[InstCombine] Missed optimization: Fold (sext(a) & c1) == c2 to (a & c3) == trunc(c2)

llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

@@ -7716,6 +7716,32 @@ Instruction *InstCombinerImpl::visitICmpInst(ICmpInst &I) {
   if (Instruction *Res = foldReductionIdiom(I, Builder, DL))
     return Res;
 
+  {
+    Value *A;
+    const APInt *C1, *C2;
+    ICmpInst::Predicate Pred = I.getPredicate();
+    if (ICmpInst::isEquality(Pred)) {
+      // sext(a) & c1 == c2 --> a & c3 == trunc(c2)
+      // sext(a) & c1 != c2 --> a & c3 != trunc(c2)
+      if (match(Op0, m_And(m_SExt(m_Value(A)), m_APInt(C1))) &&
+          match(Op1, m_APInt(C2))) {
+        Type *InputTy = A->getType();
+        unsigned InputBitWidth = InputTy->getScalarSizeInBits();
+        // c2 must be non-negative at the bitwidth of a.
+        if (C2->getActiveBits() < InputBitWidth) {
+          APInt TruncC1 = C1->trunc(InputBitWidth);
+          // Check if there are 1s in C1 high bits of size InputBitWidth.
+          if (C1->uge(APInt::getOneBitSet(C1->getBitWidth(), InputBitWidth)))
+            TruncC1.setBit(InputBitWidth - 1);
+          Value *AndInst = Builder.CreateAnd(A, TruncC1);
+          return new ICmpInst(
+              Pred, AndInst,
+              ConstantInt::get(InputTy, C2->trunc(InputBitWidth)));
+        }
+      }
+    }
+  }
+
   return Changed ? &I : nullptr;
 }
 

llvm/test/Transforms/InstCombine/load-cmp.ll

@@ -312,9 +312,7 @@ define i1 @test10_struct_arr_i64(i64 %x) {
 
 define i1 @test10_struct_arr_noinbounds_i16(i16 %x) {
 ; CHECK-LABEL: @test10_struct_arr_noinbounds_i16(
-; CHECK-NEXT:    [[TMP1:%.*]] = sext i16 [[X:%.*]] to i32
-; CHECK-NEXT:    [[TMP2:%.*]] = and i32 [[TMP1]], 268435455
-; CHECK-NEXT:    [[R:%.*]] = icmp ne i32 [[TMP2]], 1
+; CHECK-NEXT:    [[R:%.*]] = icmp ne i16 [[X:%.*]], 1
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %p = getelementptr [4 x %Foo], ptr @GStructArr, i32 0, i16 %x, i32 2

llvm/test/Transforms/InstCombine/sext-and.ll

@@ -0,0 +1,232 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt < %s -passes=instcombine -S | FileCheck %s
+
+declare void @use(i8)
+
+define i1 @fold_sext_to_and(i8 %x) {
+; CHECK-LABEL: define i1 @fold_sext_to_and(
+; CHECK-SAME: i8 [[X:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = and i8 [[X]], -127
+; CHECK-NEXT:    [[TMP3:%.*]] = icmp eq i8 [[TMP1]], 1
+; CHECK-NEXT:    ret i1 [[TMP3]]
+;
+  %1 = sext i8 %x to i32
+  %2 = and i32 %1, -2147483647
+  %3 = icmp eq i32 %2, 1
+  ret i1 %3
+}
+
+define i1 @fold_sext_to_and1(i8 %x) {
+; CHECK-LABEL: define i1 @fold_sext_to_and1(
+; CHECK-SAME: i8 [[X:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = and i8 [[X]], -127
+; CHECK-NEXT:    [[TMP3:%.*]] = icmp ne i8 [[TMP1]], 1
+; CHECK-NEXT:    ret i1 [[TMP3]]
+;
+  %1 = sext i8 %x to i32
+  %2 = and i32 %1, -2147483647
+  %3 = icmp ne i32 %2, 1
+  ret i1 %3
+}
+
+define i1 @fold_sext_to_and2(i8 %x) {
+; CHECK-LABEL: define i1 @fold_sext_to_and2(
+; CHECK-SAME: i8 [[X:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = and i8 [[X]], -126
+; CHECK-NEXT:    [[TMP3:%.*]] = icmp eq i8 [[TMP1]], 2
+; CHECK-NEXT:    ret i1 [[TMP3]]
+;
+  %1 = sext i8 %x to i32
+  %2 = and i32 %1, 1073741826
+  %3 = icmp eq i32 %2, 2
+  ret i1 %3
+}
+
+define i1 @fold_sext_to_and3(i8 %x) {
+; CHECK-LABEL: define i1 @fold_sext_to_and3(
+; CHECK-SAME: i8 [[X:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = and i8 [[X]], -126
+; CHECK-NEXT:    [[TMP3:%.*]] = icmp ne i8 [[TMP1]], 2
+; CHECK-NEXT:    ret i1 [[TMP3]]
+;
+  %1 = sext i8 %x to i32
+  %2 = and i32 %1, 1073741826
+  %3 = icmp ne i32 %2, 2
+  ret i1 %3
+}
+
+define i1 @fold_sext_to_and_multi_use(i8 %x) {
+; CHECK-LABEL: define i1 @fold_sext_to_and_multi_use(
+; CHECK-SAME: i8 [[X:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = sext i8 [[X]] to i32
+; CHECK-NEXT:    call void @use(i32 [[TMP1]])
+; CHECK-NEXT:    [[TMP2:%.*]] = and i8 [[X]], -127
+; CHECK-NEXT:    [[TMP3:%.*]] = icmp eq i8 [[TMP2]], 1
+; CHECK-NEXT:    ret i1 [[TMP3]]
+;
+  %1 = sext i8 %x to i32
+  call void @use(i32 %1)
+  %2 = and i32 %1, -2147483647
+  %3 = icmp eq i32 %2, 1
+  ret i1 %3
+}
+
+define i1 @fold_sext_to_and_multi_use1(i8 %x) {
+; CHECK-LABEL: define i1 @fold_sext_to_and_multi_use1(
+; CHECK-SAME: i8 [[X:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = sext i8 [[X]] to i32
+; CHECK-NEXT:    call void @use(i32 [[TMP1]])
+; CHECK-NEXT:    [[TMP2:%.*]] = and i8 [[X]], -127
+; CHECK-NEXT:    [[TMP3:%.*]] = icmp ne i8 [[TMP2]], 1
+; CHECK-NEXT:    ret i1 [[TMP3]]
+;
+  %1 = sext i8 %x to i32
+  call void @use(i32 %1)
+  %2 = and i32 %1, -2147483647
+  %3 = icmp ne i32 %2, 1
+  ret i1 %3
+}
+
+define i1 @fold_sext_to_and_multi_use2(i8 %x) {
+; CHECK-LABEL: define i1 @fold_sext_to_and_multi_use2(
+; CHECK-SAME: i8 [[X:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = sext i8 [[X]] to i32
+; CHECK-NEXT:    call void @use(i32 [[TMP1]])
+; CHECK-NEXT:    [[TMP2:%.*]] = and i8 [[X]], -126
+; CHECK-NEXT:    [[TMP3:%.*]] = icmp eq i8 [[TMP2]], 2
+; CHECK-NEXT:    ret i1 [[TMP3]]
+;
+  %1 = sext i8 %x to i32
+  call void @use(i32 %1)
+  %2 = and i32 %1, 1073741826
+  %3 = icmp eq i32 %2, 2
+  ret i1 %3
+}
+
+define i1 @fold_sext_to_and_multi_use3(i8 %x) {
+; CHECK-LABEL: define i1 @fold_sext_to_and_multi_use3(
+; CHECK-SAME: i8 [[X:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = sext i8 [[X]] to i32
+; CHECK-NEXT:    call void @use(i32 [[TMP1]])
+; CHECK-NEXT:    [[TMP2:%.*]] = and i8 [[X]], -126
+; CHECK-NEXT:    [[TMP3:%.*]] = icmp ne i8 [[TMP2]], 2
+; CHECK-NEXT:    ret i1 [[TMP3]]
+;
+  %1 = sext i8 %x to i32
+  call void @use(i32 %1)
+  %2 = and i32 %1, 1073741826
+  %3 = icmp ne i32 %2, 2
+  ret i1 %3
+}
+
+; Negative tests
+
+define i1 @fold_sext_to_and_wrong(i8 %x) {
+; CHECK-LABEL: define i1 @fold_sext_to_and_wrong(
+; CHECK-SAME: i8 [[X:%.*]]) {
+; CHECK-NEXT:    ret i1 false
+;
+  %1 = sext i8 %x to i32
+  %2 = and i32 %1, -2147483647
+  %3 = icmp eq i32 %2, -1
+  ret i1 %3
+}
+
+define i1 @fold_sext_to_and_wrong2(i8 %x) {
+; CHECK-LABEL: define i1 @fold_sext_to_and_wrong2(
+; CHECK-SAME: i8 [[X:%.*]]) {
+; CHECK-NEXT:    ret i1 false
+;
+  %1 = sext i8 %x to i32
+  %2 = and i32 %1, -2147483647
+  %3 = icmp eq i32 %2, 128
+  ret i1 %3
+}
+
+define i1 @fold_sext_to_and_wrong3(i8 %x) {
+; CHECK-LABEL: define i1 @fold_sext_to_and_wrong3(
+; CHECK-SAME: i8 [[X:%.*]]) {
+; CHECK-NEXT:    ret i1 false
+;
+  %1 = sext i8 %x to i32
+  %2 = and i32 %1, 128
+  %3 = icmp eq i32 %2, -2147483648
+  ret i1 %3
+}
+
+define i1 @fold_sext_to_and_wrong4(i8 %x) {
+; CHECK-LABEL: define i1 @fold_sext_to_and_wrong4(
+; CHECK-SAME: i8 [[X:%.*]]) {
+; CHECK-NEXT:    ret i1 false
+;
+  %1 = sext i8 %x to i32
+  %2 = and i32 %1, 128
+  %3 = icmp eq i32 %2, 1
+  ret i1 %3
+}
+
+define i1 @fold_sext_to_and_wrong5(i8 %x) {
+; CHECK-LABEL: define i1 @fold_sext_to_and_wrong5(
+; CHECK-SAME: i8 [[X:%.*]]) {
+; CHECK-NEXT:    ret i1 false
+;
+  %1 = sext i8 %x to i32
+  %2 = and i32 %1, -256
+  %3 = icmp eq i32 %2, 1
+  ret i1 %3
+}
+
+define i1 @fold_sext_to_and_wrong6(i8 %x) {
+; CHECK-LABEL: define i1 @fold_sext_to_and_wrong6(
+; CHECK-SAME: i8 [[X:%.*]]) {
+; CHECK-NEXT:    ret i1 true
+;
+  %1 = sext i8 %x to i32
+  %2 = and i32 %1, -2147483647
+  %3 = icmp ne i32 %2, -1
+  ret i1 %3
+}
+
+define i1 @fold_sext_to_and_wrong7(i8 %x) {
+; CHECK-LABEL: define i1 @fold_sext_to_and_wrong7(
+; CHECK-SAME: i8 [[X:%.*]]) {
+; CHECK-NEXT:    ret i1 true
+;
+  %1 = sext i8 %x to i32
+  %2 = and i32 %1, -2147483647
+  %3 = icmp ne i32 %2, 128
+  ret i1 %3
+}
+
+define i1 @fold_sext_to_and_wrong8(i8 %x) {
+; CHECK-LABEL: define i1 @fold_sext_to_and_wrong8(
+; CHECK-SAME: i8 [[X:%.*]]) {
+; CHECK-NEXT:    ret i1 true
+;
+  %1 = sext i8 %x to i32
+  %2 = and i32 %1, 128
+  %3 = icmp ne i32 %2, -2147483648
+  ret i1 %3
+}
+
+define i1 @fold_sext_to_and_wrong9(i8 %x) {
+; CHECK-LABEL: define i1 @fold_sext_to_and_wrong9(
+; CHECK-SAME: i8 [[X:%.*]]) {
+; CHECK-NEXT:    ret i1 true
+;
+  %1 = sext i8 %x to i32
+  %2 = and i32 %1, 128
+  %3 = icmp ne i32 %2, 1
+  ret i1 %3
+}
+
+define i1 @fold_sext_to_and_wrong10(i8 %x) {
+; CHECK-LABEL: define i1 @fold_sext_to_and_wrong10(
+; CHECK-SAME: i8 [[X:%.*]]) {
+; CHECK-NEXT:    ret i1 true
+;
+  %1 = sext i8 %x to i32
+  %2 = and i32 %1, -256
+  %3 = icmp ne i32 %2, 1
+  ret i1 %3
+}