A]] ], [ [[TMP1:%.*]], [[B]] ]