[InstSimplify] Add basic simplification support for {s,u}shl_sat

Proofs of simplifications added: https://alive2.llvm.org/ce/z/MELfd2

Author: goldsteinn

llvm/lib/Analysis/InstructionSimplify.cpp

@@ -6534,6 +6534,22 @@ Value *llvm::simplifyBinaryIntrinsic(Intrinsic::ID IID, Type *ReturnType,
     if (Q.isUndefValue(Op0) || Q.isUndefValue(Op1))
       return Constant::getNullValue(ReturnType);
     break;
+  case Intrinsic::ushl_sat:
+    // ushl_sat(0, X) -> 0
+    // ushl_sat(UINT_MAX, X) -> UINT_MAX
+    // ushl_sat(X, 0) -> X
+    if (match(Op0, m_Zero()) || match(Op0, m_AllOnes()) || match(Op1, m_Zero()))
+      return Op0;
+    break;
+  case Intrinsic::sshl_sat:
+    // sshl_sat(0, X) -> 0
+    // sshl_sat(INT_MAX, X) -> INT_MAX
+    // sshl_sat(INT_MIN, X) -> INT_MIN
+    // sshl_sat(X, 0) -> X
+    if (match(Op0, m_Zero()) || match(Op0, m_MaxSignedValue()) ||
+        match(Op0, m_SignMask()) || match(Op1, m_Zero()))
+      return Op0;
+    break;
   case Intrinsic::uadd_sat:
     // sat(MAX + X) -> MAX
     // sat(X + MAX) -> MAX

llvm/test/Transforms/InstCombine/fold-ext-eq-c-with-op.ll

@@ -128,8 +128,7 @@ define i8 @fold_umax_zext_eq_9(i8 %x) {
 define i8 @fold_sshl_sat_sext_eq_3_rhs(i8 %x) {
 ; CHECK-LABEL: @fold_sshl_sat_sext_eq_3_rhs(
 ; CHECK-NEXT:    [[X_EQ:%.*]] = icmp eq i8 [[X:%.*]], 3
-; CHECK-NEXT:    [[X_EQ_EXT:%.*]] = sext i1 [[X_EQ]] to i8
-; CHECK-NEXT:    [[R:%.*]] = call i8 @llvm.sshl.sat.i8(i8 [[X]], i8 [[X_EQ_EXT]])
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[X_EQ]], i8 127, i8 [[X]]
 ; CHECK-NEXT:    ret i8 [[R]]
 ;
   %x_eq = icmp eq i8 %x, 3
@@ -141,8 +140,7 @@ define i8 @fold_sshl_sat_sext_eq_3_rhs(i8 %x) {
 define i8 @fold_ushl_sat_zext_eq_3_lhs(i8 %x) {
 ; CHECK-LABEL: @fold_ushl_sat_zext_eq_3_lhs(
 ; CHECK-NEXT:    [[X_EQ:%.*]] = icmp eq i8 [[X:%.*]], 3
-; CHECK-NEXT:    [[X_EQ_EXT:%.*]] = zext i1 [[X_EQ]] to i8
-; CHECK-NEXT:    [[R:%.*]] = call i8 @llvm.ushl.sat.i8(i8 [[X_EQ_EXT]], i8 [[X]])
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[X_EQ]], i8 8, i8 0
 ; CHECK-NEXT:    ret i8 [[R]]
 ;
   %x_eq = icmp eq i8 %x, 3

llvm/test/Transforms/InstCombine/freeze-integer-intrinsics.ll

@@ -396,8 +396,7 @@ define <2 x i32> @sshl_sat_v2i32_unsafe_constant_vector(<2 x i32> %arg0) {
 
 define <vscale x 2 x i32> @ushl_sat_v2i32_scalable_zeroinitializer(<vscale x 2 x i32> %arg0) {
 ; CHECK-LABEL: @ushl_sat_v2i32_scalable_zeroinitializer(
-; CHECK-NEXT:    [[CALL:%.*]] = call <vscale x 2 x i32> @llvm.ushl.sat.nxv2i32(<vscale x 2 x i32> [[ARG0:%.*]], <vscale x 2 x i32> zeroinitializer)
-; CHECK-NEXT:    [[FREEZE:%.*]] = freeze <vscale x 2 x i32> [[CALL]]
+; CHECK-NEXT:    [[FREEZE:%.*]] = freeze <vscale x 2 x i32> [[CALL:%.*]]
 ; CHECK-NEXT:    ret <vscale x 2 x i32> [[FREEZE]]
 ;
   %call = call <vscale x 2 x i32> @llvm.ushl.sat.nxv2i32(<vscale x 2 x i32> %arg0, <vscale x 2 x i32> zeroinitializer)
@@ -407,8 +406,7 @@ define <vscale x 2 x i32> @ushl_sat_v2i32_scalable_zeroinitializer(<vscale x 2 x
 
 define <vscale x 2 x i32> @sshl_sat_v2i32_scalable_zeroinitializer(<vscale x 2 x i32> %arg0) {
 ; CHECK-LABEL: @sshl_sat_v2i32_scalable_zeroinitializer(
-; CHECK-NEXT:    [[CALL:%.*]] = call <vscale x 2 x i32> @llvm.sshl.sat.nxv2i32(<vscale x 2 x i32> [[ARG0:%.*]], <vscale x 2 x i32> zeroinitializer)
-; CHECK-NEXT:    [[FREEZE:%.*]] = freeze <vscale x 2 x i32> [[CALL]]
+; CHECK-NEXT:    [[FREEZE:%.*]] = freeze <vscale x 2 x i32> [[CALL:%.*]]
 ; CHECK-NEXT:    ret <vscale x 2 x i32> [[FREEZE]]
 ;
   %call = call <vscale x 2 x i32> @llvm.sshl.sat.nxv2i32(<vscale x 2 x i32> %arg0, <vscale x 2 x i32> zeroinitializer)