diff --git a/clang/include/clang/CIR/Dialect/IR/CIROps.td b/clang/include/clang/CIR/Dialect/IR/CIROps.td
index 4eb86f8a1b82..fda44edf4f20 100644
--- a/clang/include/clang/CIR/Dialect/IR/CIROps.td
+++ b/clang/include/clang/CIR/Dialect/IR/CIROps.td
@@ -3882,6 +3882,86 @@ def FMinOp : BinaryFPToFPBuiltinOp<"fmin", "MinNumOp">;
 def FModOp : BinaryFPToFPBuiltinOp<"fmod", "FRemOp">;
 def PowOp : BinaryFPToFPBuiltinOp<"pow", "PowOp">;
 
+//===----------------------------------------------------------------------===//
+// Assume Operations
+//===----------------------------------------------------------------------===//
+
+def AssumeOp : CIR_Op<"assume"> {
+  let summary = "Tell the optimizer that a boolean value is true";
+  let description = [{
+    The `cir.assume` operation takes a single boolean prediate as its only
+    argument and does not have any results. The operation tells the optimizer
+    that the predicate's value is true.
+
+    This operation corresponds to the `__assume` and the `__builtin_assume`
+    builtin function.
+  }];
+
+  let arguments = (ins CIR_BoolType:$predicate);
+  let results = (outs);
+
+  let assemblyFormat = [{
+    $predicate `:` type($predicate) attr-dict
+  }];
+}
+
+def AssumeAlignedOp
+    : CIR_Op<"assume.aligned", [Pure, AllTypesMatch<["pointer", "result"]>]> {
+  let summary = "Tell the optimizer that a pointer is aligned";
+  let description = [{
+    The `cir.assume.aligned` operation takes two or three arguments.
+
+    When the 3rd argument `offset` is absent, this operation tells the optimizer
+    that the pointer given by the `pointer` argument is aligned to the alignment
+    given by the `align` argument.
+
+    When the `offset` argument is given, it represents an offset from the
+    alignment. This operation then tells the optimizer that the pointer given by
+    the `pointer` argument is always misaligned by the alignment given by the
+    `align` argument by `offset` bytes, a.k.a. the pointer yielded by
+    `(char *)pointer - offset` is aligned to the specified alignment.
+
+    The `align` argument is a constant integer represented as an integer
+    attribute instead of an SSA value. It must be a positive integer.
+
+    The result of this operation has the same value as the `pointer` argument,
+    but the optimizer has additional knowledge about its alignment.
+
+    This operation corresponds to the `__builtin_assume_aligned` builtin
+    function.
+  }];
+
+  let arguments = (ins CIR_PointerType:$pointer,
+                       I64Attr:$alignment,
+                       Optional<CIR_IntType>:$offset);
+  let results = (outs CIR_PointerType:$result);
+
+  let assemblyFormat = [{
+    $pointer `:` qualified(type($pointer))
+    `[` `alignment` $alignment (`,` `offset` $offset^ `:` type($offset))? `]`
+    attr-dict
+  }];
+}
+
+def AssumeSepStorageOp : CIR_Op<"assume.separate_storage", [SameTypeOperands]> {
+  let summary =
+      "Tell the optimizer that two pointers point to different allocations";
+  let description = [{
+    The `cir.assume.separate_storage` operation takes two pointers as arguments,
+    and the operation tells the optimizer that these two pointers point to
+    different allocations.
+
+    This operation corresponds to the `__builtin_assume_separate_storage`
+    builtin function.
+  }];
+
+  let arguments = (ins VoidPtr:$ptr1, VoidPtr:$ptr2);
+
+  let assemblyFormat = [{
+    $ptr1 `,` $ptr2 `:` qualified(type($ptr1)) attr-dict
+  }];
+}
+
 //===----------------------------------------------------------------------===//
 // Branch Probability Operations
 //===----------------------------------------------------------------------===//
diff --git a/clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp b/clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp
index c24888362865..ab4525d38b55 100644
--- a/clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenBuiltin.cpp
@@ -13,6 +13,7 @@
 
 #include "CIRGenCXXABI.h"
 #include "CIRGenCall.h"
+#include "CIRGenCstEmitter.h"
 #include "CIRGenFunction.h"
 #include "CIRGenModule.h"
 #include "TargetInfo.h"
@@ -823,6 +824,44 @@ RValue CIRGenFunction::buildBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
     return RValue::get(buildScalarExpr(E->getArg(0)));
   }
 
+  case Builtin::BI__builtin_assume_aligned: {
+    const Expr *ptr = E->getArg(0);
+    mlir::Value ptrValue = buildScalarExpr(ptr);
+    mlir::Value offsetValue =
+        (E->getNumArgs() > 2) ? buildScalarExpr(E->getArg(2)) : nullptr;
+
+    mlir::Attribute alignmentAttr = ConstantEmitter(*this).emitAbstract(
+        E->getArg(1), E->getArg(1)->getType());
+    std::int64_t alignment = cast<mlir::cir::IntAttr>(alignmentAttr).getSInt();
+
+    ptrValue = buildAlignmentAssumption(ptrValue, ptr, ptr->getExprLoc(),
+                                        builder.getI64IntegerAttr(alignment),
+                                        offsetValue);
+    return RValue::get(ptrValue);
+  }
+
+  case Builtin::BI__assume:
+  case Builtin::BI__builtin_assume: {
+    if (E->getArg(0)->HasSideEffects(getContext()))
+      return RValue::get(nullptr);
+
+    mlir::Value argValue = buildScalarExpr(E->getArg(0));
+    builder.create<mlir::cir::AssumeOp>(getLoc(E->getExprLoc()), argValue);
+    return RValue::get(nullptr);
+  }
+
+  case Builtin::BI__builtin_assume_separate_storage: {
+    const Expr *arg0 = E->getArg(0);
+    const Expr *arg1 = E->getArg(1);
+
+    mlir::Value value0 = buildScalarExpr(arg0);
+    mlir::Value value1 = buildScalarExpr(arg1);
+
+    builder.create<mlir::cir::AssumeSepStorageOp>(getLoc(E->getExprLoc()),
+                                                  value0, value1);
+    return RValue::get(nullptr);
+  }
+
   case Builtin::BI__builtin_prefetch: {
     auto evaluateOperandAsInt = [&](const Expr *Arg) {
       Expr::EvalResult Res;
diff --git a/clang/lib/CIR/CodeGen/CIRGenFunction.cpp b/clang/lib/CIR/CodeGen/CIRGenFunction.cpp
index 0c7ac712284d..410fcc2a316d 100644
--- a/clang/lib/CIR/CodeGen/CIRGenFunction.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenFunction.cpp
@@ -1854,3 +1854,22 @@ CIRGenFunction::buildArrayLength(const clang::ArrayType *origArrayType,
 
   return numElements;
 }
+
+mlir::Value CIRGenFunction::buildAlignmentAssumption(
+    mlir::Value ptrValue, QualType ty, SourceLocation loc,
+    SourceLocation assumptionLoc, mlir::IntegerAttr alignment,
+    mlir::Value offsetValue) {
+  if (SanOpts.has(SanitizerKind::Alignment))
+    llvm_unreachable("NYI");
+  return builder.create<mlir::cir::AssumeAlignedOp>(
+      getLoc(assumptionLoc), ptrValue, alignment, offsetValue);
+}
+
+mlir::Value CIRGenFunction::buildAlignmentAssumption(
+    mlir::Value ptrValue, const Expr *expr, SourceLocation assumptionLoc,
+    mlir::IntegerAttr alignment, mlir::Value offsetValue) {
+  QualType ty = expr->getType();
+  SourceLocation loc = expr->getExprLoc();
+  return buildAlignmentAssumption(ptrValue, ty, loc, assumptionLoc, alignment,
+                                  offsetValue);
+}
diff --git a/clang/lib/CIR/CodeGen/CIRGenFunction.h b/clang/lib/CIR/CodeGen/CIRGenFunction.h
index 7703b6cd6ee7..c09860cb85fc 100644
--- a/clang/lib/CIR/CodeGen/CIRGenFunction.h
+++ b/clang/lib/CIR/CodeGen/CIRGenFunction.h
@@ -969,6 +969,17 @@ class CIRGenFunction : public CIRGenTypeCache {
                                      ReturnValueSlot ReturnValue,
                                      llvm::Triple::ArchType Arch);
 
+  mlir::Value buildAlignmentAssumption(mlir::Value ptrValue, QualType ty,
+                                       SourceLocation loc,
+                                       SourceLocation assumptionLoc,
+                                       mlir::IntegerAttr alignment,
+                                       mlir::Value offsetValue = nullptr);
+
+  mlir::Value buildAlignmentAssumption(mlir::Value ptrValue, const Expr *expr,
+                                       SourceLocation assumptionLoc,
+                                       mlir::IntegerAttr alignment,
+                                       mlir::Value offsetValue = nullptr);
+
   /// Build a debug stoppoint if we are emitting debug info.
   void buildStopPoint(const Stmt *S);
 
diff --git a/clang/test/CIR/CodeGen/builtin-assume.cpp b/clang/test/CIR/CodeGen/builtin-assume.cpp
new file mode 100644
index 000000000000..da807994f4b1
--- /dev/null
+++ b/clang/test/CIR/CodeGen/builtin-assume.cpp
@@ -0,0 +1,55 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -emit-cir %s -o %t.cir
+// RUN: FileCheck %s --check-prefix=CIR --input-file=%t.cir
+
+int test_assume(int x) {
+  __builtin_assume(x > 0);
+  return x;
+}
+
+//      CIR: cir.func @_Z11test_assumei
+//      CIR:   %[[#x:]] = cir.load %{{.+}} : !cir.ptr<!s32i>, !s32i
+// CIR-NEXT:   %[[#zero:]] = cir.const #cir.int<0> : !s32i
+// CIR-NEXT:   %[[#cond:]] = cir.cmp(gt, %[[#x]], %[[#zero]]) : !s32i, !cir.bool
+// CIR-NEXT:   cir.assume %[[#cond]] : !cir.bool
+//      CIR: }
+
+int test_assume_aligned(int *ptr) {
+  int *aligned = (int *)__builtin_assume_aligned(ptr, 8);
+  return *aligned;
+}
+
+//      CIR: cir.func @_Z19test_assume_alignedPi
+//      CIR:   %[[#ptr:]] = cir.load %{{.+}} : !cir.ptr<!cir.ptr<!s32i>>, !cir.ptr<!s32i>
+// CIR-NEXT:   %[[#aligned:]] = cir.assume.aligned %[[#ptr]] : !cir.ptr<!s32i>[alignment 8]
+// CIR-NEXT:   cir.store %[[#aligned]], %[[#aligned_slot:]] : !cir.ptr<!s32i>, !cir.ptr<!cir.ptr<!s32i>>
+// CIR-NEXT:   %[[#aligned2:]] = cir.load deref %[[#aligned_slot]] : !cir.ptr<!cir.ptr<!s32i>>, !cir.ptr<!s32i>
+// CIR-NEXT:   %{{.+}} = cir.load %[[#aligned2]] : !cir.ptr<!s32i>, !s32i
+//      CIR: }
+
+int test_assume_aligned_offset(int *ptr) {
+  int *aligned = (int *)__builtin_assume_aligned(ptr, 8, 4);
+  return *aligned;
+}
+
+//      CIR: cir.func @_Z26test_assume_aligned_offsetPi
+//      CIR:   %[[#ptr:]] = cir.load %{{.+}} : !cir.ptr<!cir.ptr<!s32i>>, !cir.ptr<!s32i>
+// CIR-NEXT:   %[[#offset:]] = cir.const #cir.int<4> : !s32i
+// CIR-NEXT:   %[[#offset2:]] = cir.cast(integral, %[[#offset]] : !s32i), !u64i
+// CIR-NEXT:   %[[#aligned:]] = cir.assume.aligned %[[#ptr]] : !cir.ptr<!s32i>[alignment 8, offset %[[#offset2]] : !u64i]
+// CIR-NEXT:   cir.store %[[#aligned]], %[[#aligned_slot:]] : !cir.ptr<!s32i>, !cir.ptr<!cir.ptr<!s32i>>
+// CIR-NEXT:   %[[#aligned2:]] = cir.load deref %[[#aligned_slot]] : !cir.ptr<!cir.ptr<!s32i>>, !cir.ptr<!s32i>
+// CIR-NEXT:   %{{.+}} = cir.load %[[#aligned2]] : !cir.ptr<!s32i>, !s32i
+//      CIR: }
+
+int test_separate_storage(int *p1, int *p2) {
+  __builtin_assume_separate_storage(p1, p2);
+  return *p1 + *p2;
+}
+
+//      CIR: cir.func @_Z21test_separate_storagePiS_
+//      CIR:   %[[#p1:]] = cir.load %{{.+}} : !cir.ptr<!cir.ptr<!s32i>>, !cir.ptr<!s32i>
+// CIR-NEXT:   %[[#p1_voidptr:]] = cir.cast(bitcast, %[[#p1]] : !cir.ptr<!s32i>), !cir.ptr<!void>
+// CIR-NEXT:   %[[#p2:]] = cir.load %{{.+}} : !cir.ptr<!cir.ptr<!s32i>>, !cir.ptr<!s32i>
+// CIR-NEXT:   %[[#p2_voidptr:]] = cir.cast(bitcast, %[[#p2]] : !cir.ptr<!s32i>), !cir.ptr<!void>
+// CIR-NEXT:   cir.assume.separate_storage %[[#p1_voidptr]], %[[#p2_voidptr]] : !cir.ptr<!void>
+//      CIR: }
diff --git a/clang/test/CIR/Transforms/builtin-assume.cir b/clang/test/CIR/Transforms/builtin-assume.cir
new file mode 100644
index 000000000000..72afb3812e53
--- /dev/null
+++ b/clang/test/CIR/Transforms/builtin-assume.cir
@@ -0,0 +1,40 @@
+// RUN: cir-opt --canonicalize -o %t.cir %s
+// RUN: FileCheck --input-file %t.cir %s
+// RUN: cir-opt -cir-simplify -o %t.cir %s
+// RUN: FileCheck --input-file %t.cir %s
+
+!s32i = !cir.int<s, 32>
+module {
+  // Make sure canonicalizers don't erase assume builtins.
+
+  cir.func @assume(%arg0: !s32i) {
+    %0 = cir.const #cir.int<0> : !s32i
+    %1 = cir.cmp(gt, %arg0, %0) : !s32i, !cir.bool
+    cir.assume %1 : !cir.bool
+    cir.return
+  }
+  //      CHECK: cir.func @assume(%arg0: !s32i) {
+  // CHECK-NEXT:   %0 = cir.const #cir.int<0> : !s32i
+  // CHECK-NEXT:   %1 = cir.cmp(gt, %arg0, %0) : !s32i, !cir.bool
+  // CHECK-NEXT:   cir.assume %1 : !cir.bool
+  // CHECK-NEXT:   cir.return
+  // CHECK-NEXT: }
+
+  cir.func @assume_aligned(%arg0: !cir.ptr<!s32i>) -> !cir.ptr<!s32i> {
+    %0 = cir.assume.aligned %arg0 : !cir.ptr<!s32i>[alignment 8]
+    cir.return %0 : !cir.ptr<!s32i>
+  }
+  //      CHECK: cir.func @assume_aligned(%arg0: !cir.ptr<!s32i>) -> !cir.ptr<!s32i> {
+  // CHECK-NEXT:   %0 = cir.assume.aligned %arg0 : !cir.ptr<!s32i>[alignment 8]
+  // CHECK-NEXT:   cir.return %0 : !cir.ptr<!s32i>
+  // CHECK-NEXT: }
+
+  cir.func @assume_separate_storage(%arg0: !cir.ptr<!cir.void>, %arg1: !cir.ptr<!cir.void>) {
+    cir.assume.separate_storage %arg0, %arg1 : !cir.ptr<!cir.void>
+    cir.return
+  }
+  //      CHECK: cir.func @assume_separate_storage(%arg0: !cir.ptr<!void>, %arg1: !cir.ptr<!void>) {
+  // CHECK-NEXT:   cir.assume.separate_storage %arg0, %arg1 : !cir.ptr<!void>
+  // CHECK-NEXT:   cir.return
+  // CHECK-NEXT: }
+}
\ No newline at end of file