Don't match with shl, ashr, and ashl because if the shfamt is too large we can create a poison value

Author: bababuck

llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp

@@ -909,9 +909,6 @@ static Instruction *foldSelectZeroOrFixedOp(SelectInst &SI,
 
   if (!(match(FalseVal, m_c_Mul(m_Specific(X), m_Value(Y))) ||
         match(FalseVal, m_c_And(m_Specific(X), m_Value(Y))) ||
-        match(FalseVal, m_Shl(m_Specific(X), m_Value(Y))) ||
-        match(FalseVal, m_AShr(m_Specific(X), m_Value(Y))) ||
-        match(FalseVal, m_LShr(m_Specific(X), m_Value(Y))) ||
         match(FalseVal, m_FShl(m_Specific(X), m_Specific(X), m_Value(Y))) ||
         match(FalseVal, m_FShr(m_Specific(X), m_Specific(X), m_Value(Y))) ||
         match(FalseVal, m_SDiv(m_Specific(X), m_Value(Y))) ||

llvm/test/Transforms/InstCombine/select-fixed-zero.ll

@@ -30,9 +30,10 @@ define i64 @mul_select(i64 %a, i64 %b) {
 ; (select (icmp x, 0, eq), 0, (shl x, y)) -> (shl x, y)
 define i64 @shl_select(i64 %a, i64 %b) {
 ; CHECK-LABEL: @shl_select(
-; CHECK-NEXT:    [[B_FR:%.*]] = freeze i64 [[B:%.*]]
-; CHECK-NEXT:    [[SHL:%.*]] = shl i64 [[A:%.*]], [[B_FR]]
-; CHECK-NEXT:    ret i64 [[SHL]]
+; CHECK-NEXT:    [[COND:%.*]] = icmp eq i64 [[A:%.*]], 0
+; CHECK-NEXT:    [[SHL:%.*]] = shl i64 [[A]], [[B_FR:%.*]]
+; CHECK-NEXT:    [[SELECT:%.*]] = select i1 [[COND]], i64 0, i64 [[SHL]]
+; CHECK-NEXT:    ret i64 [[SELECT]]
 ;
   %cond = icmp eq i64 %a, 0
   %shl = shl i64 %a, %b
@@ -56,9 +57,10 @@ define i64 @and_select(i64 %a, i64 %b) {
 ; (select (icmp x, 0, ne), (ashr x, y), 0) -> (ashr x, y)
 define i64 @ashr_select(i64 %a, i64 %b) {
 ; CHECK-LABEL: @ashr_select(
-; CHECK-NEXT:    [[B_FR:%.*]] = freeze i64 [[B:%.*]]
-; CHECK-NEXT:    [[ASHR:%.*]] = ashr i64 [[A:%.*]], [[B_FR]]
-; CHECK-NEXT:    ret i64 [[ASHR]]
+; CHECK-NEXT:    [[COND_NOT:%.*]] = icmp eq i64 [[A:%.*]], 0
+; CHECK-NEXT:    [[ASHR:%.*]] = ashr i64 [[A]], [[B_FR:%.*]]
+; CHECK-NEXT:    [[SELECT:%.*]] = select i1 [[COND_NOT]], i64 0, i64 [[ASHR]]
+; CHECK-NEXT:    ret i64 [[SELECT]]
 ;
   %cond = icmp ne i64 0, %a
   %ashr = ashr i64 %a, %b
@@ -69,9 +71,10 @@ define i64 @ashr_select(i64 %a, i64 %b) {
 ; (select (icmp x, 0, ne), (lshr x, y), 0) -> (lshr x, y)
 define i64 @lshr_select(i64 %a, i64 %b) {
 ; CHECK-LABEL: @lshr_select(
-; CHECK-NEXT:    [[B_FR:%.*]] = freeze i64 [[B:%.*]]
-; CHECK-NEXT:    [[LSHR:%.*]] = lshr i64 [[A:%.*]], [[B_FR]]
-; CHECK-NEXT:    ret i64 [[LSHR]]
+; CHECK-NEXT:    [[COND_NOT:%.*]] = icmp eq i64 [[A:%.*]], 0
+; CHECK-NEXT:    [[LSHR:%.*]] = lshr i64 [[A]], [[B_FR:%.*]]
+; CHECK-NEXT:    [[SELECT:%.*]] = select i1 [[COND_NOT]], i64 0, i64 [[LSHR]]
+; CHECK-NEXT:    ret i64 [[SELECT]]
 ;
   %cond = icmp ne i64 0, %a
   %lshr = lshr i64 %a, %b

llvm/test/Transforms/InstCombine/select.ll

@@ -2733,9 +2733,10 @@ define void @select_freeze_icmp_multuses(i32 %x, i32 %y) {
 
 define i32 @pr47322_more_poisonous_replacement(i32 %arg) {
 ; CHECK-LABEL: @pr47322_more_poisonous_replacement(
-; CHECK-NEXT:    [[TRAILING:%.*]] = call range(i32 0, 33) i32 @llvm.cttz.i32(i32 [[ARG:%.*]], i1 true)
-; CHECK-NEXT:    [[TRAILING_FR:%.*]] = freeze i32 [[TRAILING]]
-; CHECK-NEXT:    [[R1_SROA_0_1:%.*]] = lshr exact i32 [[ARG]], [[TRAILING_FR]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[ARG:%.*]], 0
+; CHECK-NEXT:    [[TRAILING:%.*]] = call range(i32 0, 33) i32 @llvm.cttz.i32(i32 [[ARG]], i1 true)
+; CHECK-NEXT:    [[SHIFTED:%.*]] = lshr exact i32 [[ARG]], [[TRAILING]]
+; CHECK-NEXT:    [[R1_SROA_0_1:%.*]] = select i1 [[CMP]], i32 0, i32 [[SHIFTED]]
 ; CHECK-NEXT:    ret i32 [[R1_SROA_0_1]]
 ;
   %cmp = icmp eq i32 %arg, 0