diff --git a/compiler/calls.go b/compiler/calls.go
index a44ac38a87..08952c4db6 100644
--- a/compiler/calls.go
+++ b/compiler/calls.go
@@ -32,6 +32,9 @@ const (
 	// Whether this is a full or partial Go parameter (int, slice, etc).
 	// The extra context parameter is not a Go parameter.
 	paramIsGoParam = 1 << iota
+
+	// Whether this is a readonly parameter (for example, a string pointer).
+	paramIsReadonly
 )
 
 // createRuntimeCallCommon creates a runtime call. Use createRuntimeCall or
@@ -167,6 +170,7 @@ func (c *compilerContext) flattenAggregateType(t llvm.Type, name string, goType
 				continue
 			}
 			suffix := strconv.Itoa(i)
+			isString := false
 			if goType != nil {
 				// Try to come up with a good suffix for this struct field,
 				// depending on which Go type it's based on.
@@ -183,12 +187,16 @@ func (c *compilerContext) flattenAggregateType(t llvm.Type, name string, goType
 						suffix = []string{"r", "i"}[i]
 					case types.String:
 						suffix = []string{"data", "len"}[i]
+						isString = true
 					}
 				case *types.Signature:
 					suffix = []string{"context", "funcptr"}[i]
 				}
 			}
 			subInfos := c.flattenAggregateType(subfield, name+"."+suffix, extractSubfield(goType, i))
+			if isString {
+				subInfos[0].flags |= paramIsReadonly
+			}
 			paramInfos = append(paramInfos, subInfos...)
 		}
 		return paramInfos
diff --git a/compiler/symbol.go b/compiler/symbol.go
index 749ad8f1b5..47bc0f4844 100644
--- a/compiler/symbol.go
+++ b/compiler/symbol.go
@@ -142,6 +142,11 @@ func (c *compilerContext) getFunction(fn *ssa.Function) (llvm.Type, llvm.Value)
 			nocapture := c.ctx.CreateEnumAttribute(llvm.AttributeKindID("nocapture"), 0)
 			llvmFn.AddAttributeAtIndex(i+1, nocapture)
 		}
+		if paramInfo.flags&paramIsReadonly != 0 && paramInfo.llvmType.TypeKind() == llvm.PointerTypeKind {
+			// Readonly pointer parameters (like strings) benefit from being marked as readonly.
+			readonly := c.ctx.CreateEnumAttribute(llvm.AttributeKindID("readonly"), 0)
+			llvmFn.AddAttributeAtIndex(i+1, readonly)
+		}
 	}
 
 	// Set a number of function or parameter attributes, depending on the
diff --git a/compiler/testdata/go1.20.ll b/compiler/testdata/go1.20.ll
index b1c5bd48f2..dff746667d 100644
--- a/compiler/testdata/go1.20.ll
+++ b/compiler/testdata/go1.20.ll
@@ -50,7 +50,7 @@ unsafe.String.throw:                              ; preds = %entry
 declare void @runtime.unsafeSlicePanic(ptr) #1
 
 ; Function Attrs: nounwind
-define hidden ptr @main.unsafeStringData(ptr %s.data, i32 %s.len, ptr %context) unnamed_addr #2 {
+define hidden ptr @main.unsafeStringData(ptr readonly %s.data, i32 %s.len, ptr %context) unnamed_addr #2 {
 entry:
   %stackalloc = alloca i8, align 1
   call void @runtime.trackPointer(ptr %s.data, ptr nonnull %stackalloc, ptr undef) #3
diff --git a/compiler/testdata/go1.21.ll b/compiler/testdata/go1.21.ll
index 0e8182538c..6af9776bc3 100644
--- a/compiler/testdata/go1.21.ll
+++ b/compiler/testdata/go1.21.ll
@@ -77,7 +77,7 @@ entry:
 }
 
 ; Function Attrs: nounwind
-define hidden %runtime._string @main.minString(ptr %a.data, i32 %a.len, ptr %b.data, i32 %b.len, ptr %context) unnamed_addr #2 {
+define hidden %runtime._string @main.minString(ptr readonly %a.data, i32 %a.len, ptr readonly %b.data, i32 %b.len, ptr %context) unnamed_addr #2 {
 entry:
   %0 = insertvalue %runtime._string zeroinitializer, ptr %a.data, 0
   %1 = insertvalue %runtime._string %0, i32 %a.len, 1
@@ -91,7 +91,7 @@ entry:
   ret %runtime._string %5
 }
 
-declare i1 @runtime.stringLess(ptr, i32, ptr, i32, ptr) #1
+declare i1 @runtime.stringLess(ptr readonly, i32, ptr readonly, i32, ptr) #1
 
 ; Function Attrs: nounwind
 define hidden i32 @main.maxInt(i32 %a, i32 %b, ptr %context) unnamed_addr #2 {
@@ -116,7 +116,7 @@ entry:
 }
 
 ; Function Attrs: nounwind
-define hidden %runtime._string @main.maxString(ptr %a.data, i32 %a.len, ptr %b.data, i32 %b.len, ptr %context) unnamed_addr #2 {
+define hidden %runtime._string @main.maxString(ptr readonly %a.data, i32 %a.len, ptr readonly %b.data, i32 %b.len, ptr %context) unnamed_addr #2 {
 entry:
   %0 = insertvalue %runtime._string zeroinitializer, ptr %a.data, 0
   %1 = insertvalue %runtime._string %0, i32 %a.len, 1
diff --git a/compiler/testdata/string.ll b/compiler/testdata/string.ll
index ce2bf35066..8c95323ccf 100644
--- a/compiler/testdata/string.ll
+++ b/compiler/testdata/string.ll
@@ -31,13 +31,13 @@ entry:
 }
 
 ; Function Attrs: nounwind
-define hidden i32 @main.stringLen(ptr %s.data, i32 %s.len, ptr %context) unnamed_addr #2 {
+define hidden i32 @main.stringLen(ptr readonly %s.data, i32 %s.len, ptr %context) unnamed_addr #2 {
 entry:
   ret i32 %s.len
 }
 
 ; Function Attrs: nounwind
-define hidden i8 @main.stringIndex(ptr %s.data, i32 %s.len, i32 %index, ptr %context) unnamed_addr #2 {
+define hidden i8 @main.stringIndex(ptr readonly %s.data, i32 %s.len, i32 %index, ptr %context) unnamed_addr #2 {
 entry:
   %.not = icmp ult i32 %index, %s.len
   br i1 %.not, label %lookup.next, label %lookup.throw
@@ -55,16 +55,16 @@ lookup.throw:                                     ; preds = %entry
 declare void @runtime.lookupPanic(ptr) #1
 
 ; Function Attrs: nounwind
-define hidden i1 @main.stringCompareEqual(ptr %s1.data, i32 %s1.len, ptr %s2.data, i32 %s2.len, ptr %context) unnamed_addr #2 {
+define hidden i1 @main.stringCompareEqual(ptr readonly %s1.data, i32 %s1.len, ptr readonly %s2.data, i32 %s2.len, ptr %context) unnamed_addr #2 {
 entry:
   %0 = call i1 @runtime.stringEqual(ptr %s1.data, i32 %s1.len, ptr %s2.data, i32 %s2.len, ptr undef) #3
   ret i1 %0
 }
 
-declare i1 @runtime.stringEqual(ptr, i32, ptr, i32, ptr) #1
+declare i1 @runtime.stringEqual(ptr readonly, i32, ptr readonly, i32, ptr) #1
 
 ; Function Attrs: nounwind
-define hidden i1 @main.stringCompareUnequal(ptr %s1.data, i32 %s1.len, ptr %s2.data, i32 %s2.len, ptr %context) unnamed_addr #2 {
+define hidden i1 @main.stringCompareUnequal(ptr readonly %s1.data, i32 %s1.len, ptr readonly %s2.data, i32 %s2.len, ptr %context) unnamed_addr #2 {
 entry:
   %0 = call i1 @runtime.stringEqual(ptr %s1.data, i32 %s1.len, ptr %s2.data, i32 %s2.len, ptr undef) #3
   %1 = xor i1 %0, true
@@ -72,16 +72,16 @@ entry:
 }
 
 ; Function Attrs: nounwind
-define hidden i1 @main.stringCompareLarger(ptr %s1.data, i32 %s1.len, ptr %s2.data, i32 %s2.len, ptr %context) unnamed_addr #2 {
+define hidden i1 @main.stringCompareLarger(ptr readonly %s1.data, i32 %s1.len, ptr readonly %s2.data, i32 %s2.len, ptr %context) unnamed_addr #2 {
 entry:
   %0 = call i1 @runtime.stringLess(ptr %s2.data, i32 %s2.len, ptr %s1.data, i32 %s1.len, ptr undef) #3
   ret i1 %0
 }
 
-declare i1 @runtime.stringLess(ptr, i32, ptr, i32, ptr) #1
+declare i1 @runtime.stringLess(ptr readonly, i32, ptr readonly, i32, ptr) #1
 
 ; Function Attrs: nounwind
-define hidden i8 @main.stringLookup(ptr %s.data, i32 %s.len, i8 %x, ptr %context) unnamed_addr #2 {
+define hidden i8 @main.stringLookup(ptr readonly %s.data, i32 %s.len, i8 %x, ptr %context) unnamed_addr #2 {
 entry:
   %0 = zext i8 %x to i32
   %.not = icmp ugt i32 %s.len, %0