[llvm] e11f93e - [SimplifyCFG] Support not in chain of comparisons. (#156497)

[via llvm-commits]

Author: Andreas Jonson
Date: 2025-09-08T19:16:41+02:00
New Revision: e11f93e9fdacae6e7003b6d34b32007fd3fc081c

URL: https://github.com/llvm/llvm-project/commit/e11f93e9fdacae6e7003b6d34b32007fd3fc081c
DIFF: https://github.com/llvm/llvm-project/commit/e11f93e9fdacae6e7003b6d34b32007fd3fc081c.diff

LOG: [SimplifyCFG] Support not in chain of comparisons. (#156497)

Proof: https://alive2.llvm.org/ce/z/cpXuCb

Added: 
    

Modified: 
    llvm/lib/Transforms/Utils/SimplifyCFG.cpp
    llvm/test/Transforms/SimplifyCFG/switch_create.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 86d4750f6f000..39edc4d871262 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -612,6 +612,9 @@ struct ConstantComparesGatherer {
   /// If CompValue is already set, the function is expected to fail if a match
   /// is found but the value compared to is 
diff erent.
   bool matchInstruction(Instruction *I, bool isEQ) {
+    if (match(I, m_Not(m_Instruction(I))))
+      isEQ = !isEQ;
+
     Value *Val;
     if (match(I, m_NUWTrunc(m_Value(Val)))) {
       // If we already have a value for the switch, it has to match!

diff  --git a/llvm/test/Transforms/SimplifyCFG/switch_create.ll b/llvm/test/Transforms/SimplifyCFG/switch_create.ll
index 6d2a404203d02..18c4ade46162c 100644
--- a/llvm/test/Transforms/SimplifyCFG/switch_create.ll
+++ b/llvm/test/Transforms/SimplifyCFG/switch_create.ll
@@ -1265,3 +1265,51 @@ if.then:
 if.end:
   ret void
 }
+
+define void @and_chain_trunc_nuw_not_i1_condition(i8 %x) {
+; CHECK-LABEL: @and_chain_trunc_nuw_not_i1_condition(
+; CHECK-NEXT:    [[X_OFF:%.*]] = add i8 [[X:%.*]], -1
+; CHECK-NEXT:    [[SWITCH:%.*]] = icmp ult i8 [[X_OFF]], 4
+; CHECK-NEXT:    br i1 [[SWITCH]], label [[COMMON_RET:%.*]], label [[IF_THEN:%.*]]
+; CHECK:       common.ret:
+; CHECK-NEXT:    ret void
+; CHECK:       if.then:
+; CHECK-NEXT:    tail call void @foo1()
+; CHECK-NEXT:    br label [[COMMON_RET]]
+;
+  %add = add nsw i8 %x, -2
+  %icmp = icmp ugt i8 %add, 2
+  %trunc = trunc nuw i8 %x to i1
+  %not = xor i1 %trunc, true
+  %and = select i1 %icmp, i1 %not, i1 false
+  br i1 %and, label %if.then, label %if.end
+if.then:
+  tail call void @foo1()
+  ret void
+if.end:
+  ret void
+}
+
+define void @or_chain_trunc_nuw_not_i1_condition(i8 %x) {
+; CHECK-LABEL: @or_chain_trunc_nuw_not_i1_condition(
+; CHECK-NEXT:    switch i8 [[X:%.*]], label [[COMMON_RET:%.*]] [
+; CHECK-NEXT:      i8 2, label [[IF_THEN:%.*]]
+; CHECK-NEXT:      i8 0, label [[IF_THEN]]
+; CHECK-NEXT:    ]
+; CHECK:       common.ret:
+; CHECK-NEXT:    ret void
+; CHECK:       if.then:
+; CHECK-NEXT:    tail call void @foo1()
+; CHECK-NEXT:    br label [[COMMON_RET]]
+;
+  %icmp = icmp eq i8 %x, 2
+  %trunc = trunc nuw i8 %x to i1
+  %not = xor i1 %trunc, true
+  %or = select i1 %icmp, i1 true, i1 %not
+  br i1 %or, label %if.then, label %if.end
+if.then:
+  tail call void @foo1()
+  ret void
+if.end:
+  ret void
+}