[InstCombine] Fold mul (sext bool X), Y into select X, -Y, 0 (#84792)

Alive2: https://alive2.llvm.org/ce/z/n_ns-W

Resolve #84608

Author: SahilPatidar

llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp

@@ -448,6 +448,14 @@ Instruction *InstCombinerImpl::visitMul(BinaryOperator &I) {
   if (match(Op1, m_ZExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1))
     return SelectInst::Create(X, Op0, ConstantInt::getNullValue(Ty));
 
+  // mul (sext X), Y -> select X, -Y, 0
+  // mul Y, (sext X) -> select X, -Y, 0
+  if (match(&I, m_c_Mul(m_OneUse(m_SExt(m_Value(X))), m_Value(Y))) &&
+      X->getType()->isIntOrIntVectorTy(1))
+    return SelectInst::Create(
+        X, Builder.CreateNeg(Y, "", /*HasNUW=*/false, I.hasNoSignedWrap()),
+        ConstantInt::getNullValue(Op0->getType()));
+
   Constant *ImmC;
   if (match(Op1, m_ImmConstant(ImmC))) {
     // (sext bool X) * C --> X ? -C : 0

llvm/test/Transforms/InstCombine/mul.ll

@@ -2049,3 +2049,94 @@ define i32 @zext_negpow2_use(i8 %x) {
   %r = mul i32 %zx, -16777216 ; -1 << 24
   ret i32 %r
 }
+
+define i32 @mul_sext_icmp_with_zero(i32 %x) {
+; CHECK-LABEL: @mul_sext_icmp_with_zero(
+; CHECK-NEXT:    ret i32 0
+;
+  %cmp = icmp eq i32 %x, 0
+  %sext = sext i1 %cmp to i32
+  %mul = mul i32 %sext, %x
+  ret i32 %mul
+}
+
+define i32 @test_mul_sext_bool(i1 %x, i32 %y) {
+; CHECK-LABEL: @test_mul_sext_bool(
+; CHECK-NEXT:    [[Y_NEG:%.*]] = sub i32 0, [[Y:%.*]]
+; CHECK-NEXT:    [[MUL:%.*]] = select i1 [[X:%.*]], i32 [[Y_NEG]], i32 0
+; CHECK-NEXT:    ret i32 [[MUL]]
+;
+  %sext = sext i1 %x to i32
+  %mul = mul i32 %sext, %y
+  ret i32 %mul
+}
+
+define i32 @test_mul_sext_bool_nuw(i1 %x, i32 %y) {
+; CHECK-LABEL: @test_mul_sext_bool_nuw(
+; CHECK-NEXT:    [[Y_NEG:%.*]] = sub i32 0, [[Y:%.*]]
+; CHECK-NEXT:    [[MUL:%.*]] = select i1 [[X:%.*]], i32 [[Y_NEG]], i32 0
+; CHECK-NEXT:    ret i32 [[MUL]]
+;
+  %sext = sext i1 %x to i32
+  %mul = mul nuw i32 %sext, %y
+  ret i32 %mul
+}
+
+define i32 @test_mul_sext_bool_nsw(i1 %x, i32 %y) {
+; CHECK-LABEL: @test_mul_sext_bool_nsw(
+; CHECK-NEXT:    [[Y_NEG:%.*]] = sub nsw i32 0, [[Y:%.*]]
+; CHECK-NEXT:    [[MUL:%.*]] = select i1 [[X:%.*]], i32 [[Y_NEG]], i32 0
+; CHECK-NEXT:    ret i32 [[MUL]]
+;
+  %sext = sext i1 %x to i32
+  %mul = mul nsw i32 %sext, %y
+  ret i32 %mul
+}
+
+define i32 @test_mul_sext_bool_nuw_nsw(i1 %x, i32 %y) {
+; CHECK-LABEL: @test_mul_sext_bool_nuw_nsw(
+; CHECK-NEXT:    [[Y_NEG:%.*]] = sub nsw i32 0, [[Y:%.*]]
+; CHECK-NEXT:    [[MUL:%.*]] = select i1 [[X:%.*]], i32 [[Y_NEG]], i32 0
+; CHECK-NEXT:    ret i32 [[MUL]]
+;
+  %sext = sext i1 %x to i32
+  %mul = mul nuw nsw i32 %sext, %y
+  ret i32 %mul
+}
+
+define i32 @test_mul_sext_bool_commuted(i1 %x, i32 %y) {
+; CHECK-LABEL: @test_mul_sext_bool_commuted(
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[Y:%.*]], -2
+; CHECK-NEXT:    [[YY_NEG1:%.*]] = add i32 [[TMP1]], 1
+; CHECK-NEXT:    [[MUL:%.*]] = select i1 [[X:%.*]], i32 [[YY_NEG1]], i32 0
+; CHECK-NEXT:    ret i32 [[MUL]]
+;
+  %yy = xor i32 %y, 1
+  %sext = sext i1 %x to i32
+  %mul = mul i32 %yy, %sext
+  ret i32 %mul
+}
+
+define i32 @test_mul_sext_nonbool(i2 %x, i32 %y) {
+; CHECK-LABEL: @test_mul_sext_nonbool(
+; CHECK-NEXT:    [[SEXT:%.*]] = sext i2 [[X:%.*]] to i32
+; CHECK-NEXT:    [[MUL:%.*]] = mul i32 [[SEXT]], [[Y:%.*]]
+; CHECK-NEXT:    ret i32 [[MUL]]
+;
+  %sext = sext i2 %x to i32
+  %mul = mul i32 %sext, %y
+  ret i32 %mul
+}
+
+define i32 @test_mul_sext_multiuse(i1 %x, i32 %y) {
+; CHECK-LABEL: @test_mul_sext_multiuse(
+; CHECK-NEXT:    [[SEXT:%.*]] = sext i1 [[X:%.*]] to i32
+; CHECK-NEXT:    tail call void @use(i32 [[SEXT]])
+; CHECK-NEXT:    [[MUL:%.*]] = mul i32 [[SEXT]], [[Y:%.*]]
+; CHECK-NEXT:    ret i32 [[MUL]]
+;
+  %sext = sext i1 %x to i32
+  tail call void @use(i32 %sext)
+  %mul = mul i32 %sext, %y
+  ret i32 %mul
+}

llvm/test/Transforms/InstCombine/sub-xor-cmp.ll

@@ -117,11 +117,9 @@ define i64 @sext_diff_i1_xor_sub_1(i64 %a, i1 %b, i1 %c) {
 define i64 @sext_multi_uses(i64 %a, i1 %b, i64 %x) {
 ; CHECK-LABEL: define i64 @sext_multi_uses(
 ; CHECK-SAME: i64 [[A:%.*]], i1 [[B:%.*]], i64 [[X:%.*]]) {
-; CHECK-NEXT:    [[C:%.*]] = sext i1 [[B]] to i64
-; CHECK-NEXT:    [[TMP1:%.*]] = sub i64 0, [[A]]
-; CHECK-NEXT:    [[E:%.*]] = select i1 [[B]], i64 [[TMP1]], i64 [[A]]
-; CHECK-NEXT:    [[F:%.*]] = mul i64 [[C]], [[X]]
-; CHECK-NEXT:    [[R:%.*]] = add i64 [[F]], [[E]]
+; CHECK-NEXT:    [[TMP1:%.*]] = add i64 [[X]], [[A]]
+; CHECK-NEXT:    [[TMP2:%.*]] = sub i64 0, [[TMP1]]
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[B]], i64 [[TMP2]], i64 [[A]]
 ; CHECK-NEXT:    ret i64 [[R]]
 ;
   %c = sext i1 %b to i64